1. Proteins (I)

2. Elements C H O
and N
sometimes S
Textbook p98-99

3. Testing for proteins
Biuret test (pale blue colour containing sodium hydroxide and copper sulfate)
The chemicals react with the peptide bonds found in protein, which results in a colour change to lilac. Does not require any heating

4. What are proteins made from?
Acid group
What are proteins made from?
Amino group
Amino acids
20 different types
Each amino acid has an amino group at one end and an acid group at the other.

5. R groups
Can be
Big
Postively charged
Negatively charged
Acidic
Basic
Hydrophobic
Hydrophilic
Include Sulphur
Ring structures
Such properties will influence the higher level structures of the protein – more of this later
Textbook p98-99

6. Plants Animals Manufacture the amino acids they need
Nitrate – used to form amino groups which are then bonded to organic groups.
Animals
Must take amino acids in as part of their diet.
8-10 of the 20 amino acids are essential amino acids (meat and soya)
Can’t store excess amino acids – amino group makes them toxic
Deamination

7. Forming peptide bonds Condensation reaction
Peptide bond formed. This can be broken by a hydrolysis reaction.

8. Proteins from amino acids
Dipeptides
Polypeptides (10 or more amino acids) and proteins
Amino acids in proteins are known as residues (due to loss of the water molecule and therefore part of the amino acid structure)
Draw four amino acids joined together with peptide bonds (use general structure with the R group)

9. Making polypeptides and proteins
On ribosome (protein synthesis)
Uses mRNA
According to the code on the mRNA the amino acids are assembled in the right order and then joined by a peptide bond.

11. Primary structure of proteins
What is it?
Consider a protein chain that is four amino acids long....
It has 20 x 20 x 20 x 20 possibilities = 160,000!
The primary structure of a protein is given by the specific sequence of amino acids that make up the protein
What codes for each of the proteins primary structures?

12. Breaking down proteins
Enzymes involved... Protease enzymes
Looking at two examples:
Hormone regulation
Ageing

13. Answers to Q8 from booklet