Proteins

Question 1

What are the elements in protein?

Answer 1

Carbon, hydrogen, oxygen, nitrogen and sometimes sulfur

Question 2

What are the six types of proteins by function?

Answer 2

1. Structural e.g. collagen, keratin
2. Regulatory e.g. the hormone insulin
3. Contractile e.g. myosin, actin
4. Immunological e.g. antibodies, interleukins
5. Transport e.g. haemoglobin
6. Catalytic enzymes e.g. amylase

Question 3

What are the monomers of proteins and how many are there?

Answer 3

Amino acids, 20

Question 4

What are the three functional groups found on all amino acids?

Answer 4

1. An amino group (–NH₂)
2. An acidic carbonyl group (–COOH)
3. A side chain (–R)

Question 5

What is the name given to the covalent bonds which join amino acids?

Answer 5

Peptide bonds

Question 6

What is the name given to two amino acids joined together?

Answer 6

Dipeptide

Question 7

What is the name given to three amino acids joined together?

Answer 7

Tripeptide

Question 8

What is the name given to 4-9 amino acids joined together?

Answer 8

(chainlike) peptide

Question 9

What is the name given to 10+ amino acids joined together?

Answer 9

Polypeptide

Question 10

What are the four levels of structural organisation of proteins?

Answer 10

1. Primary: 1D sequence of amino acids
2. Secondary: 2D twisting and folding of the peptide chain
3. Tertiary: 3D shape of a polypeptide chain
4. Quaternary: when a protein has more than one polypeptide chain, the arrangement of them relative to one another

Question 11

What are the two classifications of proteins by shape?

Answer 11

1. Fibrous proteins
2. Globular proteins

Question 12

List three key features of fibrous proteins and give some examples

Answer 12

1. Insoluble in water
2. Polypeptide chains are parallel to each other
3. Have structural functions
   Examples: collagen, elastin, keratin, actin, myosin

Question 13

List three key features of globular proteins and give some examples

Answer 13

1. Soluble in water
2. Polypeptide chains are spherical in shape
3. Have metabolic functions
   Examples: enzymes, antibodies, haemoglobin, insulin

Question 14

What is the term for a protein which has lost it’s shape and therefore become non-functional?

Answer 14

Denatured protein

Question 15

Why is the shape of a protein so important?

Answer 15

It allows it to interact with it’s target molecules and therefore perform it’s function