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 metabolism, cell respiration, and photosynthesis metabolism enzymes carbohydrate metabolism

Biochemical reactions are carried out by enzymes

  1. By decreasing the energy of the reactants

  2. By increasing the activation energy of the reaction

  3. By decreasing the activation energy of the reaction

  4. By increasing the energy of the products of the reaction

  5. By decreasing the energy of the products of the reaction
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Any chemical reaction includes the formation of transition state between reactant and product. The energy required for formation of the transition state is termed as activation energy. Enzymes enhance the rate of reaction by lowering down the activation energy of transition state. Thus, the correct answer is option C.

Multiple choice biology metabolism, cell respiration, and photosynthesis metabolism enzymes carbohydrate metabolism

Energy released from enzyme-substrate interaction is

  1. Activation energy

  2. Binding energy

  3. Constant energy

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

The transition state is the state of the activated complex which is highly unstable and readily changes into the product.  At the transition state, the enzyme attaches to the substrate to form an enzyme-substrate complex by forming a weak chemical bond. Binding energy is the free energy that is released by the formation of weak interactions between a complementary substrate and enzyme.

So, the correct answer is option B.

Multiple choice biology metabolism, cell respiration, and photosynthesis metabolism enzymes carbohydrate metabolism

Enzymes increase the rate of biochemical reaction through 

  1. Changing equilibrium

  2. Lowering activation energy

  3. Forming reactant-product complex

  4. Forming enzyme-product complex.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Enzymes are biological catalysts. A catalyst is a chemical that increases the rate of a chemical reaction without itself being changed by the reaction. Without a catalyst, the amount of energy required for the reaction is large. Enzymes and catalysts both affect the rate of a reaction. The lower the activation energy for a reaction, the faster the rate of chemical reaction. Thus enzymes speed up reactions by lowering activation energy.

So, the correct answer is option B.

Multiple choice bio-chemistry carbohydrate metabolism metabolism enzymes metabolism, cell respiration, and photosynthesis

An example of destructive metabolism (catabolism) is

  1. Photosynthesis

  2. Respiration

  3. Glycogenesis

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

Destructive metabolism is the breakdown of more complex substances into simpler ones with release of energy.

And Respiration is concerned with the release of energy from the oxidation of complex organic compounds.
so technically respiration is a type of Catabolism.
While the other two are anabolic because in both the process substances are synthesised and used in the body.

Multiple choice bio-chemistry carbohydrate metabolism metabolism enzymes metabolism, cell respiration, and photosynthesis

What are biochemical reactions in the body known as?

  1. Anabolic reactions

  2. Metabolic reactions

  3. Catabolic reactions

  4. Vital reactions
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
All the chemical processes which sustain life. (all cells) Sum of all the chemical reactions that take place in the body, consisting of  anabolism and catabolism. Cellular metabolism refers specifically to the chemical reactions within cells. So, the correct option is "B" (Metabolic reactions).
Multiple choice bio-chemistry carbohydrate metabolism metabolism enzymes metabolism, cell respiration, and photosynthesis

Which reactions usually release energy that is used to drive chemical reactions.

  1. Anabolic

  2. Catabolic

  3. Photosynthesis

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

Metabolism refers to series of reactions wherein product of one reaction becomes reactant for the next one. It includes catabolism (degradative pathways) and anabolism (synthetic pathways). Catabolic reactions are the reactions in which complex molecules are broken down into smaller simpler molecules. The catabolic reactions are exergonic reactions( energy releasing reactions). While photosynthesis is an anabolic reaction which requires energy for the formation of complex molecules. Hence option B is the correct answer.

Multiple choice bio-chemistry carbohydrate metabolism metabolism enzymes metabolism, cell respiration, and photosynthesis

The term metabolism indicates a variety reactions carried out at

  1. atomic level

  2. molecular level

  3. cellular level

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

The metabolism is a chemical processes that occur within a living organism in order to maintain life and basic unit of life is cell, hence all metabolic reactions occur  in cell. So, the correct option is 'Cellular level'

Multiple choice biology metabolism, cell respiration, and photosynthesis metabolism enzymes carbohydrate metabolism

An enzyme brings about

  1. Decrease in reaction time

  2. Increase in reaction time

  3. Increase in activation energy

  4. Reduction in activation energy
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Enzymes are proteins which accelerate the rate of the reaction. The substrate and product have different energy state. The energy gap between the substrate and the product is known as activation energy which is the minimum energy required to initiate a reaction. The enzymes lower the activation energy and lead to the faster conversion of substrate to the product.

So, the correct answer is option D.

Multiple choice biology metabolism, cell respiration, and photosynthesis metabolism enzymes carbohydrate metabolism

Modulators

  1. Inhibit enzyme activity

  2. Stimulate enzyme activity

  3. Function as coenzymes

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

A modulator is a type of molecule which either stimulates or inhibits enzyme activity. Those which stimulate enzyme activity are known as inducers while those which inhibit enzyme activity are known as inhibitors. The inhibitors can be competitive, non-competitive or allosteric inhibitors. 

Thus, the correct answer is option D. 

Multiple choice biology metabolism, cell respiration, and photosynthesis metabolism enzymes carbohydrate metabolism

Which of the following inactivates the enzyme by changing its shape?

  1. Competitive inhibitor

  2. Allosteric inhibitor

  3. Coenzyme

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

Allosteric means in a different steric conformation or occurrence of more than one shapes. Allosteric modulators bind to a site different from the active site and bring changes in the shape or conformation of the enzyme molecule. The change in shape can activate the enzyme or inhibit the activity of enzyme. An allosteric inhibitor will bind to allosteric site and bring in the conformational changes to reduce the enzyme activity.

Multiple choice biology metabolism, cell respiration, and photosynthesis metabolism enzymes carbohydrate metabolism

All of the following  statement about feedback inhibition of enzyme is true, with an exception of

  1. It is exerted through allosteric effects.

  2. It is directed at the enzyme that catalyzes the first committed step in a branch of a pathway.

  3. It affects the rate of reaction, not the concentration of enzyme.

  4. It acts very slowly.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Feedback inhibition is the inhibition mechanism in metabolic pathways where the end product of one reaction are the substrates for next reaction. Such feedback inhibition is usually directed at the first or first few reactions in the pathway to help conserve precious cellular resources, thus in case the end product is not required the metabolic pathway is blocked at the initial stages itself. The feed back regulation is mostly brought about by the allosteric modulators. Usually the first steps in metabolic pathways are catalysed by allosteric enzymes whose catalysis rate can be increased with the help of positive modulators and decreased with the help of negative modulators.

Multiple choice biology metabolism, cell respiration, and photosynthesis metabolism enzymes carbohydrate metabolism

Which of the following is an allosteric enzyme?

  1. Hexokinase

  2. Phosphofructokinase

  3. Succinic dehydrogenase

  4. Cytochrome oxidase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
An allosteric enzyme is the one that changes its conformational ensemble upon binding of an effector, which results in an apparent change in the binding affinity at a different ligand binding site. Hexokinase is an example of such enzymes. It undergoes an induced-fit conformational change when it binds to glucose, which ultimately prevents the hydrolysis of ATP.

So, the correct answer is 'Hexokinase'.
Multiple choice biology metabolism, cell respiration, and photosynthesis metabolism enzymes carbohydrate metabolism

An inhibitor is added to a cell culture so that succinate accumulates. The enzyme catalysing the formation of which substance has been blocked?

  1. Citrate

  2. Oxaloacetate
  3. $\alpha$-ketoglutarate

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

Succinate was placed in one of the most important cyclic pathways in metabolism, a collecting pool of catabolic and a starting point of many anabolic processes. Succinate is a product of substrate-level phosphorylation materialized in the citric acid cycle. It is involved in a macrophage-specific metabolic pathway generating and is also a downstream product of the α-ketoglutarate dehydrogenase complex, a heavily regulated multi-subunit complex.

So the correct answer is 'Citrate'.

Multiple choice biology transport in plants diffusion transport in vascular plants types of transport

Which one of the following compounds is NOT a member of the electron transport chain?

  1. Ubiquinone

  2. Cytochrome C

  3. Carnitine

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

Carnitine is an amino acid derivative responsible for transporting fatty acids into the mitochondria for beta-oxidation, but it is not part of the mitochondrial electron transport chain. Ubiquinone, Cytochrome C, and NAD (or NADH dehydrogenase) are all core components of the electron transport chain.

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

Muscles get fatigued due to accumulation of

  1. Adenosine triphosphate
  2. $CO _2$

  3. Lactic acid

  4. Phosphate molecules
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
  • The Burning of glucose during respiration requires oxygen. When a Muscle is subjected to continuous exercise there will be low availability of oxygen. This leads to the anaerobic breakdown of glucose which results in the formation of lactic acid. 
  • This accumulation of lactic acid in the muscle causes muscle fatigue.
  • Hence Muscles get fatigued due to the accumulation of lactic acid.
  • So, the correct answer is 'Lactic acid'.