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 bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

In prokaryotic cells, the number of ATP generated form one glucose molecule is _______

  1. $36$
  2. $38$
  3. $34$
  4. $32$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In the eukaryotic ell, the aerobic respiration occurs in mitochondria as well as the cytoplasm. The Electron Transport Chain (ETC) that yields the maximum ATPs is located in the inner membrane of the mitochondria. So, the NADH made during the glycolysis in cytoplasm have to be transferred to the mitochondria using the shuttle system and for this, 2 ATPs are consumed. However, in the bacterial cell, since there is no mitochondria, the whole process of respiration occurs within the cytoplasm so no ATP is consumed in transporting across the organelle. Therefore, 38 ATPs are made form one glucose in bacteria while 36 are made in an eukaryotic cell.

Hence, the correct answer is '38'

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

Energy released by oxidation of one molecule of glucose is -

  1. 800 K.cal

  2. 695 K. cal

  3. 686 K.cal

  4. 700 K.cal
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

When 1 mol (180 g) of glucose reacts with oxygen under standard conditions, 686 kcal of energy is released. 36 ATP synthesised in aerobic respiration. Total free energy stored as high energy phosphate bonds in ATP is therefore 252kcal. The remaining energy is lost. So, the correct option is '686 K.cal'.


Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

The energy stored in one molecule of NADPH and one molecule of ATP are ....... and ...... respectively.

  1. 52 kcal, 7 kcal

  2. 520 kcal, 70 kcal

  3. 150 kcal, 22 kcal

  4. 650 kcal, 90 kcal
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Nicotinamide adenine dinucleotide phosphate is abbreviated as NADP, is a cofactor used in anabolic reactions, such as lipid and nucleic acid synthesis, which require NADPH as a reducing agent. It produces 52 kCal of energy from one molecule. Adenosine triphosphate used in cells as a energy currency, often called the molecular unit of currency of intracellular energy transfer. ATP is therefore continuously recycled in organisms: the human body, which on average contains only 250 grams of ATP.  One molecule of ATP produces 7kCal of energy.

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

How many ATP are synthesized per sucrose molecule(gross synthesis) in aerobic respiration through substrate level phosphorylation?

  1. $10$
  2. $12$
  3. $30$
  4. $76$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

C- In substrate-level phosphorylation, 2 ATP are synthesized from glycolysis and 2 ATP from Krebs cycle Oxidative phosphorylation that is, 2 × 1.5 ATP or 2 × 2.5 ATP (in malate-aspartate shuttle). Thereby, from the oxidative decarboxylation of pyruvate there shall be 2 NADH+H+ and 6 from Krebs cycle making it – (a) 8 × 2.5 ATP & 2 FADH2 from the Krebs cycle, (b) 2 × 1.5 ATP; thus summing it up to 4 + 3 (or 5) + 20 + 3 = 30 (or 32) ATP per molecule of glucose.

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

Common immediate source of energy for cellular activity is

  1. Glucose.

  2. Aldohexose.

  3. ATP.

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

Adenosine triphosphate (ATP) is a nucleotide with three phosphates. It is the universal energy currency for all cellular metabolic processes. Endergonic processes are driven by energy input using hydrolysis of ATP. Exergonic processes are coupled to ATP synthesis. 

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

What is the energy coin of a cell?

  1. DNA

  2. RNA

  3. ATP

  4. Minerals
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • During cellular metabolism, energy is frequently exchanged between endergonic and exergonic reactions and molecules.
  • The ATP is a universal energy currency, which is used in these cellular energy exchanges.
  • The reason has been that is ATP can be formed easily by the process of phosphorylation of ADP as suggested by the chemiosmotic theory.
  • Further, one molecule of ATP has two terminal high energy acid anhydride bonds, which can break easily to provide energy. 
  • Therefore, ATP can be both formed easily as well as broken easily. 

    Hence, correct option is C.
Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

The number of ATP molecules produced during the production of 1 molecule of acetyl Co-A from 1 molecule of pyruvic acid is

  1. 3 ATP.

  2. 8 ATP.

  3. 36 ATP.

  4. 38 ATP.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Pyruvic acid is the end product of glycolysis. It is translocated into mitochondria for complete oxidation to carbon dioxide and water. Inside mitochondria first pyruvic acid is oxidatively decarboxylated into acetyl coA. In this process the three carbon atom containing pyruvic acid is converted to two carbon atom containing acetyl CoA and a molecule of carbon dioxide is released. The acetyl coA is fed into the Kreb's cycle. 

During oxidative decarboxylation of pyruvic acid one molecule of reduced coenzyme $NADH _2$ is synthesized. The reduced coenzyme $NADH _2$ can be metabolised by mitochondrial electron transport system, when one molecule of $NADH _2$ produces 3 ATP molecules by  the process of oxidative phosphorylation.

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

Which molecule is responsible for storing energy that can be used to do cellular work?

  1. DNA

  2. Fat

  3. ATP

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

Energy derived from light or chemical compounds is stored in the form of ATP, it is a energy resource compound found across all organisms. Which can be hydrolyzed by the cell to derive energy for all its activities

So, the correct answer is 'ATP'

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

The enzyme ATP synthase is part of the process required to synthesize ATP from ADP and inorganic phosphate in the mitochondria.

Which of the following conditions would stimulate the synthesis of ATP?

  1. A slowdown of glycolytic activity

  2. Elevated oxygen levels

  3. A build up of the proton gradient

  4. Decreased substrate-level phosphorylation in the cytoplasm
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

A build up of proton gradient in the mitochondrial matrix is used by the ATP synthase to generate ATP from ADP and iP, this is also referred to as PMF or the free energy released by passive movement of protons from the mitochondrial matrix into the cytoplasm.

So, the correct answer is 'A build up of the proton gradient'

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

One molecule of NADH$ _{2}$ on oxidation yields ............... ATP molecules.

  1. One

  2. Two

  3. Three

  4. Four
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The NADH$ _2$ and the FADH$ _2$ are produced during the cycles of respiration. These molecules are produced during the glycolysis and the Krebs cycle. These molecules are oxidized in the process of electron transport system. This is the system in which the electrons is donated from one donor to acceptor. These products are oxidized and the protons are used for creating a gradient which is used in the synthesis of ATP. NADH$ _2$ transfers the electrons to the complex I and then transfers the electrons to the complex II. This results in more number of protons which are pumped by ATP synthase. So, the more protons will result in the production of 3 ATPs.
Thus, the correct answer is option C. 
Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

The total amount of energy released from one molecule of glucose on oxidation is about 

  1. $1600 kJ$
  2. $2300 kJ$
  3. $2500 kJ$
  4. $2900 kJ$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The glucose molecule is oxidised to form pyruvic acid which is further oxidised to release water and carbon dioxide. When one glucose molecule is completely oxidised, 38 ATP molecules are formed. The energy of the 38 ATP is equal to about 2900 kJ or 686 kcal of energy. The equation of the glucose oxidation is given as 

C$ _6$ H$ _{12}$ O$ _6$ + 6O$ _2$ $\rightarrow$ 6CO$ _2$ + 6H$ _2$O + 2900 kJ energy
Thus, the correct answer is option D. 

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

How much of the energy released during aerobic respiration is approximately conserved in the form of ATP?

  1. $20\%$
  2. $40\%$
  3. $60\%$
  4. $100\%$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Aerobic respiration is a breakdown of organic material in the presence of oxygen. It takes place in the cytoplasm and mitochondria of the cell. During aerobic respiration, the first step is glycolysis in which there is a net formation of eight molecules of ATP and then the link reaction in which the pyruvic acid which is the end product of glycolysis is converted into acetyl CoA. 

This reaction leads to the formation of six molecules of ATP but these are not included in the Krebs cycle. This is acetyl CoA enter the Krebs cycle, which results in the formation of 30 molecules of ATP.
So, the net formation of ATP is 38 ATP and this round off to 40% of the total energy that is conserved as ATP.
So, the correct option is '40%'

Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

The synthesis of ATP in photosynthesis and respiration is essentially an oxidation-reduction process involving removal of energy from 

  1. Oxygen

  2. Phytochrome

  3. Cytochrome

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

Synthesis of ATP in photosynthesis as well as respiration is possible by the help of several oxidation and reduction reactions. This can be termed as redox reactions. This involves the excitation of electrons from ground state to excited state and vice - versa. ATP is called as the energy currency of cell.