Life Sciences Questions and Answers – Respiration – 1

This set of Life Sciences Multiple Choice Questions & Answers (MCQs) focuses on “Respiration – 1”.

1. Respiration is a ___________
a) Oxidative process
b) Reductive process
c) Catabolite repression
d) Intermediate process
View Answer

Answer: a
Explanation: Living organisms need free energy to survive; this free energy is supplied to them in the form of ATP. ATP is formed by the oxidation of organic compounds during respiration. So, respiration is an oxidative process.

2. What is respiratory substrate?
a) The compounds which are reduced during respiration
b) The compounds which are oxidized during respiration
c) The intermediate compounds of respiration
d) The end product of respiration
View Answer

Answer: b
Explanation: Respiratory substrates are the organic compounds which are oxidized during respiration and releases energy in the form of free energy. The respiratory substrate may be carbohydrates, fats, proteins, and organic acids. Carbohydrates are the most commonly used respiratory substrate.

3. Which of the following condition occur by incomplete oxidation of respiratory substrate?
a) Feedback inhibition
b) Feedback repression
c) Aerobic condition
d) Anaerobic condition
View Answer

Answer: d
Explanation: Anaerobic condition arises due to the absence of oxygen where incomplete oxidation of respiratory substrate takes place while aerobic reaction takes place in the presence of oxygen and undergoes in complete oxidation.

4. Which of the following is not an aerobic reaction?
a) Glycolysis
b) Citric acid cycle
c) Oxidative phosphorylation
d) Fermentation
View Answer

Answer: d
Explanation: Among all the options fermentation is anaerobic process while all other reactions take place in the presence of oxygen. Glycolysis takes place in the cytosol, the citric acid cycle takes place in mitochondrial matrix and site of oxidative phosphorylation is an inner mitochondrial membrane.

5. Glycolysis is also known as an Embden-Meyerhof pathway.
a) True
b) False
View Answer

Answer: a
Explanation: Glycolysis is an oxidative process where one molecule of glucose is partially oxidized into two molecules of pyruvate in the series of an enzyme-catalyzed reaction. It is also known as an Embden-Meyerhof pathway.
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6. Which of these enzymes in glycolysis do not take part in an irreversible reaction?
a) Hexokinase
b) Phosphofructokinase
c) Pyruvate kinase
d) Glucokinase
View Answer

Answer: d
Explanation: Hexokinase, phosphofructokinase, and pyruvate kinase catalyzed reactions in glycolysis is irreversible while rest reactions are reversible in nature. So, the regulation of glycolysis is also done by allosteric regulation of these three enzymes.

7. Name the inhibitor of glycolysis?
a) Fluoroacetate
b) Iodoacetate
c) Malonate
d) Actinomycin
View Answer

Answer: b
Explanation: Iodoacetate is an inhibitor of glyceraldehydes-3 phosphate dehydrogenase which reacts with its –SH group of cys residue and stops the glycolysis pathway.

8. Name the site of pyruvate oxidation.
a) Cytosol
b) Mitochondrial matrix
c) Mitochondrial membrane
d) Nucleus
View Answer

Answer: b
Explanation: Pyruvate oxidation takes place in the presence of oxygen inside the mitochondrial matrix and oxidized to acetyl Co-A. Pyruvate is produced in the glycolysis from where it enters to mitochondria with the help of transport protein.

9. Which of these following enzymes does not take part in pyruvate –dehydrogenase complex?
a) Glyceraldehyde-3 phosphate dehydrogenase
b) Pyruvate dehydrogenase
c) Dihydrolipoyl transacetylase
d) Dihydrolipoyl dehydrogenase
View Answer

Answer: a
Explanation: Pyruvate dehydrogenase complex consists of three individual enzymes: E1, E2, and E3, where E1 is pyruvate dehydrogenase, E2 is dihydrolipoyl transacetylase and E3 is dihydrolipoyl dehydrogenase. Oxidation of pyruvate to acetyl-Co-A is done along with coenzymes.

10. How many molecules of Co2 are produced by an acetyl group of acetyl-Co-A in a citric acid cycle?
a) 3
b) 5
c) 1
d) 2
View Answer

Answer: d
Explanation: The citric acid cycle is also known as Krebs cycle in which the condensation of oxaloacetate and an acetyl group of acetyl Co-A take place and produced two molecules of Co2.

11. Which of the following enzyme is inhibited by Fluoroacetate in Krebs cycle?
a) Citrate synthase
b) Aconitase
c) Isocitrate dehydrogenase
d) Fumarase
View Answer

Answer: b
Explanation: Fluoroacetate is a potent inhibitor of aconitase enzyme; it is a pesticide which blocks citric acid cycle by its metabolic conversion to fluorocitrate.

Sanfoundry Global Education & Learning Series – Life Sciences.

To practice all areas of Life Sciences, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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