Proteins

Question 1

What is the general structure of an amino acid?

Answer 1

Amino group - (NH2)

Carboxyl group - (carbon double bonded to oxygen and single bonded to OH)

R group - variable (20 different R groups in the body therefore 20 different amino acids)

Hydrogen

Carbon in the middle

Question 2

What is a dipeptide?

Answer 2

2 amino acids joined together by a peptide bond

Question 3

How is a dipeptide formed?

Answer 3

Condensation reaction occurs between the carboxyl (COOH) group of one amino acid and the H of the amino (NH2) group of another amino acid

-Peptide bond forms between C of carboxyl group and N of amino group producing a water molecule

Question 4

What are the 4 key proteins

Answer 4

Haemoglobin
Collagen
Keratin
Enzymes

Question 5

What are the properties of a fibrous protein and give an example

Answer 5

• Structural
• Insoluble in water
• Strong
  Eg collagen and keratin

Question 6

What are the properties of a globular protein and give an example

Answer 6

• metabolic
• spherical
• soluble in water (transport and catalyse reactions in solution)
  Eg haemoglobin and enzymes

Question 7

Describe the structure of collagen

Answer 7

• Primary structure: unbranched polypeptide chain
• Secondary structure: polypeptide chain is tightly wound into an alpha helix
• Tertiary structure: a second helix
• Quaternary structure: involves three polypeptide chains cross-linked and wound like a rope. Their starts are staggered along the fibre

Question 8

What is a polypeptide?

Answer 8

When 2 or more amino acids bond together

Question 9

What are the properties of proteins?

Answer 9

• Usually very large
• Each protein has a specific shape and structure which allows it to carry out its specific function

Question 10

What are amino acids?

Answer 10

Basic monomers that join through a condensation reaction to form polypeptides

Question 11

What bond joins amino acids?

Answer 11

Peptide bonds