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

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'.

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

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'