3.7 Type Of Proteins

Question 1

What are the two types of proteins and what secondary structures make them?

Answer 1

Globular - Alpha , after further folding in tertiary

Fibrous - beta pleated sheets

Question 2

Basic knowledge of fibrous and globular :

What proteins are soluble and what insoluble ?
What proteins made up of repeated amino acids?
What

Answer 2

1. Globular soluble (like insulin a hormone, hormones have to be soluble ), fibrous insoluble
2. Fibrous

Question 3

Which of 6 proteins are globular / fibrous?

Answer 3

Haemoglobin , insulin , catalyse = globular

Keratin, elastin, collagen = fibrous

Question 4

Structure of Haemoglobin (1)

How many polypeptide?, what conjugated , what prosthetic ?

Answer 4

-made from 4 polypeptide chains
a CONJUGATED PROTEIN=
- protein with a NON protein group attached, called a PROSTHETIC GROUP (haem group )

Question 5

More on structure of haemoglobin (2)- what about the polypeptide chains.

Answer 5

Each of 4 polypeptide chains, contain 2 ALPHA AND BETA SUBUNITS
- these each have a non protein prosthetic group called HAEM

• Each Haem group contains an ion = Iron
• oxygen binds to the iron, meaning per haemglobin 4 oxygen can attach

Question 6

What are the key features of a globular protein?

Answer 6

• made from alpha helix secondary folding
• spherical, compact, SOLUBLE
• Form in a way such that hydrophilic R groups are pushed on outside of molecule and hydrophobic r group away from aqueous
• thus becomes soluble

Question 7

Function of haemglobin

Answer 7

To bind with oxygen REVERSIBLE such that it can deliver it around the bids where it needs to, from the lungs…

• Reversible means it can bind and detach, by binding one oxygen changes the shape which makes it easier to bind to other , and by releasing one oxygen changes shape making it easier to change others

Question 8

Function of catalyse globular

Answer 8

• liver /kidneys make hydrogen peroxide as by product of metabolic reactions, however this is TOXIC
• catalase catalyse hydrogen peroxide into water and oxygen, protecting cell from OXIDATIVE DAMAGE, keeping safe

Question 9

Catalyse enzyme structure

Answer 9

• • contains 4 polypeptide groups in tertiary structure
• each polypeptide has a HAEM prosthetic group
• Haem groups have IRON ions , which allows catalyisation to happen

Question 10

Properties of catalyse

Answer 10

It’s an enzyme

As an enzyme is a biological catalyst , speeds up reactions without being used up itself

Question 11

Function of insulin globular

Answer 11

Hormone involved in regulation of blood glucose concentration
- converts glucose into glycogen in liver and muscles

Question 12

Structure of insulin

Answer 12

• two polypeptide chains , A and B
• A chain 21, B 30 amino acids
• disulphides bonds present in A chain, three in total holding both chains

Question 13

Properties of insulin?

Answer 13

• produced by beta cells in pancreas
• soluble as a hormone,
• specific shape, or it can’t work

Question 14

Fibrous proteins properties and structure

• what is special about amino acids here which give it its properties ?

Answer 14

• high proportion of amino acids with HYDROPHOBIC R groups in primary structure = insoluble molecules
• limited range amino acids , repeated and with small R GROUPS

= thus organised structures are made

Question 15

What don’t fibrous proteins do that globular don

Answer 15

Make 3D structures

Strong and unreactive, long

Question 16

Function of fibrous collagen

Answer 16

• found in skin ligaments tendons and nervous system
• act as supporting structures , gives strength and elasticity to them !!
• connective tissues

Question 17

Structure of collagen

Answer 17

• 3 polypeptide chains wounded to form a TRIPLE HELIX = tough rope like structure
• every third amino acid is glycine
• many hydrogen bonds in quaternary layer gives strength
• (H bonds give staggered ends which forms fibrils called tropocollagen which allows for cross link strength too)

Question 18

Properties of collagen

Answer 18

Long any flexible under stress, stiff and strong in stress

-insoluble

Question 19

Keratin function

Answer 19

Structural AND protective function for skin hair nails,

=reducing scratching and other damage

Question 20

Keratin structure

Answer 20

• large proportion of CYSTEINE, which has sulphur, meaning a lot of disulphide-bridges are formed
  : thus strong, inflexible, insoluble
• repeated amino acid arrangement, (shape of alpha helix )

Question 21

Keratin properties

(What makes it flexible).

Answer 21

• strong due to tight coils and a lot of disphide bridges , inflexible; rigid structure,
• insoluble ( due to how fibrous are (r groups hydrophobic)
• the DEGREE OF DISULPHIDE bridges determines flexibility, the more flexible, then LESS DISULPHIDE BRIDGE

Question 22

Elastin function

Answer 22

• provides resilience and elasticity to tissues, organs, blood vessels etc
• allows them to expand and return to normal size (recoil) (alveoli when breathing, blood arteries in pressure)

(- allows skin to return back if poked or pinched )

Question 23

Elastin structure

Answer 23

• made from many stretchY molecules = TROPOELASTIN
• These aggregate amongst themselves via hydrophobic areas,
• and then CROSS LINKS (covalent ) are formed in amino acid lysine

= thus still has flexibility , but strong

Question 24

Properties of elastin

Answer 24

• stretch and recoil without breaking
• confers strength flexibility to skin , organs, vessels etc
• stable

Question 25

Amount of polypeptide summary

Answer 25

Haemglobin = 4= + haem group iron each
Insulin = 2= A+B = DISULPHIDE bonds 
Catalyse = 4 haem group iron each = tetrahedral
Collagen = 3 = triple helix 
Keratin = a lot of dusting = DISULPHIDE bridges 
Elastin = tropoelastin= cross links too

Question 26

Difference getween globular and fibrous

Answer 26

1) soluble vs insoluble (r groups position )
2) complex r groups , wider range of them forming 3D shapes whereas fibrous =shorter aminos acid chains repeated amino acids with short basic r groups
3) change shape and reactive vs normally not change shape and unreactive
4) bodily functions whereas support vs structure
5) ALPHA HELIX VS BETW PLEATED SHEET