Protiens

b1.2

Amino acids

Amino acids

amino acids are considered as the building blocks for protiens

each amino acid molecule has s central carbon atom called alpha carbon, with single covalent bonds to four other atoms. covalent bonds to four other atom, nitrogen atom called amine group and another is carbon atom of a carboxyl group.

Carboxyl goup is acidic as it given a proton and amine group is basic as it accepts one, amino acids are amphiprotic which means that they can accept or donate protons thus they can act aicdic or basic.

Condensation

Dipeptides: two amino acids getting linked by condensation reaction

polypeptides more than 20 amino acids linked by condensation

oligopeptides less than 20 but more than 2 amino acids

polypepeides are main componenets of protiens

Amino acids are linked with peptide bonds, which are formed with condensation reaction between amine group of one amino acid and carboxyl group of another

This reaction gets catalysed in cells by ribosomes

Amine group of free amino acid is linked to carboxyl group at the end of growing chain

peptide bond remains the same, regardless the R group of amino acids

dietary requirements

ribosomes use20 different amino acids to make polypeptides, whereas plants make all by photosunethiem

two types of amino acids

essential and non essential amino acids

essnetial amino acids: they cannot be synthesized in enough quanity thus are obtained through diet

phenylalanine—> essential cannot be synthesized, whereas tyrosine a non essential amino acid which is made from phenylalanine.

non essential amino acis are synthesized through metabloic pathways, and they trun esential when need

all foods have differnt types of amino acids

Infinity variety

ribosomes link amino acids till polypeptides are formed, since bond can be formed between any amino acid, in any sequence ribsomes follow genetic code

exampls of polypeptides:

• beta-endorphin which is a natural pain killed scereted by pituitary glad which is a polypeptide of 31 amino acids

• insulin has two short polypeptides one with 21 and other with 30 amino acids

• alpha amylase single polypeptide of 496 amino acids, one chloride ion and one clacium ion

  • titin polypeptide of 34350 amino acids.

effect of ph and temp on protien stucture

protiens are stablised by bonds b/w R groups of amino acis within a molecule

R group—> weak and easy to distrupt bonds

causing change and leads to denaturation

Once a protien is denatured it is permanent change

• soluble protiens become insoluble and create percipitate

  • R- group is hydrophboic and is exposed to water

• heat causes denaturation due to virbateion in molecules cauing breaking of intermolecular bonds.

• protiens heat and temp tolerance is difference in organisms living clpser to volcanic eruptions habe higher tolerance

• extreme pH causes denaturation of protien as this chnages power in R group. either ionic bonds are broken or new bonds are created.