protein structure and amino acids Flashcards
what are proteins?
a diverse group of molecules
can exist in many different shapes and sizes
can exhibit a range of chemical and physical properties
what are the 2 general classes of proteins?
fibrous and globular proteins
describe fibrous proteins?
- important structural proteins
-long thread like tough and insoluble in water
what does fibrous proteins make?
bone, skin, tendons, cartilage, hair, wool, fur, nails, claws, scales, feathers, muscle, silk
what does fibrous proteins include>
collagens, keratin, fibrin, elastins
describe collagen?
25-35% total protein in mammals
major component of connective tissues (bones, teeth, cartilage, tendons, ligaments, blood vessels, skin)
describe collagen in bone?
found along with calcium phosphate polymer
describe collagen in tendons?
collagen forms stiff fibres with high tensile strength
describe collagen in skin?
collagen is loosely woven allowing expansion in different directions
describe keratin?
major component of skin, fur, hair
composed almost entirely of helix structures (slightly more tightly wound than -helix)
what is the basic unit of keratin?
protofibril
describe globular proteins?
have important ‘biological’ or ‘operational’ functions
roughly) spherical in shape
more soluble than fibrous proteins
glob proteins include enzymes, hameoglobin etc
what is a conjugated protein?
contain a protein component associated with a non-protein component
all protein are made from what?
20 amino acids
the amino acid side chains vary in?
size
charge
shape
chemical reactivity
what is the basic amino acid structure
draw
what are the classes of amino acids?
aliphatic
imino
hydroxy
sulphur-containing
aromatic
heterocyclic
basic
acidic (+ amide derivatives)
describe aliphatic amino acids?
c atoms in the side chain are arranged in chains. because these amino acids contain C and H they prefer to make non polar covalent bonds
-partially soluble in h20
the longer the side chain the more hydrophobic the amino acid
describe hydroxy amino acids?
side chains have a OH group
these side chains contain O as well as carbon and hydrogen (electronegatives) they prefer to make polar bonds
readily soluble in h20
sulphur containing AA
have aliphatic side chains
have thiol (SH) or thioether (S-CH3) groups
are hydrophobic amino acids
what are aromatic amino acids/
side chains contain benzene skeleton
are hydrophobic amino acids
heterocyclic amino acids?
eg. histidine
the ring structure is not composed of just one sort of atom
histidine is hydrophilic
what are basic amino acids?
+ charged at neutral pH
what are acidic amino acids?
- charged at a neutral pH
-secondary carboxylic acidic (COO-) group
-hydrophilic
-amide derivatives have an amide group instead (CONH2)
what is an imino acid?
has an aliphatic side chain, cyclised by bonding to the N atom of the amino group
hydrophobic
what is important about the amino side chain?
plays a large part in controlling its chemical and physical properties
an amino acid solubility depends on
the structure of the side chain
where would you find regions of proteins containing hydrophobic AA
may exist in hydrophobic intracellular environments (eg. within membranes)
what can bacteria do?
bacteria can synthesise all amino acids
humans can do what?
humans can only synthesise 10 from other precursor molecules
the remainder must be obtained in the diet (essential amino acids)
lysine and tryptophan
vegeatrains must have proptions of these in the diet
