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

What is the net yield of complete oxidation of stearic acid?

  1. 129 ATP

  2. 146 ATP

  3. 131 ATP

  4. 148 ATP

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

8 cycles of beta oxidation = 8 x 5 = 40 ATP, 9 acetyl Co-A entering into the TCA cycle = 9 x 12 = 108 ATP. 2 ATPs are utilised for activation of stearic acid to stearyl Co-A. So, net yield is = (108 + 40) - 2 = 146 ATP.

Multiple choice

Which of the following statements regarding metabolic pathways is incorrect?

  1. Many of the steps of glycolysis can run in reverse.

  2. Starch, sucrose or glycogen must be hydrolysed before it can enter the glycolysis.

  3. After fats are digested, glycerol enters glycolysis by forming DHAP.

  4. After fat digestion, fatty acids can no longer participate in cellular respiration.

Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Fatty acids can be used in cellular respiration, they do not have to be turned into glucose first.  Instead, the fatty acids are broken down into 2-carbon molecules that enter the cellular respiration events to make ATP.  Glucose, a 6-carbon molecule, gets broken down into 3-carbon and then 2-carbon molecules as it goes through cellular respiration.  Therefore, the 2-carbon molecules from fatty acids just join into the process where the 2-carbon molecules are normally used.   Because they join in a little late in the process, they donot yield as much energy as glucose does, but they still generate some ATP. 

Multiple choice

Cyanide poisoning is due to its direct inhibition of

  1. Electron transport chain

  2. Fatty acid biosynthesis

  3. Fatty acid oxidation

  4. Nucleic acid biosynthesis
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Cyanide binds to the iron in cytochrome c oxidase (Complex IV) in the electron transport chain, effectively halting oxidative phosphorylation and ATP production.

Multiple choice

Catabolite repression allows cells to save energy by

  1. inactivating catabolic enzymes

  2. inhibiting synthesis of total RNA

  3. regulating expression of genes required for utilization of less-efficient metabolites

  4. inhibiting translation of mRNAs encoding catabolic enzymes
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice respiration and excretion in animals human respiratory system evs respiration in human beings respiratory organs in humans respiration in humans

Respiratory quotient for three different substrates was calculated and tubulated as shown here.

Substrate R.Q.
XYZ 0.911.3

Identify X, Y and Z and select the correct option regarding them.

  1. X - Protein, Y - Fats, Z - Glucose

  2. X - Glucose, Y - Protein, Z - Organic acid

  3. X - Protein, Y - Glucose, Z - Organic acid

  4. X - Organic acid, Y - Protein, Z - Fats
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Respiratory quotient if the protein is 0.8-0.9

For glucose- 1
For  organic acids -1.3
So, the correct option is 'X - Protein, Y - glucose, Z - organic acids'.

Multiple choice botany mineral nutrition in plants mechanism of absorption mineral absorption significance of transpiration

Metabolic water is the one

  1. Used during transamination

  2. Used during photosynthesis

  3. Produced during aerobic utilization of glucose

  4. Produced during condensation or polymerisation
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Metabolic water is water produced by the body through metabolic processes. The aerobic respiration of glucose (C6H12O6 + 6O2 -> 6CO2 + 6H2O + energy) releases water as a byproduct.

Multiple choice botany mineral nutrition in plants mechanism of absorption mineral absorption significance of transpiration

In feedback inhibition, a metabolic pathway is switched off by

  1. Lack of a substrate

  2. Accumulation of the end product

  3. A rise in temperature

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

Accumulation of the end product triggers inhibition or switching off of the metabolic pathway in feedback inhibition mechanism. 

So, the correct option is 'Accumulation of the end product'. 

Multiple choice biology the respiratory system anaerobic respiration in organisms anaerobic and aerobic respiration cellular respiration

The end product of anaerobic respiration, in plants, is

  1. Pyruvic acid

  2. Malic acid

  3. Ethyl alcohol

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

Anaerobic respiration refers to the type of respiration that takes place without oxygen. In plants, the glucose is anaerobically converted to ethyl alcohol, ATP and carbon dioxide.

Therefore, the correct answer is option C.

Multiple choice biology the respiratory system anaerobic respiration in organisms anaerobic and aerobic respiration cellular respiration

ATP is stored on the myosin cross bridges for immediate energy After 5 to 6 seconds, this supply is exhausted and the muscle must rely on to quickly produce more ATP.

  1. Phosphocreatine

  2. Lactic acid

  3. Acetyl choline

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

  • Myofibril activity is required for muscle contraction on the molecular level. 
  • When ATP binds to myosin, it separates from the actin of the myofibril, which causes a contraction.
  • The muscle contraction cycle is triggered by calcium ions binding to the protein complex troponin, exposing the active-binding sites on the actin.
  • ATP then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site.
  • When ATP is exhausted lactic acid is produced 
So, the correct option is 'lactic acid'.