In the extracellular fluid are the ions and nutrients needed by the cells to maintain life. Thus, all cells live in essentially the same environment - the extracellular fluid. For this reason, the extracellular fluid is also called the internal environment of the body, or the milieu intérieur.
The extracellular fluid contains large amounts of the following substances, except:
A) Potassium ions
The intracellular fluid contains large amounts of potassium, magnesium, and phosphate ions.
Remember the mnemonic:
A. Intracellular fluid
1. Mag - magnesium
2. Palaba - phosphate
3. Ka - potassium
4. Sa - sulfate
5. Hapon - bicarbonate
6. Pati - proteins
7. Linis - lipids
8. Car - carbohydrates
B. Extracellular fluid
1. Oo - oxygen
2. Hapon - bicarbonate
3. Na - sodium
4. Clean - chloride
5. Ganyan - glucose
6. F - fatty acids
7. AM - amino acids
8. Co - carbon dioxide
What is the most abundant of all the metabolism products?
A) Carbon dioxide
The regulation of oxygen concentration in the tissues is vested principally in the:
A) Chemical characteristics of hemoglobin
Hemoglobin combines with oxygen as the blood passes through the lungs. Then, as the blood passes through the tissue capillaries, hemoglobin, because of its own strong chemical affinity for oxygen, does not release oxygen into the tissue fluid if too much oxygen is already there. However, if the oxygen concentration in the tissue fluid is too low, sufficient oxygen is released to re-establish an adequate concentration. This regulation is called the oxygen-buffering function of hemoglobin.
If potassium ion concentration decreases to less than one-half normal, a person is likely to be paralyzed as a result of the inability of the nerves to carry signals. Alternatively, if potassium ion concentration increases to two or more times normal, the heart muscle is likely to be severely depressed.
C) Only the second statement is true.
If potassium ion concentration decreases to less than one-third normal, a person is likely to be paralyzed as a result of the inability of the nerves to carry signals.
When the concentration of this ion falls below about one-half normal, a person is likely to experience tetanic contraction of muscles throughout the body.
A) Calcium
Tetanic contraction of the muscles occur because of the spontaneous generation of excess nerve impulses in the peripheral nerves.
When the concentration of this substance falls below one-half normal, a person frequently exhibits extreme mental irritability and sometime even has convulsions.
D) Glucose
All of the following are examples of a positive feedback system, except:
A) Blood loss
Which of the following is not a component of protoplasm?
C) Plasma
Protoplasm is composed mainly of five basic substance: water, electrolytes, proteins, lipids, and carbohydrates.
The principal fluid medium of the cell is water, which is present in most cells, except for:
C) Adipocytes
After water, the most abundant substances in most cells are:
C) Proteins
Proteins normally constitute 10% to 20% of the cell mass. These proteins can be divided into two types: structural proteins and functional proteins.
______________ proteins are present in the cell mainly in the form of long filaments that are polymers of many individual protein molecules.
B) Structural
A prominent use of such intracellular filaments is to form microtubules that provide the "cytoskeletons" of cellular organelles.
All of the following characterize functional proteins, except:
C) They are often immobile in the cell fluid.
In contrast to the fibrillar proteins, the functional proteins are often mobile in the cell fluid.
What are the most important lipids, constituting only about 2% of the total cell mass?
B) Phospholipids and cholesterol
The significance of phospholipids and cholesterol is that they are mainly insoluble in water and therefore are used to form the cell membrane and intracellular membrane barriers that separate the different cell compartments.
In adipocytes, this lipid accounts for as much as 95% of the cell mass.
A) Triglycerides
Triglycerides is also called as neutral fat. The fat store in adipocytes represents the body's main storehouse of energy-giving nutrients that can later be used to provide energy wherever in the body it is needed.
Most human cells do not maintain large stores of carbohydrates, with its amount usually averaging about 1% of their total mass. However, carbohydrate in the form of dissolved glycogen is always present in the surrounding extracellular fluid so that it is readily available to the cell.
C) Only the first statement is true.
However, carbohydrate in the form of dissolved glucose is always present in the surrounding extracellular fluid so that it is readily available to the cell.
A small amount of carbohydrate is stored in the cells in the form of glycogen, which is an insoluble polymer of glucose that can be depolymerized and used rapidly to supply the cells’ energy needs.
Without the mitochondria, how many percent of the cell's energy release from nutrients would cease immediately?
A) 95%
The lipids in the membranes provide a barrier that impedes movement of water and water-soluble substances from one cell compartment to another. Proteins molecules often penetrate all the way through the membrane, providing specialized pathways for passage of specific substances.
B) Both statements are true.
Also, many of the other membrane proteins are enzymes that catalyze a multitude of different chemical reactions.
The cell membrane envelops that cell and is a thin, pliable, inelastic structure only 7.5 to 10 nm thick. It is composed almost entirely of proteins and lipids.
B) Only the second statement is true.
The cell membrane, also known as the plasma membrane, envelops that cell and is a thin, pliable, elastic structure only 7.5 to 10 nm thick.
Which of the following is incorrect the the composition of the plasma membrane?
B) 25% carbohydrates
The approximate composition of the plasma (cell) membrane is proteins,(55%), phospholipids (25%), cholesterol (13%), other lipids (4%), and carbohydrates (3%).
The basic lipid bilayer is composed of three main types of lipids: phospholipids, sphingolipids, and cholesterol. Cholesterol is the most abundant of the cell membrane lipids.
A) Only the first statement is true.
Phospholipids are the most abundant of the cell membrane lipids. The phosphate end of the phospholipid is hydrophilic, and the fatty acid portion is hydrophobic.
The lipid layer in the middle of the membrane is impermeable to water-soluble substances, such as ions, glucose, and alcohol. Conversely, fat-soluble substances, such as oxygen, carbon dioxide, and urea, can penetrate this portion of the membrane with ease.
A) Both statements are false.
The lipid layer in the middle of the membrane is impermeable to water-soluble substances, such as ions, glucose, and urea. Conversely, fat-soluble substances, such as oxygen, carbon dioxide, and alcohol, can penetrate this portion of the membrane with ease.
Sphingolipids, derived from the amino alcohol sphingosine, also have hydrophobic and hydrophilic groups and are present in small amounts in the cell membranes, especially in muscle cells. Complex sphingolipids in cell membranes are thought to serve several functions, including protection from harmful environmental factors, signal transmission, and as adhesion sites for extracellular proteins.
A) Only the second statement is true.
Sphingolipids, derived from the amino alcohol sphingosine, also have hydrophobic and hydrophilic groups and are present in small amounts in the cell membranes, especially in nerve cells.
These lipids mainly help determine the degree of permeability (or impermeability of the bilayer to water-soluble constituents of body fluids.
B) Cholesterol
The cholesterol molecules in the cell (plasma) membrane are also lipids because their steroid nuclei are highly fat soluble. These molecules, in a sense, are dissolved in the bilayer of the membrane.
These lipids control much of the fluidity of the cell membrane.
B) Cholesterol
Which of the following is not true about integral proteins?
B) Provide functional channels through which water molecules and water-soluble substances can diffuse between the extracellular and intracellular fluids
Integral proteins provide structural channels through which water molecules and water-soluble substances can diffuse between the extracellular and intracellular fluids.
The entire outside surface of the cell often has a loose carbohydrate coat called the:
C) Glycocalyx
The carbohydrate moieties attached to the outer surface of the cell serve the following functions, except:
D) Give most cells an overall positive surface charge that repels other positively charged objects
The carbohydrate moieties give most cells an overall negative surface charge that repels other negatively charged objects.
The jelly-like fluid portion of the cytoplasm in which the particles are dispersed is called cytosol. The cytosol mainly contains dissolved proteins, electrolytes, and lipids.
D) Only the first statement is true.
The cytosol mainly contains dissolved proteins, electrolytes, and glucose.
This organelle helps process molecules made by the cell and transport them to their specific destinations inside or outside the cell.
C) Endoplasmic reticulum
Which of the following is true about the endoplasmic reticulum?
A) The space inside the vesicles and tubules is filled with endoplasmic matrix, a watery medium that is different from the fluid in the cytosol outside the endoplasmic reticulum.
The space inside the endoplasmic reticulum is connected with the space between the two membrane surfaces of the nuclear membrane.
The vast surface area of this organelle and the multiple enzyme systems attached to its membranes provide the machinery for a major share of the metabolic functions of the cell.
B) Endoplasmic reticulum
The total surface of the endoplasmic reticulum in ____________ can be as much as 30 to 40 times the cell membrane area.
B) Hepatocytes
Attached to the inner surfaces of many parts of the endoplasmic reticulum are large numbers of minute granular particles called ribosomes. The ribosomes are composed of a mixture of RNA and proteins, and they function to synthesize new protein molecules in the cell.
B) Only the second statement is true.
Attached to the outer surfaces of many parts of the endoplasmic reticulum are large numbers of minute granular particles called ribosomes.
The agranular endoplasmic reticulum has no attached ribosomes. This reticulum functions for the synthesis of lipid substances and for other processes of the cells promoted by intracellular enzymes.
C) Only the first statement is true.
The agranular endoplasmic reticulum, also known as smooth endoplasmic reticulum, functions for the synthesis of lipid substances and for other processes of the cells promoted by intrareticular enzymes.
Which of the following does not describe Golgi apparatus?
D) It has membranes similar to those of the granular endoplasmic reticulum.
The Golgi apparatus has membranes similar to those of the agranular (smooth) endoplasmic reticulum.
Small "transport" vesicles intermittently pinch off from the endoplasmic reticulum and shortly thereafter fuse with the Golgi apparatus. The transported substances are then processed in the Golgi apparatus to form lysosomes, secretory vesicles, and other cytoplasmic components.
B) Only the second statement is true.
Small "transport" vesicles continually pinch off from the endoplasmic reticulum and shortly thereafter fuse with the Golgi apparatus.
The lysosomes provide an intracellular digestive system that allows the cell to digest:
D) All of these
Hydrolytic enzymes are highly concentrated in lysosomes. Ordinarily, the membrane surrounding the lysosome prevents the enclosed hydrolytic enzymes from coming in contact with other substances in the cell and therefore prevents their digestive actions.
C) Both statements are true.
However, some conditions of the cell break the membranes of some of the lysosomes, allowing release of the digestive enzymes. These enzymes then split the organic substances with which they come in contact into small, highly diffusible substances such as amino acids and glucose.
Peroxisomes are similar physically to lysosomes, but they are different in which ways?
D) Peroxisomes contain oxidases rather than hydrolases, and these oxidases are capable of combining oxygen with hydrogen ions derived from different intracellular chemicals to form hydrogen peroxide.
Peroxisomes are formed by self-replication or perhaps by budding off from the smooth endoplasmic reticulum rather than from the Golgi apparatus.
Hydrogen peroxide is a highly oxidizing substance. It is used in association with catalase, another oxidase enzyme present in small quantities in peroxisomes, to oxidize many substances that might otherwise be poisonous to the cell.
A) Only the first statement is true.
Hydrogen peroxide is used in association with catalase, another oxidase enzyme present in large quantities in peroxisomes, to oxidize many substances that might otherwise be poisonous to the cell.
Which of the following is not true about the mitochondria?
C) Many infoldings of their inner membrane form shelves or tubules called cristae onto which hydrolytic enzymes are attached.
Many infoldings of the inner membrane of the mitochondria form shelves or tubules called cristae onto which oxidative enzymes are attached.
The cytoskeleton of the cell not only determines the cell shape but also:
C) All of these
Which of the following is not true about the nuclear membrane?
B) Its inner membrane is continuous with the endoplasmic reticulum of the cell cytoplasm.
The outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum of the cell cytoplasm. The space between the two nuclear membranes is also continuous with the space inside the endoplasmic reticulum.
Which of the following does not characterize the nucleous?
C) It is an accumulation of large amounts of DNA and proteins of the types found in ribosomes.
The nucleolus is an accumulation of large amounts of RNA and proteins of the types found in ribosomes.
This refers to the ingestion of minute particles that form vesicles of extracellular fluid and particulate constituents inside the cell cytoplasm.
C) Pinocytosis
Meanwhile, phagocytosis refers to the ingestion of large particles, such as bacteria, whole cells, or portions of degenerating tissue. Pinocytosis and phagocytosis are the principal forms of endocytosis.
Pinocytosis:
A) Occurs continually in the cell membranes of most cells, but it is especially rapid in some cells
Pinocytosis is the only means by which most large macromolecules, such as protein molecules, can enter cells.
Pinocytosis requires the presence of ATP, as well as calcium ions in theextracellular fluid, which probably react with contractile protein filaments beneath the coated pits to provide the force for pinching the vesicles away from the cell membrane.
Pinocytosis occurs so rapidly in macrophages that about ___ of the total macrophage membrane is engulfed in the form of vesicles each minute.
C) 3%
Phagocytosis is initiated when a particle such as a bacterium, a dead cell, or a tissue debris binds with receptors on the surface of the phagocyte. In the case of bacteria, each bacterium is usually already attached to a specific antibody, and it is the antibody that attaches to the phagocyte receptors, dragging the bacterium along with it.
B) Both statements are true.
Almost immediately after a pinocytotic or phagocytic vesicle appears inside a cell, one or more lysosomes become attached to the vesicle and empty their acid hydrolases to the inside of the vesicle. Thus, a transport vesicle is formed inside the cell cytoplasm in which the vesicular hydrolases begin hydrolyzing the proteins, carbohydrates, lipids, and other substances in the vesicle.
A) Only the first statement is true.
Thus, a digestive vesicle is formed inside the cell cytoplasm in which the vesicular hydrolases begin hydrolyzing the proteins, carbohydrates, lipids, and other substances in the vesicle.
The residual body:
B) Both of these
Tissues of the body often regress to a smaller size. For instance, this regression occurs in the uterus after pregnancy, in muscles during prolonged periods of inactivity, and in mammary glands at the end of lactation. Which of the following organelles is responsible for such regression of tissues?
A) Lysosomes
The lysosomes contain bactericidal agents that can kill phagocytized bacteria before they can cause cellular damage. These agents include the following, except:
B) Acid at pH of 3.0
It should be acid at pH of 5.0.
Which of the following bactericidal agents binds to iron and other substances before they can promote bacterial growth?
D) Lysoferrin
The lysozyme dissolves the bacterial cell membrane, while the acid activates hydrolases and inactivates bacterial metabolic systems.
Which of the following organelles play a key role in the process of autophagy?
D) Lysosomes
Autophagy, which literally mean "to eat oneself", is a housekeeping process by which obsolete organelles and large protein aggregates are degraded and recycled.
This process contributes to the routine turnover of the cytoplasmic components and is a key mechanism for tissue development, for cell survival when nutrients are scarce, and for maintaining homeostasis.
A) Autophagy
Autophagy refers to the recycling of cell by the lysosomes. Meanwhile, autolysis refers to the digestion of a severely damaged cell by the lysosomes.
In these cells, the average mitochondrion normally has a life span of only about 10 days before it is destroyed.
B) Hepatocytes
The ribosomes extrude some of the synthesized protein molecules directly into the cytosol. However, they also extrude many more through the wall of the endoplasmic reticulum to the exterior of the endoplasmic vesicles and tubules, into the endoplasmic matrix.
B) Only the first statement is true.
Ribosomes also extrude many more of the protein molecules through the wall of the endoplasmic reticulum to the interior of the endoplasmic vesicles and tubules, into the endoplasmic matrix.
The smooth endoplasmic reticulum synthesizes lipids, especially phospholipids and sphingolipids. These lipids are rapidly incorporated into the lipid bilayer of the endoplasmic reticulum itself, thus causing the endoplasmic reticulum to grow more extensive.
D) Only the second statement is true.
The smooth endoplasmic reticulum synthesizes lipids, especially phospholipids and cholesterol.
To keep the endoplasmic reticulum from growing beyond the needs of the cell, small vesicles called transport vesicles continually break away from the rough reticulum. Most of these vesicles then migrate rapidly to the Golgi apparatus.
C) Only the second statement is true.
To keep the endoplasmic reticulum from growing beyond the needs of the cell, small vesicles called transport vesicles continually break away from the smooth reticulum. Take note that the smooth portion of the reticulum is the one that synthesizes lipids, which are then incorporated into the lipid bilayer of the reticulum itself.
This organelle provides the enzymes that control glycogen breakdown when glycogen is to be used for energy.
C) Smooth endoplasmic reticulum
Smooth endoplasmic reticulum is also known as agranular endoplasmic reticulum.
This organelle is capable of synthesizing hyaluronic acid and chondroitin sulfate.
A) Golgi apparatus
The Golgi apparatus is capable of synthesizing carbohydrates that cannot be formed in the endoplasmic reticulum. This is especially true for the formation oflarge saccharide polymers bound with small amounts of protein such as hyaluronic acid and chondroitin sulfate.
Some of the functions of hyaluronic acid and chondroitin sulfate in the body are as follows, except:
D) They are major components of ground substance, or fibrous components of the extracellular matrix.
Hyaluronic acid and chondroitin sulfate are the major components of ground substance, or nonfibrous components of the extracellular matrix.
Exocytosis, in most cases, is stimulated by the entry of which ions into the cell?
D) Calcium
The calcium ions interact with the vascular membrane in some way that is not understood and cause its fusion with the cell membrane, followed by exocytosis.
The cell membrane loses much of its substance every time it forms a phagocytic or pinocytotic vesicle. The vesicular membranes of this organelle is responsible for continually replenishing the cell membrane.
D) Golgi apparatus
Energy currency of the cell
D) ATP
To reconstitute the cellular ATP as it is used up, energy derived from the cellular nutrients causes ADP and phosphoric acid to recombine to form new ATP.
About how many percent of the cell's ATP formation occurs in the mitochondria?
D) 95%
Upon entry into the cells, glucose is subjected to enzymes in the cytoplasm that convert it to pyruvic acid. This process is called glycolysis. A small amount of ADP is changed into ATP by the energy released during this conversion, but this amount accounts for less than 5% of the overall energy metabolism of the cell.
Energy from ATP is used to promote:
D) All of these
Which of the following cells exhibit/s ameboid motion?
C) All of these
Ameboid locomotion begins with protrusion of a pseudopodium from one end of the cell. The pseudopodium projects away from the cell body and partially secures itself in a new tissue area, and then the remainder of the cell is pulled toward the pseudopodium.
What is the most important initiator of ameboid motion?
C) Chemotaxis
Most cells that exhibit ameboid motion move toward the source of a chemotactic substance - that is, from an area of lower concentration toward an area of higher concentration - which is called positive chemotaxis.
In the nasal cavity and lower respiratory airways, the whiplike motion of cilia causes a layer of mucus to move at a rate of _____ toward the pharynx, continually clearing these passageways of mucus and particiles that have become trapped in the mucus.
D) 1 cm/min
The flagellum of a sperm is similar to a cilium in terms of structure and contractile mechanism. The flagellum, however, is much shorter and moves in quasi-sinusoidal waves instead of whiplike movements.
B) Only the first statement is true.
The flagellum, however, is much longer and moves in quasi-sinusoidal waves instead of whiplike movements.
Effective means for moving fluids from one part of the surface to another
C) Ciliary movement
Because most ciliated cells have large numbers of cilia on their surfaces and because all the cilia are oriented in the same direction, ciliary movement is an effective means for moving fluids from one part of the surface to another.
What is/are the condition/s necessary for continued beating of the axoneme after removal of the other structures of the cilium?
C) Availability of ATP
It should be appropriate ionic conditions, especially of magnesium and calcium.
All of the following are basic chemical compounds involved in the formation of DNA, except:
B) None of these
Purines:
D) Neither
There are four nitrogen bases in each DNA. Two of them are purines (adenine and guanine), while the other two are pyrimidines (cytosine and thymine).
All of the following chemical compounds form the backbone of the DNA molecule, except:
B) Nitrogenous bases
The phosphoric acid and deoxyribose form the two helical strands that are the backbone of the DNA molecule. The nitrogenous bases lie between the two strands and connect them.
Each DNA strand is composed of alternating phosphoric acid and deoxyribose molecules. Purine and pyrimidine bases are attached to the sides of the phosphoric acid molecules.
C) Only the first statement is true.
Purine and pyrimidine bases are attached to the sides of the deoxyribose molecules.
By means of loose hydrogen bonds between the purine and pyrimidine bases, the two respective DNA strands are held together. Because of the looseness of the hydrogen bonds, the two strands can pull apart with ease.
C) Both statements are true.
Each purine base adenine of one DNA strand always bonds with a pyrimidine base of thymine of the other strand. Similarly, each purine base of guanine always bonds cytosine.
C) Both statements are true.
How many pairs of nucleotides are present in each full turn of the helix in the DNA molecule?
C) 10
Which of the following is not true about RNA synthesis?
B) The code triplets in the DNA causes the formation of supplementary code triplets in the RNA.
The code triplets in the DNA causes the formation of complementary code triplets in the RNA, known as codons.
The basic building blocks of RNA are almost the same as those of DNA, except for:
A) Both of these
The sugar ribose contains an extra hydroxyl ion appended to the ribose ring structure.
The ribose nucleotide bases always combine with the deoxyribose bases in the following combinations, except:
A) DNA base: adenine + RNA base: thymine
It should be DNA base: adenine + RNA base: uracil. Note that the RNA bases are the same bases as in DNA, except that uracil in RNA replaces thymine in DNA.
A large immature single strand of RNA that is processed in the nucleus to form a mature messenger RNA is called:
B) Precursor messenger RNA
The pre-mRNA includes two different types of segments called introns, which are removed by a process called splicing, and exons, which are retained in the final mRNA.
Which type of RNA directs the splicing of pre-mRNA to form mRNA?
C) snRNA
SnRNA stands for small nuclear RNA.
Which type of RNA carries the genetic code to the cytoplasm for controlling the type of protein formed.
A) mRNA
MRNA stands for messenger RNA.
The transfer RNA (tRNA) transports activated amino acids to the ribosomes to be used in assembling the protein molecule.
The ribosomal RNA (rRNA), along with about 75 different proteins, forms ribosomes.
The small nuclear RNA (snRNA) directs the splicing of pre-mRNA to form mRNA.
Which type of RNA can regulate gene transcription and translation?
A) miRNA
MicroRNA (miRNA) are single-stranded RNA molecules of 21 to 23 nucleotides that can regulate gene transcription and translation.
The specific code in the tRNA that allows it to recognize a specific codon is again a triplet of nucleotide bases and is called an anticodon. This anticodon is located approximately at the end of the tRNA molecule.
B) Only the first statement is true.
This anticodon is located approximately in the middle of the tRNA molecule.
The ribosomal RNA constitutes about ___ of the ribosome.
C) 60%
The remainder of the ribosome is protein, including about 75 types of proteins that are both structural proteins and enzymes needed in the manufacture of protein molecules.
The ribosome always functions in association with which types of RNA?
A) tRNA and mRNA
The tRNA transports amino acids to the ribosome for incorporation into the developing protein molecule, whereas the mRNA provides the information necessary for sequencing amino acids in proper order for each specific type of protein to be manufactured.
The ____________ acts as a manufacturing plant in which protein molecules are formed.
B) Ribosome
Ribosomal RNA is specially processed in the nucleus, where it binds with "ribosomal proteins" to form granular condensation products that are primordial subunits of ribosomes. These subunits are then released and transported through the large pores of the nuclear envelope to almost all parts of the cytoplasm.
C) Only the second statement is true.
Ribosomal RNA is specially processed in the nucleolus, where it binds with "ribosomal proteins" to form granular condensation products that are primordial subunits of ribosomes.
Proteins are formed in which part of the cell?
D) Cytoplasm
After the primordial subunits of ribosomes enter the cytoplasm, they are assembled to form mature, functional . Therefore, proteins are formed in the cytoplasm of the cell, not in the nucleus because the nucleus does not contain mature ribosomes.
Noncoding RNA
A) MicroRNA
The microRNA (miRNA) are encoded from the transcribed DNA of genes, but they are not translated into proteins and are therefore often called noncoding RNA.
True or False: In glandular cells, most proteins synthesized by the ribosomes are released directly into the cytosol instead of into the endoplasmic reticulum.
True
In glandular cells, large amounts of protein-containing secretory vesicles are formed.
DNA is replicated in much the same way that RNA is transcribed from DNA, except for following differences. Which of the following statements below does not depict such differences?
C) DNA helixes can be uncoiled from each other by enzymes that continuously cut each helix along its entire length, rotate each segment enough to cause separation, and then resplice the helix.
DNA helixes can be uncoiled from each other by enzymes that periodically cut each helix along its entire length, rotate each segment enough to cause separation, and then resplice the helix.
The human cells contains how many chromosomes?
B) 46
The human cell contains 46 chromosomes arranged in 23 pairs.
Once each chromosome has been replicated to form the two chromatids, in many cells, mitosis follows automatically within:
B) 1 or 2 hours
What is the first stage of mitosis?
A) Prophase
During prophase, the chromosomes of the nucleus(which in the interphase consist of loosely coiled strands) become condensed into well-defined chromosomes.
Stage of mitosis wherein multiple microtubules from the aster attach to the chromatids at the centromeres
A) Prometaphase
Stage of mitosis wherein the chromatids are pulled tightly by their attached microtubules to the very center of the cell, lining up to form the equatorial plate of the mitotic spindle
D) Metaphase
During this stage of mitosis, the two chromatids of each chromosome are pulled apart at the centromere.
C) Anaphase
During this stage of mitosis, the two sets of daughter chromosomes are pushed completely apart.
D) Telophase
During the telophase, the mitotic apparatus dissolutes, and a new nuclear membrane develops around each set of chromosomes. This membrane is formed from portions of the Golgi apparatus that are already present in the cytoplasm.
D) Only the first statement is true.
This membrane is formed from portions of the endoplasmic reticulum that are already present in the cytoplasm.
These serve as protective caps that prevent the chromosome from deterioration during cell division.
A) Telomeres
With each cell division, the copied DNA loses additional nucleotides from the telomere region. The nucleotide sequences provided by the telomeres therefore prevent the degradation of genes near the ends of chromosomes. Without telomeres, the genomes would progressively lose information and be truncated after each cell division.
True or False: Ribosomes are comprised of RNA that has been synthesized directly by the nucleus.
True
Vesicles differ from vacuoles in that vesicles are usually produced for the purpose of causing something to leave the cell.
False
Vesicles are usually produced for the purpose of causing something to enter the cell.
The Golgi apparatus plays a direct role in producing the complete cell membrane.
False
The selective permeability of a cell membrane functions under active transport mechanisms.
True
The __________ of a cell is the most critical factor in determining its function.
B) Shape
The _________ of the cell directs its overall activities as well as houses its genetic material.
A) Nucleus
Which feature is not a characteristic of the cell membrane?
C) It is made up of phospholipid monolayer.
The cell membrane is made up of phospholipid bilayer.
Molecules that are soluble in ___________ can pass through the fatty acid portion of the cell membrane unassisted.
B) Lipid
Proteins that guide cells on the move in the bloodstream to their destination at a wound site are called:
C) Cell adhesion molecules
Choose the correct statement about cell membranes.
A) Ion channels function as gates, opening or closing to specific ions, under certain conditions.
___________ provide/s both structural support and the enzymes needed to make proteins from amino acid building blocks.
D) Ribosomes
The tubular transport system that moves molecules throughout the cell is/are the:
A) Endoplasmic reticulum
This organelle consists of microtubules and functions both in distributing chromosomes during cell division and in forming portions of cilia and flagella.
A) Centrosome
In what part of the nucleus does ribosome production occur?
B) It occurs in the area of nucleolus.
By which process does a glucose molecule move through a cell membrane via a protein carrier from a region of greater concentration to one of lower concentration?
A) Facilitated diffusion
Cells use up to 40% of their daily energy expenditure engaged in what important process?
D) Active transport
During what phase of the cell cycle does DNA replication occur?
A) S phase
S phase, also known as the synthesis phase, is the phase of the cell cycle in which DNA is replicated, occurring between G1 phase and G2 phase.
Chromosomes align midway between centrioles during what phase of mitosis?
B) Metaphase
Which types of genetic control normally holds mitosis in check?
D) Tumor suppressor genes
The ___________ of the cell has a function directly related to the synthesis of proteins.
C) Ribosome
The _____________ is a system of membranes designed to transport molecules within and out of cells.
D) Endoplasmic reticulum
This organelle produces the microtubules important in cell division.
A) Centrosome
DNA can be found within chromosomes during division but prior to division DNA exists as long thin __________ strands.
A) Chromatin
Which chemicals on the surface of cells function to attach to and recognize hormones?
C) Proteins
The term ______________ can be used to imply all of the chemical reactions within a cell.
D) Metabolism
In the liver, the ____________ may play a role in producing the enzymes that help detoxify drugs.
D) Smooth endoplasmic reticulum
The cristae are structures found within the:
C) Mitochondrion
The ____________ serves as the source of the flagellum in sperm.
D) Centriole
The movement of particles from an area of higher to lower concentration is called:
A) Diffusion
True or False: Cancer cells are more sensitive to drugs and radiation than normal cells.
True
Cancer cells will have a higher chance of being damaged by radiation or chemicals because of their rapid rate of division. Cells are most susceptible to DNA errors during active division and this is the theoretical basis for radiation and chemotherapy.
True or False: There are many possible causes of cancer including viruses, radiation or exposure to chemicals.
True
Cancer is a process that can be initiated by many stimuli (or inducers) including the carcinogens in the environment, altered oncogenes, viruses, or some disturbance in the bodies immune or defense system.
True or False: Oncogenes are gene segments that normally act to inhibit the formation of abnormal cancer cells.
False
Oncogenes are tumor genes that encode information that will initiate abnormal development of cells and possible cancer. This is why some cancers are said to be genetic in origin or tend to run in families.
True or False: The cell membrane is the fixed, outer layer of a cell that functions like a filter to prevent certain molecules from escaping the cell.
False
The cell membrane is a complex, constantly changing region comprised of layers of molecules that actively control permeability.
True or False: The human cell membrane and nucleus are discernible under a light microscope.
False
An electron microscope is needed to magnify the image more than 50,000 times in order to discern the details of the membrane. The membrane appears as a blurred area under a light microscope at 1,000 magnification.
True or False: The phospholipid molecules of a membrane are arranged to have their phosphate ends facing the exterior surface.
True
The phosphate groups give the layer its water solubility, while the internal fatty acid ends are hydrophobic or water insoluble.
True or False: Cholesterol is a lipid that tends to make cell membranes more rigid with it than without it.
True
The cholesterol in the membrane provides a degree of stable rigidity to the structure of the otherwise oily lipids.
True or False: One mechanism in the skin that prevents cells from becoming loose and separating is the presence of junctions called desmosomes.
True
Desmosomes are intercellular junctions that often hold skin cells together.
True or False: A TEM is a device that is used to magnify a cell only about 1,000 times.
False
A transmission electron microscope can magnify a cell 1,000,000 times.
True or False: Smooth endoplasmic reticulum has a significant function in protein synthesis.
False
The term smooth is used to indicate the absence of ribosomes, which are the sites for protein synthesis.
True or False: Selectively permeable membranes allow proteins to pass through them.
False
Selectively permeable membranes control the movements of molecules to pass through that are relatively small. Large molecules such as proteins do not readily pass through a membrane but are transported by way of vesicle formation.
True or False: Lysosomes degrade bacteria and worn cells, and can cause disease by destroying normal tissues.
True
The lysosomes have enzymes that could degrade anything including normal structures and have been implicated in the etiology of muscle degenerations and other conditions such as aging.
True or False: Hydrogen peroxide is a chemical toxic to most cells and is produced by some human cells.
True
The peroxisomes contain enzymes that help synthesize hydrogen peroxide that can be used to kill bacteria.
This organelle plays a role in the detoxification of alcohol.
B) Peroxisome
Peroxisomes contain enzymes that oxidize alcohol and attempt to convert it into forms that can be eliminated from the body.
True or False: The centrioles are microtubules that play a significant role in ATP and energy production.
False
The centrioles are important for producing the fibers that move the chromosomes during cell division.
True or False: The nucleus is an organelle enclosed in a double layer of membrane.
True
The nucleus is bound by two layers of membrane called the nuclear envelope.
True or False: The nucleolus functions mainly in the synthesis of DNA.
False
The nucleolus functions in the synthesis of RNA, which becomes part of the ribosomes.
True or False: Chromatin is the term for the loosely coiled appearance of DNA in a non-dividing cell.
True
Thin strands of DNA are called chromatin. When they become thickened, they become visible as chromosomes.
True or False: In the process of apoptosis, cells shrink and die but the basic structure of the organelles remains constant.
False
During aging or apoptosis, the structure and function of the organelles and chromosomes undergo many degenerative changes.
True or False: DNA has chemicals that direct metabolic processes as well as reproduction.
True
The DNA in the chromosomes contain the genes that govern division as well as direct cell chemical activities when in the chromatin form.
True or False: At the point of equilibrium, during diffusion, there is no further movement of any molecules.
False
At equilibrium there is movement of molecules in all directions, but the concentrations of the particles is the same at all points.
True or False: In general, the rate of diffusion of a molecule is faster in areas of higher temperature.
True
Since diffusion is based on the random movements of particles, molecules move faster at higher temperatures because of the increase in kinetic, heat energy.
True or False: The sugar added to a water solution is termed the solvent.
False
Particles that are dissolved in a media are referred to as the solute, while the liquid media is referred to as the solvent. In this case, the sugar is the solute and the water is the solvent.
True or False: During renal dialysis, a type of diffusion, it possible to remove all of a metabolic waste such as urea, from the blood.
False
Dialysis, as a type of diffusion, will not remove all of a substance but will proceed until a 50% equilibrium rate is achieved.
True or False: Osmosis is the movement of water and can occur through any type of permeable membrane.
True
The type of membrane is not the main factor involved with osmosis. The main factor is the concentrations of the molecules on two sides of the membrane.
True or False: During osmosis, water moves from an area of lower concentration to the side with the higher concentration.
True
Concentration usually refers to the solute particles. In osmosis the water has a higher concentration on the side with the lower concentration of particles.
True or False: Osmosis is considered a special case of diffusion and is passive in nature.
True
Osmosis is a passive diffusion through a membrane which expends no energy in the process.
True or False: It is possible for an intravenous solution that is labeled isotonic, to be hypotonic to a patient.
True
The terms for tonicity are all relative to each other. If a patient's blood has a higher concentration than normal, an isotonic solution could be relatively hypotonic to it.
True or False: In active transport, energy is consumed by the cell membrane in the form of ATP.
True
Active transport uses energy (ATP) to move a molecule in a direction that is otherwise not physically possible. Usually, the movement is from lower to higher concentration, such as the sodium pump.
True or False: Endocytosis is a passive transport process.
False
Any process, such as endocytosis, that causes massive changes in the cell membrane must expend energy and be active by definition.
True or False: Bone cells contain genes for nerve cells that have been repressed.
True
Every cell, including those of bone, has the potential genes in all cell types. During differentiation, certain genes are repressed while others are activated.
What is the basic structural unit of the body?
D) Cell
The cell is the basic unit of life or fundamental functional unit of the body. The properties of an organism are related to the properties of the cells that comprise it.
Which of the following are the smallest cells?
A) Red blood cells
The red blood cell (erythrocyte) is 7.5 micrometers in diameter; the white blood cell (leukocyte) is 10 micrometers; and the ovum is 140 micrometers.
Two major parts of a cell are the nucleus and:
B) Membrane
All eukaryotic eukaryotic consist of a nuclear area and the fluid and structures that surround it, the cytoplasm, enclosed by a plasma membrane.
A ribosome is an example of a/an
B) Organelle
An organelle is a structure within a cell with a known function. The ribosomes are associated with protein synthesis.
A cell membrane allows only needed substances to pass and is therefore called:
C) Selective
A selectively permeable membrane actively controls the movement of molecules in or out of the cell in response to metabolic needs.
A human cell membrane is comprised of the following except which one?
A) Nucleic acids
Nucleic acids are found within the nucleus and cytoplasm and are not an essential part of the membrane structure.
The following terms belong together except which one?
D) Protein
The cell membrane has phospholipid molecules that have water soluble (hydrophilic) as well as water insoluble (hydrophobic) portions.
The following molecules freely pass through a cell membrane except which one?
A) Amino acids
The water insoluble lipid components of a membrane restrict the free movements of water-soluble substances such as amino acids or sugars.
Hormones come in contact with the _____________ molecules in a membrane.
D) Rod-like protein
Globular and integral proteins usually do not combine with hormones but act as structural entities.
The selective movement of ions through a membrane occurs through areas called:
A) Channels
A channel is an abstract conception of an opening in a membrane that may selectively allows certain substances to pass. A pore is a relatively fixed opening.
The ________________ proteins in a membrane function as enzymes.
C) Peripheral
The peripheral proteins line the inner surface of the cell membrane and act as enzymes that increase certain reaction rates.
The cells in heart muscle are often held together by areas called:
D) Gap junctions
Gap junctions are areas of tubular channels that interconnect cardiac muscle as well as muscle in the digestive tract.
The inside lining of the digestive tract is lined with cells that are held together by:
A) Tight junctions
Tight junctions are a type of intercellular junction that hold together certain cells. There is no connective tissue in the inner lining of the digestive tube.
The ________________ contains enzymes that are associated with protein synthesis.
B) Ribosome
The ribosome is named for the fact that they contain ribonucleic acid molecules and enzymes that play roles in manufacturing proteins.
The ______________ functions to package molecules into vesicles that can be transported out of a cell.
A) Golgi apparatus
The Golgi apparatus contains membranes that are able to condense molecules into packages that can transported. The centriole functions in cell division.
A combination of a sugar with a protein is a:
D) Glycoprotein
Glycoproteins are combinations of protein and some sugars that are packaged by the Golgi apparatus and function in several ways including certain activities of hormones and lymphocytes.
The ______________ function/s as a sac-like or tubular network of structures that provides transport.
B) Endoplasmic reticulum
The reticulum is a network of sacs and tubules that allows molecules to be transported through various locations in a cell.
The _______________ is the source of most of the cellular energy.
B) Mitochondrion
The mitochondria are the enzyme-rich organelles that perform the metabolic syntheses that produce most of the ATP energy.
The cristae are the shelf-like portions of the:
C) Mitochondria
The inner surface of the mitochondria is lined with folds called cristae which contain enzymes used in energy production by synthesis of nucleotides such as adenosine triphosphate.
The _____________ contain enzymes that are used to degrade foreign particles as well as cell structures.
A) Lysosomes
Lysosomes have degradative enzymes that can break down bacteria as well as large molecules. Peroxisomes also can break down molecules but not cell structures.
Catalase is an enzyme, which degrades:
D) Hydrogen peroxide
Catalase converts hydrogen peroxide into oxygen and water, rendering it harmless.
This organelle plays a complex function in cell reproduction.
A) Centrosome
Each centrosome organelle is comprised of two centrioles. Chromosomes are chemical aggregates that contain DNA but are not considered organelles.
The structures that cause fluids and mucus to move across their surface are the:
D) Cilia
The cilia are processes of a cell which move in a wavelike pattern; each is attached to a basal body. Ciliated cells can be found lining the respiratory as well as other membranes.
Flagella can occur on the cells of the following, except:
B) Intestines
Flagella cause motility of sperm but are also found on other cells. The intestines are lined with cells that contain processes called microvilli that have a different structure than cilia or flagella.
Membranous sacs that contain fluids or particles for transport are called:
C) Vesicles
Microtubules are not membranous sacs.
The protein actin is found in _____________, which results in some type of movement or contraction.
D) Microfilaments
Cilia cause movements but do not contain actin.
The following belong together except which one?
C) Microfilaments
Microtubules provide a means of maintaining the shape of cells as well as play a role in cell division. Microfilaments are more important for allowing movement to occur.
What is the term for chemical particles in a cell which appear lifeless and have no obvious function?
C) Inclusion
The term inclusion is used for something that has no known purpose; many areas that were once called inclusions, such as viral particles, are now known to have functions.
The following are inclusions except which one?
C) Vesicles
Vesicles are membranous sacs that can be considered organelles because they have known functions.
The movement of particles from higher to lower concentration is termed:
B) Diffusion
Diffusion causes molecules to move from were they are more concentrated to areas where they are less concentrated until a net equilibrium is reached.
The following will increase the rate of diffusion except which factor?
D) Increased molecular weight
Higher molecular weight particles will move slowerthrough a media because of the nature of the attractive forces involved.
Movement of particles from higher to lower concentrations through a membrane, such as in dialysis, occurs by:
B) Diffusion
Dialysis is almost identical to diffusion except that the particles must be passed through a membrane until equilibrium is attained.
Insulin usually increases the movement of glucose through a cell membrane by a process called:
B) Facilitated diffusion
Glucose moves into a cell by facilitated diffusion which is similar to active transport except no ATP energy is expended.
Membranes that have a higher osmotic pressure on one side, tend to:
C) Draw water towards that side
Osmotic pressure is a force that attracts water towards the higher pressure (concentration).
Hypertonic solutions tend to causes cells to:
A) Shrink
Cells will lose water and shrink in a hypertonic media because of the high osmotic pressure.
Normal isotonic sodium chloride solution is _____%.
D) 0.9
A 0.9% mixture of NaCl will be the same isotonic value as human blood. A 5% solution of glucose is also isotonic.
The movement of a salt through a membrane, such as in a kidney, because of pressure differences is called:
C) Filtration
Diffusion refers to random molecular movement.
Hydrostatic refers to pressure of:
D) Solvent
In biological systems, water is the solvent. Water pressure is hydrostatic pressure.
Movement of molecules from low to high concentrations is known as:
B) Active transport
In active transport the membrane utilizes energy to transport molecules across a membrane against their concentration gradients.
The ability of leukocytes to engulf bacteria is due to the process of:
D) Phagocytosis
In phagocytosis, large particles are brought into a cell by a method that traps particles in a membrane pseudopod or extension. Pinocytosis is reserved for small particles such as water.
In receptor-mediated endocytosis, an LDL particle of cholesterol is attracted to cells that contain:
B) Apoprotein B-receptors
Apoprotein-B is a protein which surrounds a particle of LDL or low density lipoprotein.
During mitosis, the number of chromosomes:
A) Is doubled
Mitosis doubles the number of cells and therefore must double the DNA content.
The process, which divides the cytoplasm in half, is specifically termed:
D) Cytokinesis
There are two phases of division, karyokinesis in which the nuclear content divides into two daughter nuclei and cytokinesis in which the rest of the cytoplasm divides in half.
The process that results in daughter cells with half of the original chromosome number is:
B) Meiosis
Meiosis is a process used by reproductive cells to reduce the chromosome number to one-half.
At which stages does the chromosome number double?
C) Interphase
Even before any visible movement of chromosomes becomes evident, their number has doubled during interphase, particularly during the S phase.
Chromosomes are aligned along the equatorial line during the _____________ stage of division.
D) Metaphase
Chromosomes are paired along a line midway in the cell during metaphase, before they are brought to the poles by the spindle fibers.
The _____________ stage occurs when two daughter cells have completely formed.
A) Telophase
During the last stage, telophase, the daughter cells are formed and new membranes are created that wrap around the cell and the nucleus.
Two chromatids are attached at the _____________ region.
A) Centromere
The centromere is the region near the middle of a chromosome that represents the attachment of two arms of a chromosome which are termed chromatids.
The centromeres divide during the ___________ stage of mitosis.
C) Anaphase
During anaphase, which precedes telophase, the centromeres and chromosomes pull apart and begin migration towards the opposite poles.
This process explains how embryonic cells become specialized and diverse.
D) Differentiation
Differentiation is the process in which a single cell can produce daughter cells that are different from each other. In this way, the few embryonic cells can become the many diverse bone, blood, muscle, and other cell types.
The main division process in the early embryo is:
A) Mitosis
The original sex gametes were produced by meiosis, but once the zygote is formed, the remainder of the divisions are mitotic.
Cancer cells can disseminate to other areas by a process called:
D) Metastasis
Metastasis occurs when cancer cells migrate to other parts of the body than originally found. This could occur by way of the blood or lymphatic vessels.
During hyperplasia, cells are dividing at a rapid rate and may progress towards a __________ state.
B) Cancer
Hyperplasia differs from mitosis in that the rate of division is faster than normal and the control mechanisms that usually limit growth are no longer operative. This may lead to cancer.
Which channel-blocker medication can be used to treat hypertension or angina pectoris?
B) Calcium
Calcium channel blockers are used to treat conditions such as hypertension because they weaken myocardial force, slow the heart rate, and increase coronary flow.
What type of cell is a bacterium?
A) Prokaryotic
Bacteria do not have a distinct nucleus and therefore cannot be eukaryotic.
True or False: The addition of oxygen to a cell during glycolysis will increase the amount of ATP produced by this metabolic pathway.
False
Which of the following pairs are the major cation and anion of the intracellular compartment?
C) Potassium and phosphate
The main anion and cation of the intracellular compartment of the body is potassium and phosphate, whereas the main anion and cation of the extracellular compartment of the body is sodium and chloride.
These are important to consider when corrected fluid balances/interpreting electrolyte results in pathophysiology.
Which kind of ion channels are located at the nodes of Ranvier in a myelinated neuron?
D) Voltage-gated sodium channels
Voltage-gated sodium channels are located at the nodes of Ranvier in a myelinated neuron. This morphology facilitates faster action potential propagation in myelinated neurons by a process called saltatory conduction. The myelin between the nodes of Ranvier reduces the inevitable loss of positive electrical charge in the form of the exit of sodium ionsfrom a neuron's interior as an action potential propagates between nodes, preserving the voltage signal that opens the voltage-gated sodium channels at the nodes of Ranvier. This self-regeneration of the action potential at the nodes of Ranvier facilitates faster propagation of the action potential in a myelinated neuron than consecutive activation of adjacent voltage-gated sodium channels in an unmyelinated neuron.
Which of the following neurotransmitters is in the amino acid class?
B) Glutamate
Neurotransmitters can be classed by their structure. Glutamate is an amino acid neurotransmitter, along with GABA, glycine and aspartate.
Dopamine, noradrenaline, serotonin and histamine are all monoamines.
Peptides include neurotransmitters such as opioids, oxytocin, somatostatin and vasopressin.
What is the main intracellular ion?
B) Potassium
This helps to explain why skeletal muscle cell breakdown, known as rhabdomyolysis, can cause cardiac arrhythmias. The potassium released from these cells leads to high serum potassium levels, known as hyperkalaemia, which disturb the cardiac conduction by disrupting the flow of ions determining cardiac rhythm. This also explains why blood samples left for a long time without being processed can give a false result of hyperkalaemia when potassium is measured, known as artefactual hyperkalaemia, because as red blood cells break down during this time without processing, they release intracellular potassium, raising potassium levels to levels higher than those in the sample before this breakdown of red blood cells.
The resetting of which of the following ion channels gives rise to the refractory period of neurons?
C) Voltage-gated sodium channels
The resetting of voltage-gated sodium channels from their active state, in which they permit sodium entry into neurons, to their inactive and then resting states, gives rise to the refractory period of neurons because until these channels have been reset and can be activated again, there can be no sodium entry into neurons and so no depolarisation and action potential propagation.
Which of the following ions triggers the release of neurotransmitter from synaptic vesicles into the synaptic cleft?
C) Calcium
When an action potential arrives at the axon terminal, it activates voltage-gated calcium channels in the cell membrane. Calcium ions or Ca 2+, which is present at a much higher concentration outside the neuron than inside, rush into the cell. The Ca2+ ions allow synaptic vesicles to fuse with the axon terminal membrane, releasing neurotransmitter into the synaptic cleft. The molecules of neurotransmitter diffuse across the synaptic cleft and bind to receptor proteins on the postsynaptic cell.
The other options are incorrect as the other ions are involved in the post-synaptic membrane's process of depolarization or hyperpolarization. Activation of postsynaptic receptors subsequently leads to the opening or closing of ion channels in the cell membrane. This may be depolarizing—making the inside of the cell more positive—or hyperpolarizing—making the inside of the cell more negative—depending on the neurotransmitter and ions involved. For example, a neuronal synapse that uses the excitatory neurotransmitter glutamate will cause the influx of Na+ and K+ across the post-synaptic membrane causing depolarization, whereas, the inhibitory neurotransmitter GABA will cause the influx of Cl- across the post-synaptic membrane causing hyperpolarization.
Which of the following enzymes increases intracellular calcium levels?
B) Phospholipase C
Phospholipase C increases intracellular calcium levels. This explains why alpha-1 adrenoreceptor antagonists such as doxazosin are used to lower blood pressure by relaxing vascular smooth muscle cells because alpha-1 adrenoreceptor activation leads to phospholipase C activation and the greater the level of intracellular calcium, the greater the contraction of smooth muscle cells.
Nitric oxide synthase catalyses the production of nitric oxide from arginine. Nitric oxide activates guanylyl cyclase and ultimately leads to vascular smooth muscle relaxation.
Guanylyl cyclase catalyses the conversion of guanosine triphosphate to cyclic guanosine monophosphate (cGMP), which ultimately relaxes vascular smooth muscle cells.
Protein kinase G is the effector of the reduction in intracellular calcium levels and consequent smooth muscle relaxation in response to cGMP.
Adenylyl cyclase catalyses the conversion of adenosine triphosphate into cyclic adenosine monophosphate. It has no effect on intracellular calcium levels.
In which part of a neuron is an action potential initiated?
D) Axon hillock
Action potentials are initiated in the axon hillock of a neuron. This is because there is a higher expression of voltage-gated sodium channels in the axon hillock, which allows an increase in electrical charge to the level of, or above, the threshold required to initiate an action potential by allowing the entry of sodium ions into the neuron in response to increased electrical charge in the form of sodium ions that entered the neuron proximal to the axon hillock. These areas include dendrites and the cell body, which contain ligand-gated sodium channels that open in response to neurotransmitter release from a presynaptic neuron. An action potential travels through the axon and terminates at the axon terminal.
Some mutations in the gene CFTR give rise to cystic fibrosis because the protein is misfolded and therefore cannot be transported to the cell membrane. In which organelle would the CFTR protein accumulate?
D) Endoplasmic reticulum
The misfolded CFTR protein accumulates in the endoplasmic reticulum. This is because one of the roles of the endoplasmic reticulum is the folding of proteins. This is achieved through the use of chaperones.
The exact mutation, in this case, is ΔF508, resulting in a loss of phenylalanine at the 508th amino acid. It is the most common CFTR mutation.
The Golgi apparatusalso modifies newly made proteins however in general folding is not one of its functions. The Golgi adds sugars to proteins and packages them into vesicles to be trafficked to the cell membrane (in the case of CFTR) or other locations in the cell.
In which phase of the cell cycle is DNA replicated?
D) S phase
S phase: synthesis phase, part of the interphase; synthesize a complete copy of the DNA; duplicates centrosomes for separation of DNA in M phase
G1 phase: gap phase 1; cell grows physically larger; copies its organelles and produces the necessary molecular building blocks
G2 phase: cell grows more; more organelles replicated; reorganization of contents of G2 ends when mitosis begins (M phase)
M phase: mitosis phase; copies of chromosomes are separated; cell divides; chromosomes are highly condensed; DNA is wrapped around histones
At what point of time does the oocyte complete meiosis?
A) After fertilization
At ovulation, the oocyte is arrested at metaphase II, and only completes meiosis II immediately after fertilization.
Female germ cells undergo multiple mitotic divisions in the embryo, and at birth, the female usually has around 1-2 million primary oocytes, all arrested at prophase I (of Meiosis I). A consequence of this is that, unlike in males, females have a fixed maximum number of oocytes at birth (as oocytes do not undergo mitotic divisions after birth).
From puberty (menarche) to menopause, a group of oocytes complete Meiosis I and are arrested at metaphase II. Each cycle, at ovulation a single oocyte enters the fallopian tube to await fertilisation. The completion of Meiosis II does not occur until fertilisation.
What is the location of transcription in a eukaryotic cell?
C) Nucleus
Nucleus: transcription takes place DNA to RNA (central dogma); pre-mRNA to mRNA via splicing in the nucleus, mRNA leaves the nucleus for translation (RNA to protein)
Cytoplasm: cytosol and organelles; most cellular activity takes place in the cell cytoplasm (e.g. glycolysis)
Mitochondrion: commonly known as the 'powerhouse' of the cell; involved ATP production for metabolic processes; contains its own mitochondrial genetic material
Endoplasmic reticulum: primary site of protein synthesis, specifically the rough endoplasmic reticulum (RER) with ribosomes; membrane-enclosed sacs (cisternae); continuous with the outer membrane of the nucleus
Which of the following enzymes reduces intracellular levels of the second messenger cyclic adenosine monophosphate (cAMP)?
B) Phosphodiesterase
Phosphodiesterase reduces intracellular cAMP levels by degrading cAMP to 5'-AMP. This explains why drugs that inhibit phosphodiesterase such as theophylline are used as bronchodilators because the greater the level of intracellular cAMP, the more relaxed smooth muscle cells are.
Protein kinase A is activated by cAMP and is not involved in its synthesis or inactivation. It is the effector of the muscle cell relaxing-effect of cAMP.
Protein kinase C is also not involved in cAMP formation or degradation and opposes the relaxing effect of cAMP on smooth muscle cell contraction because it raises intracellular levels of calcium, which stimulates smooth muscle cell contraction.
Protein kinase G is activated by cyclic guanosine monophosphate (cGMP) and, again, is not involved in cAMP synthesis or inactivation. However, protein kinase G also relaxes smooth muscle contraction, but by a different mechanism to protein kinase A; it reduces intracellular calcium levels.
Phospholipase C catalyses the conversion of the plasma membrane phospholipid phosphatidylinositol 4,5-diphosphate (PIP2) into diacylglycerol (DAG) and inositol triphosphate (IP3). This leads to the activation of protein kinase C and, ultimately, raised intracellular calcium levels and muscle cell contraction.
Author
carminaorlino
ID
355602
Card Set
Basic Concepts of General Physiology (Cell, Muscle, and Nerve)
