ProteinsProteins

ProteinsProteins Functions- structural, regulating cell Functions- structural, regulating cell

functions (enzymes), antibodies, functions (enzymes), antibodies, hormoneshormones

Made of chains of amino acidsMade of chains of amino acids There are 20 amino acids that are used by There are 20 amino acids that are used by

all living organisms to make proteinsall living organisms to make proteins Proteins can be any length and any Proteins can be any length and any

combination of amino acids therefore there combination of amino acids therefore there are millions of proteins used by living are millions of proteins used by living organisms.organisms.

Amino acids contain an amino Amino acids contain an amino group, a carboxyl group, a carbon group, a carboxyl group, a carbon

and a unique R groupand a unique R group

http://www.biotopics.co.uk/as/aa.html

http://www.johnkyrk.com/aminoacid.html

Polar R groups make the amino acid hydrophilic

Ionic R groups make the amino acid hydrophilic

Non-polar R groups make the amino acid hydrophobic

Functions of amino acidsFunctions of amino acids

Protein synthesis, energy reserve, Protein synthesis, energy reserve, hormones (thyroxin)hormones (thyroxin)

20 different amino acids used in protein 20 different amino acids used in protein synthesis though others do occur in nature.synthesis though others do occur in nature.

Essential amino acids cannot be Essential amino acids cannot be synthesised by the organism and must form synthesised by the organism and must form part of their dietpart of their diet

http://www.biotopics.co.uk/JmolApplet/jcontentstable.htmlhttp://www.biotopics.co.uk/JmolApplet/jcontentstable.html http://www.biology.arizona.edu/biochemistry/problem_sets/aa/aa.htmlhttp://www.biology.arizona.edu/biochemistry/problem_sets/aa/aa.html

© 2007 Paul Billiet

N C C-OH

R

H

OH

H

N C C-OH

R

H

OH

H

Condensation reaction

N C C

R

H

OH

HN C C-OH

R

H

OH+ H2O

The peptide bond

A dipeptide is formed

© 2007 Paul Billiet ODWS

Formation of a Dipeptide

http://www.biotopics.co.uk/as/aminocon.htmlhttp://www.biotopics.co.uk/as/dipeptidehydrolysis.html

Formation of a PolypeptideFormation of a Polypeptide

Serine Valine Tyrosine Cysteine

3 H2O

ProteinProteinss

When many amino acids bond together to create When many amino acids bond together to create long chains, the structure is called a protein (it is long chains, the structure is called a protein (it is also called a also called a polypeptidepolypeptide because it contains many because it contains many peptide bonds).peptide bonds).