Biology OCR F212 perfect essay answers

These are 'perfect answers' to some of the essay questions seen in F212 (usually 6-8 marks). Each bullet point is one mark. There may be more points than available so it is not essential to remember every single one and remember, not every question below will come up. These are probably best learnt 'parrot fashion' in order to achieve maximum marks.

MOLECULES

Describe the structure of haemoglobin:

• 4 polypeptide chains
• 2 alpha chains, 2 beta chains
• primary structure- a chain of amino acids
• joined by peptide bonds
• secondary structure- alpha helix
• secondary strucuture undergoes further folding
• hydrophilic R groups on the outside (water soluble)
• 4 haem per molecule
• Haem is a prosthetic group containing Fe(2+)

Describe the structure of collagen:

• Fibrous protein
• 3 polypeptide chains
• in a 'twisted rope'
• covalent bonds form strong cross-links
• insoluble in water
• left handed helix structures
• primary structure- chain of amino acids (mainly gylcine)

Describe how a DNA molecule is replicated:

• DNA unwinds
• DNA helicase unzips hydrogen bonds
• Hydrogen bonds break
• Free DNA nucleotides bond with exposed bases
• Complementary base pairing
• C-G, A-T, purine to pyrimidine
• Hydrogen bonds reform
• Sugar-phosphate backbone reforms
• Using covalent bonds
• Process is semi-conservative replication

Explain how an antibody's structure is related to its function:

• Constant…