Biology

Cellular Respiration and Enzymes

1,721 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 biology animal tissue muscular tissues muscle tissue muscle tissues

The ready source of energy in living cells is

  1. Glucose

  2. ATP

  3. Glycogen

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

In living cells, energy for immediate use is stored as molecules of ATP or adenosine triphosphate. When the energy is used, one of the phosphates attached to ATP is released, giving ADP or adenosine diphosphate. it is known as the energy currency of a cell and these are produced in the mitochondria. So, the correct answer is option B.

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

The pentose monophosphate shunt is more advantageous than Krebs cycle as

  1. It yields more ATP

  2. Ribose sugar is released, which helps in nucleic acid formation

  3. It releases more oxygen

  4. It utilizes less oxygen
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Pentose phosphate pathway is also known as HMP shunt. This pathway provides an alternative route for carbohydrate breakdown. HMP shunt produces some glycolytic intermediates like glyceraldehyde-3-phosphate and fructose-6-phosphate. These intermediates can directly involve in the glycolysis pathway and then in the Krebs cycle. The cycle provides ribose sugar which can be used for the synthesis of nucleic acids. This pathway is considered as advantageous since the ribose sugar is made available. 

Thus, the correct answer is option B. 

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

A respiratory cycle where mainly ${NADPH _2}$ are produced is 

  1. Calvin cycle

  2. Kreb's cycle

  3. EMP pathway

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

During Calvin cycle, $NADH _2$ are not produced. 
During Krebs cycle, 2 $NADH _2$, 1 $FADH _2$, 1GTP are produced. 
During EMP pathway 2 NADH, 2 ATP are produced. 
During HMP pathway, $NADPH _2$ are produced. So, in respiratory cycle  mainly $NADPH _2$ are produced is HMP pathway. Thus, option D is correct.

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

Pentose phosphate pathway is a mode of

  1. Amphibolic pathway

  2. Anabolic pathway

  3. Aerobic respiration

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

Pentose phosphate pathway is an alternative pathway to glycolysis which involves the oxidation of glucose-6-phosphate to 6-phosphogluconic acid which in turn gets converted into pentose phosphates. This pathway involve the direct oxidation of glucose-6-phosphate without entering glycolysis and hence is termed as direct oxidation. 

Thus, the correct answer is option C. 

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

Which of the following is generated in the oxidative phase of pentose phosphate pathway?

  1. NADPH

  2. FADH

  3. GTP

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

The Pentose Phosphate Pathway is an alternative pathway to glycolysis and TCA cycle. It occurs in both prokaryotes and eukaryotes in their cytoplasm

Glucose is broken down by a series of pathways.
The pathway has 2 phases- Oxidative and Non-oxidative.
In the oxidative stage, there are 2 steps where NADP⁺ gets converted to NADPH.
1. Glucose 6-phosphate converts to 6-phosphogluconolactone
2. 6-phosphogluconate converts to Ribulose 5- phosphate
So, the correct option is 'NADPH'

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

Pentose phosphate pathway takes place only in the

  1. Cytoplasm

  2. Mitchondria

  3. Peroxisome

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

The pentose phosphate pathway is a metabolic pathway which is carried out in most of the organisms. This pathway occurs parallel to glycolysis. This pathway produces pentoses from glucose 6-phosphate. The pathway takes place in the cytoplasm in most of the organisms. In the case of plants, there are certain reactions which occur in the plastids.

Thus, the correct answer is option A. 

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

Pentose phosphate pathway takes place only in the

  1. Cytoplasm.

  2. Mitochondria.

  3. Peroxisome.

  4. Chloroplast.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The pentose phosphate pathway is a metabolic pathway which is carried out in most of the organisms. This pathway occurs parallel to glycolysis. This pathway produces pentoses from Glucose 6-phosphate. The pathway takes place in the cytoplasm in most of the organisms. In the case of plants, there are certain reactions which occur in the plastids.
Thus, the correct answer is option A. 
Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

An enzyme used in pentose phosphate pathway is

  1. RUBP.

  2. Aldolase.

  3. Pyruvate kinase.

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

In the pentose phosphate pathway 6-Phosphogluconate dehydrogenase (6PGD) is an enzyme that produces NADPH by converting 6-phosphogluconate to ribulose 5-phosphate. NADPH is used for lipid production. Thus the correct answer is option D.

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

Consider the following statements.


a. The Pentose Phosphate Pathway supplies Erythrose-$4$-Phosphate which is the starting material the synthesis on lignin.
b. The Pentose Phosphate pathway also occurs in plastids.
c. NADPH is generated by the Pentose phosphate pathway

Which of the statements given are correct?

  1. $a$ and $b$ only
  2. $a$ and $c$ only
  3. $b$ and $c$ only
  4. $a, b$ and $c$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

The substrate for pentose phosphate pathway is

  1. Glucose 6-phosphate.

  2. Glucose 1-phosphate.

  3. Fructose 6-phosphate.

  4. Fructose 1-phosphate.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Pentose Phosphate Pathway runs parallel to glycolysis and takes place in the cytoplasm. The oxidation steps, utilizing glucose-6-phosphate (G6P) as the substrate, occur at the beginning of the pathway and are the reactions that generate NADPH and also give five carbon compound for glycolysis.

So the correct option is 'Glucose 6-phosphate'.

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

Which one of the following produces more energy per glucose molecule?

  1. Alcoholic fermentation

  2. Glycolysis

  3. Pentose phosphate pathway

  4. Lactic acid fermentation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Glycolysis is a common pathway between the aerobic and anaerobic respiration. The net amount of ATP formed during glycolysis is two.

Alcoholic fermentation and lactic acid fermentation are both of pathways involved in the anaerobic respiration in which the pyruvic acid formed after glycolysis is converted into lactic acid or ethanol and carbon dioxide. The energy released during anaerobic respiration is much less as compared to the aerobic respiration.
So the correct option is, 'pentose phosphate pathway'

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

In hexose monophosphate shunt, the net formation of ATP molecules is

  1. 36

  2. 35

  3. 38

  4. 34
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hexose monophosphate shunt is an alternative pathway to glycolysis or the tricarboxylic acid cycle for glucose oxidation. It occurs in the cytoplasm and has two phases; the oxidative phase and the non-oxidative phase. 

This is the only process that generates reduced NADPH₂ which act as the reducing agent in the biosynthetic processes.
6 glucose molecules that enter hexose monophosphate shunt, produces 12 NADPH₂ and 6 carbon dioxide.
12 NADPH₂ molecules when undergo ETS forms  36 molecules of ATP.
So, the correct option is '36'

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry


Which of the following is not a pathway that relates to generation of ATP?

  1. Pentose phosphate shunt

  2. Embden-Meyerhof pathway

  3. Oxidative-phosphorylation

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

  • Pentose phosphate shunt is the pathway that is used for the synthesis of a 5 carbon molecules such as ribose and deoxyriose which can be used for the synthesis of nucleotides, no ATP is produced during this reaction.
  • EMP pathway is the glycolysis process where 2 ATP are produced at the end of the reaction.
  • Oxidative phosporylation is the pathway that is used to reduce the NADH and FADH for the formation of ATP
  • And photosynthesis is the pathway in the plant that is used for the production of the carbohydrates that are used in the catabolic pathway for the synthesis of the ATP in cellular respiration.
  • Therefore the correct answer is option is 'Pentose phosphate shunt'.











Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

Production of $NADPH _2$ is not linked with ATP generation in

  1. Photorespiration

  2. Light recation

  3. Hexose monophosphate pathway

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

Hexose monophosphate pathway (HMP) or pentose phosphate shunt is an alternate glucose metabolism that occurs in adipose tissues, liver, erythrocytes, testes, adrenal glands, mammary glads etc. This pathway is performed to generate the $NADPH _2$ to facilitate the cholesterol synthesis, steroid and lipid production and fatty acid synthesis. Thus signifying that HMP pathway readily takes place in tissues associated with lipogenesis like liver and adipose tissue. It is not linked with ATP generation. Also, the ribose sugars generated are used in DNA and RNA and many nucleotides like $ATP$, $FADH _2$ $CoA$ etc.

Photorespiration, light reaction and dark reaction are associated with phosphorylation.
Hence, the correct answer is 'Hexose monophosphate pathway'

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

Warburg-Dickens pathway is also known as

  1. P.P.P.

  2. TCA cycle.

  3. EMP pathway.

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

Pentose phosphate pathway (PPP) is variously called as Warburg-Dickens pathway and hexose monophosphate shunt. This metabolic pathway had been discovered through a number of experiments of Lippman, Warburg (1935) and Dickens (1938).