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 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.

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

Which one of the following is energy currency of the cell?

  1. Phosphate

  2. ATP

  3. ADP

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

The major energy currency molecule of the cell is ATP. This complex  molecule is critical for all life froms, the simplest to the most complex. It is one of the end products of photophosphorylation, cellular respiration and fermentation and used by enzymes and structural proteins in many cellular processes.

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

Number of ATP molecules formed during complete oxidation of fructose 1, 6-diphosphate is 

  1. 20

  2. 32

  3. 36

  4. 40
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Fructose-1, 6-bisphosphate is formed during glycolysis as an intermediate product when glucose-1,6-bisphosphate is converted into fructose-1, 6-bisphosphate and enzme phosphofructokinase is used for this. Fructose generally results in the formation of a higher amount of energy after oxidation and in this case, it is more than glucose.

So, the correct option is '40'

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

The net gain of energy from one gram mole of glucose during aerobic respiration is

  1. 2 ATP

  2. 4 ATP

  3. 38 ATP

  4. 40 ATP.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If a cell is undergoing aerobic respiration then it will first undergo glycolysis which is the first breakdown of glucose in the cell and then Krebs cycle.

The net gain of ATP in glycolysis is 8 and the net gain of ATP in Krebs cycle including the substrate phosphorylation and oxidative phosphorylation is 30. So, the total gain of ATP is 38 from one molecule of glucose.
So, the correct option is '38 ATP'

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

Common immediate source of energy in cellular activity is 

  1. DNA

  2. ATP

  3. RNA

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

ATP stands for adenosine triphosphate. The energy released by oxidation of organic molecules is transferred into high energy phosphate bonds of ATP, which can be readily utilised when a cell needs energy. One of the three phosphates of ATP is broken down to release energy. Thus, ATP is the intermediate energy transferring compound. 

So, the correct option is  'ATP'

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

Energy currency (reservoir) of the cells is

  1. AMP

  2. ATP

  3. ENA

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

ATP or adenosine triphosphate is considered to be the energy currency of the cell as it has three high energy phosphate bonds.

When the cell needs energy on of the first bond of the ATP is broken down and energy is used for cellular needs.
In the entire body wherever energy or heat generation takes place it results in the conservation of energy in the form of ATP so that the minimum amount of heat is lost and the body can store ATP for future use.
So, the correct option is 'ATP'

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

Oxidation of a molecule of acetyl CoA produces

  1. 12 ATP

  2. 15 ATP

  3. 6 ATP

  4. 19 ATP.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The acetyl CoA produced from pyruvic acid as a result of link reaction enters Krebs' cycle by forming citric acid from oxaloacetic acid. When 1 molecule of acetyl CoA completes 1 round of Krebs' cycle, it produces 3 NADH+H+, 1 FADH2 and 1 ATP. So after going through ETS, a total of 12 ATP is yielded ( 3*3  + 1*2  + 1 ).

So the answer is '12ATP'.

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

Maximum amount of energy/ATP is liberated on oxidation of

  1. Fats

  2. Proteins

  3. Starch

  4. Vitamins
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Fats are complex molecules composed of fatty acids and glycerol. The body needs fats for growth and energy.
Fats are the slowest source of energy but the most energy-efficient form of food. Each gram of fat supplies the body with about 9 grams of energy. 
The oxidation of fats releases the maximum amount of energy.
So, the correct option is 'Fats'
Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

Number of ATP molecules which can be built on complete oxidation of pyruvic acid is

  1. 6

  2. 2

  3. 15

  4. 30
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The breakdown glucose takes place during glycolysis in which there is a net gain of 8 ATP. The pyruvic acid so formed undergoes oxidative decarboxylation and thus forms acetyl CoA. This reaction leads in the formation of 2 NADH₂ molecules. It results in the formation of 6 ATP.

Therefore if the complete oxidation of pyruvic acid takes place when there is a net gain of 15 ATP.
So, the correct option is '15ATP'

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

Out of 36 ATP molecules produced per glucose molecule during respiration

  1. 2 are produced outside glycolysis and 34 during respiratory chain

  2. 2 are produced outside mitochondria and 34 inside mitochondria

  3. 2 during glycolysis and 34 during Krebs cycle

  4. All are formed inside mitochondria
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

2 ATP from glycolysis which takes place in the cytoplasm and other cellular respiration processes takes place in mitochondria which gives 34 ATP.

So, the correct option is '2 are produced outside mitochondria and 34 inside mitochondria.'