PROTEINS Flashcards
What are proteins?
Sequence of amino acids
1 or more polypeptides
C,N,H,O
What are amino acids?
Amine group, R group, hydrogen, carbon and carboxylic group
What is the variable part of an amino acid?
The R group
20 amino acids commonly found in cells
5 are non essential- body can make them from OTHER amino acids
9 are ESSENTIAL- made from what we eat
6 are conditionally essential- young children growing
How do plants get amino acids
Make their own amino acids from glucose and nitrate ions
How are peptides made?
Amino acids joining
Carboxylic acid and amine group react
Oh in one of AA react with H in another
Peptide bond froms, h20 released , peptidyl transferase
Polypeptide?
1 reguarly repeating backbone, NCCNCCNCC
And a variable part(different R chains)
Are polypeptides polar ?
Have polarity
Ends are different with amine at one end and carboxylic at the other
Primary level of protein
Specific sequence of amino acids PEPTIDE BONDS (carboxyl of one and amine of next) Particular amino acids in the sequence influence how the peptide folds to give the proteins final shape, determining its function
SECONDARY level of protein
Coiling or folding of polypeptide backbone into a 3d shape
Folding takes place as the polypetide chain grows longer, to prevent tangling
Alpha helix( secondary level)
O,H,N of amino acids reacts
Stabilized by H bonds between oxygen of a C=O and hydrogen of N-H
R groups not involved
Beta pleated sheet( secondary level)
Backbone fully extended- NOT coiled
CHains lie parallel to one another, joined by H bonds
SHeet like structure
same bonding as alpha
TERTIARY level of protein
Final 3D shape( determines protein function)
Structure is stabilized by bonds between R groups
What are the interactions between R groups in tertiary structure
Disulphide bonds
Ionic
Hydrophilic and phobic interactions
Hydrogen
QUATERNARY level of protein
2 or more individual proteins( subunits)
Same interactions as in the 3rd structure BUT between different molecules
e.g. haemoglobin
What are globular proteins
VARIED amino acid sequence
Soluble in water
Compact and spherical
Form when proteins fold into 3rd stucture
Insulin
GLOBULAR
Hormone involved in regulation of blood sugar concentration
Soluble ( blood)
Made of 2 polupeptide chains joined by disulphide bonds
ALPHA chain - starts with a chain
BETA CHAIN- ends with B pleated sheet
Haemoglobin
GLOBULAR
4 polypeptides- 2 a and 2 b subuntis
Each subunit contains a prosthetic haem group
fe2+ able to combine reversibly with oxygen
HELIX , water soluble
Catalase
GLOBULAR Enzyme Converts H202 - water and oxygen Used iron ion to assist 4 subunits
Congugated protein
Globular proteins that contain a non protein component called a proshetic group
WITHOUT a prosthetic group= simple
Fibrous proteins
Long, insoluble Hydrophobic R group majorities Limited range of AA, higher packing AA repetiitive -organised long chains which run PARALLEL, cross bridges= stable Not usually 3d
COLLAGEN
High tensile strength, insoluble, nonreactive
CONNECTIVE tissue
3 polypeptides wound together in a long and strong rope like structure( triple helix)
Flexible
Skin, tendon, ligaments
ELASTIN
Found in elastic fibers
Stretch and recoil
QUATERNARY
Elastic fibres found in blood vessel walls, alveoli
Made from covalent joined elastic molecules
KERATIN
Hair, skin, nails
Primary sequence contains many cysteine amino acids
Can form strong disulphide bonds
Strong, inflexible and insoluble
Degree of disulphide bonds determines flexibility
Why are globular proteins soluble
Hydrophobic r groups get away from aqueous environments and hydrophilic on outside of the protein = soluble
