1. Biology Induction

2. Course Content

4. AS Biology

5. A-Level Biology

6. AS Practical Work

7. Career options

8. Degree options

9. Research Based IS Task
Due date: 1st lesson back after the summer holidays
Compare and contrast the structure and function of prokaryotic and eukaryotic cells. This should be no longer than 750 words
Reducing sugars are a type of carbohydrate molecule. Produce an ISA style apparatus list, method and risk assessment to describe how you would safely test for the presence of reducing sugars in an unknown solution – Solution A
Both tasks require you to carry out independent research and your sources of information must be listed at the end of each task.

10. Lesson Objectives Know the biochemical structure of protein molecules
Work independently to carry out Biuret tests to investigate if foods contain protein
Be confident at safely carrying out investigations in the science laboratory in preparation for the Unit 3 ISA/PSA skills tests

11. Biological Molecules - Proteins
Biological molecules are made up of subunits called MONOMERS
Monomers join together in chains to form POLYMERS

12. Proteins Made up of: CHONS
Carbon
Hydrogen
Oxygen
Nitrogen
Sulphur (sometimes)
The monomers in proteins are called AMINO ACIDS
There are 20 different commonly occurring amino acids

13. Proteins - Amino Acids Amino acids are made up of 3 groups Amino group
(-NH2)
Carboxyl group (carboxylic acid group)
(-COOH)
R group (side chain)
(Varies with the amino acid) H
H2N-C-COOH R

15. There are 20 different amino acids and so there are 20 different R groups

16. Condensation reactions
Condensation reactions create peptide bonds which hold the individual amino acid monomers together
This creates a peptide
Water
Amino acid monomer R’
Amino acid monomer R

17. Condensation reaction – creating a peptide
More peptides can join to form a polypeptide
Proteins are made up of one, 2 or more polypeptides R’ R R R’
Di-peptide

18. Hydrolysis - Breakdown of Proteins

19. Hydrolysis – addition of water
OH- H+
H2O R’ R
This reaction occurs by boiling in dilute HCl or by protease enzymes

20. Protein Structure Proteins are made up of 4 different structures
Primary -1o
Secondary -2o
Tertiary -3o
Quarternary –4o

21. YouTube - Protein Structure

22. Primary structure Order of amino acid monomers in the peptide chain
The sequence of amino acids determines the 3-D shape
A simple protein may be made up of one polypeptide chain

23. Secondary Structure
When the amino acids join together as a peptide they form shapes or patterns
Weak Hydrogen bonds form between polar molecules
Peptide bonds contain polar H atoms and Polar O atoms
Polar H atoms on the amino group have a small +ve charge
Polar O atoms of the carboxyl group have a small -ve charge

24. Secondary Structure
The charges allow H bonds to form between peptide bonds in different parts of the chain

25. Secondary Structure 2 shapes formed Alpha helix Beta-pleated sheet
The secondary shape depends on the primary structure, i.e. the order of the amino acids

26. Tertiary Structure 3-D shape Determines the function of the protein
Very important in creating the active site in enzymes
Shape is held together by
Hydrogen bonds – numerous but easily broken
Ionic Bonds – formed by any carboxyl and amino group not involved in forming peptide bonds
Easily broken by pH changes
Disulphide bonds – fairly strong

27. Hydrogen bonds are weak and easily disrupted
Ionic bonds formed between carboxyl group and amino group – NOT peptide formation
Easily broken with pH changes
Disulphide bonds are covalent bonds between sulphur atoms in R groups
Fairly stong, not easily broken

28. Tertiary Structure 3 types of bonds lead to 2 main kinds of protein
Fibrous
Globular

29. Globular Proteins Approximately spherical in shape
Usually water soluble
Tend to have a biochemical function rather than structural
E.g. Enzymes or haemoglobin

30. Fibrous Proteins
Polypeptides join together to form long fibres or sheets
Very strong
Insoluble in water
Tend to have structural functions
E.g. fingernails and hair – Keratin
E.g. Skin, Bone, Blood vessels and teeth - collagen

31. Fibrous Proteins 1o structure is an unbranched polypeptide chain
2o structure is very tightly wound
3o structure is a chain twisted into a second helix
4o structure 3 of the 3o structure chains wound together like fibres in a rope

32. Quarternary Structure
A number of polypeptide chains
Associated non-protein components called prosthetic groups
Together producing the quarternary structure

33. Testing for protein molecules in unknown solutions
You will be investigating 5 unknown solutions and carrying out a simple practical investigation to determine whether they contain protein, dipeptides or none

34. Testing for Protein Molecules
Biuret test
Biuret 1 = Sodium Hydroxide solution
Biuret 2 = Copper (II) Sulphate solution
Copper atoms in the copper (II) sulphate solution form a complex with the N atoms in the amino group of the peptide bond – this causes a colour change
Blue
No proteins or peptides
Violet/Lilac
Proteins
Pink
Peptides

35. Method
Add equal volume of Sodium Hydroxide solution to the solution being tested
Add a few drops of copper (II) Sulphate solution
Sodium Hydroxide solution creates alkaline conditions
Evaluate this method!
Could you carry out this investigation with the information that you have been supplied with in this method?

36. Testing for protein molecules in unknown solutions
Health and Safety
MSDS/MSDS_Caustic_50_TDC_2010.pdf