OCR Biology A - 2.1.2 - Biological Molecules Part 6

All 4 polypeptide chains are attached to a haem group

Fe 2+ ions and they bond with O2

2 alpha chains
2 beta chains
4 haem groups

Alpha helix and beta sheets
Globular shape has an complementary active site
Active site holds Cl- (co-factor - essential for correct action)

2 polypeptides held together by disulphide bridges
Globular protein w/ spp, fixed shape
Specific 3D shape complementary to glycoproteins receptor

Form long strands and usually insoluble
Have structural roles in the body
Regular sequence of amino acids
Unreactive

3 polypeptide chains wound around each other
Fibrous protein that is flexible but does not strech
Not easily stretched
Found in walls of arteries and tendons

2 coiled polypeptide chains containing sulfur
Protect delicate things e.g. nails,claws, hair, feathers, hooves
Found in outer layers of skin cells (permeability)

Linking tropelastin fibres
Coiled and can be stretched and recoiled
Used where stretching is required e.g. alveoli, walls of arteries, airways, bladder

Add HCl to sample whilst heating iin a water bath > 80 degrees (to hydrolyse sample)
Add NaOH (to neutralise sample)
Then conduct test for reducing sugars

Between the hydroxide from the amine group and the H from the carboxyl group

Increased kinetic energy 
Molecule vibrates 
H bonds break 
Change in 3’ structure 
Denatures

Separation of proteins, carbs, vitamins or nucleic acids

Maltose

Strong cohesive forces between water molecules at the water surface mean that it is a good medium for support
H bonds attract water molecules to each other but are weak so that water molecules can move easily in relation to one another

Crush the solid w/ water
Filter out the solid
Continue test as normal

Filter sol. and weigh ppt. formed, the heaver the ppt, the more conc.
Compare colours after benedict's test - less accurate

Make up several sol. of KNOWN glucose conc. (serial dilution)
Carry out Benedicts's test - same vol. of reagent
Remove any ppt
Using colorimeter measure absorbance
Plot calibration curve , with glucose conc. on x and absorbance on y

Set up w/ red filter - no effect w/ blue
Add distilled water to cuvette to calibrate colorimeter- light should pass through clear side
Use a pippette to transfer each solution of sol. of known glucose conc into seperate cuvettes
Measure absorbance for each

Determines conc of glucose in a solution
Glucose oxidase immobilised to electrodes, binds to and catalyses oxidation of glucose
Creates a charge which is then converted by a transducer
The electrical signal is then processed to work out the glucose conc.

Where the molecules can move
Solvent (ethanol) in bother paper and TLC
The more time spent here the faster/ further up the stationary phase

Where the molecules can't move

| Paper in paper chromatography or silica gel on a glass plate in TLC

Sterol
4 carbon rings w/ hydroxyl group
Hydroxyl group is polar o rest of molecule is hydrophobic

Membrane formation and the creation of hydrophobic barrier
Hormone production
Electrical insulation (nerves)
Waterproofing

Follow normal TLC procedure but after silica gel plate has been allowed to dry, spray w/ ninhydrin spray to give a purple/brown colour

4' protein w 4 haem groups

| Fe2+ speeds up the breakdown of H2O2 - common by-product of metabolism but dangerous if accumulates

Membrane formation and the creation of hydrophobic barrier Hormone production Electrical insulation (nerves) Waterproofing

Follow normal TLC procedure but after silica gel plate has been allowed to dry, spray w/ ninhydrin spray to give a purple/brown colour

4' protein w 4 haem groups | Fe2+ speeds up the breakdown of H2O2 - common by-product of metabolism but dangerous if accumulates