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 enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Enzymes concerned with transfer of electrons are

  1. Hydrolase

  2. Dehydrogenase

  3. Transaminase

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

Dehydrogenases catalyze dehydrogenation reactions, which involve addition or removal of electrons. Addition or removal of electrons will lead to reduction or oxidation of substrates. Dehydrogenases are a type of oxidoreductases.

Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Most of the biochemical reactions differ from those occurring in the non-living world in ________________.

  1. Requiring energy

  2. Releasing energy

  3. Being enzymatic

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

Biochemical reactions are unique because they are mediated by enzymes, which lower activation energy and increase reaction rates under physiological conditions.

Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Lactic dehydrogenase (LDH) which catalyzes pyruvate to lactate is an example of

  1. Apoenzyme

  2. Antienzyme

  3. Isoenzyme

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

Some enzymes have several molecular forms, example: 16 for $\alpha$-amylase and 5 for lactate dehydrogenase (LDH). They are called as isoenzymes or isozymes. They differ in substrate affinity, maximum activity and regulatory properties.

Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Enzymes which act similarly are called as

  1. Isoenzyme

  2. Cofactor

  3. Coenzymes

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

Isoenzymes are enzymes that catalyze identical chemical reactions but are composed of different amino acid sequences. They are sometimes referred to as isozymes. Isoenzymes are produced by different genes. They occur in many tissues throughout the body and are important for different developmental and metabolic processes. Alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) are examples of isoenzymes.

Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Hexokinase (Glucose $+$ ATP $\longrightarrow$ Glucose 6-P $+$ ADP) belongs to the category

  1. Transferases

  2. Lysases

  3. Oxidoreductases

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

Transferase is an enzyme which transfers a group from one molecule to another molecule. Hexokinase is the enzyme which transfers one phosphate from ATP to glucose and forms glucose 6-phosphate.

(Glucose ++ ATP ⟶⟶ Glucose 6-P ++ ADP)
Thus, the correct answer is A.

Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Enzymes functional in cells are called

  1. Endoenzymes

  2. Exoenzymes

  3. Apoenzymes

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

Endoenzyme is the cells which function inside the cell. It is also known as intracellular enzymes. It helps in the catalysis of the intracellular metabolic reaction. 

Exoenzymes are the enzymes which function outside the cell.
Isoenzyme is also known as isozyme. When the two enzymes differ in amino acid sequence but catalyze the same chemical reaction they are known as isoenzyme. They are two different molecular form of the enzyme.
Enzymes are proteins which help to catalyze the biochemical reaction. The enzyme has a protein part which is not active is known as apoenzyme.
So, the correct answer is option A.

Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Which enzyme is concerned with transfer of electrons?

  1. Desmolase

  2. Hydrolase

  3. Dehydrogenase

  4. Transaminase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Desmolase catalyzes the formation or destruction of carbon-carbon bonds within a molecule. It is involved in the transfer of electrons.
Hydrolase is the enzyme which catalyzes the splitting of compounds by addition of water.
Dehydrogenase is an enzyme which participates in the oxidoreductase reaction by using an electron acceptor.
Transaminase catalyzes aminotransferase reaction between an amino acid and a α-keto acid.
So, the correct answer is option B.
Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Match and find the correct option.

$(a)$ Oxidoreductases $(i)$ Linking of the compounds
$(b)$ Isomerases $(ii)$ Removal of group from substrate
$(c)$ Ligases $(iii)$ Interconversion of isomers
$(d)$ Lyases $(iv)$ Dehydrogenases
$(v)$ Hydrolysis
  1. $a - iv, b - i, c - iii, d - ii$
  2. $a - iv, b - iii, c - i, d - ii$
  3. $a - iii, b - iv, c - ii, d - v$
  4. $a - ii, b - v, c - iii, d - i$
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation
Oxidoreductase is a dehydrogenase which acts as an acceptor of hydrogen or electrons. 
Isomerases are class of enzymes that convert a molecule from one isomer to another isomer. 
Ligase is an enzyme that can catalyze the joining of two large molecules by forming a new chemical bond between them. 
An enzyme that forms double bonds by removing groups from a substrate other than by hydrolysis, is called lyases.
So the correct answer is B. 
Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Which class of enzyme catalyzes following reaction?
$\overset { X }{ \underset { C }{ | }  } \overset { Y }{ \underset { C\longrightarrow \quad X-Y+C=C }{ | }  } $

  1. Hydrolases

  2. Lyases

  3. Ligases

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

Hydrolases are biological enzymes that catalyze the hydrolysis of a chemical reaction. They usually divide larger molecules into two smaller molecules. It is a class containing more than 200 enzymes. Some common hydrolases are esterases, proteases, lipases etc.

So, the correct option is 'Hydrolases'.

Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Choose the type of enzyme involved in the following reaction.


$S - G + S' \longrightarrow S + S' - G$

  1. Dehydrogenase

  2. Transferase

  3. Hydrolase

  4. Lyase

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

Based on the type of reaction catalyzed, the international union of biochemist have classified enzymes into six major classes- Oxidoreductase, Transferase, Hydrolase, Lyase, Ligase and Isomerase.
Transferase is the general name for the class of enzymes that enact the transfer of specific functional groups (e.g. a methyl or glycosyl group) from one molecule (called the donor) to another (called the acceptor).

Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

The cytochromes are 

  1. Peroxidase

  2. Iron protoporphyrin

  3. Pyridine nucleotides

  4. Metal containing flavoproteins
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Cytochromes are iron-porphyrin or heme proteins discovered by MacCunn. Cytochromes are bound to inner mitochondrial membrane and are primarily responsible for the generation of ATP via mitochondrial electron transport system. Whereas all other cytochromes have iron only, the cytochrome a possesses both iron and copper. With iron it picks up electrons and through copper it hands over electrons to oxygen.

Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Which one of them catalyzes oxidation-reduction reactions?

  1. Oxidase

  2. Oxidoreductase

  3. Oxygenase

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

Certain enzymes carry oxidation reduction reactions. Oxidation is defined as the chemical process which involves loss of electron whereas reduction is the process in which a substrate accepts electron.
An oxygenase is any enzyme that oxidizes a substrate by transferring the oxygen from molecular oxygen O$ _2$ (as in air) to it.

An oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule, the reductant, also called the electron donor, to another, the oxidant, also called the electron acceptor.
An oxidase is any enzyme that catalyzes an oxidation-reduction reaction, especially one involving molecular oxygen (O$ _2$) as the electron acceptor.

Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Enzymes that catalyse endergonic synthesis, coupled with exergonic hydrolysis of ATP are

  1. Ligases

  2. Isomerases

  3. Lyases

  4. Transferases
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
There are six major classes of enzymes, as follows:
(1) Oxidoreductases - Catalyze oxidationreduction reactions.
(2) Transferases - Catalyze the transfer of a functional group from a donor molecule to an acceptor molecule.
(3) Hydrolases - Catalyze hydrolysis reactions. 
(4) Isomerases - Catalyze conversion of a molecule from one isomeric form to another.
(5) Ligases - Ligases or synthetases are enzymes that catalyse endergonic synthesis, coupled with the exergonic hydrolysis of ATP
(6) Lyases - Catalyze certain reactions in which double bonds form or break.
Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

Enzyme concerned with transfer of electrons are

  1. Hydrolase

  2. Dehydrogenase

  3. Transaminase

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

Dehydrogenases are the enzymes which catalyze oxidation-reduction reactions by addition or removal of electrons. These reactions are used to synthesize reduced coenzymes like NADH$ _2$ and FADH$ _2$. For example phosphoglyceraldehyde dehydrogenase.

So, the correct answer is 'Dehydrogenase'.