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 biology life processes in living organisms- part 1 fermentation cell respiration living organisms and energy production

The energy releasing process in which the substrate is oxidized without an external electron acceptor is called as

  1. Aerobic respiration

  2. Glycolysis

  3. Fermentation

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

Fermentation is an energy releasing process in which substrate like sugar is oxidized into organic acids or alcohol without an external electron acceptor. The final electron acceptor is either acetaldehyde or pyruvate. Aerobic respiration is a process in which energy is produced in the presence of oxygen. Glycolysis is a process of converting glucose into two molecules of pyruvate. Photorespiration is a process in which RuBisCO enzyme oxygenates RuBP by wasting some amount of energy.

Thus, the correct answer is option C.

Multiple choice biology respiration in plants fermentation cell respiration living organisms and energy production

Conversion of pyruvic acid into ethyl alcohol is facilitated by enzyme(s)

  1. Carboxylase

  2. Phosphatase

  3. Dehydrogenase

  4. Decarboxylase and dehydrogenase
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
When the pyruvic acid converts into alcohol in the presence of enzymes by bacteria and also exhibited by some in the lack of oxygen.
$2CH _3COOH\rightarrow2CH _3CHO+2CO _2$ is takes place in the presence of decarboxylase which removes carbon dioxide
$2CH _3CHO+2 NADH _2\rightarrow2C _2H _5OH+2NAD$ is takes place in the presence of alcohol dehydrogenase.
So the correct option is 'Decarboxylase and dehydrogenase'.
Multiple choice biology life processes in living organisms- part 1 fermentation cell respiration living organisms and energy production

The anaerobic respiration is also called as.

  1. Fermentation

  2. Fragmentation

  3. Oxidation

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

Fermentation is an anaerobic process in which energy can be released from glucose even though oxygen is not available. Fermentation occurs in yeast cells, and a form of fermentation takes place in bacteria and in the muscle cells of animals. So, the correct answer is option A.

Multiple choice biology life processes in living organisms- part 1 fermentation cell respiration living organisms and energy production

Choose the correct answers from the alternatives given :
Which of these is not true of fermentation?

  1. Net gain of only two ATP

  2. Occurs in cytosol

  3. NADH donates electrons to electron transport system

  4. Begins with glucose
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

  • Fermentation is the process that takes place after the glycolysis in the cells where the anaerobic respiraton occurs due to absence or lack of oxygen.
  • Pyruvic acid which is formed at the end of the glycolysis by the break down of the glucose molecule enters the fermentation reaction in the anaerobic cells.
  • During fermentation reaction the pyruvic acid is converted to lactic acid and one molelcule of NADH is formed per molecule of pyruvic acid.
  • This molecule of NADH will only form ATP when it will undergo oxidative phosphorylation in the electron transport chain which takes place in mitochondria, but for this process presence of oxygen is required so the organisms or the cells performing anaerobic respiration cannot perforem this process therefore the NADH formed will not donate electron to the ETS and no ATP will be formed by that.
  • Therefore the answer option 'NADH donates electrons to electron transport system' is correct.










Multiple choice biology respiration in plants fermentation cell respiration living organisms and energy production

State whether the following statements are true or false.
When not enough oxygen gets to muscle cells during a sprint, energy is provided by glycolysis of glucose to pyruvic acid and then conversion of these molecules to lactic acid.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Glycolysis is the first part of both aerobic and anaerobic respiration.
  • The end product of glycolysis is pyruvic acid which is produced in the cytoplasm and no oxygen is required for the process of glycolysis.
  • The pyruvic acid formed can enter either kerb cycle for the reactions of aerobic respiration or it can undergo anaerobic reaction in the cells where there is absence of oxygen.
  • There are 2 process under anaerobic reaction in which pyruvic acid can take part. First is where pyruvic acid is converted to lactic acid and second is where it converted to Ethanol and carbon dioxide. These reaction are called fermentation reaction.
  • Fermentation reaction of pyruvic acid takes place when there is no presence of oxygen. Sometimes during some of the physical activities when not enough oxygen is not reaching the muscles the energy for the contraction and relaxation of the muscles is provided by the process of glycolysis (2ATP) and then the pyruvic acid undergoes fermentation reaction forming Lactic acid and releasing 1 molecule of NADH per Pyruvic acid molecule.
  • Therefore the above sentence is correct and the answer option 'True' is correct.
Multiple choice biology life processes in living organisms- part 1 fermentation cell respiration living organisms and energy production

Choose the correct answers from the alternatives given :
Which of these pairs of processes are anaerobic?

  1. Fermentation and glycolysis

  2. Fermentation and the Krebs cycle

  3. Glycolysis and the Krebs cycle

  4. The Krebs cycle and the electron transport system
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Respiration is of two types -

Aerobic respiration - It is the process of complete oxidation of organic foods into carbon dioxide and water in the presence of oxygen. it has three steps ;
  • Glycolysis - It occurs in the cytoplasm in which glucose breaks into two molecules of pyruvate. It occurs in both aerobic and anaerobic respiration.
  • Krebs cycle occurs in the mitochondria where oxidative decarboxylation of pyruvate takes place to form acetyl CoA.
  • Electron transport system - Here series of coenzymes and cytochromes acts as a passage of electron.
Anaerobic respiration - It is the process of incomplete oxidation of organic foods. oxygen is not utilized in this process, this occurs in the process of fermentation.
So, the correct option is ' Fermentation and glycolysis'.

Multiple choice biology respiration in plants fermentation cell respiration living organisms and energy production

Formation of lactic acid from pyruvate requires

  1. Decarboxylation

  2. Reduction

  3. Oxidation

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

Pyruvate + NADH $\rightarrow$ Lactic acid + NAD$^{+}$
Muscle cells convert pyruvate into lactate. Here, pyruvate (a metabolite of glucose) is reduced to lactic acid by accepting electrons from NADH, which oxidizes NADH back to NAD$^{+}$ to allow glycolysis to continue under anaerobic conditions. 

Multiple choice biology life processes in living organisms- part 1 fermentation cell respiration living organisms and energy production

Anaerobic respiration following glycolysis is

  1. Oxidative phosphorylation

  2. Krebs cycle

  3. Fermentation

  4. Both A and B
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Following glycolysis, if the oxygen is available, end products of glycolysis directly enter Krebs' cycle for further oxidation and energy production. In anaerobic conditions, it chooses to get fermented and the end product is another organic substance which is incompletely oxidised, producing less energy.

So, the correct answer is 'Fermentation'.

Multiple choice biology life processes in living organisms- part 1 fermentation cell respiration living organisms and energy production

Anaerobic respiration is

  1. Complete oxidation

  2. Incomplete oxidation

  3. Anabolic reaction

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

The process of fermentation is the form of anaerobic respiration carried by some microorganisms. Many microorganisms such as fungus and bacteria can grow and flourish in the complete absence of oxygen. Such microorganisms can utilize sugars to convert it into ethanol and evolve carbon dioxide. Since it is the incomplete breakdown of glucose, it yields small amount of energy which is sufficient to maintain the life of organisms like yeast and bacteria. 

Thus, the correct answer is 'Fermentation'.

Multiple choice biology molecular biology fermentation cell respiration living organisms and energy production

Which of the following is the byproduct of anaerobic respiration in muscles?

  1. Sugar

  2. Lactic acid

  3. HCl

  4. Oxygen
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Anaerobic respiration is the breakdown of glucose in the absence of oxygen. In humans, oxygen-starved muscle cells will respire anaerobically under stress such as heavy physical activity. The by-product of anaerobic respiration in muscles is the lactic acid which causes the puffed out feeling. There is a build-up of lactic acid in the muscles during vigorous exercise. The lactic acid needs to be oxidised to carbon dioxide and water later.
So, the correct answer is 'Lactic acid'.

Multiple choice biology plant growth other plant hormones cytokinins, ethylene and abscisic acid plant hormones

Consider the following statements.
a. Copper is present in Cytochrome oxidase
b. Pantothenic acid is the precursor of Coenzyme A
c. Thiamine pyrophosphate is the prosthetic group in decarboxylases
d. Zinc is present in RNA and DNA polymerases
Which of these statements are correct?

  1. $1$ and $2$
  2. $2, 3$ and $4$
  3. $1, 2, 3$ and $4$
  4. $1, 3$ and $4$
Reveal answer Fill a bubble to check yourself
A Correct answer
Multiple choice zoology endocrine system and adolescence control of blood glucose endocrine system and hormone hormones in human reproduction

Which of the following are incorrectly matched

  1. Synthesis reaction-anabolism

  2. Decomposition reaction-catabolism

  3. Hydrolysis-anabolism

  4. Dehydration reaction-synthesis reaction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Hydrolysis is the cleavage of biomolecules where a water molecule is consumed to affect the separation of a larger molecule into component parts. So, hydrolysis is a type of decomposition and that's why it is regarded as catabolism.
Hence, the correct answer is 'Hydrolysis-anabolism'
Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Select the type of enzyme involved in the above reaction.

$\boxed{S - G + S' \rightarrow S + S' - G}$

  1. Dehydrogenase

  2. Transferase

  3. Hydrolase

  4. Lyase

  5. Isomerase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Transferases are the enzymes that catalyze group transfer reactions. In the figure, one group G has been transferred to another group S'. It is a classical example of a group transfer reaction.