Biology · Chemistry

Biomolecules and Enzymes

1,501 Questions

This topic focuses on biomolecules, specifically proteins, enzymes, and amino acids. It includes questions on enzyme structures, protein folding, and catalysis. These concepts are crucial for medical and biology competitive exams.

Enzyme catalysisProtein structuresAmino acid synthesisPolypeptide chainsBiomolecule properties

Biomolecules and Enzymes Questions

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

Which one of the following pair is wrongly matched?

  1. Detergents - lipase

  2. Alcohol - nitrogenase

  3. Fruit juice - pectinase

  4. Textile - amylase
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

This question relates to the industrial applications of enzymes. Alcohol is not produced by the use of nitrogenase. Nitrogenase performs complex functions of nitrogen fixation by bacteria. Alcohol is produced by the fermentation process of sugars carried out by Yeast.

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

Which one is not an example for hydrolases?

  1. Dehydrogenase

  2. Protease

  3. Amylase

  4. Esterase

  5. Sucrase
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Dehydrogenases catalyze dehydrogenation reactions which involve addition or removal of electrons. The addition or removal of electrons will lead to reduction or oxidation of substrates. Dehydrogenases are a type of oxidoreductases. Some of the important hydrolases includes amylases, sucrase, lactase, maltase, protease, esterase etc.

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

Enzyme amylase belongs to class 

  1. Transferases

  2. Hydrolases

  3. Isomerases

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

Hydrolases are the enzymes which break large molecules into smaller ones with the help of hydrogen and hydroxyl groups of water molecules, this phenomenon is known as hydrolysis. Amylase is the enzyme produced by the salivary gland and is found in saliva. It breaks starch into glucose. Thus, the correct answer is B.

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

Which is false about prosthetic groups?

  1. Proteins

  2. Non-proteins

  3. Metal compounds

  4. Tightly bound to enzymes
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Many enzymes show enzymatic activity only in association with certain non protein substances. Such substances are known as cofactors. Cofactors may be simple ions such as magnesium or potassium ions or complex organic compounds. An organic non-protein cofactor which is easily separable from the enzyme is called coenzyme and the non-protein organic cofactor which is tightly bound to and non-dissociable from the enzyme is termed as prosthetic group. The organic cofactors directly reduce the activation energy and thus form a functional part of active site of enzyme. They act as carriers of chemical groups, atoms or electrons removed from the substrates during reactions.

Thus, the correct answer is option A.  

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

Enzymes with heme as prosthetic group are 
(a) Catalase
(b) Carboxypeptidase
(c) Succinic dehydrogenase
(d) Peroxidase

  1. a and d

  2. a ony

  3. a and b

  4. b and c

  5. c and a
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Certain enzymes are made up of two parts - a protein part of enzyme called apoenzyme and a non-protein part called cofactor. Such enzymes are called conjugated enzymes. The working combination of apoenzyme and cofactor together form the holoenzyme. Organic cofactors are of two types- coenzymes and prosthetic groups. Coenzymes are easily separable organic cofactors while prosthetic groups are non-protein organic cofactors firmly associated with protein part of enzyme called apoenzyme. Heme is iron containing prosthetic group in hemoglobin, myoglobin, cytochrome, catalase and peroxidase. Catalase and peroxidase cause the breakdown of hydrogen peroxide to oxygen and water. Carboxypeptidase requires zinc for its activity.

Thus, the correct answer is option A.  

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

A simple enzyme is

  1. Succinate dehydrogenase

  2. Urease

  3. Transaminase

  4. Ribozyme
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
Succinate dehydrogenase is a enzyme which is present in the inner mitochondrial membrane. It plays an important role in citric acid cycle and the electron transport chain.
It catalyzes the oxidation of succinate to fumarate. It is a conjugated protein as it has flavo protein which has FMN or FAD molecule as a prosthetic group.
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

Hydrolytic enzymes which act on low pH are called as : -

  1. Protease

  2. -Amylase

  3. Hydrolases

  4. Peroxidase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
The stomach has low pH due to the secretion of HCl. Protease, an enzyme for digesting protein acts in low pH i.e. in the stomach. Amylase is a starch (carbohydrate) digesting enzyme and carbohydrate digestion does not occur in the stomach. All digestive enzymes are hydrolases. Peroxidase is an iron-containing enzyme, found mainly in plants but also present in leucocytes and milk, that catalyses the dehydrogenation (oxidation) of various substances in the presence of hydrogen peroxide.

So, the correct answer is 'Hydrolases'.
Multiple choice biology enzymes classification of enzyme enzymes classification and cofactors the origin of cells and cell division

In which one of the following enzymes, is copper necessarily associated as an activator? 

  1. Carbonic anhydrase

  2. Tryptophanase

  3. Lactic dehydrogenase

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

Tyrosinase is a copper-containing enzyme present in plant and animal tissues that catalyzes the production of melanin and other pigments from tyrosine by oxidation, as in the blackening of a peeled or sliced potato exposed to air. In animals it is found inside melanosomes which are synthesised in the skin melanocytes.

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

An enzyme which catalyses the conversion of aldose sugar to ketose would be classified as

  1. Transferases

  2. Isomerases

  3. Hydrolases

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

Isomerases are the enzymes which catalyse transfer of groups within molecules to yield isomeric bonds. As aldose and ketose sugars are isomers, their interconversion is catalyzed by isomerases.

Transferases will catalyze group transfer reactions. 
Hydrolases will catalyze hydrolytic reactions and ligases catalyze formation of C-C, C-S, C-O and C-N bonds by condensation reactions coupled to ATP cleavage.