AS Biology | 1A Summary | Biological Molecules

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1A ­ Biological Molecules Summary
Polymers are long chains of monomers joined Benedict's test for sugars Iodine test for starch.
together. Add iodine dissolved in potassium iodide to a sample. If
Monomers are small basic molecular units that starch is present the sample changes from browny-orange to
can join to form polymers a dark blue/black colour.
Most polymers are formed via condensation Lipids
reactions which release a molecule of water.
Polymers are broken down via hydrolysis One molecule of glycerol with three fatty acids attached
reactions where a molecule of water is used to Insoluble in water because of long tails on the fatty acids
break the bond. made from hydrocarbons which are hydrophobic
The fatty acids can be saturated or unsaturated
Monosaccharides are the monomers that make Formed by condensation reactions with an ester bond
up carbohydrates between the glycerol and fatty acid
A disaccharide is two monosaccharides joined Energy storage molecules
together by a glyosidic bond in a condensation Don't affect the water potential of cells
Polysaccharides are formed when more than
two monosaccharides are joined together.
Same structure as a triglyceride apart from one fatty acid
Starch Glycogen
has been replaced by a phosphate group
A mixture of amylose Very branched
The phosphate group is hydrophilic and the tails are
and amylopectin, both molecule so glucose
formed from can be released hydrophobic
glucose. quickly Make up the bilayer of cell membranes
Made of one or more polypeptides. A dipeptide is Insoluble in water and Compact molecule so Emulsion test:
so doesn't affect so good for storage
made from two amino acids joining together. A
no water will move 1. Shake the test sample with ethanol for about 1 minute
polypeptide is made from more than two amino
into the cell via and pour the solution into water
acids joining together. Amino acids have the osmosis
Variable group 2. Any lipids will show up as a milky emulsion
same general structure: Cellulose 3. The more lipids there are the stronger the milky colour
Amine group R Carboxyl group Long unbranched chains of glucose
Hydrogen bonds form fibres called microfibrils
H2N C COOH between chains

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A ­ Biological Molecules Summary
Proteins (continued) Enzymes Temperature
Amino acids are linked together by condensation Enzymes can speed up reactions by acting as
reactions to form dipeptides and polypeptides. biological catalysts. They are proteins which Increasing temperature increases the rate of enzyme
have an active site which is a specific shape and controlled reactions as the particles have more kinetic energy
The bonds between the amino acids are called and so collisions increase.…read more


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