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 properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

With reference to enzymes, which one of the following statements is true?

  1. Apoenzyme = Holoenzyme+ Coenzyme

  2. Holoenzyme= Apoenzyme + Coenzyme

  3. Coenzyme= Apoenzyme + Holoenzyme

  4. Holoenzyme= Coenzyme+ Apoenzyme
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Enzymes work efficiently in association with various factors which enhances it's activity. These factors may be;

Coenzymes are organic molecules that are mostly derivatives of vitamins soluble in water by phosphorylation. Example of coenzyme include thiamine pyrophosphate (TPP), flavin adenine dinucleotide (FAD), biotin

Apoenzyme is an inactive form of enzyme lacking the association of coenzyme and/or cofactors. Activation of the enzyme occurs upon binding of an organic or inorganic cofactor.

Holoenzyme is a complete and catalytically active form of enzyme. An apoenzyme together with its cofactor is holoenzyme.  Examples of holoenzymes include DNA polymerase and RNA polymerase which contain multiple protein subunits.

So the correct option is 'Holoenzyme= Apoenzyme + Coenzyme'.
Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

Arrange the steps of catalytic action of an enzyme in order and select the correct option.
I.   The enzyme release the products of the reaction      and the enzyme is free  to bind to another                substrate.
II.  The active site of enzyme is in close proximity of      the substrate and breaks the chemical bonds of     the subtrate.
III. The binding of sustrate induces the enzyme to          alter its shape fitting more tightly around the           sustrate. 
IV.The substrate binds to the active site of the              enzyme.

  1. IV, III, II, I

  2. III, II, I, IV

  3. IV, II, I, III

  4. II, I, IV, III
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Four Steps of Enzyme Action:
1) The enzyme and the substrate are in the same area. Some situations have more than one substrate molecule that the enzyme will change.
2) The enzyme grabs on to the substrate at a special area called the active site. A process called catalysis.
3) The binding of substrate induces the enzymes to alter its shape to fit around the substrate. 
4) The enzyme breaks the chemical bonds of the substrate and releases the product of the reaction and the enzyme is free to bind to another substrate.

So, the correct option is 'IV, III, II, I'.

Multiple choice properties of enzyme enzyme properties enzymes biomolecules: chemical constituents of living cells biology

In biochemical reactions, the enzymes act by

  1. By decreasing the energy of the reactants

  2. By increasing the activation energy of the reaction

  3. By decreasing the activation energy of the reaction

  4. By increasing the energy of the products of the reaction

  5. By decreasing the energy of the products of the reaction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The minimum energy requirement that must be met for a chemical reaction to occur is called the activation energy. The activation energy is the energy difference between the reactants and the activated complex, also known as transition state. In a chemical reaction, the transition state is defined as the highest-energy state of the system. If the molecules in the reactants collide with enough kinetic energy and this energy is higher than the transition state energy, then the reaction occurs and products form. In other words, the higher the activation energy, the harder it is for a reaction to occur and vice versa. However, if a catalyst is added to the reaction, the activation energy is lowered because a lower-energy transition state is formed. Enzymes can be thought of as biological catalysts that lower activation energy. Enzymes are proteins or RNA molecules that provide alternate reaction pathways with lower activation energies than the original pathways. Enzymes affect the rate of the reaction in both the forward and reverse directions; the reaction proceeds faster because less energy is required for molecules to react when they collide. Thus, the rate constant (k) increases.
So, the correct answer is option C.

Multiple choice physics the essence of change forms of energy and energy conservation energy for everything forms of energy

The energy stored in food is :

  1. Electrical

  2. Heat

  3. Chemical

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

 chemical energy is the potential of a chemical substance to undergo a transformation through a chemical reaction to transform other chemical substances.

heat energy is due to temperature.
in food different different reaction occurs which provide energy to run the body, so energy possessed in food is chemical energy.
option C.

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'.