Cell Molecular Exam 3 Flashcards
(35 cards)
Compare and contrast each of the following. Give an example of each.
a. Channels, transporters, and ATP-powered pumps
Channel - No energy, gated
(facilitated transport, specific protein)
Transporters - protein-lined pathway, hydrophobic barrier
(specific protein, Solute transported against its gradient, Driven by movement of a cotransported ion down its gradient)
ATP-powered pumps - hydrolyzed to bring molecules against concentration gradient
(Requires specific protein, Solute transported against its gradient, Coupled to ATP hydrolysis)
Compare and contrast each of the following. Give an example of each.
b. Uniporters, symporters, and antiporters
Uniporters - transports glucose and amino acids across cellular membrane (facilitated transport)
Symporters - Glucose and amino acid against high concentration gradient. (Cotransport, solute against concentration gradient, driven by movement of cotransport ion)
Transport in the same direction
Antipoter - Transports various ions and sucrose
(Cotransport, solute against concentration gradient, driven by movement of cotransport ion)
Transport in opposite direction
Compare and contrast each of the following. Give an example of each.
c. Simple diffusion, facilitated transport, cotransport, and active transport
Simple diffusion - O2, CO2, steroid hormones, many drugs
(requires no energy)
Facilitated transport - Uniporters and Channels
(Requires specific protein)
Cotransport - uses the energy released by ion (H+/ Na+) movement down its electrochemical gradient
(Requires specific protein, solute against concentration gradient, driven by movement of cotransport ion
Active transport - ATP-powered pumps (Requires specific protein, Solute transported against its gradient, Coupled to ATP hydrolysis)
Describe the structure and function of each of the following.
a. GLUT1
Function: uniporter transports glucose across cellular membranes.
Structure: Hydrophobic central cavity. Two conformation outside open vs inside open.
The cycle
1) Outward open
2) Ligand-bound occluded
3) Inward open
4) Ligand-free occluded
Describe the structure and function of each of the following.
b. Na+/K+ ATPase
P-class pump (1 atp hydrolysis domain)
antiporter (pumps in opposite directions)
Inward binds three Na and outward binds two K. (binding site for 5 ions)
The cycle
Moves three Na+ ions out of and two K+ ions into the cell per ATP molecule hydrolyzed
Describe the structure and function of each of the following.
c. CFTR
Function: Transports Cl ions
Structure: Dephosphorylated closed, phosphorylated R domain removed, ATP-bound open
2 Subunits (channel with use of ATP, doesn’t pump ions but opens and closes using ATP)
ABC class protien
Describe the structure and function of each of the following.
d. K+ channel
Structure: pore helix, selectivity filter. Amino acids around are just the right size/interactions
simple channel no ATP hydrolysis
Describe the structure and function of each of the following.
e. Na+/galactose symporter
Na+-linked symporters enable animal cells to import glucose and amino acids against high concentration gradients.
Na+ linked to galactose
Sodium down gradient, galactose against
Multiple transmembrane helix’s
Binding sites for Na and galactose
Symporter – driven by sodium down gradient
Opens one side to bind both together
Outside open vs inside open
How is the resting membrane potential maintained in an animal cell?
Generated by the ATP-powered Na+/K+ pump and nongated K+ channels.
(Channels and proteins)
How does the electrochemical gradient across a cell membrane determine the direction of ion movement across the membrane? What two forces are acting on the ions?
Ion concentration gradient
Membrane electric potential
How is pH maintained in the cytoplasm and organelles of eukaryotic cells?
Proton pumps that pump hydrogen
V-class pumps (hydrolysis ATP to pump protons into vacule to acidicize it)
How are molecules transported across intestinal epithelial cells from the intestinal lumen to the blood? Which transporters in the apical and basolateral membranes are involved?
Carbon dioxide transport in blood requires a Cl−/HCO3− antiporter.
Needs three channels: one across the apical membrane, the basolateral, and one that pumps sodium.
Define each of the following:
a. Chemiosmosis
The interconversion of three forms of biological potential energy: chemical bond energy, chemical gradients across membranes, and electrical gradients across membranes.
Define each of the following:
b. Proton-motive force
Energy is stored in proton electrochemical gradient and used in ATP synthesis.
Define each of the following:
c. Electron carrier
H2O to O2
Define each of the following:
d. Aerobic oxidation
Cells use a four-stage process to convert energy released from glucose/fatty acid oxidation into ATP phosphoanhydride bond.
Compare and contrast aerobic oxidation and photosynthesis. In which organelle does each take place? What is the energy source? What are the end products?
Aerobic Oxidation - Mitochondria use AO of carbon containing molecules to generate ATP.
Photosynthesis - Chloroplasts; Plant photosynthesis principal end products are O2 and polymers of 6-carbon sugars (starch and sucrose).
Light-capturing and ATP-generating photosynthesis reactions occur in chloroplast thylakoid membranes.
Each - have their own DNA, ATP production
What are the 4 stages of aerobic oxidation? Where does each step take place?
1) GLYCOLYSIS - Cytosolic enzymes convert glucose to 2 molecules of pyruvate and generate 2 molecules each of NADH and ATP.
2) CYTRIC ACID CYCLE - the 3-carbon pyruvate molecule is oxidized to generate one molecule each of CO2, NADH, and acetyl CoA, which is oxidized to CO2 by the citric acid cycle
3) ELECTRON-TRANSPORT CHAIN - flow of electrons from NADH/FADH2 through the electron transport chain complexes provides energy to drive H+ transport across the inner mitochondrial membrane, generating a proton-motive force (voltage and pH gradients).
4) CALVIN CYCLE - Reduction potentials of the electron carriers favor unidirectional, “downhill,” electron flow from NADH and FADH2 to O2 to form H2O.
What are the 4 stages of photosynthesis? Where does each step take place?
1) light absorption, generation of high-energy electrons, and O2 formation from H2O (Thylokoid)
2) Electron transport leading to reduction of NADP+ to NADPH and PMF generation (Thylokoid)
3) ATP synthesis (Thylokoid)
4) conversion of CO2 into carbohydrates (carbon fixation) (Stroma)
What is the energy yield of glycolysis? Is it aerobic or anaerobic? How is the rate of glycolysis regulated? What are the possible fates of pyruvate?
2 molecules of pyruvate and generate 2 molecules each of NADH and ATP.
Anaerobic process
Metabolize pyruvate to lactic acid or ethanol and CO2 to convert NADH back to NAD+ required for glycolysis
What is the energy yield of the citric acid cycle? Is it aerobic or anaerobic?
3-carbon pyruvate molecule is oxidized to generate one molecule each of CO2, NADH, and acetyl CoA, which is oxidized to CO2 by the citric acid cycle
aerobic
What is the function of each of the following?
a. NADH and FADH2
Provides energy to drive H+ transport across inner mitochondrial membrane.
What is the function of each of the following?
b. Acetyl-CoA
The end product of fatty acid oxidation and glycolysis. Important intermediate in the aerobic oxidation of pyruvate, fatty acids, and many amino acids
Contributes acetyl groups to many biosynthetic pathways
What drives progression through the electron transport chain?
proton-motive force
Reduction potentials of the electron carriers favor unidirectional, “downhill,” electron flow from NADH and FADH2 to O2 to form H2O.
