Amino acids and proteins

Functions of proteins

• structural- i/e collagen (bone , cartilage, tendon), keratin(hair) , actin, muscle

• enzymes , i/e amylase , pepsin, catalase etc (100,000 others)

• hormones i/e-insulin, glucagon

• receptors i/e- rhodopsin

• antibodies i/e- IgG

• blood clotting - thrombin, fibrin

• lubrication-i/e glycoproteins in synovial fluid

• toxins -i/e dipheria toxin

• contractile - actin, myosin

• antifreeze- glycoproteins in arctic flea

Levels of protein structure

• primary

• secondary

• tertiary

• quaternary

What elements do proteins contain

carbon, hdyorgen , oxygen and nitrogen( cytosine- amino acids has sulfuric acid in it

Primary structure

specific sequence of amino acids joined together by peptide bonds to form a polypeptide

Why is primary structure so important

sequence dtermines the shape and therefore function, of the protein

What do ALL amino acids have

ALL AMINO ACIDS HAVE:

• a central C atom attached to

• an H atom

• an alkaline Amine group (-NH2)

• an acid carboxyl group (-COOH)

• a variable group - there are 20 naturally occurring amino acids , each with a different -R group

Why are amino acids said to be atmospheric nature

• in solution the amino end can act as a base (by accepting H+ ions)

• carboxyl end can act as an acid (by giving H+ ions)

• atmospheric molecules act as a buffers

What gives amino acids variation

side chains give each amino acids a unique chemistry that influeces how it interacts with other amino acids

What can amino acids be calssified as

• non polar

• polar

• acidic (negatively charged)

• basic (positively charged)

What type of bonds are between amino acids when they join togeether

peptide bonds

How are peptide bonds (in amino acids)formed and is the type of raction that joins amino acids together

condensation reaction

How are peptide bonds ( in amino acids) broken

• hydrolysis reaction

What happens when 2 amino acids are joined together

a dipeptide are formed

When many amino acids joined together what forms

when many amino acids are formed a long chain polypeptide is formed

What type of reaction forms a polypeptide

a polymerisation reaction

What shapes form and what do they do in the seondary structure

• polypeptides become twisted and coiled giving additional strength to the structure

2 common secondary structures ?

• alpha-helix

• beta-pleated sheet

What type of bonds formed between structures and what atoms are involved in the bonding

• structures form due to hydrogen bonds between atoms involvedin peptide bonds - a positive NH group on one side and a negative C=O in the other side

In tertiary structure what does a polypeptide fold into

Polypeptide chains to form a specific 3D structure

In tertiatery structure what part of the amino acid is involed in forming bonds

there is bonding between R groups( van der waals forces)

What are the 3 bonds in the teriary structure

• hydrogen bonds

• ionic bonds(salt bridges)

• disulphide bridge(cysteine)

What are the atoms inolved , affected by and relative stability of the hydrogen bond

• atoms involved: -OH , H2N-

• affected by: temp and pH

• relative stability: easily broken

What are the atoms inolved , affected by and relative stability of the ionic bond

• atoms involved: -NH3+, COO-

• affected by: affected by pH

• relative stability: stronger than H bonds

What are the atoms inolved , affected by and relative stability of the disulphide bonds

• atoms involved: -CH2S, SCH2-

• relative stability: covalent bind formed from oxidation reaction- only broken by reducing agents

Quaternary Structure

• some proteins have more than 1 polypeptide chain

• each chain is held together in a precise structure

• conjugated proteins have non-protein groups called a prosthetic group- i/e metals , carbs(glycoproteins), lipids (lipoproteins)

What test to use for proteins and what does it do

biuert test- detects presensce of peptide bond which indicates protein is present

What happens in test for protein

• place a sample of oslution to be tested into a test tube and add an equal volume of sodium hydroxide solution at room temp

• add a few drops of very dilute (0.05%) copper II sulphate solution and mix gently

• colour change from blue to purple indicates a positive result- protein present