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 respiration amphibolic pathway living organisms and energy production life processes in living organisms- part 1

Which one of the following reactions is an example of oxidative decarboxylation?

  1. Conversion of succinate to fumarate.

  2. Conversion of fumarate to malate.

  3. Conversion of pyruvate to acetyl Co-A.

  4. Conversion of citrate to isocitrate.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The conversion of pyruvate to acetyl-CoA is a linker step between glycolysis and Krebs cycle. After the entry of pyruvate in the mitochondria the acetylation takes place in the perimitochondrial space which is the space between the inner and outer mitochondrial membrane. Each molecule of pyruvic acid is oxidatively decarboxylated to acetyl coA by the action of an enzyme complex pyruvate dehydrogenase. The acetyl coA then enters the Krebs cycle.  Thus the correct answer is option C.

Multiple choice biology respiration amphibolic pathway living organisms and energy production life processes in living organisms- part 1

The importance of the Kreb's cycle is 

  1. Production of amino acid

  2. Production of vitamin

  3. Production of ATP molecule through oxidative phosphorylation

  4. ATP formation through oxidative and substrate level phosphorylation
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The pyruvic acid enters Krebs cycle in form of acetyl CoA where it is oxidatively decarboxylated into CO$ _2$. The complete Kreb cycle leads to the net formation of 2 molecules of ATP by substrate-level phosphorylation, 8 molecules of NADH plus 2 molecules of FADH$ _2$ (via succinate dehydrogenase). The NADH and FADH$ _2$ then enter the ETS to drive ATP production by substrate level phosphorylation. 

So, the correct answer is option D.

Multiple choice biology respiration amphibolic pathway living organisms and energy production life processes in living organisms- part 1

An amphibolic pathway is

  1. TCA cycle

  2. Calvin cycle

  3. Terminal oxidation

  4. Electron transport chain
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Kreb's cycle consists of 8 cyclic steps which take place in the mitochondrial matrix. Each step is catalyzed by a specific enzyme. In Kreb's cycle, the entrant molecule is 2- carbon acetyl coenzyme A and the receptor molecule is 4- carbon oxaloacetate. Since the process involves both catabolic and anabolic reactions. it is an amphibolic pathway. It degrades acetyl coenzyme A and yields carbon dioxide and energy which is used to produce NADH, H+, and FADH+

Thus, the correct answer is option A. 

Multiple choice zoology excretion in living organisms excretion - animals human excretory system and products excretory system and products excretion - plants excretion in plants

Most abundant, harmful and universal waste product of metabolism is

  1. Uric acid
  2. $H _20$
  3. $CO _2$

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

The end products of aerobic metabolism of carbohydrates are carbon dioxide and water. Carbon dioxide remains dissolved in the blood and is carried by the veins to the lungs for oxygenation. If carbon dioxide is not removed from the metabolizing tissues, it will be toxic for that tissue and stop metabolism.

So, the correct option is 'Carbon dioxide'.

Multiple choice zoology excretion in living organisms excretion - animals human excretory system and products excretory system and products excretion - plants excretion in plants

Which is not a ketone body?

  1. Succinic acid

  2. Acetone

  3. Acetoacetic acid

  4. p-hydroxybutyric acid
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Chemicals that the body makes when there is not enough insulin in the blood and it must break down fat instead of the sugar glucose for energy. The ketone bodies -- acetone,  acetoacetate, and beta-hydroxybutyrate -- are toxic acidic chemicals. They build up in the blood and then spill over into the urine. The body can also rid itself of acetone through the lungs. This gives the breath a fruity odor.

So, the correct option is 'Succinic acid'.

Multiple choice zoology excretion in living organisms excretion - animals human excretory system and products excretory system and products excretion - plants excretion in plants

Study the following.


(i) Uricase enzyme is not found in apes and man.
(ii) Purine metabolism leads to the formation of uric acid.
(iii) In ureotelic organisms, carbondioxideCO2 and ammonia converted into urea through the Cori cycle.
(iv) More energy consumed is for the production of uric acid.
(v) TMO (Trimethylamine oxide) protects the proteins from the effect of urea in Chondrichthyes fishes.

Which of the given statements are correct?

  1. All, except II

  2. All, except III

  3. All, except IV

  4. All, except V
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

When muscles work continuously enough, oxygen is not reached to muscles to burn glucose aerobically in such conditions glucose is converted into lactic acid i.e anaerobic glycolysis. The lactic acid produced in muscles is moved to the liver and converted to glucose. In ureotelic organisms, lactic acid is converted into Glucose through the Cori cycle. This metabolic cycle was discovered by Carl Ferdinand Cori and  Gerty Cori, hence named Cori cycle.

So, the correct answer is 'Option B'.

Multiple choice bio-chemistry cell membrane regulation of respiration transport of respiratory gases buffer and its role

Steps of respiration are controlled by

  1. Substrates

  2. Enzymes

  3. Hormone

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

  •  Cellular respiration is the process by which cells convert glucose into carbon dioxide and water. 
  • Cellular respiration takes place in three steps: glycolysis, the citric acid cycle and oxidative phosphorylation.
  • The main role of enzymes during the respiration reaction is to assist in transferring electrons from one molecule to another. e.g. In glycolysis, the enzyme dehydrogenase is used. Hence, the steps of respiration are controlled by enzymes.
So, the correct answer is  'enzymes'.

Multiple choice botany cell cycle difference between meiosis and mitosis division for growth and reproduction meiosis

The proton-pumps provide energy to cells through.

  1. pH gradient and electro potential gradient

  2. ATP and ADP

  3. Auxins and hormones

  4. Carbolwdrates and lipids
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Proton pumps create a proton motive force, which consists of a pH gradient (chemical gradient) and an electrical potential gradient across the membrane, providing energy for various cellular processes.

Multiple choice biology animal tissue muscular tissues muscle tissue muscle tissues

Immediate source of energy for muscle contraction is

  1. Glucose

  2. GTP

  3. ATP

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

Muscles have two major proteins actin and myosin. These are mostly contractile proteins. The energy from the hydrolysis of ATP by myosin head is directly used in the power stroke i.e., flexing of myosin head during muscular contraction. ATP is also used during muscle relaxation in the absence of ATP the myosin head will continue to bind with actin head and the muscle fibre shall remain contracted. So, the correct answer is option C.

Multiple choice biology animal tissue muscular tissues muscle tissue muscle tissues

The ready source of energy in living cells is

  1. Glucose

  2. ATP

  3. Glycogen

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

In living cells, energy for immediate use is stored as molecules of ATP or adenosine triphosphate. When the energy is used, one of the phosphates attached to ATP is released, giving ADP or adenosine diphosphate. it is known as the energy currency of a cell and these are produced in the mitochondria. So, the correct answer is option B.

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

The pentose monophosphate shunt is more advantageous than Krebs cycle as

  1. It yields more ATP

  2. Ribose sugar is released, which helps in nucleic acid formation

  3. It releases more oxygen

  4. It utilizes less oxygen
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Pentose phosphate pathway is also known as HMP shunt. This pathway provides an alternative route for carbohydrate breakdown. HMP shunt produces some glycolytic intermediates like glyceraldehyde-3-phosphate and fructose-6-phosphate. These intermediates can directly involve in the glycolysis pathway and then in the Krebs cycle. The cycle provides ribose sugar which can be used for the synthesis of nucleic acids. This pathway is considered as advantageous since the ribose sugar is made available. 

Thus, the correct answer is option B. 

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

A respiratory cycle where mainly ${NADPH _2}$ are produced is 

  1. Calvin cycle

  2. Kreb's cycle

  3. EMP pathway

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

During Calvin cycle, $NADH _2$ are not produced. 
During Krebs cycle, 2 $NADH _2$, 1 $FADH _2$, 1GTP are produced. 
During EMP pathway 2 NADH, 2 ATP are produced. 
During HMP pathway, $NADPH _2$ are produced. So, in respiratory cycle  mainly $NADPH _2$ are produced is HMP pathway. Thus, option D is correct.

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

Pentose phosphate pathway is a mode of

  1. Amphibolic pathway

  2. Anabolic pathway

  3. Aerobic respiration

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

Pentose phosphate pathway is an alternative pathway to glycolysis which involves the oxidation of glucose-6-phosphate to 6-phosphogluconic acid which in turn gets converted into pentose phosphates. This pathway involve the direct oxidation of glucose-6-phosphate without entering glycolysis and hence is termed as direct oxidation. 

Thus, the correct answer is option C. 

Multiple choice hmp shunt alternative to glycolysis carbohydrate metabolism respiration bio-chemistry

Which of the following is generated in the oxidative phase of pentose phosphate pathway?

  1. NADPH

  2. FADH

  3. GTP

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

The Pentose Phosphate Pathway is an alternative pathway to glycolysis and TCA cycle. It occurs in both prokaryotes and eukaryotes in their cytoplasm

Glucose is broken down by a series of pathways.
The pathway has 2 phases- Oxidative and Non-oxidative.
In the oxidative stage, there are 2 steps where NADP⁺ gets converted to NADPH.
1. Glucose 6-phosphate converts to 6-phosphogluconolactone
2. 6-phosphogluconate converts to Ribulose 5- phosphate
So, the correct option is 'NADPH'