1. Which one of the following is the terminal electron acceptor?

a) Molecular CO₂             
b) Molecular O₂
c) Molecular H₂
d) NADPH₂

2. In electron transport system, which of the following acts as a final hydrogen acceptor

a) Oxygen          
b) Hydrogen      
c) Calcium           
d) Ubiquinone

3. If a starving plant is provided with glucose, the rate of respiration would

a) First rise then fall        
b) Become constant       
c) Decrease       
d) Increase

4. Which one is product of aerobic respiration?

a) Malic acid      
b) Ethyl alcohol
c) Lactic acid      
d) Pyruvic acid

5. Given below the diagrammatic presentation of ATP synthesis in mitochondria. Identify A-C and Choose the correct option accordingly

a) A-H⁺,B-F₁,C-F₀

b) A-3H⁺,B-F₀,C-F₁

c) A-2H⁺,B-F₀,C-F₁

d) A-5H⁺,B-F₁,C-F₀

6. In Krebs’ cycle,

a) ADP is converted into ATP

b) Pyruvic acid is converted into CO₂ and H₂O

c) Glucose is converted into CO₂

d) Pyruvic acid is converted into ATP

7. Decline in the activity of the enzyme Hexokinase by glucose-6-phosphate is caused by

a) Non-competitive

b) Competitive inhibitors

c) Allosteric modulators
d) Denaturation of enzyme

8. In which of the following reactions of glycolysis, oxidation takes place?

a) Glucose 6-PO₄ to fructose 6-PO₄

b) Glyceraldehydes 3-phosphate to 1, 3-diphosphoglycerate

c) 1,3-diphosphoglycerate to 3-phosphoglycerate

d) 2-phosphoglycerate to phosphoglycerate

9. During conversion of pyruvic acid into acetyl Co-A, pyruvic acid is

a) Oxidized        
b) Reduced        
c) Isomerized    
d) Condensed

10. During anaerobic respiration in yeast

a) H₂ O and CO₂ are end-products

b) CO₂, ethanol and energy are end-products

c) CO₂, and H2O are end-products

d) CO₂, acetic acid and energy are end-products

MCQ on Respiration in Plants  

MCQ on Respiration in Plants  

1              (a)

Oxaloacetic acid – 4C. Phosphoglyceric acid – 3C

Ribulose bisphosphite – 3C. Phosphoenl pyruvate – 3C

2              (b)

In the non-competitive inhibition of enzymes, the inhibitor (cyanide) has no structural similarity with the substrate (cytochrome-c) and binds to the enzyme at a point other than its active site which leads to change in globular structure of enzyme. Hence, even if the substrate is able to bind with the enzyme, catalysis will not take place.

3              (a)

During anaerobic respiration, one molecule of glucose gives two molecules of ATP. Thus, 8 molecules of ATP are produced.

4              (b)

Peter Mitchell (1961) proposed the chemiosmotic mechanism of ATP synthesis which, states that ATP synthesis occurs due to H⁺ flow through a membrane. It includes development of proton gradient and proton flow.

5              (d)

In the process of glycolysis, 6-carbon molecules of glucose are split into two 3-carbon molecules of pyruvic acid. In this, two molecules of NAD⁺ are reduced for each glucose molecule. The energy stored within the NADH is released in the electron transport chain.

6              (a)

Citric acid cycle is also known as Tricarboxylic acid cycle (TCA)

7              (d)

In respiration, whether it is aerobic or anaerobic glucose undergoes oxidation to form energy. In plants glucose is derived from sucrose which is the end product of photosynthesis or from storage carbohydrate. Sucrose is converted into glucose and fructose by the enzyme invertase to enter into the first step of respiration which is glycolytic pathway

8              (a)

Fat breakdown into fatty acid and glycerol before entering into the respiratory pathway

9              (d)

In glycolysis, water molecule is removed during conversion of 2-phosphoglycerate to phosphoenol pyruvate.Conversion of fructose-6-phosphate to fructose 1-6 biphosphate is characterized by phosphorylation.

10           (b)

Pentose Phosphate Pathway (or Warburg-Lippman Dickens cycle) is an alternate method of aerobic respiration, which occurs in the cytoplasm of mature cell. This pathway accounts for 60% of total respiration in liver cells. In this, for every six molecules of glucose, one molecule is completely oxidized in CO₂ and reduced coenzymes, while 5 are regenerated.