Proteins and Enzymes

Question 1

Polypeptide

Answer 1

A polymer of many amino acids linked together by peptide bonds

Question 2

Primary structure

Answer 2

The level of protein structure referring to the specific linear sequence of amino acids.

Question 3

Primary structure

Answer 3

A linked series of amino acids with a unique sequence. The primary structure in turn dictates secondary and tertiary structure, due to the chemical nature of the backbone and the side chains (R groups) of the amino acids positioned along the chain.

Question 4

Secondary structure

Answer 4

Regions of repetitive coiling or folding of the polypeptide backbone of a protein due to hydrogen bonding between constituents of the backbone (not the side chains)
α-helix
A coil held together by hydrogen bonding between every fourth amino acid.
β-pleated sheet
In this structure two or more strands of the polypeptide chain lying side by side (called β strands) are connected by hydrogen bonds between parts of the two parallel polypeptide backbones.

Question 5

Tertiary structure

Answer 5

The overall shape of a protein molecule due to interactions of amino acid side chains, including hydrophobic interactions, ionic bonds, hydrogen bonds, and disulfide bridges.
The irregular folding pattern produced by weak interactions between the R groups of the polypeptide. The folding in tertiary structure is irregular because the sequence of R groups is irregular.

Question 6

Quaternary structure

Answer 6

Some proteins consist of more than one polypeptide, called oligomeric proteins, the overall structure is called its quaternary structure.
The particular shape of a complex, aggregate protein, defined by the characteristic three-dimensional arrangement of its constituent subunits, each a polypeptide.
Collagen (3 subunits) and haemoglobin (4 subunits) are classic examples of oligomeric proteins.
The polypeptides of an oligomeric protein are generally held together by weak interactions, but can also be linked by covalent bonds.

Question 7

Denaturation

Answer 7

In proteins, a process in which a protein loses its native shape due to the disruption of weak chemical bonds and interactions, thereby becoming biologically inactive; in DNA, the separation of the two strands of the double helix. Denaturation occurs under extreme (noncellular) conditions of pH, salt concentration, or temperature

Question 8

Enzyme

Answer 8

A macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction. Most enzymes are proteins

Question 9

Substrate

Answer 9

The reactant on which an enzyme works

Question 10

Active site

Answer 10

The specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs.