Download Bio102 Problems

Bio102 Problems
Anaerobic Respiration
1. When proteins are used for energy, they usually enter the central metabolic pathways at which
step?
A.
B.
C.
D.
E.
Citric Acid Cycle
Transition Step
-Oxidation Cycle
Glycolysis
Electron Transport
2. The goal of fermentation is to
A. make ATP in the absence of oxygen.
B. produce oxidized co-enzymes.
C. produce lactate which can be used to synthesize amino acids.
D. move carbon-containing molecules into the mitochondria.
E. destroy co-enzymes that have been used up.
3. Which one of the following statements correctly describes feedback inhibition?
A. The substrate of a pathway is broken down by the pathway.
B. The substrate of a pathway is also a competitive inhibitor.
C. The end product of a pathway is also an allosteric inhibitor.
D. The end product of a pathway is removed from the cell.
E. The substrate of a pathway is also an allosteric inhibitor.
4. Is CO2 produced in anaerobic metabolism? If so, in which step of anaerobic metabolism?
Sometimes. In some species (e.g. plants and fungi) CO2 is made during fermentation
5.
What carbon-containing molecules are the substrates for  -oxidation? What carbon-containing
molecules are the products of  -oxidation?
Substrate
Product
-oxidation
Fatty Acids
6.
Acetyl-CoA
A very simplistic metabolic pathway is outlined below.
A
Enzyme #1
B
Enzyme #2
C
Enzyme #3
D
Enzyme #4
E
If we double the amount of molecule C present in the cell, how will that affect the rate at which
enzyme #1 works? How will that affect the rate at which enzyme #4 works? Please explain your
answer.
This will slow the rate of Enzyme #1 and increase the rate of Enzyme #4. Higher concentrations of
molecule C means that Enzyme #3 gets more substrate that means it moves to the right on it’s
Michaelis-Menten curve, yielding a higher vi. Thus, more ‘D’ is made to speed up Enzyme #4 by the
same reasoning.
7. Name the cellular process that carries out the following energy transfers.
___Chemiosmosis___ transfers energy from a proton gradient to ATP.
___Electron Transport transfers energy from NADH and FADH2 to a proton gradient.
___Fermentation____ transfers energy from NADH to lactate.
8. Name the cellular process that carries out the following carbon transformations.
___Citric Acid Cycle changes acetyl-CoA to CO2.
___Glycolysis______ changes one molecule of glucose into two molecules of pyruvate.
___Fermentation___ changes pyruvate to ethanol and CO2.
___Transition Step changes pyruvate to acetyl-CoA and CO2.
9. Why is a fermentation step required for a cell to survive anaerobically?
To re-oxidize coenzymes, allowing glycolysis to continue.
10. Which
one statement is not true about AMPK (the AMP-dependent kinase)?
A. It phosphorylates many different proteins.
B. It’s activity leads to an increase in the amount of glycolytic enzymes.
C. It becomes active only when the cell is experiencing a shortage of ATP.
D. It is one of many substrates of PFK.
E. It increases the rate of glycolysis.
11. If a cell is deprived of oxygen, the Citric Acid Cycle always stops because
A. the cell dies.
B. pyruvate is no longer produced.
C. there are insufficient amounts of NAD+ and FAD available.
D. the G value for the synthesis of citrate becomes positive.
E. there is no way to produce any additional Ac-CoA, which is a substrate for the Citric Acid
Cycle.
12. Phosphofructokinase (PFK) is a key enzyme in glycolysis and is heavily regulated. Which one
mechanism listed below is NOT used to regulate PFK?
A. PFK can be allosterically activated by AMP.
B. PFK can be phosphorylated by AMPK.
C. More PFK can be produced by increasing transcription of the PFK gene.
D. PFK can be activated by having higher concentrations of its substrate.
E. PFK can be allosterically activated by ATP.
13. Which one type of molecule can be consumed anaerobically to produce ATP?
A. Complex carbohydrates
B. Fatty acids
C. Amino acids
D. Triglycerides
14. The product of one metabolic pathway is often the substrate for another metabolic pathway or
process. For each pair of processes below, identify the product/substrate that connects the two. (6
points)
Transition step 
Glycolysis 
-oxidation 
Acetyl-CoA
Pyruvate
Acetyl-CoA
 Citric acid cycle
 Transition step
 Citric acid cycle
15. Why can your cells produce more usable cellular energy per carbon atom from a lipid molecule
than from a carbohydrate molecule?
Both are ultimately expelled from the body as CO2. To get there, each carbon atom from a
lipid must be more oxidized more times than each carbon atom from a carbohydrate. With
each of these oxidations, a reduced coenzyme is produced which will ultimately be used to
synthesize more ATP by oxidative phosphorylation.
16. The AMPK enzyme becomes active when
A. PFK activity is inhibited.
B. AMP concentrations are high.
C. oxygen is abundant.
D. Photosystem II is inhibited.
E. ATP concentrations are high.
17. Glycolysis produces two molecules of ATP per molecule of glucose consumed. Despite this
positive yield, a cell can’t survive by running only glycolysis. Why not?
Glycolysis also reduces two molecules of NAD+ to NADH. If we just keep running glycolysis, we’ll
run out of NAD+ and thus glycolysis will have to halt. The fermentation step regenerates the
NAD+ to allow glycolysis to continue.
18. Unlike carbohydrates, neither fats nor proteins can be burned for fuel anaerobically by humans.
Why not?
Fats get catabolized to acetyl-CoA, which has to be used in the Citric Acid Cycle. Most amino acids
get deaminated and then enter the Citric Acid Cycle. Catabolism by the Citric Acid Cycle produces
large amounts of reduced co-enzymes. Oxidative phosphorylation is the only way to regenerate the
reduced coenzymes.