3.7 Types of Proteins

Question 1

What is the structure and function of globular proteins?

Answer 1

-Compact
-Water soluble, easily transported in water,as hydrophilic R-group are on outside of protein, this is caused by hydrophilic and hydrophobic interactions in the proteins tertiary structure
-Roughly spherical shape
-Essential for life process, eg. chemical reactions, immunity, muscular contraction

Question 2

What are example of globular proteins?

Answer 2

Haemoglobin, Insulin, Amylase

Question 3

What is a conjugated protein?

Answer 3

Globular proteins which contain a non-protein component called a prosthetic group

Question 4

What is a prosthetic group?

Answer 4

Non-protein component of a globular protein

Question 5

Explain the structure and function of haemoglobin

Answer 5

-Globular protein
-Carries oxygen around the body in red blood cells
-Quaternary protein, contain 4 polypeptides (2 alpha and 2 beta subunits)
-Contains a prosthetic heam group, which contains iron for oxygen to bind to

Question 6

Explain the structure and function of insulin

Answer 6

-Globular protein
-Hormone secreted by the pancreas, to help regular blood glucose level
-Soluble, so can be transported in the blood to tissues where it acts
-Consists of two polypeptide chains, held together by disulfide bonds

Question 7

Explain the structure and function of amylase

Answer 7

-Globular protein
-Enzyme which catalyses breakdown of starch
-Single chain of amino acids, secondary structure consists of both alpha-helixes and beta-pleated sheets

Question 8

What type of protein are most enzymes?

Answer 8

Globular

Question 9

Explain the structure and function of catalyse

Answer 9

-Enzyme which increases rate of reactions
-Quaternary protein containing 4 prosthetic heam groups
-Presence of iron in heam groups allow catalase to interact with hydrogen peroxide and speed up its breakdown

Question 10

What is a fibrous protein?

Answer 10

-Long insoluble molecules, due to presence of high proportion of amino acids within hydrophobic R-groups
-Strong
-Structural proteins, fairly unreactive
-Organised structures, due to respective sequence of amino acids within primary structure
-Usually not folded into complex 3-D shapes

Question 11

What are examples of fibrous proteins?

Answer 11

Collagen, Keratin, Elastin

Question 12

Explain the structure and function of collagen

Answer 12

-Fibrous protein
-Animal connective tissue found in skin, tendons, ligaments
-3 polypeptides wound together in a long, strong rope-like structure
-Has flexibility
-Very strong
-Minerals can bind to protein to increase rigidity
-Small size allows it to closely pack together

Question 13

Explain the structure and function of keratin

Answer 13

-Fibrous protein
-Found in external structures of humans such as skin, hair, nails
-Can be either flexible or hard and tough
-Large protection of sulfur-containing amino acid cysteine, forms many strong disulfide bridges

Question 14

Explain the structure and function of elastin

Answer 14

-Fibrous protein
-Quaternary protein
-Found in alveoli, blood vessel walls
-Gives structures flexibility to expand when needed, but also return to normal size
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