3.7 Type Of Proteins Flashcards
What are the two types of proteins and what secondary structures make them?
Globular - Alpha , after further folding in tertiary
Fibrous - beta pleated sheets
Basic knowledge of fibrous and globular :
What proteins are soluble and what insoluble ?
What proteins made up of repeated amino acids?
What
- Globular soluble (like insulin a hormone, hormones have to be soluble ), fibrous insoluble
- Fibrous
Which of 6 proteins are globular / fibrous?
Haemoglobin , insulin , catalyse = globular
Keratin, elastin, collagen = fibrous
Structure of Haemoglobin (1)
How many polypeptide?, what conjugated , what prosthetic ?
-made from 4 polypeptide chains
a CONJUGATED PROTEIN=
- protein with a NON protein group attached, called a PROSTHETIC GROUP (haem group )
More on structure of haemoglobin (2)- what about the polypeptide chains.
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
What are the key features of a globular protein?
- 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
Function of haemglobin
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
Function of catalyse globular
- 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
Catalyse enzyme structure
- contains 4 polypeptide groups in tertiary structure
- each polypeptide has a HAEM prosthetic group
- Haem groups have IRON ions , which allows catalyisation to happen
Properties of catalyse
It’s an enzyme
As an enzyme is a biological catalyst , speeds up reactions without being used up itself
Function of insulin globular
Hormone involved in regulation of blood glucose concentration
- converts glucose into glycogen in liver and muscles
Structure of insulin
- 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
Properties of insulin?
- produced by beta cells in pancreas
- soluble as a hormone,
- specific shape, or it can’t work
Fibrous proteins properties and structure
- what is special about amino acids here which give it its properties ?
- 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
What don’t fibrous proteins do that globular don
Make 3D structures
Strong and unreactive, long
Function of fibrous collagen
- found in skin ligaments tendons and nervous system
- act as supporting structures , gives strength and elasticity to them !!
- connective tissues
Structure of collagen
- 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)
Properties of collagen
Long any flexible under stress, stiff and strong in stress
-insoluble
Keratin function
Structural AND protective function for skin hair nails,
=reducing scratching and other damage
Keratin structure
- 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 )
Keratin properties
(What makes it flexible).
- 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
Elastin function
- 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 )
Elastin structure
- 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
Properties of elastin
- stretch and recoil without breaking
- confers strength flexibility to skin , organs, vessels etc
- stable
Amount of polypeptide summary
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
Difference getween globular and fibrous
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
