Practice Questions

The active site is a 3D pocket formed by amino acid residues brought together via the protein's tertiary folding. It is complementary to the substrate's shape and chemistry, and models like "induced fit" show it is flexible, not rigid.

Unsaturated fatty acids contain kinks due to double bonds, preventing tight packing of the hydrocarbon tails. This increased space between lipids makes the membrane more fluid and permeable compared to a membrane rich in straight-chained saturated fatty acids.

Denaturation unfolds a protein by disrupting the non-covalent interactions (hydrogen bonds, ionic bonds, hydrophobic interactions) that stabilize secondary, tertiary, and quaternary structures. The primary structure's covalent peptide bonds usually remain intact.

The model proposes a dynamic, fluid phospholipid bilayer where individual lipid molecules can move laterally. Proteins are not just on the surface but are integral or peripheral, creating a "mosaic" pattern that floats within the fluid lipid sea.

A conjugated protein (holoprotein) consists of a protein part (apoprotein) and a non-protein part (prosthetic group). If the prosthetic group is a cofactor and the protein is an enzyme, its removal yields an inactive apoenzyme. The term specifically relates to the loss of the non-protein component.

The fundamental function of an enzyme is to act as a biological catalyst, lowering the activation energy and speeding up a reaction while remaining unchanged at the end. Specificity is about substrate choice, sensitivity relates to environmental factors, and regulation refers to control of its activity.

Secondary structure refers to the regular, repeated local spatial conformations of the polypeptide backbone, stabilized by hydrogen bonds between backbone atoms. The primary structure is the sequence, tertiary is the overall 3D fold of one chain, and quaternary is multi-subunit assembly.

Triglycerides are composed of a single glycerol backbone esterified to three fatty acid chains. Saponification or enzymatic hydrolysis breaks these ester bonds, yielding the original components.

A peptide bond is a covalent bond formed via a dehydration reaction between the α-carboxyl group (-COOH) of one amino acid and the α-amino group (-NH2) of another, releasing a water molecule. R-groups are involved in tertiary structure interactions, not the primary backbone linkage.

The most fundamental structural difference is that DNA is a stable, double-stranded helix, whereas RNA is usually single-stranded. While sugar differences (deoxyribose vs. ribose) are also key, the overall strandedness is a major distinguishing feature. DNA contains thymine, RNA contains uracil.