MCQs

The tertiary structure of an enzyme, which dictates the shape of the active site, is stabilized by hydrogen bonds, ionic interactions, hydrophobic interactions, van der Waals forces, and covalent disulfide bonds.

Enzymes are biological catalysts that accelerate reactions by decreasing the activation energy. They do not provide energy, alter the equilibrium constant, or change the free energy change (ΔG) of the overall reaction.

Pinocytosis is a type of endocytosis where the membrane invaginates to take in fluid.

Its ability to regulate its own composition and environment is a fundamental property of a living membrane.

Immune cells use recognition markers to identify infected or foreign cells (e.g., pathogens).

Cholesterol is a steroid, characterized by its four-ring hydrocarbon structure.

Both facilitated and simple diffusion are passive processes driven by concentration gradients.

Peripheral proteins sit on the outside (or inside) surface of the bilayer.

Carrier proteins bind specific molecules and shift conformation to move them across the membrane.

The phosphate group is negatively charged and highly attracted to water.

Saturated chains pack tightly, resulting in a more rigid, less fluid membrane.

The cell membrane's surface markers are crucial for identifying "self" vs "non-self" cells.

Plasmalemma is essentially the plasma membrane of a cell.

Small, non-polar molecules move easily through the non-polar lipid bilayer.

Mosaic implies a diverse pattern of different components (proteins, lipids, carbs) packed together.

While proteins may contribute more by mass, phospholipids are the most numerous molecules.

Because facilitated diffusion uses a limited number of proteins, the rate can reach a maximum (saturation).

The Robertson model (Unit Membrane) described a fixed, trilaminar structural arrangement.

The fatty acid tails create a hydrophobic region that prevents passage of polar substances.