This set of Structural Biology Multiple Choice Questions & Answers (MCQs) focuses on “Globular Proteins”.
1. Which of the following is insoluble in water?
a) Fibrous proteins
b) Globular proteins
c) Membrane proteins
d) Hormones
View Answer
Explanation: Globular proteins are folded into a spherical shape as a result of the hydrophobic amino acids facing the interior of the protein and the hydrophilic groups facing outwards. This results in dipole interactions between the amino acids and the surrounding solvent, in turn making it soluble in nature.
2. The reason for stability of globular proteins is ______
a) Free energy released due to protein folding is small
b) Free every released due to protein folding is large
c) Helmholtz energy released due to protein folding is small
d) Helmholtz energy released due to protein folding is large
View Answer
Explanation: While large, unfolded chains or proteins explore the many stable conformational states available, the entropy during this process is also large. Once a protein starts settling into it’s native conformational state, the entropy starts decreasing. This results in the decrease in the free energy release.
3. Which law governs the energy difference between the folded and unfolded states of proteins?
a) Zeroth law of Thermodynamics
b) First law of Thermodynamics
c) Second law of Thermodynamics
d) Third law of Thermodynamics
View Answer
Explanation: According to the second law ‘total entropy of the system cannot decrease’, the entropy of the entire system doesn’t not decrease. As proteins fold into globular structures, the entropy of protein folding decreases. Due to hydrophobic collapse, the entropy of water molecules around the protein increases. Thus, the second law is conserved.
4. Which of the following is not a function of globular proteins?
a) Provide structural stability
b) Catalyze organic reactions
c) Transport biomolecules through membranes
d) Regulate various bio-reactions
View Answer
Explanation: Globular proteins mainly participate in regulatory, catalytic and transportation functions whereas fibrous proteins engage in provide structural stability.
5. Enzymes are an example of fibrous proteins.
a) True
b) False
View Answer
Explanation: Globular proteins have irregular amino acid sequences, which makes them sensitive to small changes in pH, temperature, etc. These protein chains fold into a specific manner with correct orientation to expose an active binding site for their respective substrates.
6. Which structural conformation is most crucial for proper functioning of globular proteins?
a) Primary
b) Secondary
c) Tertiary
d) Quaternary
View Answer
Explanation: Quaternary protein structure is the spatial arrangement of protein subunits. We know that globular proteins have enzymatic functions, which require a specific conformational fold of the protein chain for substrate-protein interaction. This is achieved when the protein chain folds into its quaternary form.
7. What is a holoenzyme?
a) Molecular interaction between co-enzyme and cofactor
b) Molecular interaction between enzyme and it’s cofactor
c) Molecular interaction between enzyme and substrate
d) Molecular interaction between enzymes
View Answer
Explanation: Any enzyme activity primarily depends upon the affinity towards cofactors. They have a lock and key pattern of binding pattern, which enables the enzyme to carryout it’s functions. The molecular relationship of an enzyme and its cofactor is termed holoenzyme.
8. What does the tertiary structure of globular proteins represent?
a) Interaction with other globular proteins
b) Interaction with cofactors
c) Interaction with surrounding solvent
d) Interactions within the structure
View Answer
Explanation: In the tertiary structure of globular proteins, hydrophilic residues like proline, serine, glycine are exposed to the outer surface of the protein, i.e. to the solvent face. These groups interact with the solvent, while on the inner side of the proteins, the hydrophobic groups interact with each other and stabilize the structure.
9. Globular proteins are classified as _____
a) Alpha, beta, gamma
b) Alpha, beta, alpha and beta, alpha or beta
c) Alpha, beta, delta
d) Alpha, beta, gamma, delta, mu
View Answer
Explanation: The alpha category has a majority of alpha helices, the beta category has a majority of beta strands, alpha + beta category has approximately equal amounts of alpha helices and antiparallel beta sheets and the alpha or beta category has alternating alpha helices and parallel beta sheets.
Sanfoundry Global Education & Learning Series – Structural Biology.
To practice all areas of Structural Biology, here is complete set of Multiple Choice Questions and Answers.
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