exam 3 test questions Flashcards
1) Anaerobic glycolysis can produce ATP at a much faster rate than aerobic oxidative phosphorylation.
Answer: TRUE
2) Which of the following types of reaction does NOT occur in glycolysis? A) Isomerization B) Nucleophilic attack C) Aldol condensation D) Oxidation E) Dehydration
Answer: C
3) The standard free energy change of the glycolytic pathway to pyruvate is -79.9 kJ/mol, while the standard free energy change associated with gluconeogenesis from pyruvate is -42.7 kJ/mol. What would the standard free energy change be for a direct reversal of the glycolytic pathway.
Answer: +79.9kJ/mol
4) Glycolysis is regulated primarily by:
A) the availability of glucose-6-phosphate.
B) three strongly endergonic, nonequilibrium reactions.
C) three strongly exergonic, nonequilibrium reactions.
D) allosteric effectors of pyruvate kinase.
E) phosphorylation of phosphofructokinase.
Answer: C
5) Which of the following statements about regulation of phosphofructokinase is FALSE?
A) AMP is an activator.
B) ADP is an activator.
C) Citrate is an inhibitor.
D) Fructose 2,6-bisphosphate is an activator.
E) ATP decreases the apparent Km for fructose-6-phosphate.
Answer: E
6) Liver pyruvate kinase is activated by dephosphorylation in response to glucagon.
Answer: FALSE
7) Hexokinase, phosphofructokinase and pyruvate kinase are each subject to ________ control.
Answer: allosteric
8) Fructose-1,6-bisphosphate is a feedforward ________ activator of liver pyruvate kinase.
Answer: allosteric
9) The oxidation of glucose to lactate has a standard free energy change of approximately -196 kJ/mol. Calculate the efficiency of energy conversion if the standard free energy change for the production of ATP from ADP and inorganic phosphate is +32.2 kJ/mol.
Answer: 33.8%
10) All of the reactions of both glycolysis and gluconeogenesis occur in the cytosol.
Answer: FALSE
11) The flux rate through the gluconeogenic pathway is directly proportional to the amount of carbohydrate in the diet.
Answer: FALSE
12) Much of the regulation of gluconeogenesis is a result of the inhibition of glycolysis.
Answer: TRUE
13) Which of the following cannot be used as a precursor for gluconeogenesis? A) Glycerol B) Pyruvate C) Lactate D) Leucine E) Alanine
Answer: D
14) Flux through the pentose phosphate pathway is controlled mainly by the NADP+/NADPH ratio in the cell.
Answer: TRUE
15) The primary gluconeogenic organ in animals is: A) skeletal muscle. B) kidney medulla. C) kidney cortex. D) liver. E) heart muscle.
Answer: D
16) ________ from muscle working anaerobically is released to blood and can be taken up by liver where it is converted to pyruvate by the enzyme lactate dehydrogenase.
Answer: Lactate
17) The Pasteur effect describes the observation that yeast-metabolizing glucose anaerobically will dramatically increase their rate of glucose utilization when provided with air.
Answer: FALSE
18) Both glycolysis and gluconeogenesis are controlled by fructose 2,6-bisphosphate in response to hormones.
Answer: TRUE
19) Pyruvate carboxylase and phosphoenolpyruvate carboxykinase catalyze reactions of gluconeogenesis that bypass the reaction of glycolysis that is catalyzed by ________.
Answer: pyruvate kinase
20) Glycogen is a major energy source for skeletal muscle contraction.
Answer: TRUE
21) Polysaccharide digestion and glycogen breakdown involve sequential cleavage from ________ ends of glucose polymers.
Answer: non-reducing
22) The major product from the action of glycogen phosphorylase and the debranching enzyme glucantransferase is ________.
Answer: glucose-1-phosphate
23) Which of the following is NOT involved in glycogen synthesis? A) UDP-glucose B) Glycogenin C) Amylo-(1,4 to 1,6)-transglycosylase D) Glycogen synthase E) Glycogen phosphorylase
Answer: E
24) Which statement about control of glycogen metabolism is INCORRECT?
A) Epinephrine signals glycogen breakdown in muscle.
B) Glucagon signals glycogen breakdown in liver.
C) Glycogen phosphorylase is activated by phosphorylation.
D) Glycogen synthase is phosphorylated at only one site.
E) Glycogen synthase is activated by dephosphorylation.
Answer: D
25) Phosphorylases and phosphatases catalyze the same reaction, the removal of a phosphate group.
Answer: FALSE
26) The pentose phosphate pathway provides ________ for reductive biosynthesis and ________ for nucleic acid biosynthesis.
Answer: NADPH, ribose-5-phosphate
1) Saturated fatty acids are different to unsaturated fatty acids because they:
A) have an even number of carbon atoms.
B) have short hydrophobic tails.
C) have no C=C double bonds.
D) exhibit free rotation about the carbon carbon bonds in the hydrocarbon tail.
E) mostly have cis double bonds.
Answer: C
2) Which of the following statements is FALSE?
A) The longer the chain length of a saturated fatty acid, the higher the melting temperature.
B) The difference in melting temperature between a saturated fatty acid and an unsaturated fatty acid with the same chain length is only a few degrees C.
C) Most types of fat in many animals is used in energy production.
D) Some unsaturated fatty acids are liquid at physiological temperatures.
E) Fatty acids exist in the anionic form (RCOO-) at physiological pH.
Answer: B
3) Linolenic acid has cis double bonds with the formula CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH. Write out the abbreviated systematic numbering for this fatty acid.
Answer: 18:3△c9,12,15
4) Which of following lipids can be a major component of biological membranes? A) Phosphatidic acid B) Phosphatidylcholine C) Phosphatidylinositol D) Cholesterol E) B and D
Answer: E
5) Sphingomyelin contains a fatty acid linked by an ________ bond and phosphocholine linked via the C-3 hydroxyl group of sphingosine.
Answer: amide
6) Which of the following is unlikely to be a characteristic of a membrane protein?
A) Largely hydrophobic transmembrane segments
B) α-helical membrane-spanning motifs.
C) Covalently attached lipid moities
D) Symmetric orientation across the membrane
E) β-sheet membrane-spanning motifs
Answer: D
) In an aqueous environment the hydrocarbon tails of lipids tend to associate by entropy-driven ________ and by Van der Waals interactions.
Answer: hydrophobic effects
8) Raft platforms in membranes have functional roles in cell signaling and sorting of proteins into specific ________ in the cell.
Answer: organelles
9) Which of the following statements about biological membranes is FALSE?
A) They are composed of a mixture of lipids and proteins in which lateral diffusion of components is possible.
B) Lipids and proteins move laterally at approximately the same rate within the membrane.
C) The faces of biological membranes are distinct and usually different in both composition and structure.
D) Phospholipids often require a specialized enzyme to facilitate movement across (flipping) the membrane.
E) They are often organized into smaller regions of specific function.
Answer: B
10) Integral membrane proteins can be inserted into the membrane and folded into the normal 3D structure during translation.
Answer: TRUE
11) Lipid rafts are small long-lived structures that respond to stimuli to transiently associate with each other to form larger raft platforms.
Answer: FALSE
12) Which of the following is NOT relevant to facilitated transport across biological membranes?
A) An ionophore is a carrier protein that increases the permeability of a membrane to ions.
B) Some permeases can transport their substrates in both directions.
C) A symport will transport two molecules in the same direction across a membrane.
D) ATP hydrolysis is required.
E) An antiport will move substrates in opposite directions across a membrane.
Answer: D
13) Which of the following mechanisms is responsible for the selectivity of aquaporins for water? A) Size exclusion B) Electrostatic repulsion C) Dynamic hydrogen bonding D) Prevention of ion gradient formation E) All of the above
Answer: E
14) Mediated transport or diffusion will ultimately result in the concentration of diffusing substance being the same on both sides of the membrane.
Answer: FALSE
15) Passive facilitated cotransport can move some substrate across a membrane against its concentration gradient.
Answer: TRUE
16) The rate of nonmediated diffusion tends to increase as the ________ character of the diffusing substance increases.
Answer: hydrophobic
17) Active transport can move a substance across a membrane ________ its concentration gradient.
Answer: against
18) The standard free energy that is required for the sodium-potassium ATPase to pump two K+ ions into the cell and three Na+ ions is +43.8 kJ/mol but the standard free energy change of hydrolysis of ATP is only -32 kJ/mol. This apparent imbalance of free energy can be accounted for because:
A) the movement of Na+ ions is down the concentration gradient.
B) the movement of K+ ions is down the concentration gradient.
C) the membrane potential favours the flow of ions.
D) more than one ATP is hydrolyzed.
E) the free energy provided from the hydrolysis of one ATP is sufficient under physiological conditions.
Answer: E
19) Digitoxin can act as a short term cardiac stimulant by inhibiting the Na+-K+ pump.
Answer: TRUE
20) The sodium-glucose cotransport system is an example of: A) an antiport transporter. B) passive transport. C) facilitated transport. D) an ATP-dependent transporter. E) none of the above.
Answer: C
21) The Na+-K+ ATPase uses the free energy of ATP hydrolysis in an active transport process to move Na+ and K+ across a membrane. What would the rate of nonmediated transport be given that the permeability coefficient for K+ through a human erythrocyte membrane is 2.4 × 10-10 cm/s. K+ ions must be moved from a concentration of 4 mM on the outside of the cell to 155 mM inside the cell?
Answer: 3.62 × 10-8 cm/s
22) Action potentials are propagated along a nerve axon by sequentially opening and closing a series of voltage-gated potassium and sodium channels.
Answer: TRUE
1) Carbohydrates are components of the following: A) the membrane of red blood cells. B) nucleic acids. C) the hormone erythropoietin. D) the bacterial cell wall. E) all of the above.
Answer: E
2) Which of the following is an example of a monosaccharide? A) Galactose B) Lactose C) Amylose D) Maltose E) None of the above
Answer: A
3) Glyceraldehyde has a chiral carbon so has two stereoisomers, which are called diastereomers.
Answer: FALSE
4) Pentoses and hexoses can form stable ring structures by internal hemiacetal formation.
Answer: TRUE
5) Which of the following is considered to be the smallest carbohydrate? A) Glucose B) Dihydroxyacetone C) Ribose D) Xylose E) Formaldehyde
Answer: B
6) D-ribose can form a ring structure with either four or five carbons in the ring.
Answer: TRUE
7) Maltose has a (1→4) α linkage between glucose and ________.
Answer: glucose
8) Synthesis of sugar polymers is enzyme catalyzed and requires activated monomers like ________ in lactose biosynthesis.
Answer: UDP-galactose
9) Amylose and amylopectin are the principle storage polysaccharides of: A) bacteria. B) plants. C) animals. D) mollusks. E) insects.
Answer: B
10) The storage polysaccharides are ________ in plants and ________ in animals.
Answer: starch, glycogen
11) N-linked glycans are attached to proteins through N-acetylglucosamine or N-acetyl galactosamine to the amide side chain of: A) glutamine. B) histidine. C) asparagine. D) arginine. E) lysine.
Answer: C
12) Glycosaminoglycans are polysaccharides composed of repeating disaccharide units in which one of the sugars is always N-acetylgalactosamine.
Answer: FALSE
13) Proteins are marked for secretion from the cell by the post translational addition of oligosaccharides.
Answer: TRUE
14) Heparin is a highly sulphated glycosaminoglycan that act as an ________.
Answer: anticoagulant
15) O-linked glycans are attached to proteins through the hydroxyl group of serine or ________ and sometimes ________.
Answer: threonine, tyrosine
