Biology · Chemistry

Biomolecules and Enzymes

1,432 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

Macro molecule chitin is:

  1. simple polysaccharide

  2. nitrogen containing polysaccharide

  3. phosphorus containing polysaccharide

  4. sulphur containing polysaccharide
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Chitin is a nitrogen-containing polysaccharide composed of N-acetylglucosamine units. The nitrogen comes from the acetyl group attached to each sugar molecule. Simple polysaccharides (like starch) contain only carbon, hydrogen, and oxygen, while chitin's nitrogen makes it chemically distinct and structurally stronger.

Multiple choice

The effects of pH on enzyme-catalysed reaction include which of the following? A. The direction of the reaction may be influenced by the [H+]. B. The ionisation state of enzymes dissociating groups may be modified. C. The ionisation state of substrate may be modified. D. The protein may be denatured at certain pH values.

  1. Only A and B

  2. Only A and C

  3. Only A, B and C

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

The pH of the medium will have its effect on a enzyme-catalysed reaction in one or the other form. The options B and C define the action of protons on the dissociating groups and substrate. Availability of H+ will enhance the ionising ability and therefore, will affect the direction of reaction. It is obvious for protein to get partially denatured during the process when pH fluctuates.

Multiple choice

Directions: Read the following information and answer the question given below: Proteins acquire specific and precise folds to perform a desired function. Therefore, the foldings of the proteins are highly essential and specific. Folds are further composed of two major 2o structures, i.e. alpha helices and beta sheets.

What is the helical rise (pitch) for a normal alpha-helix?

  1. 5.4 Ao

  2. 3.6 Ao

  3. 4.0 Ao

  4. 5.1 Ao
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The pitch of the alpha-helix is 5.4 Å or 0.54 nm, which is equal to 1.5 (translation height) * 3.6 (residues in one turn). Therefore, the length of 153 amino acid protein will be 153/.54 = 283 nm.

Multiple choice

Directions: Read the following information and answer the question given below: Proteins acquire specific and precise folds to perform a desired function. Therefore, the foldings of the proteins are highly essential and specific. Folds are further composed of two major 2o structures, i.e. alpha helices and beta sheets.

If a protein is a 153 residues protein and given that its structure is a continuous alpha-helix, what would be the length of the protein?

  1. 552 nm

  2. 360 nm

  3. 534 nm

  4. 283 nm
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The pitch of the alpha-helix is 5.4 Å or 0.54 nm, which is equal to 1.5 (translation height) * 3.6 (residues in one turn). Therefore, the length of 153 amino acid protein will be 153/.54 = 283 nm

Multiple choice

Proteins are the building blocks of life. All the major processes in body are regulated by one or the other protein. Therefore, it becomes very vital to assess proteins in a professional manner, for which many sophisticated techniques and protocols are available. The standard protein assessment protocol includes: Purification, Digestion, Sequencing, Assays. Based on the provided information and knowledge of protein assessment methods, answer the following question:

Which of the following would you use before the sequencing of a peptide?

  1. Dansylation

  2. Microarray protein expression

  3. Enzymatic fragmentation

  4. Fast Protein Liquid Chromatography
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Before sequencing of peptides using mass spectrometry and after purification of peptides from the mixture, peptides need to be cleaved by different enzymes in order to have standardized sequencing. 

Multiple choice

Proteins are the building blocks of life. All the major processes in body are regulated by one or the other protein. Therefore, it becomes very vital to assess proteins in a professional manner, for which many sophisticated techniques and protocols are available. The standard protein assessment protocol includes: Purification, Digestion, and Sequencing. Based on the provided information and knowledge of protein assessment methods, answer the following question:

Which of the following is not a method for protein purification?

  1. High-performance liquid chromatography (HPLC)

  2. Mass spectrometry

  3. Fast protein liquid chromatography (FPLC)

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

Amongst the above, mass spectrometery is used to sequence or analyse the peptide sequence, while all others are used to purify peptides or proteins.

Multiple choice

PDB is an important data archive for protein structures and their structural information. Majority of structures available are obtained from X-ray crystallography. PDB file contains the coordinate information of the atoms including their spatial organisation. The water molecules are represented as HETATM (heteroatoms to the primary structure), which denotes the atoms that are not primary to the structure of the protein, i.e. non-main chain atoms. Which among the following properties justifies the presence of water in the PDB files or protein structure?

  1. Electrical conductivity

  2. Hydrogen bonding

  3. Dielectric constant

  4. Bent structure of water

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

In a PDB file, the water atom is represented as ‘HOH’ that symbolises its arrangement of atoms. In crystallisation, water exists as water of crystallisation, where water is added to the protein to stabilise the crystal. Proteins are charged molecules and are localised in the cell where water is the solvent. So, in order to maintain its folded structure, water forms hydrogen bonds and therefore, is added to stabilise the structure outside of the cell. During simulation process, the water which acts as a solvent can be removed but the water molecules present as water of crystallisation cannot be removed. 

Multiple choice

PDB is an important data archive for protein structures and their structural information. Majority of structures available are obtained from X-ray crystallography. PDB file contains the coordinate information of the atoms including their spatial organisation. The water molecules are represented as HETATM (heteroatoms to the primary structure), which denotes the atoms that are not primary to the structure of the protein, i.e. non-main chain atoms.

How are water molecules symbolised in PDB files that contain coordinate information?

  1. HOH

  2. H2O

  3. WTR

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

In a PDB file, the water atom is represented as ‘HOH’ that symbolises its arrangement of atoms. In crystallisation, water exists as water of crystallisation, where water is added to the protein to stabilise the crystal. Proteins are charged molecules and are localised in the cell where water is the solvent. So, in order to maintain its folded structure, water forms hydrogen bonds and therefore, water is added to stabilise the structure outside of the cell. During simulation process, the water which acts as a solvent, can be removed but the water molecules present as water of crystallisation cannot be removed.

Multiple choice

PDB is an important data archive for protein structures and their structural information. Majority of structures available are obtained from X-ray crystallography. PDB file contains the coordinate information of the atoms including their spatial organisation. The water molecules are represented as HETATM (heteroatoms to the primary structure), which denotes the atoms that are not primary to the structure of the protein, i.e. non-main chain atoms.

During molecular dynamics studies of biological proteins, these PDB files are used. The protein structures need to be normalised before subjecting them to actual simulation process, so non-required information is discarded from PDB files. Majority of water molecules are removed but at certain places, water is retained. Why are selective water molecules retained?

  1. Because water is life and it is required to stabilise the protein activity

  2. Because water molecules act as space fillers owing to their small size

  3. Because water molecules are used in crystallisation process to stabilise the protein structure

  4. Because water is very essential to protein function without which it cannot be simulated

Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

In a PDB file, the water atom is represented as ‘HOH’ that symbolises its arrangement of atoms. In crystallisation, water exists as water of crystallisation, where water is added to the protein to stabilise the crystal. Proteins are charged molecules and are localised in the cell where water is the solvent. So, in order to maintain its folded structure, water forms hydrogen bonds and therefore, water is added to stabilise the structure outside of the cell. During simulation process, the water which acts as a solvent can be removed but the water molecules present as water of crystallisation cannot be removed.