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 zoology skeleton and movements features of a muscle muscle features muscle contraction and its effects

In the anaerobic reaction of muscle, lactic acid is produced which causes painful tiredness. Where and by which mechanism lactic acid is catabolized?

  1. In muscle by monokinase action

  2. In muscle by Lohmans reaction

  3. In liver by Cori cycle

  4. In liver by phosphogen reaction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • Generally, the glucose undergoes metabolism in the presence of oxygen to form ATP (Adenosine triphosphate) which is essential for the muscle contraction but during strenuous exercise, the body cannot meet the oxygen demand and the glucose undergoes metabolism in the absence of oxygen which results in the formation and accumulation of lactic acid.
  • This accumulated lactic acid is moved to the liver and converted into glycogen thorough Cori cycle.
  • Cori cycle takes place in the liver.
  • Hence In the anaerobic reaction of muscle, lactic acid is produced which causes painful tiredness. The lactic acid accumulated is catabolized by the mechanism of the Cori cycle in the liver.
  • So, the correct answer is 'In liver by Cori cycle'
Multiple choice zoology skeleton and movements features of a muscle muscle features muscle contraction and its effects

Lactic acid generated during muscle contraction is elaborated to form glycogen in

  1. Liver

  2. Pancreas

  3. Kidney

  4. Muscle
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
  • Generally, the glucose undergoes metabolism in the presence of oxygen to form ATP(adenosine triphosphate) which is essential for the muscle contraction but during vigorous exercise, the body cannot meet the oxygen demand and the glucose undergoes metabolism in the absence of oxygen which results in the formation and accumulation of lactic acid.
  • This Lactic acid generated during muscle contraction is elaborated to form glycogen in Liver through Cori cycle.
  • So, the correct answer is 'Liver'.
Multiple choice zoology skeleton and movements features of a muscle muscle features muscle contraction and its effects

Feeling of fatigue after running fast for some time is due to

  1. Loss of energy

  2. Accumulation of lactic acid in muscles

  3. Formation of succinic acid

  4. Formation of biuret crystals
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
  • Generally, the glucose undergoes metabolism in the presence of oxygen to form ATP(adenosine triphosphate) which is essential for the muscle contraction but during vigorous exercise, the body cannot meet the oxygen demand and the glucose undergoes metabolism in the absence of oxygen which results in the formation and accumulation of lactic acid.
  • Feeling of fatigue after running fast for some time is due to the accumulation of lactic acid in muscles.
  • So, the correct answer is 'Accumulation of lactic acid in muscles'.
Multiple choice zoology skeleton and movements features of a muscle muscle features muscle contraction and its effects

Anaerobic breakdown of glycogen due to repeated activation of muscles leads to accumulation of

  1. Uric acid

  2. Phenylalanine

  3. Lactic acid

  4. Glutamic acid

  5. Tyrosine
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The body prefers to generate most of its energy using aerobic methods. During physical exercise such as lifting heavy weights, energy production is faster than our bodies can adequately deliver oxygen. In those cases, the working muscles generate energy anaerobically. This energy comes from glucose through a process called glycolysis, in which glucose is broken down or metabolized into a substance called pyruvate. When the body has plenty of oxygen, pyruvate is shuttled to aerobic pathway to be further broken down for more energy. But when oxygen is limited, the body temporarily converts pyruvate into a substance called lactate and accumulates in the muscle. 

So, the correct answer is 'Lactic acid'.

Multiple choice zoology skeleton and movements features of a muscle muscle features muscle contraction and its effects

When  muscles begin converting glucose into lactic acid?

  1. Muscles run out of oxygen

  2. Accumulation of creatine in the muscles

  3. Muscle collapse

  4. All the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

  • When you exercise, your muscles move more vigorously than when you are at rest. Their metabolic rate increases. 
  • They need more energy, so they produce more of the chemical energy molecule ATP. 
  • Your muscles begin converting glucose into lactic acid instead of energy when anaerobic exercise takes over, power output drops and fatigue sets in. Hence, when Muscles run out of oxygen muscles begin converting glucose into lactic acid.
So, the correct answer is 'Muscles run out of oxygen'.

Multiple choice biology mineral nutrition in plants nutrients and nutrition essential and non-essential mineral elements transport in the xylem of plants

Oxygen $(O _2)$ is utilised by an organism to?

  1. Perform formation of nutritive molecules

  2. Breakdown the nutrient molecules

  3. Obtain nourishment from the food

  4. Burn the organic compounds directly
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cellular respiration uses molecular oxygen to oxidize and breakdown nutrient molecules like glucose, releasing energy in the process.

Multiple choice biology mineral nutrition in plants nutrients and nutrition essential and non-essential mineral elements transport in the xylem of plants

Enzyme catalysed reactions can be inhibited by

  1. $Mg^{2+}$
  2. $Cu^{2+}$
  3. $Hg^{2+}$
  4. $Zn^{2+}$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Heavy metals like mercury (Hg2+) act as non-competitive or irreversible inhibitors by binding to the sulfhydryl groups of enzymes, thereby denaturing them or blocking their active sites.

Multiple choice evs the muscular system and digestive system in human beings human muscular system closer look into muscular system muscles and its types

The cycle of reactions by which muscle lactic acid is transformed to muscle glycogen is known as

  1. Glycolactic cycle

  2. Glycolysis

  3. Cori cycle

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

The Cori cycle (also known as lactic acid cycle), refers to the metabolic pathway, in which lactate produced by anaerobic glycolysis in the muscles moves to the liver and is converted to glucose, which then returns to the muscles and is metabolised back to lactate.

Multiple choice zoology respiratory system do plants breathe? plant respiration respiration-plants

2 NADH $(H^+)$ produced during anaerobic glycolysis yield

  1. 6 ATP molecules

  2. 4 ATP molecules

  3. 8 ATP molecules

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

The process of glycolysis yields 2 net ATPs and 2 NADH molecules. NADH is converted into ATP in mitochondrial electron transport chain if oxygen is present. In anaerobic respiration, there is no oxygen available so NADH does not lead to the formation of ATP molecules. Without oxygen, NADH builds up and the cell can run out of NAD. Without NAD glycolysis stops. To regenerate NAD, cells with anaerobic respiration carry out the process of fermentation in which NADH gets converted into NAD to restart glycolysis. 

Thus, the correct answer is option D. 

Multiple choice zoology respiratory system do plants breathe? plant respiration respiration-plants

Which of the following is a direct oxidation pathway performed without glycolysis cycle?

  1. HMP pathway

  2. TCA

  3. Both of A and B

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

The HMP pathway or pentose phosphate pathway that produces 5 carbon compound and NADPH in the form of energy. Additionally, these pathways can operate in the anabolic direction to transform glycolytic intermediates into other compounds. So, HMP pathway is a  direct oxidation pathway performed without glycolysis cycle. HMP shunt produces some glycolytic intermediated like glyceraldehyde-3-phosphate and fructose-6-phosphate that can directly involve in the glycolysis pathway or EMP. Thus, the correct answer is option A.

Multiple choice zoology respiratory system do plants breathe? plant respiration respiration-plants

Common phase between aerobic and anaerobic modes of respiration is

  1. Krebs cycle

  2. EMP/glycolysis

  3. Oxidative phosphorylation

  4. Pentose phosphate pathway
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Aerobic respiration is a type of respiration in which the breakdown of organic compounds takes place with the presence of oxygen and release a large amount of energy in the form of ATP.

In anaerobic respiration, the partial breakdown of organic compound takes place without using oxygen and release only a fraction of energy. The first breakdown of glucose takes place through glycolysis which is the common pathway between the aerobic and anaerobic respiration and it takes place in the cytoplasm.
So, the correct option is 'EMP/Glycolysis'

Multiple choice zoology respiratory system do plants breathe? plant respiration respiration-plants

End products of aerobic respiration are

  1. Sugar and oxygen

  2. Water and energy

  3. Carbon dioxide, water and energy

  4. Carbon dioxide and energy
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Aerobic respiration is the complete oxidation of sugars in presence of oxygen.

The carbohydrates are broken down into CO₂ and H₂O and this releases energy. This energy is stored in the form of ATP and later used in the body.
So, the correct option is 'Carbon dioxide, water, and energy'

Multiple choice zoology respiratory system do plants breathe? plant respiration respiration-plants

General formula for aerobic respiration is

  1. 6CO$ _2$ + 6H$ _2$O $\rightarrow$ C$ _6$H$ _{12}$O$ _6$ + 6O$ _2$
  2. C$ _6$H$ _{12}$O$ _6$ + 6O$ _2$ $\rightarrow$ 6CO$ _2$ + 6H$ _2$O + 686 kcal
  3. C$ _6$H$ _{12}$O$ _6$ $\rightarrow$ 2C$ _2$H$ _5$OH + 2CO$ _2$ + 2ATP
  4. C$ _6$H$ _{12}$O$ _6$ $\rightarrow$ 2C$ _3$H$ _6$O$ _3$+2 ATP
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Aerobic respiration requires oxygen and it takes place in mitochondria and produces carbon dioxide, water and 686 kilo calories of energy.

So the correct option is '

C$ _6$H$ _12$O$ _6$ + 6O$ _2$ → 6CO$ _2$ + 6H$ _2$O + 686 kcal.'

Multiple choice zoology respiratory system do plants breathe? plant respiration respiration-plants

Products of anaerobic respiration are

  1. Ethyl alcohol and carbon monoxide

  2. Ethyl alcohol and lactic acid

  3. Lactic acid and glycogen

  4. Acetic acid and carbon dioxide
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Anaerobic respiration occurs in the absence of oxygen and is less efficient than aerobic respiration. Unlike aerobic respiration, the end products here are ethyl alcohol as in alcoholic fermentation and lactic acid as in animal cells. So the answer is 'Ethyl alcohol and lactic acid'.