proteins definition
complex organic substance made of carbon, hydrogen, oxygen, nitrogen
- >50% of dry mass of most cells
proteins are built up of…
- monomers: amino acids
- two amino acids undergo condensation reaction
-> bond between two amino acids is strong covalent bond (peptide bond) - amino acids linked up by peptide bonds -> polypeptide
some roles of proteins
- enzymatic reactions
- structural support
- storage
- transport
- cellular communication
- movement and defense against foreign substances
amino acid structure
1) R group/side chain
- confers different chemical properties and identities of amino acids
2) amino group
- lhs (HNH)
- nitrogenous component
- basic (alkaline)
3) carboxylic acid group
- rhs
- acidic
amino acid categorisation (4)
1) non-polar neutral
2) polar neutral
3) polar acidic
4) polar basic
non polar neutral categorisation
- non-polar: hydrophobic r group
- neutral: no charge
methionine
- CH2, CH2, S, CH3
tryptophan
- CH2, indole ring – hydrophobic component
polar neutral categorisation
- polar: hydrophilic R group
- neutral: no charge
threonine
- CH, CH3, OH
tyrosine
- OH
OH groups (hydroxyl)
polar acidic categorisation
- polar: hydrophilic R group
- acidic: weak acid
aspartic acid
- CH2, C = O - O
glutamic acid
- CH2, CH2,C = O, O
COOH- carboxyl group
polar basic categorisation
- polar; hydrophilic R group
- basic: weak alkali
arginine
- CH2, CH2, CH2, NH, C =H2N, - NH2
(what group) extremely basic because its positive charge is stabilised by resonance
hisidine
C, HN, CH, HC=NH
- nitrogens have weak affinity for an H+ and are only partly positive at neutral PH
non-essential amino acids
- can be synthesised by the body, even if not directly consumed in diet
- body typically produces them through metabolic processes involving other amino acids or intermediates
eg: amino acid glutamine can be synthesised from glutamate by incorporating ammonia - vital for physiological function
essential amino acids
- acids ghat the human body cannot synthesise internally
- inability due to lack of specific enzymes or metabolic pathways needed to produce these compounds
- essential amino acids must be obtained through dietary sources (meat, diary, eggs, etc)
- play important role in protein synthesis, tissue repair, various metabolic processes essential for growth, immune function, overall health
peptide bonds
- linkage between amino acids and polypeptide chain
(the amino group of one amino acid and the carboxyl group of another - through condensation
- catalysed by enzymes
dipeptide
2 amino acids joined by a single bond
peptide
more than two amino acids joined by multiple peptide bonds
denaturation
- proteins/nucleic acids lose the quaternary structure, tertiary structure and seconding structure, present in their native state
- loss of specific #D conformation of a protein molecule
denaturation processes (6)
acids/base
organic solvents
salt solution
pressure
heat
mechanical force
