MCQs

Viral envelopes originate from host cell membranes and contain viral glycoproteins essential for attachment and entry.

Tobacco Mosaic Virus (TMV) is a classic example of a helical, positive-sense single-stranded RNA virus infecting plants.

Helical viruses have capsomeres arranged helically around the viral nucleic acid, producing a rod-like appearance.

Icosahedral viruses have a highly symmetrical capsid composed of 20 triangular faces, providing maximum stability.

Bacteriophages are viruses that specifically infect bacteria and play important roles in bacterial genetics and biotechnology.

Retroviruses, such as HIV, possess ssRNA and the enzyme reverse transcriptase, enabling synthesis of DNA from RNA.

Viruses contain either DNA or RNA as their genetic material, never both. This is the most fundamental basis of viral classification.

Enzyme activity depends on maintaining proper structural integrity and environmental conditions. Even with abundant substrate, unsuitable temperature or pH reduces catalytic efficiency.

Initially, substrate concentration limits the reaction. After saturation, enzyme concentration becomes the limiting factor.

Cold-adapted enzymes function efficiently at low environmental temperatures and are less stable at higher temperatures.

Extremely alkaline conditions may permanently disrupt the enzyme's tertiary structure, preventing recovery of activity.

At Vmax, enzyme saturation has occurred. Additional substrate cannot increase the reaction rate.

Increasing substrate concentration increases the likelihood that substrate molecules encounter enzyme active sites.

Each enzyme has unique active-site residues whose catalytic function depends on a specific protonation state.

When substrate is abundant, all enzyme molecules can function at maximum capacity, making enzyme concentration the principal variable.

Excessive heat disrupts hydrogen bonds and hydrophobic interactions, leading to denaturation and loss of catalytic activity.

More substrate molecules increase the frequency of effective collisions with enzyme active sites until saturation is reached.

Each enzyme has a characteristic optimum temperature and pH where its catalytic efficiency is greatest because its active site has the proper conformation and ionization state.

When substrate is limiting, many enzyme molecules remain free, preventing the reaction from reaching its maximum rate.