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 digestion and absorption liver functions of the liver secretory organs

Lactic acid is converted into glycogen most readily in

  1. Muscles

  2. Liver

  3. Kidney

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

Instead of accumulating inside the muscle cells, lactate produced by anaerobic fermentation is taken up by the liver. This initiates the Cori cycle. In the liver, gluconeogenesis occurs, which reverses both glycolysis and fermentation by converting lactate first into pyruvate, and finally back to glucose. The glucose is then supplied to the muscles through the bloodstream. If muscle activity has stopped, the glucose is used to replenish the supplies of glycogen through glycogenesis.

Multiple choice biology digestion and absorption liver functions of the liver secretory organs

The process of breaking down excess amino acids in the liver is known as

  1. Amination

  2. Denitrification

  3. Deamination

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

  • Deamination is the process by which amino acids are broken down if there is an excess of protein intake.  It is the removal of an amine group from a molecule in the presence of an enzyme called deaminase. It takes place in the liver. Hence the process of breaking down excess amino acids in the liver is known as Deamination. 

So, the correct answer is 'deamination'.

Multiple choice biology digestion and absorption liver functions of the liver secretory organs

Maximum energy is available on complete oxidation of

  1. Glucose

  2. Fat

  3. Protein

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

Fats (lipids) have a higher energy density than carbohydrates or proteins because they are more reduced. Upon complete oxidation, fats yield approximately 9 kcal/g, whereas carbohydrates and proteins yield approximately 4 kcal/g.

Multiple choice biology digestion and absorption liver functions of the liver secretory organs

Consider the following statements.
a. Beta-oxidation takes place only in glyoxisomes and not in cytosol.
b. When fatty acids undergo betaoxidation to form acetyl coA, only NADH is produced and not $FADH _2$.
Which of the statements given is/are correct?

  1. $1$ only
  2. $2$ only
  3. Both $1$ and $2$
  4. Neither $1$ nor $2$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Beta-oxidation occurs in the mitochondria and peroxisomes (not just glyoxisomes) of the cytosol. During beta-oxidation, both NADH and FADH2 are produced in each cycle.

Multiple choice biology digestion and absorption liver functions of the liver secretory organs

Cell organelle showing xenobiotics with the help of cytochrome $P450$ is also involved in

  1. Glycosylation process

  2. Glycolate oxidation or metabolism

  3. Glycogen metabolism

  4. Glyoxylate metabolism
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
Cytochrome P450 is an enzyme found in cell organelles such as mitochondria and is involved in the metabolism of xenobiotics. Glyoxalate cycle involves the production of glucose from fatty acids and a part of the cycle also occurs in the mitochondria. Therefore, the cell organelle involved in xenobiotic metabolism with the help of cytochrome P450 is also involved in glyoxalate metabolism. 
So, the correct option is 'Glyoxalate metabolism'.
Multiple choice

Which process is the most efficient at generating ATP molecules?

  1. aerobic respiration

  2. lactic acid fermentation

  3. alcoholic fermentation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Aerobic respiration is highly efficient because it utilizes oxygen as a final electron acceptor, allowing for the complete oxidation of glucose into CO2 and water, yielding significantly more ATP than fermentation pathways.

Multiple choice

Which step of cellular respiration generates the most ATP?

  1. glycolysis

  2. Krebs Cycle

  3. electron transport chain

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

The electron transport chain (oxidative phosphorylation) produces the vast majority of ATP during cellular respiration through the action of ATP synthase.