Proteins

Question 1

How are proteins formed?

Answer 1

Two amino acids bond in a condensation reaction to form a dipeptide, with a peptide bond forming in between.

Question 2

What are the two types of secondary protein structures?

Answer 2

Alpha helices and beta pleated

Question 3

Describe an alpha helix

Answer 3

A chain of amino acids may twist to form an alpha helix. Within the helix, hydrogen bonds for, between the c- -o and the -NH which stabilizes the shape.

Question 4

How are beta pleated sheets formed?

Answer 4

Several chains may link together with hydrogen bonds, this holds the parallel chains in a beta pleated sheet

Question 5

How is a final tertiary structure maintained?

Answer 5

Chemical bonds and hydrophobic interactions between R groups

Question 6

How are the hydrophobic R groups arranged?

Answer 6

They are arranged so that they face the inside of the protein, excluding water from the center of the molecule.

Question 7

What are classified as quaternary structures?

Answer 7

Only proteins with several polypeptide chains. Single chain structures stop at tertiary level.

Question 8

What is meant by a conjugated protein?

Answer 8

They have another chemical group associated with their polypeptide chain

Question 9

What are the two types of proteins and explain?

Answer 9

1. Globular (metabolic functions)
   The polypeptide chain is folded into a compact spherical shape. They are soluble because of the hydrophilic side chains that project from the outside of the molecules.
2. Fibrous (structural functions)
   These don’t fold up into a ball shape but remain as long chains. These can be cross linked for additional strength