1. Which of the following amino acids is an exception to the Ramachandran plot?
a) Proline and lysine
b) Alanine and Proline
c) Valine and glycine
d) Glycine and proline
Explanation: Glycine and proline are an exception to the Ramachandran plot. Glycine is a very simple amino acid because it contains hydrogen atom as its R group. Proline has a complex fused ring structure.
2. Which of the following amino acid is sterically unhindered and is therefore found in loops/turns in protein tertiary structure?
a) Tyrosine
b) Tryptophan
c) Proline
d) Glycine
Explanation: Glycine is an amino acid with hydrogen as its R group, hence, glycine is quite sterically unhindered. Therefore, glycine is found in loops/turns in the protein tertiary structure.
3. Which of the following amino acid is sterically hindered?
a) Serine
b) Alanine
c) Glycine
d) Proline
Explanation: Proline is an amino acid that is quite sterically hindered. Proline has a closed ring structure. Hence, due to its fused R group, it shows a very high steric hindrance. It is also known as a helix breaker. It does not contain a free R group.
4. Ramachandran plot can be used to predict which of the following structure?
a) Quaternary structure
b) Tertiary structure
c) Primary structure
d) Secondary structure
Explanation: Ramachandran plot shows the allowed and disallowed angles for left-handed alpha-helix, Beta-sheets, and right-handed alpha-helix. Hence, it can be used to predict the secondary structure of proteins.
5. Which among the following amino acids is known as a helix breaker?
a) Glycine
b) Alanine
c) Lysine
d) Proline
Explanation: Proline is known as a helix breaker. When it is inserted in a helix it usually breaks the helix and is, therefore, known as a helix breaker. Proline shows this property due to its high steric hindrance.
6. Which amino acids are buried deep inside a protein structure?
a) Either hydrophobic or hydrophilic
b) Both hydrophobic and hydrophilic
c) Hydrophilic
d) Hydrophobic
Explanation: Hydrophobic amino acids are buried deep inside a protein structure. The environmental conditions of a globular protein molecule are usually aqueous, and hence, hydrophilic. Thus, to avoid unstable interactions the hydrophobic amino acids are buried deep inside a protein structure.
7. Which of the following amino acids are likely to be present on the surface of a globular protein?
a) Both hydrophobic and hydrophilic
b) Either hydrophobic or hydrophilic
c) Hydrophobic
d) Hydrophilic
Explanation: Hydrophilic amino acids are likely to be present on the surface of a globular protein. These hydrophilic amino acids form stable interactions with the aqueous environment when they are present on the surface of a protein. Hence, they are most likely to be present on the surface.
8. Which of the following class of proteins helps a newly made protein molecule to fold properly?
a) Mitochondrial proteins
b) Ribosomal proteins
c) Immunoglobulins
d) Chaperones
Explanation: Chaperones are a class of proteins that help a newly made protein molecule to fold properly. Many of the newly made proteins fold properly on their own, but some require assistance in folding. These chaperones assist these proteins to fold properly.
9. To which of the special class of proteins do heat-shock proteins belong?
a) Immunoglobulins
b) Chloroplast proteins
c) Catalytic proteins
d) Chaperones
Explanation: Heat-shock proteins belong to a special class of proteins called chaperones. These proteins are produced in large amounts in certain bacteria upon exposure to high temperatures. These proteins help bacteria thrive in the higher temperature environment.
10. Which of the following chaperones act early in the life of many proteins?
a) Hsp50
b) Hsp40
c) Hsp60
d) Hsp70
Explanation: There are several major families of eukaryotic chaperones, including the Hsp60 and Hsp70 proteins. The Hsp70 acts early in the life of many proteins, binding to a string of amino acids before the protein leaves the ribosome.