AS biology- 1A, Biological Molecules

Biology Topic 1A- Biological Molecules
(Hannif)

Carbohydrates
* Carbs =polymer = chains of monomers
eg monosaccharides(glucose(hexose sugar) fructose galactose)
*condensation reactions- 2 molecules join & form new chemical bond with the release of water to form glycosidic bonds (mono join together)

*Hydrolysis- bond broken by the addition of a water molecule (polymers broken down to monomers) eg carbs-mono
*benedicts reagent reducing (all mono, some di) add the reagent (blue) boil +ve = coloured PPT. non reducing: add dilute HCL, neutralise with hydrogen sodium hydrogen carbonate

*Glycogen- stores excess glucose as glycogen (animal cells) side branches for quick release, compact= good storage
*cellulose- longe unbrached chains beta glucose, bond for straight chains linked by H bonds to form strong fibres 'microfibrils' structural support in cells

Lipids
*Tricglycerides-1x glycerol 3x fatty acid, hydrophobic hydrocarbon tail tail varies
* tails make lipids insoluble in water
*joined in a condensation reaction, ester bond formed water molecule released
*saturated no x2/ unsaturated 1+ (kink)
*phospholipids, 2 fatty acid + phosphate

emulsion test for lipids
- shake sample with ethanol for a minute to dissolve
- pour into water
+ve forms a milky emulsion

Proteins
*proteins made of 1 or more polypeptides
*variable in c containing R group but same carboxl (-COOH)and amino group (-NH2)
*join condensation reaction to form peptide bonds, reverse in digestion

*Enzymes- spherical due to tight poly
*Antibodies- immune, 2x light 2x heavy vary * transport proteins, cell membranes hydro pho+phil, transport of molecules & ions *structural- pysically strong long poly parallel & cross links- keratin collagen *biuret test- alkalin + sodium hydroxide then add copper(II) sulfate+p

*Enzyme Action*
*lower activation energy- "substrate to be joined enzymes hold closer reducing repulsion, breaking puts strain on bonds.
*lock and key model, new evidence shows enzyme substrate complex changes shape - induced fit model, explains why so specific

*enzyme action*

substrate conc: higher conc faster ROR more collisions until saturation point substrate conc decreases time
competitive inhibitor: similar shape competes active site , lower ROR
non competitive: change shape no longer fit increasing substrate conc makes no diff.

*enzyme controlled reactions*
alter a different variable eg pH (add a buffer with diff. pH) everything else to be constant
*interpret graphs: compare ROR and initial ROR, use knowledge to explain why make comparisons. pg 14 15