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 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 '$24$'

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

When one molecule of sucrose is subjected to phosphorylation how many ATPs are consumed?

  1. 2

  2. 6

  3. 3

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

During the conversion of fructose-1,6-bis-phosphate to lactate, the pathway generates a total of four molecules of ATP, resulting in a net yield of two ATP per glucose consumed.

correct answer is A.

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

In which of the following steps dehydrogenate occurs? 

  1. glucose $\rightarrow$ glucose 6-phosphate
  2. 3 - PGA $\rightarrow$ 2 - PGA
  3. PEPA $\rightarrow$pyruvate
  4. PGAL $\rightarrow$ 1, 3diPGA
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
The G6PDwhich is glucose dehydrogenate gene provides instructions for making an enzyme called glucose-6-phosphate dehydrogenase. This enzyme, which is active in virtually all types of cells, is involved in the normal processing of carbohydrates. This enzyme helps protect red blood cells from damage and premature destruction.
So, the correct answer is glucose $\rightarrow$ glucose 6-phosphate

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

In pentose phosphate pathway, which of the following process is lacking?

  1. Kreb's cycle

  2. Glycolysis

  3. Oxidative phosphorylation

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

The pentose phosphate pathway also called the hexose monophosphate shunt, is a shunt from glycolysis designed to produce either NADPH or ribose or both. There are two distinct phases in the pathway. The first is the oxidative phase, in which NADPH is generated, and the second is the non-oxidative synthesis of 5-carbon sugars. In the pentose phosphate pathway, glucose 6-phosphate is directly oxidized without entering glycolysis. Even Kreb's cycle and oxidative phosphorylation doesn't happen in pentose phosphate pathway.

So, the correct answer is 'All of the above'.


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

During the complete oxidation of one glucose, how many reduced coenzymes are produced due to following processes?
(A) Link reaction
(B) Glycolysis
(C) Krebs cycle
Choose the correct option from the following.

  1. $A = 1, B = 1, C = 4$
  2. $A = 2, B = 2, C = 4$
  3. $A = 2, B = 2, C = 3$
  4. $A = 2, B = 2, C = 8$
Reveal answer Fill a bubble to check yourself
A,D Correct answer
Explanation

In the oxidation of one glucose molecule, during aerobic respiration, 2NADH2 in link reaction, 2NADH2 in glycolysis, 8NADH2 in Krebs cycle are formed.

So, the correct option is ‘A=1, B=1, C=4 or A=2, B=2, C=8’.

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

How many ${ CO } _{ 2 }$ molecules are produced from one pyruvate on complete oxidation :-

  1. 1

  2. 2

  3. 3

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

During the complete oxidation of pyruvate, two carbon atoms are lost in the form of CO2 - one during the conversion of isocitrate to alpha-ketoglutarate and the second during the conversion of alpha-ketoglutarate to succinyl CoA.
So, the correct answer is '2'.
Multiple choice bio-chemistry respiration in organisms glucose metabolism the need for energy in living organism respiratory function

Sequence of aerobic metabolic breakdown of glucose is

  1. Glycolysis-transition-citric acid cycle-electron transport system

  2. Transition-glycolysis-electron transport-citric acid cycle

  3. Electron transport system-citric acid cycle- transition-glycolysis

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

  • For the aerobic respiration the substrate glucose has  to undergo a following set of process 
  • First of which is glycolysis where the molecule of glucose is broken down to 2 molecules of pyruvate.
  • These pyruvate molecules are to be cconverted to Acetyl CoA so that it can enter the mitochondrial membrane and undergo kerb cycle.
  • After being converted to acetyl coA it takes part in kerb cycle where molecules of NADH, FADH and ATP are formed.
  • These NADH, FADH molecules are the electron acceptors which are used in ETS to transport electron and hydrogen ions through the complexs.
  • These electrons and hydrogen ions are used for the formation of ATP via ATP synthase.
  • Therefore the process for the aerobic breakdown of glucose is Glycolysis followed by transition of pyruvate then citric acid cycle which is followed by electron transport system.
  • Therefore the correct answer is 'Glycolysis-transition-citric acid cycle-electron transport system'








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

How many oxygen atoms are required for the complete oxidation of one molecule of pyruvate?

  1. 2

  2. 5

  3. 4

  4. 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Under Anaerobic conditions, Pyruvic Acid enters in matrix of mitochondrion and undergoes oxidative decarboxylation to form 2 carbon energy rich compound called Acetyl Co A.

This process utilizes 2 oxygen atoms. Incomplete oxidation of Pyruvate leads to the formation of lactic acid in muscles and formation of ethyl alcohol in yeast as a process of fermentation.

So, the correct answer is '2'

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

How many molecules of NADH are produced when four molecules of phosphoglyceraldehde are converted into four molecules of pyruvate?

  1. $2$
  2. $6$
  3. $8$
  4. $4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Glycolysis is a series of reactions that extract energy from glucose by splitting it into two three-carbon molecules called pyruvates. Glycolysis takes place in the cytosol of a cell, and it can be broken down into two main phases: the energy-requiring phase and  the energy-releasing phase. Each three-carbon sugar is converted into another three-carbon molecule, pyruvate, through a series of reactions. In these reactions, ATP molecules and one NADH molecule are made. Because this phase takes place twice, once for each of the two three-carbon sugars, it makes four ATP and two NADH overall.

So the correct option is '2'.