small, simple cells with no defined nucleus or organelles
The ___ ____ is a sensor of signals and enables the cell to respond and adapt to changes in its environment.
proteins embedded in the plasma membrane that do most of its functions
has a polar end attracted to water and another repelled by water
Why does the cell membrane automatically repair itself when torn?
to eliminate contact of the hydrophobic tails with water
3 lipids that make up the cell membrane?
cholesterol, phospholipids, and glycolipids
extend across the membrane bilayer and are in contact with ECF and ICF
Functions of transmembrane proteins?
transport, transduction of EC signals into IC messages
connect neighboring cells and function to confine proteins to an area of the membran
have organelles with membranes and specific functions
Organelles are elaborately organized by a protein network called the _____.
3 types of protein filaments that make up the cytoskeleton?
Which plays a large role in cell movement?
What cells is it abundant in?
actin, microtubules, and intermediate filaments
Functions of microtubules?
Where are they found?
originate at cell center / centrosome & radiate out to cell perimeter
guide orderly transport of organelles and visicles in cytoplasm & equally distrubute chromosomes during cell division
Describe the 2 membranes of the nucleus.
The inner membrane goes all the way around the nucleus and has binding sites for proteins that organize the chromosomes inside. The outer membrane is continuous with the ER and resembles it in structure and function
How is genetic material in the nucleus protected?
the nuclear pores are selective about what is allowed into the nucleus
Role of ER in cell?
synthesis of membrane components (proteins, lipids) & products to be secreted from the cell
coated with ribosomes
What are ribosomes?
complexes of protein & RNA from the nucleus that synthesize proteins
What are they?
signal recognition particles
special proteins that bind to sequence of codons that direct the ribosomee responsible for its synthesis
2 functions of smooth ER?
lipid metabolism & Ca storage
What type of cells have a lot of smooth ER?
liver cells - produce lipoproteins & detoxify harmful lipid soluble substances (alcohol)
muscle cells - stores Ca and releases it when stim for muscle contractions
Golgi apparatus role in protein synthesis?
receives proteins by way of ER transport vesicles -> modified by enzymes that attach or rearrange carb molecues -> put in golgi complex transport vesicles -> pm, lysosome, or other area needed
What cellular structure functions in making it occur? This is called ____.
cell becomes smaller and more energy efficient
what is formed when a WBC ingests particles
How are phagosomes digested?
They fuse with a lysosome
What are the end products of lysosomal digestion?
simple molecules - AA, fatty acids, and carbs that can be used by cell or secreted as cellular waste
inclusion cell disease - lack the enzyme mannose -6-phosphate that attaches a marker to send enzymes to the lysosomes and sends them outside the cell instead - lysosomes have no enzymes and cannot function
What is their function?
What cells are they most found in?
bags of enzymes that perform degradative functions
liver and kidney cells where they detoxify various substances
Difference b/t lysosomes and peroxisomes?
lysosomes contain hydrolase enzymes and peroxisomes contain oxidative enzymes that produce hydrogen peroxide & peroxisomes aquire enzymes from cytoplasm instead of golgi complex
What happens to hydrogen peroxide produced by peroxisomes?
used by enzyme catalase to degrade toher organic molecules
3 functions of catalase?
- 1. degrade other organic molecules
- 2. prevent accumulation of excess hydrogen peroxide by converting it to water and O2
- 3. oxidize fatty acids to produce acetyl coenzyme A used in cellular metabolism
Cells with high energy needs have increased _____ organelles such as ___ and ____ cells.
cariac or skeletal muscle cells
How is the energy in ATP used?
phosphate bonds are broken by hydrolysis(with water) and release energy (approx 11-13 kcal)
How is the energy released from ATP used?
enzymes use the energy to break or make other chemical bonds
Why must each cell produce its own ATP?
How is ATP usually produced?
ATP cannot cross the plasma membrane
breakdown of glycogen and fat
During starvation, body ____ can e used for energy production by a process called ____.
2 separate and opposite phases of cellular metabolism?
anabolism and catabolism
What are anabolism and catabolism?
Which uses energy / releases energy?
anabolism - synthesis of complex molecules such as fat that uses energy
catabolism - breakdown of nutrient sources that releases energy/ATP for use
4 steps of catabolism?
- 1. absorption of simple molecules by the small intestine
- 2. glycolysis
- 3. citric acid cycle
- 4. oxidative phosphorylation
What is glycolysis?
anaerobic process that produces 2 AT, 2 NADH, & 2 pyruvate molecules per glucose molecule used
Why is glycolysis necessary?
anaerobic and used in reduced cellular oxygenation - resp, and cardiac probs
dangerous condition with excess lactate in blood stream due to severe or prolonged lack of oxygen
during glycolysis pyruvate is released and excess is converted to lactic acid and released into the bloodstream
What happens to the products of glycolysis?
pyruvate enters mitochondria and is converted to acetyl CoA with release of CO2 molecule
How do cells with no mitochondria get ATP?
red blood cells
Purpose of the citric acid cycle?
break by oxidation the C-C & C-H bonds of compounds produced in glycolysis
After pyruvate and fatty acids enter the mitochondria after glycolysis what occurs?
pyruvate and fatty acids enter mitochondria from glycolysis -> converted to acetyl CoA -> 1CO2, 1NADH & 1 acetyl CoA formed by cleaving of pyruvate & 1 NADH & 1 FADH2 formed by cleaving of fatty acids
Citric acid cycle process?
Where does it occur?
acetyl groups supplied by acetyl CoA are oxidized to form a lot of H- (hydride ions) that are carried to the respiratory chan by NADH AND FADH2
in the mitochondrial matrix
End products of the citric acid cycle of one molecule of glucose?
2 GTP, 4 CO2, 2 FADH2, & 6 NADH
2 important cariier molecules that carry energy used to produce ATP in oxidative phosphorylation?
NAD & FAD that are reduced by H- in the citric acid cycle to NADH & FADH
How are H-, NADH, AND FADH used in oxidative phosphorylation?
Why is it considered an aerobic process>
H- gives energy for the electron transport chain in mitochondira & NADH & FADH are carrier molecules that bring the H- to the mitochondria
at the end of the transport chain O2 is needed to form H20
____ reactions occur all along the electron transport chain.
What is the purpose of the transport chain?
transport electrons and from a proton (H+) gradient that provides energy for ATP synthesis
A special enzyme in the inner mitochondiral membrane __ ____, allows protons to flow back into the mitochondira down their electrochemical gradient.
Under normal cellular conditions a total of ____ ATP are formed by the complete oxidation of glucose into CO2 & H2O, ___ from glycolysis, ___ from the citric acid cycle in the form of ___, and ___ in the oxidative phosphorylation.
ATP is produced by ____ ____, a protein in the mitochondrial membrane.
How does this occur?
ATP synthase captures the energy of th epoton gradient and uses it to form a bond b/t ADP and inorganic phosphate
2 types & what they are?
cellular ingestion of ECF molecules in vesicles
pinocytosis- ingesting fluids & small particles
phagocytosis - ingestion of large particles
Why are endocytosis and exocytosis needed?
large molecules cannot pass through trasport proteins and must be transported through vesicles
cellular secretion from vesicles
Why are there receptors for molecules that are transported by endocytosis?
receptors regulate what comes in cell and how much of it
more receptors can be added or taken away to regulate intake of specific molecules
The mast cell, a type of WBC, releases ____ when its cell surface receptors are activated. This is an example of _____.
How are small water-soluble molecules transported across PM?
3 types of membrane trasport proteins?
ATP driven pumps, carriers, & channel proteins
water pores in the PM that allow certain size and charge water-soluble membranes into the cell
How do pumps and carrier proteins transport molecules?
bind to them and transport them through
2 types of transport through membrane proteins?
active and passive
ions diffuse pasively b/cof electrochemical gradient due to differences in ICF and ECF charge and/or conc gradients
Secondary active transport?
transport protein uses flow of other molecules down gradient to move another substance uphill against its gradient
How does water move across the plasma membrane?
By what process does this occur?
channels called aquaportins
protein transport pumps move solutes across the membrane against an electrochemical or concentration gradient
What occurs with every pump of the Na-K pump?
moves 3 Na out and 2 K in for every pump
Functions of the Na-K pump?
maintain cell volume by controlling osmosis, secondary active transport
Cell cytoplasm is kept high/low, in the cell cytoplasm and is transported by 2 Ca pumps,1 in the ____ ____ and 1 in the ___ ____ of the cell.
How is excess Ca in the ICF removed?
How does this affect ATP production?
Ca pumps pump Ca into mitochondria using energy from the proton gradient used in ATP production
ATP production is inhibited b/c Ca is using its pathway - this is dangerous to the cell
Process of drug resistance?
bacteria use ABC transporters to pump antibiotics out of the cell
Function of Na driven carriers?
Na gradient created by Na K pum is used to power secondary active transport of other molecules
Na tranports Ca out of cardiac muscle cells (decreases contraction), takes H+ out to control pH, transports glucose and AA into epi cellsreuptake of neurotransmitters from synapses
Passive transport carriers?
always present in PM and let substances in based on their concentration in the ECF
Bcells of pancreas detect blood glucose transport glucose based on its conc in ECF, & release insulin
How does pancreas lower blood glucose?
releases insulin in response to blood glucose level that goes to other cells that take up glucose and enters glucose carriers -> transported into cell -> lower blood glucose
Membrane channel proteins?
selective proteins that form water-filled pores in the membrane and allow specific ions to flow through by simple diffusion
3 ways that ion channels/membrane channel proteins are stim to open?
- 1. voltage gated
- 2. mechanical gated
- . ligand-gated
voltage gated ion channels?
respond to change in membrane potential
mechanical- gated ion channels?
respond to mechanical deformation
ligand gated ion channels?
respond to the binding of a signaling molecule/hormone/neurotransmitter to a receptro in the cell surface
Why are ion channels important to nerves and muscles cells?
responsible for membrane potentials
resting membrane potential - electrical charge present inside the cell when no net ion movement across the PM
Major determinant of the RMP of a cell?
differnce in K across the membrane
K concentration > in ECF or ICF?
30 X greater in ICF
At rest the membrane if permeable to ___, but not to other + ions inculding ___ & ____.
Why does K remain in the cell?
attraction of fixed ICF anions pulls K (Na & Ca are not permeable) in -> as K conc increases in ICF the conc gradient of K favors K moving back out of cell =processes balance out when cell at rest
Action potential? How is it triggered?
electrical exceitatios of the membrane that are mediated by ion channels that open and close in response to changes in voltage across the membrane
by membrane depolarization
How is depolarization triggered and carried out in nerve and muscle cells?
neurotransmitter binds to cell surface receptor -> channels in membrane open and allow Na to enter the cell & K to leave the cell -> threshold is reached when a section of membrane is suffiiciently deplarized to activate voltage-gated Na channels in the membrane -> open and allow more Na ions in -> ongoing chain more Na = more Na gates opening
2 factors that cause cellular repolarization?
Na inflow is stopped by closing Na channels & k outflow through K channels decreases
How is cardiac muscle tetany prevented?
Ca is allowed into the cells during repolarization and prolongs action potential allowing contraction to finish before another impules is conducted
3 ways that cells communicate with each other?
- 1. gap junctions - directly connect the cytoplasm of adjoining cells
- 2. direct cell-to-cell contact of PM or ECF molecules ass with the cell
- 3. secretion of chmical mediators (ligands) that influence cells some ditance away
What type of molecules can and cannot pass through gap junctions?
small molecules can - ions, glucose, aa, nucleotides, and vitamins
large molecules cannot - molecules formed by many of the small molecules together (protein, nucleic acids)
occurs only in cells of the NS, & occurs at synapses small distances apart
neuron secretes a chem neurotransmitter into the synapse of the nerve and the target cell -> NT diffuses cross synaptic cleft and binds receptors on postsynaptic cell
chemicals secreted into a localized area and are rapidly destroyed so that only cells in the imm area are affected
specialized endocrine cells secrete hormones that ravel via the bloodstream to target cells widly distributed in body
cells are able to respond to signaling molecules that they secrete
Why do target cells respond to ligand signaling?
they have specific protein receptors for that ligand
The cellular response to signaling molecules is regulated both by the array of ____ they cell carries and by the ____ _____ the receptors are linked to.
- internal structures
Why do most hormones, local chemical mediators, and NT's need receptor mediated transport?
most are water soluble
Ion channel-linked receptors?
bind NT, causing specific ion channels in the membrane to open or close
Enzyme- linked receptors?
catalyze enzyme reactions when they are activated by appropriate ligands
act indirectly througha membrane-bound trimeric g-protein that binds to GTP when activated by the receptor-> influences activity of specific enzymes -> produce 2nd messengers that cause a cascade to change the cell function
Intracellular receptor -mediated responses?
some lipid soluble hormones pass through PM and interact with receptors inside the cell
2 ways the body controls rate of cell death and proliferation?
- 1. protein mitogens and growth factors are required in specific combos for growth and proliferation
- 2. cells respond to spatial signals from ECF & neighboring cells that indicate how much room is available