Proteins

Question 1

What determines the shape of a protein?

Answer 1

The sequence of amino acids determines the shape of a protein.

Question 2

What are the four components bonded to the central atom in an amino acid?

Answer 2

1. Amino group
2. Carboxyl group
3. Hydrogen atom
4. R-group

Question 3

What are the five classes of amino acids based on their side groups?

Answer 3

1. Nonpolar amino acids
2. Polar uncharged amino acids
3. Positive amino acids
4. Negative amino acids
5. Aromatic amino acids

Question 4

What are proteins made of?

Answer 4

A long chain of amino acids called a polypeptide.

Question 5

In general, what causes a polypeptide to fold into a specific shape?

Answer 5

Interactions between side groups.

Question 6

Identify and explain the four levels of protein structure

Answer 6

1. Primary: Linear sequence of amino acids joined by peptide bonds in the polypeptide chain. It is unstable, not functional, and is temporary.
2. Secondary: Hydrogen bonding between peptide groups cause segments of the polypeptide to be collected and folded into one of two shapes: alpha helices and beta sheets. This structure remains unstable and not functional.
3. Tertiary: Attractive forces between R-group side chains on different sections of the polypeptide causes folding into a stable ‘final’ 3D shape.
4. Quaternary: Consists of more than two polypeptide chains to form the overall protein structure.

Question 7

What is denaturation?

Answer 7

When a polypeptide chain quickly unravels and loses its shape due to physical and chemical factors (e.g. high temperatures, pH, salt concentration, and denaturation agents).

Question 8

What is renaturation?

Answer 8

When a polypeptide chain refolds into its native shape after denaturation, restoring its function.

Question 9

What are denaturation agents?

Answer 9

Substances that react with the amino acid side chains, disrupting the hydrogen bonds, ionic bonds, and covalent bonds that maintain the protein’s shape.