Prepare for NEET Biology Biomolecules with MCQs & PYQs on NEET.GUIDE. Get free practice, previous year questions, and expert explanations of carbohydrates, proteins, and more.
Which amino acid substitution in a protein is MOST likely to disrupt a beta-sheet structure due to steric hindrance?
Glycine to Valine
Alanine to Glycine
Valine to Isoleucine
Serine to Threonine
A protein rich in proline residues is likely to exhibit which characteristic?
Formation of extensive alpha-helices
Increased tendency to form beta-sheets
Disruption of regular secondary structure (e.g., alpha-helices and beta-sheets)
Enhanced protein stability at high temperatures
The isoelectric point (pI) of a polypeptide with a high content of lysine and arginine residues would be expected to be:
Acidic
Neutral
Basic
Close to 7
Which chromatographic technique is BEST suited for separating proteins based on their differences in net charge at a given pH?
Size exclusion chromatography
Affinity chromatography
Ion exchange chromatography
Hydrophobic interaction chromatography
A researcher isolates an enzyme from a thermophilic bacterium and finds that its activity dramatically decreases when incubated at 25ยฐC compared to its optimal temperature of 70ยฐC. This decrease in activity is MOST likely due to:
Increased substrate affinity at lower temperatures.
Changes in the enzyme's three-dimensional structure affecting the active site.
A decrease in the activation energy of the catalyzed reaction.
An increase in the concentration of competitive inhibitors at lower temperatures.
Which of the following statements is INCORRECT regarding the regulation of metabolic pathways?
Feedback inhibition involves the end-product of a pathway inhibiting an earlier enzyme.
Allosteric regulation exclusively involves the binding of molecules to the active site of an enzyme.
Covalent modification, like phosphorylation, can alter enzyme activity.
Enzyme compartmentalization within organelles can regulate metabolic flux.
A novel organism is discovered that utilizes a unique metabolic pathway where the standard free energy change (Gยฐ) for the overall reaction is +25 kJ/mol. Which of the following strategies could this organism employ to make this pathway thermodynamically feasible?
Increase the concentration of products.
Decrease the concentration of reactants.
Couple the endergonic reaction to a highly exergonic reaction.
Decrease the temperature of the reaction.
In a metabolic pathway, enzyme A catalyzes the conversion of substrate X to intermediate Y. Enzyme B then catalyzes the conversion of Y to product Z. If a mutation in enzyme B renders it completely inactive, which of the following is MOST likely to occur?
Increased production of substrate X.
Accumulation of intermediate Y and depletion of product Z.
No change in the concentrations of X, Y, or Z.
Increased activity of enzyme A to compensate for the loss of enzyme B.
Which statement BEST describes the relationship between catabolism and anabolism?
Catabolism and anabolism are independent processes with no interaction.
Anabolism provides the energy for catabolism.
Catabolism and anabolism utilize the same enzymes.
Catabolism provides the energy and building blocks for anabolism.
A competitive inhibitor of an enzyme:
I. Increases the of the enzyme.
II. Decreases the of the enzyme.
III. Can be overcome by increasing substrate concentration.
IV. Binds to the allosteric site of the enzyme.
I and II only
II and IV only
I and III only
III and IV only
