3.7 Types of proteins

Question 1

what are the 3 types of proteins

Answer 1

• globular
• conjugated
• fibrous

Question 2

properties of globular proteins

Answer 2

• compact
• water soluble
• roughly spherical
• formed when folding into tertiary structure

Question 3

example of a globular protein

Answer 3

INSULIN

• regulates blood glucose concentration
• soluble as it is transported in blood
• fit into specific receptors so has precise shapes

Question 4

properties of conjugated proteins

Answer 4

• globular proteins with prosthetic group

e. g. haem groups, metal ions/molecules, lipids/carbohydrates

Question 5

examples of conjugated proteins (2)

Answer 5

HAEMOGLOBIN
-quaternary
-each subunit has haem group
-iron ions combine reversibly with oxygen (allows transportation)
CATALASE
-enzyme
-quaternary with 4 prosthetic haem groups
-iron ions allow it to interact with hydrogen peroxide(byproduct of metabolism)and speed its breakdown

Question 6

properties of fibrous proteins

Answer 6

• formed from long, insoluble molecules
• due to high proportion of amino acids with hydrophobic R-groups
• very organised structures
• strong+long molecules

Question 7

examples of fibrous proteins (3)

Answer 7

KERATIN

ELASTIN

COLLAGEN

Question 8

properties of keratin

Answer 8

• in hair/skin/nails
• strong disulfide bonds
• strong, inflexible and insoluble
• unpleasant smell when burnt due to sulfur

Question 9

properties of elastin

Answer 9

• in elastic fibres (give flexibility to expand and return to normal size)
• quaternary protein

Question 10

properties of collagen

Answer 10

• connective tissue in skin, tendons, ligaments and nervous system
• 3 polypeptides would in long, rope-like structure
• flexible