Question

1. In the complex reactions that make up cellular respiration, energy is transferred by

A. phosphorylation reactions

B. redox reactions  

C. neither 1 or 2

D. both 1 and 2

2. Respiration of carbohydrate substrates provides more energy than proteins substrates because

A. proteins have no C-H bonds

B. proteins cannot be processed by glycolysis

C. proteins compete with NADH reduction reactions

D. proteins release NH3

3. Which of the 4 stages of respiration is anaerobic, and can continue without oxygen?

A. citric acid cycle

B. glycolysis

C. electron transport and oxidative phosphorylation

D. pyruvate processing

4. ATP is a regulatory molecule for the allosteric enzyme phospho-fructose kinase. This regulatory mechanism of the activity of glycolysis is called:

A. interference inhibition

B. competitive inhibition

C. feedback inhibition

D. active site inhibition

5. The NET output of glycolysis of 1 glucose molecule is

A. 4 ATP, 2 NADH

B. 2ATP, 2 FADH2

C. 2 ATP, 2 NADH

D. 2 ATP, 2 FADH2

6. Which of the four stages of respiration does NOT take place in mitochondria

A. pyruvate processing

B. glycolysis

C. Citric acid cycle

D. electron transport and oxidative phosphorylation

7. The citric acid cycle is a set of sequential reactions where 2 carbon atoms from Acetyl CoA (that derives from a glucose molecule) are coupled to a 4 carbon molecule. The carbon atoms from Acetyl CoA are released as CO2. Redox reactions and phosphorylation reactions are used to harvest energy in the form of ATP, NADH and FADH2. The product of these reactions is again a 4 carbon molecule that can be coupled with 2 carbon atoms from another Acetyl CoA to repeat the whole process

A. true, this is a correct description of the citric acid cycle

B. false, the citric acid cycle starts with pyruvate as substrate

C. false, the citric acid cycle employs only redox reactions

D. false, the citric acid cycle does not yield NADH

8. The net total output of energy rich molecules from respiration of a molecule of glucose after the citric acid cycle is

A. 2 ATP, 50 NADH, 4 FADH2

B. 2 ATP, 10 NADH, 2 FADH2

C. 4 ATP, 10 NADH, 2 FADH2

D. 4 ATP, 2 NADH, 10 FADH2

9. In the absence of oxygen, cellular respiration switches to fermentation. Fermentation is a set of alternative reactions to complete glycolysis and produce 2 ATP for a glucose molecule, by making sure that the following reagent is available

A. NAD (oxidized electron carrier)

B. EtOH (alcohol)

C. NADH (reduced electron carrier)

D. Acetyl CoA (substrate for citric acid cycle)

Answer 1

1. In the complex reactions that make up cellular respiration, energy is transferred by

Ans. D. Both 1 and 2

Explanation: Typically in cellular respiration, glucose is broken down and ATP (energy) is produced. ATP is produced by phosphoylation and thus energy is transferred by phosphorylation. Cellular respiration also involves oxidation-reduction reactions or redox reactions. And in these redox reactions, where there is a transfer of electrons, there is transfer of energy also.

2. Respiration of carbohydrate substrates provides more energy than proteins substrates because

Ans. D. Proteins release NH3

Explanation: Carbohydrate substrates provide more energy than protein substrates becuase one of the end product of the breakdown of proteins is Ammonia or NH3 and the production of NH3 itself requires energy. Moreover, ammonia is a waste product that is excreted from the body either directly or via conversion into urea or uric acid and this conversion also requries energy. Thus, the excretion of NH3 also requires energy.

Proteins have C-H bonds and they can also enter glycolysis in the form of amino acids. They are involved in NADH reduction reactions and they have a regulatory function here. For these reasons, we can rule out options A, B, and C given for this question.  

3. Which of the 4 stages of respiration is anaerobic, and can continue without oxygen?

Ans. B. Glycolysis

Explanation: Cellular respiration, comprising of glycolysis, pyruvate oxidation, Kreb's cycle and oxidative phosphorylation, is generally an aerobic process. However, the nine steps of glycolysis can happen without oxygen and thus we can say that Glycolysis is the anaerobic step of cellular respiration. Pyruvte oxidation occurs in the mitochondria and requires oxygen. In the lack of oxygen energy can be produced from glucose through a process called fermentation.

4. ATP is a regulatory molecule for the allosteric enzyme phospho-fructose kinase. This regulatory mechanism of the activity of glycolysis is called:

Ans. C. Feedback inhibition

Explanation: One of the enzymes involved in the negative nd positive regulation of glycolysis is phospho-fructose kinase. This regulation is an allosteric inhibition where the regulator binds to a regulator site, i.e. a site other than the active site of the enzyme, and changes the structure or shape of the enzyme. Allosteric inhibition is typically not a competitive inhibition as competitive inhibitors bind to the active site. ATP is one of the end products of glycolysis. When sufficient ATP is produced, there is something called feedback inhibition where the end product negatively regulates the process. Binding of ATP to phospho-fructose kinase decreases the affinity of the enzyme for fructose 6-phosphate and thus high levels of ATP causes this type of inhibition which we call feedback inhibition.

5. The NET output of glycolysis of 1 glucose molecule is

Ans. C. 2 ATP, 2 NADH

Explanation: The net output of 1 glucose molecule is 2 ATP and 2 NADH and of course two molecules of pyruvate too. When 1 glucose is converted to 2 Pyruvate molecules, the output is 4 ATP but since 2 ATP is the input for 1 molecule of glucose, the net output is 2 ATP.