Biology

Cellular Respiration and Enzymes

1,551 Questions

Explore key concepts of cellular respiration, including glycolysis, the Krebs cycle, and the electron transport chain. These questions also cover ATP production, anaerobic respiration, and essential metabolic pathways. This topic forms a core part of the biology syllabus for many competitive examinations.

Glycolysis and metabolic pathwaysKrebs cycle processesElectron transport chainATP production countAnaerobic respiration products

Cellular Respiration and Enzymes Questions

Multiple choice bio-chemistry organization of life concept of metabolism metabolism in animals metabolism

State whether the following statements are true or false .
A metabolic pathway is a sequence of chemical reactions in which each step is controlled by its own specific enzymes.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Enzymes are organic catalysts which aid in facilitating chemical reactions in the body. Each metabolic pathway consists of a series of biochemical reactions that are connected by their intermediates: the products of one reaction are the substrates for subsequent reactions, and so on. Any metabolic pathway inside our body (for example glycolysis) requires several enzymes working in a sequential manner. 

So, the correct option is 'True'.

Multiple choice bio-chemistry organization of life concept of metabolism metabolism in animals metabolism

Choose the correct answers from the alternatives given .
All the biochemical pathways in a cell constitute

  1. Coupling reactions

  2. Endergonic reactions only

  3. Exergonic reactions only

  4. Metabolism
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

There are various biochemical reactions taking inside a cell. Some of these reactions may result in absorption of energy (called as endergonic reactions) or release of energy (called as exergonic reactions). Often both these types of reactions are coupled, to get the energy to those endergonic reactions, they are paired up with energy-releasing exergonic reactions (known as coupling reactions). Although, there are a wide variety of reactions taking place inside the body apart from these reactions. Metabolism is a term that is used to describe all these biochemical reactions involved in maintaining the living state of the cells and the organism. 

So, the correct option is 'Metabolism'.


Multiple choice evs deficiency diseases need for nutrients nutrients needed by the body balanced diet and malnutrition food for health nutrition and its deficiency nutrition and its need

Reduced coenzyme NADPH $(H^+)$ is produced in respiration during

  1. Glycolysis

  2. PPP

  3. Krebs cycle

  4. Terminal oxidation.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

PPP or pentose phosphate pathway is an important pathway that takes place in the cytoplasm.

 It is an alternative path for the Krebs cycle and is the only pathway that forms reduced NADH. The enzyme transhydrogenase, that transfers the hydrogen of NADPH to NAD and forms NADH.
So, the correct option is 'PPP'

Multiple choice biology life processes in living organisms- part 1 amphibolic pathway living organisms and energy production respiration in plants

Which of the following forms the connecting link between glycolysis and Kreb's cycle?

  1. Glucose

  2. Ethyl alcohol

  3. Lactic acid

  4. Pyruvic acid
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Pyruvic acid is produced as a final end product of glycolysis. This pyruvic acid then forms acetyl CoA. This acetyl CoA, acts as initial compound of Kreb's cycle.
So, the correct answer is 'Pyruvic acid'
Multiple choice biology respiration in plants amphibolic pathway living organisms and energy production life processes in living organisms- part 1

Out of 38 molecules of ATP produced after aerobic respiration of glucose, the break up in ATP production in glycolysis (P). pyruvic acid to acetyl CoA formation (Q) and Krebs cycle (R) is 

  1. P = 2, Q = 6, R = 30

  2. P = 8, Q = 6, R = 24

  3. P = 8, Q = 10, R = 20

  4. P = 2, Q = 12, R = 24
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Glycolysis produces 8 ATP (2 net ATP + 2 NADH yielding 6 ATP via shuttle), link reaction produces 6 ATP (2 NADH), and the Krebs cycle produces 24 ATP (6 NADH, 2 FADH2, 2 GTP/ATP). The total is 38 ATP.

Multiple choice biology respiration in plants amphibolic pathway living organisms and energy production life processes in living organisms- part 1

Which of the two statements together support that respiratory pathway is an amphibolic pathway.
i) Fats breakdown to glycerol and fatty acids, subsequently yields acetyl CoA
ii) In respiration C-C bonds of complex compounds breakdown through oxidation leading to release of energy
iii) Acetyl CoA from respiratory pathway is withdrawn for synthesis of fatty acids
iv) Proteins are degraded by protease to amino acids and enter the respiratory pathway

  1. i, ii

  2. i, iv

  3. ii, iv

  4. ii, iii
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Statement ii describes the catabolic nature (breakdown of C-C bonds), while statement iii describes the anabolic nature (withdrawal of intermediates like Acetyl CoA for fatty acid synthesis), together defining the amphibolic pathway.

Multiple choice biology respiration in plants amphibolic pathway living organisms and energy production life processes in living organisms- part 1

Largest amount of phosphate bound energy is produced in the process of respiration during 

  1. Anaerobic respiration

  2. Glycolysis

  3. Krebs cycle

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

During the process of glycolysis 8 ATP molecules are produced in aerobic respiration. In the case of Krebs cycle 30 ATP molecules can be produced.

Multiple choice biology respiration in plants amphibolic pathway living organisms and energy production life processes in living organisms- part 1

The process by which the energy of glucose is released under aerobic respiration was discovered by

  1. Hopkins

  2. Lister

  3. Krebs

  4. Pasteur
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The process by which the energy of glucose is released under aerobic respiration, was discovered by Hans Krebs. The Krebs cycle is a part of cellular respiration. It is a series of chemical reactions used by all aerobic organisms to generate energy.

Multiple choice biology respiration in plants amphibolic pathway living organisms and energy production life processes in living organisms- part 1

Kerbs cycle __________________.

  1. Liberates a minor part of energy during respiration

  2. Is operative in photorespiration

  3. Reactions are independent of oxygen supply

  4. Is a like between carbohydrate and nitrogen metabolism
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The Krebs cycle is a major metabolic pathway that releases energy in the form of NADH, FADH2, and ATP/GTP. While it is a central hub, it is primarily responsible for the oxidation of acetyl-CoA.

Multiple choice biology respiration in plants amphibolic pathway living organisms and energy production life processes in living organisms- part 1

In Kreb's cycle, OAA accepts acetyl CoA to form 

  1. Citric acid

  2. Oxalosuccinate

  3. Fumarate

  4. Succinyl CoA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The citric acid cycle starts with the condensation of acetyl group with oxalo acetic acid and water to yield citric acid. The reaction is catalysed by the enzyme citrate synthase and a molecule of CoA is released.

Image result for citric acid cycle
So the correct option is 'citric acid'.

Multiple choice biology respiration in plants amphibolic pathway living organisms and energy production life processes in living organisms- part 1

In Kreb's cycle formation of ___________________.

  1. $34$ ATP takes place
  2. $38$ ATP takes place
  3. $15$ ATP from each acetyl Co-A takes place
  4. $12$ ATP from each acetyl Co-A takes place $(24\ ATP)$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

In the Krebs cycle, each acetyl CoA oxidation yields 3 NADH, 1 FADH2, and 1 GTP (equivalent to 1 ATP), which collectively generate 12 ATP molecules through oxidative phosphorylation in older traditional calculations often referenced in textbooks. Thus, the formation of 12 ATP from each acetyl CoA is the standard representation for this pathway.

Multiple choice biology respiration in plants amphibolic pathway living organisms and energy production life processes in living organisms- part 1

How many oxidation step take place during glycolysis, link reaction and Kreb's cycle.

  1. $1, 1 and 1$
  2. $1, 1 and 4$
  3. $1, 1 and 3$
  4. $1, 1 and 8$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Glycolysis has 1 oxidation step (G3P to 1,3-BPG), the link reaction has 1 (pyruvate to acetyl-CoA), and the Krebs cycle has 4 (isocitrate to alpha-ketoglutarate, alpha-ketoglutarate to succinyl-CoA, succinate to fumarate, and malate to oxaloacetate).

Multiple choice biology respiration in plants amphibolic pathway living organisms and energy production life processes in living organisms- part 1

During amphibolic pathway, acetyl Co-A can perform the biosynthesis of 

  1. Amino acid

  2. Gibberellic acid

  3. Fatty acid

  4. All of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Fatty acid synthesis takes place in the cytoplasm of the cell. It is the creation of fatty acids from acetyl-CoA and NADPH through the action of enzymes called fatty acid synthases. Most of the acetyl-CoA which is converted into fatty acids is derived from carbohydrates via the glycolytic pathway. 

So, the correct option is 'Fatty acid'.

Multiple choice biology respiration in plants amphibolic pathway living organisms and energy production life processes in living organisms- part 1

Find the incorrect match (with respect to ATP gain) -

  1. Bacterial cell - $38$ ATP or $2$ ATp
  2. Citric Acid Cycle - $12$ ATP
  3. Nerve cell - $38$ ATP
  4. Liver cell - $38$ ATP
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The Kreb’s Cycle gives 3 moles of NADH, 1 mole of FADH and 1 mole of ATP per cycle of substrate i.e per 1 mole of Acetyl CoA. However net ATP i.e after ETS which would make the answer to 12 ATP(9+2+1) respectively.

36 ATPs are produced in Aerobic Respiration involving the complete breakdown of glucose molecule into carbon-dioxide and water using oxygen as final electron aceptor

Complete oxidation of glucose molecule takes place in 3 sequential reactions -

1.Glycolysis occuring in cytoplasm

2.Kreb cycle occuring in mitochondrial matrix

3 Electron transport chain (ETC )and oxidative phosphorylation occuring in inner mitochondrial membrane . So,total number of ATPs produced in aerobic respiration are

Glycolysis - 6/8 ATPs

Link reaction and kreb cycle - 30ATPs

Total -36/38 ATPs.


So, the correct option is 'Option A'.