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 biology food and it's constituents energy giving food carbohydrate and its test biological molecules

Which one will yield less than $4$ ${kcal}/{mol}$ of energy when phosphate bond is hydrolysed?

  1. ADP

  2. ATP

  3. Creatine phosphate

  4. Glucose 6-phosphate
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The bond between two phosphate groups is a phosphoanhydride bond which is considered as high energy bond. ATP has two high energy phosphoanhydride bond. ADP has one phosphoanhydride bond. Creatine phosphate also has high phospahte bond between the nitrogen and phosphate. The phosphate bond in glucose phosphate is the weakest so it will yield less than 4kcal/mol of energy when phosphate bond is hydrolysed.

So, the correct answer is option D.

Multiple choice biology food and it's constituents energy giving food carbohydrate and its test biological molecules

How much energy is utilised in the synthesis of one gram mole of glucose?

  1. $673$ kcal
  2. $686$ kcal
  3. $666$ kcal
  4. $696$ kcal.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

$686$ kcal energy is utilised in the synthesis of one gram mole of glucose. 

When $1$ mol of glucose means $180$ g of glucose reacts with oxygen under standard conditions, so $686$ kcal is released in the reaction.
Hence, the correct option is B.

Multiple choice biology human system gas exchange and smoking gas exchange gas exchange in humans

The energy releasing process in living organisms is

  1. Reflex action

  2. Respiration

  3. Blood circulation

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

  • Respiration is the movement of oxygen from the outside environment to the cells within tissues and the transport of carbon dioxide in the opposite direction.
  •  During cellular respiration, glucose is broken down in the presence of oxygen to produce carbon dioxide and water. 
  • The energy released during the reaction is captured by the energy-carrying molecule ATP (adenosine triphosphate). Hence, The energy releasing process in living organisms is respiration.
So, the correct answer is 'respiration'.

Multiple choice biology digestive system of human assimilation of food and egestion assimilation of food components and importance of food

What fraction of $CO _2$ exhaled by animals is generated by the reactions of citric acid cycle, if glucose is the sole source of energy?

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

One molecule of glucose (C6H12O6) produces 6 molecules of CO2. In the citric acid cycle, 2 CO2 are produced per acetyl-CoA, and 2 acetyl-CoA are produced per glucose, totaling 4 CO2 from the cycle. The remaining 2 CO2 come from the pyruvate dehydrogenase reaction.

Multiple choice biology digestion and absorption digestion in small intestine digestive glands and their secretions alimentary canal

Isomaltase catalyzes the hydrolysis of bonds as shown in

  1. glc(1-6)glc

  2. glc(1-4)glc

  3. gal(1-6)glc

  4. fru(1-6)glc
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Isomaltase is an enzyme that breaks the bonds linking saccharides, which cannot be broken by amylase or maltase. It digests polysaccharides at the alpha 1-6 linkages

So, the correct option is 'glc(1-6)glc'

Multiple choice evs louis pasteur contribution of louis pasteur discoveries by louis pasteur discovery of microorganisms

Pasteur effect is due to

  1. Change from aerobic to anaerobic

  2. Providing oxygen to anaerobically respiring structures

  3. Rapid utilisation of ATP

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

Most microorganisms such as fungi and bacteria can grow and flourish in the complete absence of oxygen and is known as fermentation. Pasteur described that fermentation is directly associated with the growth of metabolism of living matter. He observed that the rate of fermentation was considerably higher under anaerobic conditions as compared to aerobic conditions. The inhibition of anaerobic breakdown of sugars into carbon dioxide and ethyl alcohol due to the presence of oxygen under aerobic conditions is known as Pasteur effect. 

Thus, the correct answer is 'Providing oxygen to anaerobically respiring structures'.

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

What is ATP?

  1. A hormone

  2. A protein

  3. An enzyme which brings about oxidation

  4. A molecule which contains high energy bond
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

  • Adenosine triphosphate (ATP) is a nucleotide with three phosphates. The ATP is produced by the addition of phosphorous to nucleoside adenosine.
  • The first phosphate is attached by an ester bond. This bond is a normal covalent bond and not a high energy bond. 
  • The two-terminal phosphates are bonded by high energy acid anhydride bonds. 

Thus one molecule of ATP contains two high energy bonds.

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

ATP stands for which of the following?

  1. Adenosine phosphate

  2. Adenine triphosphate

  3. Adenosine diphosphate

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

Chemically ATP is a nucleotide. In fact it is a higher order nucleotide because it contains not one but three phosphates. Compounds made up of (pentose) sugar and a nitrogenous base are called nucleosides. If the base is adenine, the nucleoside will be called adenosine. 

If one phosphate is attached to adenosine through an ester bond then the compound becomes a nucleotide and in this case it is called adenylic acid or adenosine monophosphate.
When second phosphorous is attached to the first phosphorous, through an acid anhydride bond, the nucleotide is called adenosine diphosphate. When third phosphorous is attached to the second phosphate through another acid anhydride bond, the nucleotide is called adenosine triphosphate or ATP.

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

Conversion of ATP to ADP releases

  1. Energy

  2. Enzyme

  3. Hormone

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

Adenosine Triphosphate or ATP has stored energy in its bond with the third phosphate group. However when required, ATP loses its third phosphate group to release energy and gets converted back to ADP. The energy released is in the form of chemical energy that the cells can use.

So the answer is 'Energy'.

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

If two moles of glucose are oxidized in the body through respiration, the number of moles of ATP produced are.

  1. 19

  2. 38

  3. 57

  4. 76
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Cellular respiration can be an anaerobic or aerobic respiration, depending on whether or not oxygen is present. Anaerobic respiration makes a total of 2 ATP. Aerobic respiration is much more efficient and can produce up to 38 ATP with a single molecule of glucose.
Anaerobic respiration consists of two steps.
               1. Glycolysis (2 ATP)
               2. Fermentation 
               Total = 2 ATP
Aerobic respiration consists of three steps.
               1. Glycolysis (2 ATP)
               2. Krebs Cycle (2 ATP) 
               3. Electron Transport Chain (34 ATP)
               Total = 38 ATP
If two moles of glucose is oxidized in the body through respiration, the number of moles of ATP produced are 38 x 2 = 76.
So the answer is option D '76'. 
Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

The number of ATP molecules produced during the oxidation of $1$ molecule of glucose is 

  1. $12$
  2. $18$
  3. $32$
  4. $38$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
1. Glycolysis: 
 C$ _{6}$H$ _{12}$O$ _{6}$ +  2 ATPs  → 2 Pyruvic Acid + 4 H$ _{2}$ + 4 ATPs
2. Formation of Acetyl CoA:
 2 Pyruvic Acid + 2 CoA → 2 Acetyl CoA + 2 CO$ _{2}$ + 2 H$ _{2}$
3. Krebs Cycle:
 2 Acetyl CoA + 3 O$ _{2}$ → 6 H$ _{2}$ + 4 CO$ _{2}$ + 2 ATPs
4. Electron Transport System:
 12 H$ _{2}$+ 3 O$ _{2}$ → 6 H$ _{2}$O + 34 ATPs
Overall Reaction:
C$ _{6}$H$ _{12}$O$ _{6}$ + 6 O$ _{2}$→ 6 CO$ _{2}$ + 6 H$ _{2}$O + 38 ATPs
So, the correct option is '38'.
Multiple choice bio-chemistry carbohydrate metabolism energy output living organisms and energy production respiration in cell

At the end of Krebs cycle, but before the electron transport chain, the oxidation of glucose has produced a net gain of -

  1. $ 3CO _2 , 5 NADH _2 , 1 FADH _2 , 2 ATP$
  2. $ 6CO _2 , 10 NADH _2 , 2 FADH _2 , 4 ATP$
  3. $ 6CO _2 , 10 NADH _2 , 2FADH _2 , 38 ATP$

  4. None of these
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 molecules of CO$ _{2}$ and 2 NADH$ _{2}$. These 2 Acetyl Co-A will enter into Kreb's cycle and will release 4CO$ _{2}$, 6NADH$ _{2}$, 2FADH$ _{2}$ and 2ATP.

so, the total gain before the ETC comes out to be 6 CO$ _{2}$, 10NADH$ _{2}$, 2FADH$ _{2}$ and 4ATP.
Hence, the correct answer is '6CO$ _{2}$, 10NADH$ _{2}$, 2FADH$ _{2}$, 4ATP'.

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

The energy liberated in the breakdown of glucose molecule is not at all in the form of heat, but a large part of it is converted into chemical energy. What is the chemical form into which the energy is converted to?

  1. GTP

  2. ATP

  3. ADP

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

The energy in an organism is stored in the form of ATP molecule called Adenosine Triphosphate. It is also considered as the energy currency of the cell and break down of one molecule of glucose in the process of respiration. It occurs mainly in mitochondria gives 38 ATP molecules. Single ATP provides around 30.5 KJ of energy.

So the correct option is 'ATP'.

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

During the complete oxidation of one sucrose molecule, how many ATP are produced by $FADH _2$ of Krebs cycle?

  1. $24$
  2. $8$
  3. $3$
  4. $4$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Sucrose is made up of glucose and fructose. From one molecule of glucose, 38 ATP molecules can be produced during cellular respiration. During Kreb cycle, 2 molecules of FAD are reduced to FADH$ _2$. Now 2 FADH$ _2$ produce 2 x 2 = 4 ATP molecules. Fructose is converted to fructose-6-phosphate by hexokinase enzyme. This fructose-6-phosphate then enters the glycolysis and produces same amount of ATP as glucose molecule does. Hence, it will also produce 4 ATP molecules by FADH$ _2$ of Krebs cycle. Hence, total ATP produced will be 8 molecules phosphorylation by FADH$ _2$ of Krebs cycle.

Thus, the correct answer is '8.'

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

Which of the following derives maximum energy per molecule of glucose?

  1. Alcoholic fermentation

  2. Lactic acid fermentation

  3. Aerobic respiration in unicellular organisms

  4. Glycolysis in liver cells
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Aerobic respiration is the process of producing cellular energy involving oxygen. Cells break down food in the mitochondria in a long, multistep process that produces roughly 36 ATP. The first step in is glycolysis, the second is the citric acid cycle and the third is the electron transport system.


So the correct option is 'Aerobic respiration in unicellular organisms'.