Biochemistry: Biomolecules

What are the four chemical groups attached to the central alpha-carbon of a standard amino acid?

An amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable R-group (side chain).

Describe the chemical reaction and the specific atoms involved in the formation of a peptide bond.

A dehydration synthesis (condensation) reaction occurs between the carboxyl carbon of one amino acid and the amino nitrogen of another, releasing a water molecule.

What specific interaction stabilizes the alpha-helix and beta-pleated sheet structures in proteins?

Hydrogen bonding between the carbonyl oxygen and the amide hydrogen of the polypeptide backbone.

Name four types of interactions between R-groups that stabilize the tertiary structure of a protein.

Hydrophobic interactions, hydrogen bonds, ionic bonds (salt bridges), and disulfide bridges.

Define quaternary structure in the context of protein folding.

The spatial arrangement and interaction of multiple polypeptide chains (subunits) to form a functional multi-subunit protein complex.

How does a significant change in pH lead to protein denaturation?

It alters the ionization state of R-groups, disrupting ionic bonds and hydrogen bonds that maintain the protein's three-dimensional shape.

What functional group distinguishes an aldose from a ketose in monosaccharides?

An aldose contains an aldehyde group at the end of the carbon chain, while a ketose contains a ketone group, usually at the C2 position.

Explain the structural difference between alpha-1,4-glycosidic bonds and beta-1,4-glycosidic bonds.

In alpha-1,4 bonds, the -OH on the anomeric carbon is below the ring plane (trans to C6), while in beta-1,4 bonds, it is above the ring plane (cis to C6).

Why is sucrose considered a non-reducing sugar while maltose is a reducing sugar?

Sucrose has both anomeric carbons locked in a glycosidic bond, whereas maltose has a free anomeric carbon that can open into a reactive aldehyde.

How does the branching of glycogen compare to amylopectin, and why is this biologically significant?

Glycogen is more highly branched (every 8-12 residues) than amylopectin (every 24-30), allowing for faster glucose mobilization in animals.