Types Of Proteins

Question 1

what are the two main types of protein?

Answer 1

• globular
• fibrous

Question 2

what are some features of globular proteins?

Answer 2

• compact
• water soluble
• roughly spherical in shape.

Question 3

how are globular proteins formed?

Answer 3

when proteins fold into their tertiary structure in a way whereby hydrophobic R groups of the amino acids are kept away from the aqeuous environment. hydrophilic R groups are on the outside so they are soluble in water.

Question 4

what are globular proteins useful for?

Answer 4

• chemical reactions.
• immunity.
• muscle contractions.

Question 5

what is an example of a globular protein?

Answer 5

insulin

Question 6

what is the role of insulin?

Answer 6

involved in the regulation of blood glucose concentration.

Question 7

why do hormones (insulin) need to be soluble?

Answer 7

they are transported in the bloodstream.

Question 8

why do hormones need to have a specific shape?

Answer 8

they have to fit into the specific receptors on cell-surface membranes to have their effect.

Question 9

what are conjugated proteins?

Answer 9

they are globular proteins that contain a non-protein component called a prosthetic group.

Question 10

what is an example of a prosthetic group?

Answer 10

haem groups. catalase and haemoglobin both contain haem groups.

Question 11

what is haemoglobin?

Answer 11

the red, oxygen carrying pigment found in red blood cells. It is a quaternary protein made up of two alpha and two beta subunits (haem group with each subunit.)

Question 12

how does haemoglobin transport oxygen around the body?

Answer 12

iron 2 ions present in haem groups are able to combine reversibly with an oxygen molecule.

Question 13

what is catalase?

Answer 13

an enzyme; a quaternary protein containing four haem groups

Question 14

how many haem prosthetic groups does catalase contain?

Answer 14

4

Question 15

what are some examples of fibrous proteins?

Answer 15

• keratin
• collagen
• elastin

Question 16

how are fibrous proteins formed?

Answer 16

formed from long, insoluble molecules. this is due to the high proportion of amino acids with hydrophobic R-groups in their primary structure. amino acid structure quite repetitive.

Question 17

what are features of fibrous proteins?

Answer 17

• strong
• long
• insoluble
• not folded into complex three dimensional shapes.

Question 18

where is keratin present?

Answer 18

hair, skin, nails.

Question 19

do more or less disulphide bonds make it more or less flexible?

Answer 19

less bonds - more flexible.

Question 20

are disulphide bonds strong?

Answer 20

yes.

Question 21

why does burnt skin/hair smell bad?

Answer 21

large presence of sulfur.

Question 22

where are elastic fibres found?

Answer 22

walls of blood vessels and alveoli.

Question 23

what is elastin?

Answer 23

a quaternary protein made from any stretchy molecules called tropoelastin.