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

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

  1. Photorespiration

  2. Glycolysis

  3. Fermentation

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

Fermentation is incomplete oxidation of food substances in absence of oxygen (external electron acceptor) into alcohol or lactic acid with the small amount of energy being released. Aerobic respiration uses oxygen as an electron acceptor for oxidation of substrates. Glycolysis is the first common stage of both fermentation and aerobic respiration. Photorespiration is oxidation of RuBP by enzyme RUBISCO and does not produce energy. Thus, the correct answer is option C.

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

Incomplete breakdown of glucose in muscles results in the formation of 

  1. Alcohol and water

  2. Alcohol and lactic acid
  3. ${CO _2}$ and Water

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

The type of fuel used during physical activity also depends on the efficiency with which oxygen is delivered to muscle cells. The complete breakdown of glucose occurs when $O _2$ is present which is called as aerobic metabolism. When $O _2$ is unavailable, glucose breakdown is incomplete and it results in the formation of lactic acid. Accumulation of lactic acid leads to sore muscles. 
Incomplete breakdown of glucose does not result in the formation of alcohol, water or $CO _2$. 

Thus, the correct answer is option D.

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

Glucose is oxidised to ethyl alcohol during the process of

  1. Respiration.

  2. Aerobic respiration.

  3. Anaerobic respiration.

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

The process of anaerobic respiration takes place in the absence of oxygen. In this type, glucose is oxidized to ethyl alcohol, and it releases carbon dioxide. For example, breathing in yeast is a type of anaerobic respiration.

So, option C is the correct answer.

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

The formation of NAD via anaerobic pathway takes place by

  1. Glycolysis.

  2. Fermentation.

  3. Krebs cycle.

  4. Electron transport chain.

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

In anaerobic conditions, glycolysis produces NADH. To continue glycolysis, NADH must be oxidized back to NAD+, which occurs during the fermentation process.

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

A sudden change from anaerobic to aerobic process produces ________________.

  1. Pasteur effect

  2. Emerson effect

  3. Blackmans law

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

Answer is option A i.e. "Pasteur effect"
Pasteur effect is exhibited in yeast cells during anaerobic fermentation. Pasteur effect influences the rate of glycolysis and occurs in presence of oxygen which  decreases the rate of sugar breakdown in yeast.
While, Blackman's law and Emerson effect is related to determining the rate of  photosynthesis. Chargraff's rule is a rule for base equivalence in DNA.

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

Anaerobic process after glycolysis is known as

  1. TCA cycle

  2. Krebs cycle

  3. Calvin cycle

  4. None of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A) Lactic acid fermentation is the process that occurs after glycolysis when there is lack of oxygen.

B) TCA or Krebs cycle occurs glycolysis in the presence of oxygen and converts Acetyl coenzyme into oxaloacetic acid to yield ATP.
C) Calvin cycle is the common pathway for $C _3$ and $C _4$ plants.
So the correct option is 'None of the above'.

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

 Anaerobic respiration of animals/humans produces

  1. Glucose and O$ _2$
  2. C$ _2$H$ _5$OH and CO$ _2$

  3. Lactic acid and water
  4. CO$ _2$ and H$ _2$O
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Cellular respiration in animals is predominantly aerobic in nature. However in stressful conditions, the respiration turns anaerobic to meet the energy demands. End products of anaerobic respiration are lactic acid and water. End products in plants for aerobic respiration are alcohol and carbon dioxide.

So the answer is 'Lactic acid and water'.

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

Three major ways for metabolism of pyruvic acid produced in glycolysis are

  1. Lactic acid fermentation, alcoholic fermentation and aerobic respiration.

  2. Oxaloacetic acid fermentation, lactic acid fermentation, aerobic fermentation.

  3. Alcoholic fermentation, oxaloacetic acid fermentation, citric acid fermentation.

  4. Citric acid fermentation, lactic acid fermentation, alcoholic fermentation.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Glycolysis the common pathway of lactic acid fermentation, alcoholic fermentation and aerobic respiration in which glucose is converted into pyruvic acid in a multi-step reaction which includes ten major steps involve various enzymes.

So the correct option is 'Lactic acid fermentation, alcoholic fermentation and aerobic respiration.'

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

The incomplete breakdown of sugars in anaerobic respiration results in the formation of 

  1. Fructose and water
  2. Glucose and $CO _{2}$
  3. Alcohol and $CO _{2}$
  4. Water and $CO _{2}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Anaerobic respiration involves the incomplete breakdown of glucose. It releases around 5% of the energy released by aerobic respiration, per molecule of glucose. In yeast it can be observed, as alcoholic fermentation. A biological process in which molecules such as glucose, fructose, and sucrose are converted into cellular energy and thereby produce ethanol and carbon dioxide as metabolic waste products.

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

In anaerobic respiration, acetaldehyde is reduced to form alcohol by utilising $NADH _2$ obtained from

  1. Glycolysis

  2. Terminal oxidation

  3. Krebs cycle

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

Anaerobic respiration starts with the process of glycolysis. The NADH2 thus formed from glycolysis are used to further oxidise acetaldehyde to form alcohol and CO2. The NAD formed are then recycled back to be used in glycolysis.

So the answer is 'Glycolysis'.

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.