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 parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Anaerobic process that takes place after glycolysis is called as

  1. TCA

  2. Calvin cycle

  3. Krebs cycle

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

Anaerobic process after glycolysis is called as fermentation. Fermentation could be defined as a metabolic process, that converts sugar into acids, gases and alcohol. It occurs in yeast and bacteria, but also in oxygen-starved muscle cells, as in the case of lactic acid fermentation.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

What is common in common pathway of aerobic respiration

  1. Glycolysis in both aerobic and anaerobic respiration

  2. Krebs cycle common with HMP

  3. Terminal oxidation in both aerobic and anaerobic respiration

  4. Krebs cycle in both aerobic and anaerobic respiration
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Aerobic respiration is the oxidative breakdown of respiratory substrates with the help of atmospheric oxygen. It takes place in three steps: Glycolysis, Kreb's cycle and electron transport chain. Anaerobic respiration is the breakdown of respiratory substrates in the absence of atmospheric oxygen. The first step of aerobic respiration as well as anaerobic respiration is same and takes place in the cytoplasm of cells. Glycolysis is the common pathway of both the processes in which glucose is broken down anaerobically into two molecules of pyruvic acid. 

Thus, the correct answer is option A. 

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Read the following four statements (A-D)
A) In fermentation, less than seven percent of the energy in glucose is released
B) Glycolysis occurs in the cytoplasm of the cell and is present only in anaerobic organisms
C) The number of ATP molecules synthesized in ETS depends on the nature of the electron donor
D) In glycolysis, glucose undergoes coin, complete oxidation to form two molecules pyruvic acid
How Many of the above statements are correct?

  1. 1

  2. 2

  3. 3

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

A) In fermentation, less than seven percent of the energy in glucose is released because only two ATPs are produced at this stage compared to the total number of 32 ATPs in aerobic respiration. The percentage of energy produced is thus (2/32)*100=6.25%.


C) When electrons are transferred from one carrier to next carrier via complexes I to IV in ETS, they are coupled to the production of proton motive force by transport of protons from the lumen to the inner mitochondrial membrane. The number of protons displaced will ultimately determine the number of ATP molecules that will be produced, i.e. for NADH it will be 2.5 and for FADH2 it will be 1.5.


So, the correct option is '2'.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

If one triose phosphate completely oxidized inside the prokaryotic cell, then the net gain of ATP of energy is equal to

  1. $5$ ATP
  2. $4$ ATP
  3. $20$ ATP
  4. $19$ ATP
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If one triose phosphate completely oxidized inside the prokaryotic cell, then the net gain of ATP of energy is equal to the summation of the ATPs produced at different steps. In the glycolysis step 2 ATP and 1 NADH will be produced followed by 1 NADH in the gateway reaction and 1 GTP, 3 NADH and 1 FADH2 in the TCA cycle. This will add up to 20 ATPs.


So, the correct option is '20 ATP'.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

The total number of ATP's formed when one molecule of glucose is oxidized to $CO _2$ to $H _2 O $ is

  1. 32

  2. 38

  3. 42

  4. 40
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
One molecule of the glucose that enters in the glycolysis produces 2 molecules pyruvate and 2 molecules of NADH$ _{2}$ and 2 ATP.  2 molecules of pyruvate will form 2 molecules of Acetyl Co-A and this will release 2 NADH$ _{2}$. These 2 Acetyl Co-A will enter into Kreb's cycle and will release 6NADH$ _{2}$, 2FADH$ _{2}$ and 2ATP.
so, the total gain before the ETC (electron transport chain) comes out to be  10NADH$ _{2}$, 2FADH$ _{2}$ and 4ATP.
Now, during the electron transport chain, 
10NADH$ _{2}$ will give 10 X 3=30 ATP
2FADH$ _{2}$ will give 2 X 2= 4 ATP
So, 34 ATP from ETC and 4 ATP from Kreb's cycle will be 38 ATP.
Hence, the correct answer is '38'
Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Total $ATP$ through aerobic EMP pathway can be

  1. $6$
  2. $10$
  3. $2$
  4. $8$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Glycolysis is also known as 'EMP pathway'. It was discovered by three scientist Gustav Embden, Otto Meyerhof, and Jakub Karol Parnas. That's why glycolysis is also known as the EMP pathway. In the EMP pathway, total 8 ATP are produced.

So, the correct answer is '8 ATP'.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Hydrogen acceptor in cellular respiration is 

  1. NAD

  2. FAD

  3. NADP

  4. Both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

NAD (Nicotinamide adenine nucleotide) is an electron carrier. It is reduced by accepting a single hydrogen atom and an electron pair from H$ _2$ atom and other electron freed into the medium. NAD is reduced to NADH in citric acid cycle and glycolysis.
FAD (Flavin adenine dinucleotide) is an electron carrier. It is reduced by accepting a full hydrogen H$ _2$ atom. The FAD is reduced to  FADH$ _2$ in the citric acid cycle.
NADP is also an electron carrier. NADP is reduced into NADPH in the photosynthesis.
So, the correct answer is ' NAD & FAD '.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

For glycolysis to continue,all cells require

  1. O2

  2. Mitochondria

  3. ETS

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

Glycolysis is the only process of extraction of energy in anaerobic organisms. Thus, It never requires O$ _2$ for its completion. Since the process takes place solely in cytoplasm so never requires any other organelle for its completion. As ETS takes place in mitochondria so it never takes part in glycolysis. For uninterrupted working of glycolysis, we require NADP$^+$ as it is required for the production of NADP$^+$+H$^+$ during conversion of 3-Phosphoglyceraldehyde to 1,3-bisphospho glyceraldehyde. 

So, the correct answer to the question is 'NADP$^+$'.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

The net gain of ATP molecules through glycolysis is

  1. 6

  2. 4

  3. 8

  4. 36
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Although four ATP molecules are produced in the second half, the net gain of glycosis is only two ATP because two ATP molecules are used in the first half of glycosis.
Glycosis produces 2 ATP, 2 NADH, and 2 pyruvate molecules.
2ATP + 2 NADP $\rightarrow$ 8 ATP
So, the correct answer is '8 ATP'.
Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Glycolysis is a:

  1. Redox process

  2. Aerobic process

  3. Oxidative process

  4. Reductive process
Reveal answer Fill a bubble to check yourself
A,B Correct answer
Explanation

Glycolysis is a redox as well as an aerobic process. It takes place in presence of oxygen that's why this process is known as an aerobic process. In glycolysis oxidation as well as reduction takes place that's why this process is also known as redox process.


So, the correct answer is 'Glycolysis is a redox as well as an aerobic process'.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Which of the following steps of respiration is amphibolic?

  1. Glycolysis

  2. Oxidative decarboxylation of pyruvate

  3. TCA cycle

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

The term amphibolic is used to describe a biochemical pathway that involves both catabolism and anabolism. These are the most common ways smaller organic molecules can be formed into more complex ones and applies to the formation of carbs, proteins, lipids, and nucleic acids. Other type called reduction reaction, which involves the adding of hydrogens and electrons to a molecule. it gains calories of energy because energy is released when a hydrocarbon bond is split. Pathways of glycolysis are amphibolic pathways because they provide ATP and chemical intermediates to build new cell material. The fundamental metabolic pathways of biosynthesis are similar in all organisms, in the same way, that protein synthesis or DNA structure are similar in all organisms.

So the correct option is 'glycolysis'.

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

Which of the following is the major regulatory enzyme of Glycolysis?

  1. Hexokinase

  2. phosphofructokinase

  3. aldolase

  4. phosphor-triose-isomerase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • In first step of glycolysis, glucose is converted in to glucose -6- phosphate by the enzyme Hexokinase or Glucokinase.
  • Hexokinase is available for all cell where as Glucokinase acts only for liver cell.
  • It also require magnesium as cofactor.
  • Hexokinase is the major regulatory enzyme of Glycolysis.
Hence, the correct answer is 'Hexokinase'

Multiple choice parts of respiration cellular respiration the respiratory system breathing for energy biology types of respiration

During the stage in the complete oxidation of glucose are the greatest number of ATP molecules formed from ADP.

  1. Glycolysis

  2. Krebs cycle

  3. Conversion of pyruvic acid to acetyl Co-A

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

Glycolysis, part of cellular respiration, is a series of reactions that constitute the first phase of most carbohydrate catabolism, catabolism meaning the breaking down of larger molecules into smaller ones. The word glycolysis is derived from two Greek words and means the breakdown of something sweet. Glycolysis breaks down glucose and forms pyruvate with the production of two molecules of ATP. The pyruvate end product of glycolysis can be used in either anaerobic respiration if no oxygen is available or in aerobic respiration via the TCA cycle which yields much more usable energy for the cell.

So the correct option is 'glycolysis'.