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 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
D Correct answer
Explanation

The Pentose Phosphate Pathway (PPP) produces Erythrose-4-phosphate, which is a precursor for aromatic amino acids and lignin biosynthesis. It occurs in the cytosol and in plastids (such as chloroplasts), and it generates NADPH as a primary reducing equivalent.

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

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). 

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

Oxidation of glucose to CO$ _2$ and water occurs during

  1. Glycolysis

  2. Pentose phosphate pathway

  3. Krebs cycle

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

Pentose phosphate pathway is the only pathway in which glucose is completely oxidised to CO$ _2$ and H$ _2$O. It is also called HMP (hexose monophosphate shunt) as it is an alternate pathway to glycolysis. The primary substrate glucose is first phosphorylated to glucose-6-phosphate in presence of G6PD by consuming 1 ATP. A net gain of 35 ATP is achieved by oxidation of 1 molecule of glucose.

So the answer is 'Pentose phosphate pathway'.

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

Which of the following enzyme helps in conversion of 6-phosphogluconate to ribulose-5-phosphate?

  1. 6-phosphogluconate dehydrogenase

  2. Hexokinase

  3. Alpha-ketoglutarate

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

This conversion takes place during the oxidative phase of the pentose phosphate pathway.

Here, When 6-phosphogluconate converts to ribose 5-phosphate, the enzyme used is 6-phosphogluconate dehydrogenase. 
In this step an NADP⁺ converts to NADPH and CO₂ is released.
So, the correct option is '6-phosphogluconate dehydrogenase.'

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry
Which of the following cellular metabolic processes can occur both in the presence or absence of ${O} _{2}$?

  1. Glycolysis

  2. Fermentation

  3. TCA cycle

  4. Electron transport coupled with chemiosmosis
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Glycolysis is an oxidative process in which one molecule of glucose is partially oxidised into two molecules of pyruvate in a series of enzyme catalysed reactions. Glycolysis, the major pathway for glucose metabolism, occurs in the cytosol of cells. It is a unique pathway that occurs aerobically as well as anaerobically and does not involve molecular oxygen.

Multiple choice bio-chemistry respiration in organisms glucose metabolism the need for energy in living organism respiratory function
Which is true about the end products of glycolysis?
  1. $2\,pyruvic \,acid+2ATP+{2NADH} _{2}$
  2. $2\,pyruvic \,acid+{2NADH} _{2}$
  3. $1\,pyruvic \,acid+2ATP+{2NADH} _{2}$
  4. $2\,pyruvic \,acid+1ATP+{1NADH} _{2}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
In glycolysis, two molecules of ATP are consumed during two phosphorylation reactions to form fructose 1, 6-biphosphate. In return, four molecules of ATP are produced by substrate-level phosphorylation (conversion of 1, 3-biphosphoglycerate to 3-phosphoglycerate and phosphoenolpyruvate to pyruvate). Two molecules of ${NADH} _{2}$ are formed at the time of oxidation of glyceraldehyde 3-phosphate to 1, 3-biphosphoglycerate. The net reaction of glycolysis is as follows:

$Glucose+{2NAD}^{+}+2ADP+{2H} _{3}{PO} _{4}\rightarrow2Pyruvate+2NADH+{2H}^{+}+2ATP$

Each NADH is equivalent to 3 ATP, so the net gain in glycolysis is 8 ATP.

So the correct answer is '$2\,pyruvic \,acid+2ATP+{2NADH} _{2}$'.
Multiple choice bio-chemistry respiration in organisms glucose metabolism the need for energy in living organism respiratory function

For the start of respiration, a living cell requires

  1. Glucose
  2. Glucose + $O _2$
  3. $O _2$

  4. Glucose + ATP
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The mechanism of respiration is initiated by breaking down glucose to pyruvic acid without the help of oxygen. The initial process occurs in the cytosol of cells which requires glucose as well as ATP molecules which provide energy for the process to start. This initial process is known as glycolysis and it takes place in 10 steps in which total 4 ATP molecules are produced and 2 ATP molecules are consumed. Thus, these are the net production of 2 ATP molecules. 

Thus, the correct answer is option D. 

Multiple choice bio-chemistry respiration in organisms glucose metabolism the need for energy in living organism respiratory function

How many ATP are produced in mitochondria on complete oxidation of glucose?

  1. $24$
  2. $30$
  3. $34$
  4. $38$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Name of process   Site  Total ATP formation
 Glycolysis  Cytoplasm  2NADH(i.e. 6ATP)+ 2ATP = 8ATP 
 Conversion of pyruvate to acetyl CoA  Cytoplasm  2NADH = 6ATP
 Kreb's cycle  Mitochondria  6NADH + 2 FADH + 2GTP= 18ATP +4ATP + 2ATP  = 24 ATP

 1 NADH = 3 ATP, 1 FADH = 2 ATP

So, the correct answer is '$24$'