What property prevents the ligands of cell-surface receptors from entering the cell?
C. The molecules are hydrophilic and cannot penetrate the hydrophobic interior of the plasma membrane.
The secretion of hormones by the pituitary gland is an example of:
B. endocrine signaling.
Why are ion channels necessary to transport ions into or out of a cell?
A. Ions are charged particles and cannot diffuse through the hydrophobic interior of the membrane.
Where do DAG and IP3 originate?
C. They are the cleavage products of the inositol phospholipid, PIP2.
What property enables the residues of the amino acids serine, threonine, and tyrosine to be phosphorylated?
D. They contain a hydroxyl group.
What is the function of a phosphatase?
B. A phosphatase removes the phosphate group from phosphorylated amino acid residues in a protein.
Apoptosis can occur in a cell when the cell is;
B. all of the choices are correct.
What is the effect of an inhibitor binding an enzyme?
B. The enzyme is inactivated.
Immature lymphocytes undergo screening to differentiate self and non-self proteins.
True
False
True
Which type of molecule acts as a signaling molecule in yeasts?
B. mating factor
Quorum sensing is triggered to begin when,
A. treatment with antibiotics occurs.
B. bacteria release growth hormones.
C. bacterial protein expression is switched on. D. a sufficient number of bacteria are present.
D. a sufficient number of bacteria are present.
A signaling molecule binds itself to a receptor and turns gene function on or off. Which is an example of the signaling molecule?
B. Acyl-homoserine lactone
When an organism needs to coordinate major changes in various tissues of the body, such as during puberty or metamorphosis, what type of signaling is it likely to use?
B. endocrine signaling
Horizontal cells in the retina of the vertebrate eye help regulate the photoreceptor cells. In lab you carefully injected a single horizontal cell with a small, membrane-impermeable fluorescent dye. You immediately see the star-shaped dendrites of the cell you injected. After some time, however, you see that all the nearby horizontal cells have also lit up like a complex web. You conclude that these cells likely communicate by,
A. gap junction signaling.
Angiogenesis is the process of forming new blood vessels. Chemical signals in the body can either enable the repair of damaged blood vessels or enable the formation of new ones. Other chemicals in the body are called angiogenesis __________ because they hinder the process of blood vessel formation.
D. inhibitors
A neurotransmitter, acetylcholine, opens ion channels in skeletal muscle cells by binding to receptors on the cell membrane’s surface. During this process, the nicotinic acetylcholine (nACh) receptor, which is a(n) ____ receptor, allows the ions to enter the cells.
B. ion-channel linked
Which characteristic(s) is/are common to both G-protein-linked receptors and enzyme-linked receptors? (Select all that apply.)
A. They all mediate gene expression.
B. They all have an external ligand-binding domain.
C. They all have a hydrophobic membrane-spanning region.
D. They all have an intracellular domain inside the cell.
E. They are all cell-surface receptors.
B. They all have an external ligand-binding domain.
C. They all have a hydrophobic membrane-spanning region.
D. They all have an intracellular domain inside the cell.
E. They are all cell-surface receptors.
There are specific lymphocytes (white blood cells) that when stimulated by foreign antigens produce a growth factor, which causes them to quickly divide, producing more of these lymphocytes. This creates a stronger immune response to the antigens. Which type of cell signaling occurs with these lymphocytes?
D. autocrine
Cancer cells produce a growth factor that causes them to quickly and continuously produce more cancer cells at an uncontrolled rate. What would you predict would cause uncontrolled growth of cancer cells?
D. abnormal autocrine signaling
A woman has had a chronic disease with a variety of symptoms, including lingering fatigue, skin and hair problems, constipation, and feeling cold. Her doctor said her symptoms were consistent with an endocrine problem, since they were,
B. long-term and in a variety of body tissues.
To treat a disease, you need to design a drug to BLOCK the activation of a certain cell signaling pathway. Which strategy or strategies might prevent the normal level of pathway activation? (Select all that apply.)
A. A drug that binds the receptor's transmembrane domain, preventing any conformational change even when ligand binds it.
B. A drug that tightly binds the receptor's ligand binding site, but without activating the pathway.
C. A drug that was similar to the receptor's binding site, to act as a decoy for the ligand.
D. A drug that tightly binds the receptor's ligand binding site just like the ligand does.
A. A drug that binds the receptor's transmembrane domain, preventing any conformational change even when ligand binds it.
B. A drug that tightly binds the receptor's ligand binding site, but without activating the pathway.
C. A drug that was similar to the receptor's binding site, to act as a decoy for the ligand.
Certain receptors are implicated in a variety of diverse physiological responses. For instance, the receptor for orexin (also called hypocretin) is important for the control of appetite, wakefulness, and levels of hormones. How can one pathway control a diversity of outputs? (Select all that apply.)
D. A pathway may regulate neuronal activity, and neurons are connected into different brain circuits.
D. One pathway may control several outputs within a cell.
E. One pathway may control different outputs in different cell types.
Certain cellular proteins called RGSs interact with G alpha subunits, and function to speed up the hydrolysis of GTP to GDP. What consequence will an RGS have for the signal transduction by a GPCR?
C. It will rapidly terminate the activation of the pathway.
Consider the exoskeleton of a fly, which is covered by evenly spaced hairs. During development, some of the cells are assigned to make a hair, while nearby ones are assigned to make hairless chitin. What type of signaling is likely to establish this pattern?
A. paracrine signaling
Some cells integrate signaling pathways, and only carry out a response if two different criteria are met. Choose the example of signal integration that acts as an "AND gate" (requiring two criteria to both be true).
A. An immune cell will attack a target if either of two different antigens activates a receptor. B. A certain gene is transcribed only if two transcriptional inhibitors are degraded. One is degraded by signaling through pathway A, the other is degraded by signaling through pathway B.
C. Some receptors, like receptor tyrosine kinases (RTKs), dimerize and cross-phosphorylate each other when they are both bound by ligand.
D. The EGF Receptor (EGFR) can bind to a variety of ligands and activate its signaling pathway.
B. A certain gene is transcribed only if two transcriptional inhibitors are degraded. One is degraded by signaling through pathway A, the other is degraded by signaling through pathway B.
You have just discovered a bizarre splice variant of the receptor tyrosine kinase you have been studying. The normal protein is a typical RTK, with extracellular ligand binding domain, transmembrane domain, and intracellular kinase domain. The splice variant, however, creates a protein with only the extracellular ligand binding domain, which appears to be secreted from the cell. What possible role could this serve?
C. It could act as a decoy receptor, lowering activation of the standard pathway.
Cell responses to cuts must be quick in order to immediately begin the process of blood clotting. Which type of cell signaling would best facilitate this response?
C. paracrine
Many signaling pathways use kinases to propagate signals intracellularly. Imagine an organism in an environment where phosphorus has become very limiting. If they evolved an alternative way of propagating signals, what is the crucial aspect that would be required?
A. The new mechanism would need to create a conformational change in the downstream target that would allow further propagation of the signal.
Communication between cells.
intercellular signaling
Communication with cells.
intracellular signaling
Molecule produced by a signaling cell that binds with specific receptor, delivering a signal in the process.
Ligand
Chemical signal (neurotransmitter) that travels between nerve cells.
synaptic signal
Signaling that is sent and received by the same or similar nearby cells.
autocrine signal
Cell that releases ligands involved in endocrine signaling (hormones).
endocrine cell
Long-distance signal that is delivered by ligands (hormone) traveling through an organisms circulatory system from signaling cell to the target cell.
endocrine signal
Cell-surface receptor that forms a plamsa membrane channel, which opens when a ligand binds that pass through the plasma membrane.
ion channel-linked receptor
Enzyme that removes the phosphate group from a molecule that has been previously phosphorylated.
phosphotase
Catalyst in a biochemical reaction that is usually a complex or conjugated protein.
enzyme
In the digestive tract, the absorption of nutrients requires transport proteins. Consuming food is one way to acquire energy. Which type of transport protein should an organism employ while eating?
A: Active transport should be used. Even though active transport requires ATP, it is a more efficient mechanism because of its ability to move more nutrients against the concentration gradient.
B: Active transport should be used. Facilitated diffusion requires ATP, whereas active transport requires only a concentration gradient.
C: Facilitated diffusion should be used. Active transport requires ATP, whereas facilitated diffusion requires only a concentration gradient.
D: Facilitated diffusion should be used. It is a more efficient mechanism for moving nutrients across the membrane.
A: Active transport should be used. Even though active transport requires ATP, it is a more efficient mechanism because of its ability to move more nutrients against the concentration gradient.
Some integral proteins span the cell membrane seven times. What characteristics would you expect to see in these seven protein regions that span the membrane? (Select all that apply.)
A :The regions would be mostly hydrophilic.
B :The regions would be mostly hydrophobic.
C :The regions would be somewhat uniform in length.
D :The regions would be highly variable in length.
B :The regions would be mostly hydrophobic.
C :The regions would be somewhat uniform in length.
Digoxin, a cardiac poison found in the foxglove plant, binds to and interferes with the Na+/K+ pump in cardiac muscle. Sodium levels in the cells become too Select your answer _____ and potassium levels become too _____ , preventing the heart from beating.
D. High, Low
A colleague approaches you with an idea for a new drug to prevent HIV infection. She says, "If we could develop a drug to bind to CD4 glycoprotein on T-cells, then HIV would not be able to bind to it, and the cell would be protected." What is a possible problem with this strategy?
A: The HIV virus does not use cellular glycoproteins to infect cells.
B: If a cellular glycoprotein was blocked, that would likely inhibit the normal function of the glycoprotein.
C: Glycoproteins that viruses bind to are on the inside layer of the cell membrane; therefore, getting a drug into the cell would be problematic.
D: Glycoproteins typically do not bind to other substances; therefore, designing a drug that could stick would be too difficult.
B: If a cellular glycoprotein was blocked, that would likely inhibit the normal function of the glycoprotein.
Some cells have membrane proteins called aquaporins that can actively transport water; however, not all cells have aquaporins or other active transporters for water. What other mechanism can cells use to increase the amount of water in the cytoplasm?
A: They can actively transport solute out of the cell, which would then increase the osmolarity outside the cell which, in turn, would draw water into the cell.
B: They can actively transport solute into the cell, which can then increase the osmolarity inside the cell which, in turn, would draw water into the cell.
C: They can actively transport solvent out of the cell, which can then increase the osmolarity inside the cell, in turn, which would draw water into the cell.
D: They can actively transport solvent into the cell, which can then increase the osmolarity inside the cell which, in turn, would draw water into the cell.
B: They can actively transport solute into the cell, which can then increase the osmolarity inside the cell which, in turn, would draw water into the cell.
Your artist friend has asked you for some feedback on “Mosaic”, a sculpture inspired by the cell membrane’s structure. You see a bilayer of metal objects shaped like phospholipids with varying degrees of bending in their "tails." These "tails" face toward each other, and the round metallic "heads" face outward and away from each other. What feedback would be accurate?
A: The sculpture emphasizes the diversity of the fluid mosaic model by showing various levels of saturation in the fatty acid tails; however, the heads and tails are not in the correct orientation.
B: The sculpture emphasizes the diversity of the fluid mosaic model by showing various levels of saturation in the fatty acid tails. The heads and tails are in the correct orientation.
C: The phospholipids are properly arranged; however, the diversity of the fluid mosaic model is not represented due to the absence of proteins and carbohydrates in the sculpture.
D: The sculpture does not emphasize the diversity of the fluid mosaic model, and the heads and tails are not in the correct orientation.
C: The phospholipids are properly arranged; however, the diversity of the fluid mosaic model is not represented due to the absence of proteins and carbohydrates in the sculpture.
You discover a new species of thermophilic bacteria that can survive in near boiling temperatures. Compared to bacteria that typically grow at 37°C, you would expect that this bacteria would have a higher portion of _____ fatty acid tails in their phospholipids.
Saturated
Unsaturated
Saturated
_______is an enzyme that catalyzes the hydrolysis of ATP into ADP.
ATPase
Your friend is having trouble understanding osmosis and says, "I don't understand how water can move from an area of high concentration to an area of lower water concentration. That doesn't make any sense. How can water be concentrated?” Which statement best explains the concept?
A: The hypotonic side has fewer water molecules per unit volume.
B: The side with more solute has more water molecules per unit volume.
C: The side with more solute has fewer water molecules per unit volume.
D: The isotonic side has more water molecules per unit volume.
C: The side with more solute has fewer water molecules per unit volume.
Which statement is true about active transport?
A: Active transport liberates great amount of energy.
B: Active transport is always coupled with a reaction that requires energy.
C: Active transport results in accumulation of a solute above the equilibrium point.
D: Active transport moves molecules down a concentration gradient.
C: Active transport results in accumulation of a solute above the equilibrium point.
Imagine you are a crime scene investigator who is analyzing the body of a drowning victim that was found floating in the ocean. When you look at the body’s lung tissue, you find that most of the cells in the lungs have expanded and lysed, whereas many of the other cells that were in contact with the water are shriveled. What could you infer from this finding?
A: The person drowned in a hypertonic, fresh water environment (e.g., a bathtub) and later was moved into the ocean, to make the death look like a swimming accident.
B: The person drowned in a hypotonic, fresh water environment (e.g., a bathtub) and later was moved into the ocean, to make the death look like a swimming accident.
C: The person drowned in an isotonic, fresh water environment (e.g., a bathtub) and later was moved into the ocean, to make the death look like a swimming accident.
D: The person didn't drown at all, but was killed by another means before being moved into the ocean to make the death look like a swimming accident.
B: The person drowned in a hypotonic, fresh water environment (e.g., a bathtub) and later was moved into the ocean, to make the death look like a swimming accident.
Which of the following also uses secondary active transport?
A: Storage of high energy H+ in mitochondria
B: Storage of glycogen in the liver
C: Storage of acid in the stomach
D: Storage of Ca+ in muscle cells
A: Storage of high energy H+ in mitochondria
Exocytosis and endocytosis depend mainly on which cell organelle?
When you mix phospholipids in water they will spontaneously self-assemble into droplets called micelles, with the hydrophobic tails in the middle and the charged heads on the outside. If you mixed phospholipids in oil, they would form micelles with the tails on the outside and the charged heads in the middle.
True
False
True
What would primarily affect reabsorption and secretion activities in the human kidney?
A: Osmosis
B: Diffusion
C: Endocytosis
D: Active transport
D: Active transport
Which statement is true about exocytosis?
A: Exocytosis is the process by which cells absorb molecules.
B: Exocytosis plays an important role in engulfing foreign materials.
C: Exocytosis requires energy for the things that move against their gradient.
D: Exocytosis is used when small molecules cannot move across the cell membrane.
C: Exocytosis requires energy for the things that move against their gradient.
Hypothetically, if a medical condition were to exist that caused the liver to overproduce albumin in the blood, what would the net effect be on blood osmolarity? (Select all that apply.)
A :The osmolarity of the blood would increase.
C :The blood would become more hypertonic.
A cell placed in a hypotonic solution increases in size and the diffusion process slows down. _____ is the factor that is responsible for this change.
Solubility
Distance Traveled
Permeability
Distance Traveled
Which one of the following pumps would most likely be responsible for the acidification of the stomach?
When an organism needs to coordinate major changes in various tissues of the body, such as during puberty or metamorphosis, what type of signaling is it likely to use?
Horizontal cells in the retina of the vertebrate eye help regulate the photoreceptor cells. In lab you carefully injected a single horizontal cell with a small, membrane-impermeable fluorescent dye. You immediately see the star-shaped dendrites of the cell you injected. After some time, however, you see that all the nearby horizontal cells have also lit up like a complex web. You conclude that these cells likely communicate by
Angiogenesis is the process of forming new blood vessels. Chemical signals in the body can either enable the repair of damaged blood vessels or enable the formation of new ones. Other chemicals in the body are called angiogenesis __________ because they hinder the process of blood vessel formation.
Which characteristic(s) is/are common to both G-protein-linked receptors and enzyme-linked receptors? (Select all that apply.)
A :They all mediate gene expression.
B :They all have an external ligand-binding domain.
C :They all have a hydrophobic membrane-spanning region.
D :They all have an intracellular domain inside the cell.
E :They are all cell-surface receptors.
B :They all have an external ligand-binding domain.
C :They all have a hydrophobic membrane-spanning region.
D :They all have an intracellular domain inside the cell.
E :They are all cell-surface receptors.
There are specific lymphocytes (white blood cells) that when stimulated by foreign antigens produce a growth factor, which causes them to quickly divide, producing more of these lymphocytes. This creates a stronger immune response to the antigens. Which type of cell signaling occurs with these lymphocytes?
Cancer cells produce a growth factor that causes them to quickly and continuously produce more cancer cells at an uncontrolled rate. What would you predict would cause uncontrolled growth of cancer cells?
You got it right.A woman has had a chronic disease with a variety of symptoms, including lingering fatigue, skin and hair problems, constipation, and feeling cold. Her doctor said her symptoms were consistent with an endocrine problem, since they were
A: localized to one part of the body.
B: of rapid onset and with similar effects in different tissues.
C: long-term and in a variety of body tissues.
D: likely to represent the effects of the different tissues signaling to themselves directly.
C: long-term and in a variety of body tissues.
To treat a disease, you need to design a drug to BLOCK the activation of a certain cell signaling pathway. Which strategy or strategies might prevent the normal level of pathway activation? (Select all that apply.)
A :A drug that binds the receptor's transmembrane domain, preventing any conformational change even when ligand binds it.
B :A drug that tightly binds the receptor's ligand binding site, but without activating the pathway.
C :A drug that was similar to the receptor's binding site, to act as a decoy for the ligand.
D :A drug that tightly binds the receptor's ligand binding site just like the ligand does.
A :A drug that binds the receptor's transmembrane domain, preventing any conformational change even when ligand binds it.
B :A drug that tightly binds the receptor's ligand binding site, but without activating the pathway.
C :A drug that was similar to the receptor's binding site, to act as a decoy for the ligand.
Certain receptors are implicated in a variety of diverse physiological responses. For instance, the receptor for orexin (also called hypocretin) is important for the control of appetite, wakefulness, and levels of hormones. How can one pathway control a diversity of outputs? (Select all that apply.)
C :A pathway may regulate neuronal activity, and neurons are connected into different brain circuits.
D :One pathway may control several outputs within a cell.
E :One pathway may control different outputs in different cell types.
Certain cellular proteins called RGSs interact with G alpha subunits, and function to speed up the hydrolysis of GTP to GDP. What consequence will an RGS have for the signal transduction by a GPCR?
A: It will rapidly terminate the activation of the pathway.
B: It will extend the period of activation of the pathway.
C: It will block the pathway so it cannot be activated.
D: It will permanently activate the pathway.
A: It will rapidly terminate the activation of the pathway.
Consider the exoskeleton of a fly, which is covered by evenly spaced hairs. During development, some of the cells are assigned to make a hair, while nearby ones are assigned to make hairless chitin. What type of signaling is likely to establish this pattern?
Some cells integrate signaling pathways, and only carry out a response if two different criteria are met. Choose the example of signal integration that acts as an "AND gate" (requiring two criteria to both be true).
A: An immune cell will attack a target if either of two different antigens activates a receptor.
B: A certain gene is transcribed only if two transcriptional inhibitors are degraded. One is degraded by signaling through pathway A, the other is degraded by signaling through pathway B.
C: Some receptors, like receptor tyrosine kinases (RTKs), dimerize and cross-phosphorylate each other when they are both bound by ligand.
D: The EGF Receptor (EGFR) can bind to a variety of ligands and activate its signaling pathway.
B: A certain gene is transcribed only if two transcriptional inhibitors are degraded. One is degraded by signaling through pathway A, the other is degraded by signaling through pathway B.
You have just discovered a bizarre splice variant of the receptor tyrosine kinase you have been studying. The normal protein is a typical RTK, with extracellular ligand binding domain, transmembrane domain, and intracellular kinase domain. The splice variant, however, creates a protein with only the extracellular ligand binding domain, which appears to be secreted from the cell. What possible role could this serve?
A: It could serve to increase the activation of the standard pathway.
B: It could act as a decoy receptor, lowering activation of the standard pathway.
C: It would block activation of the standard pathway, since the secreted protein will bind to the ligand-binding site.
D: It could not serve a function and is undoubtedly just an occasional splicing mistake.
B: It could act as a decoy receptor, lowering activation of the standard pathway.
Cell responses to cuts must be quick in order to immediately begin the process of blood clotting. Which type of cell signaling would best facilitate this response?
Many signaling pathways use kinases to propagate signals intracellularly. Imagine an organism in an environment where phosphorus has become very limiting. If they evolved an alternative way of propagating signals, what is the crucial aspect that would be required?
A: No change would be selected upon, since kinases do not use phosphate -- only phosphatases do.
B: The new mechanism would require the transfer of another negatively charged group, such as sulfate.
C: The new mechanism would require that changes in gene transcription ultimately occur for all the pathways.
D: The new mechanism would need to create a conformational change in the downstream target that would allow further propagation of the signal.
D: The new mechanism would need to create a conformational change in the downstream target that would allow further propagation of the signal.
