OCR AS Unit 2 Biology: Biological Molecules, Food & Health, Biodiversity & Evolution

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METABOLISM-the total sum of all the biochemical reactions taking place in the cells of an organism.
Carbohydrates-energy storage and supply, structure.
Proteins-structure, transport, enzymes, antibodies, hormones.
Lipids-membranes, energy supply, insulation, protective layers.
Nucleic acids-information molecules, carry instructions for life.
Water-takes part in many reactions, support in plants, solvent/medium for metabolic reactions.

Carbohydrate-Monomer-monosaccharide, polymer-polysaccharide.
Protein-Monomer-amino acids, polymer-polypeptides and proteins.
Nucleic acid-Monomer-nucleotides, polymer-DNA and RNA.
Condensation-a water molecule is released. A new covalent bond is formed, a larger molecule is formed by the bonding together of smaller molecules.
Hydrolysis-a water molecule is used, a covalent bond is broken, smaller molecules are formed by the splitting of larger molecules.

Alpha-OH on bottom, Beta-OH on top.
Two monosaccharide molecules can be joined together in a condensation reaction, where a new bond called a glycosidic bond forms, and water is eliminated. Building polysaccharides such as starch and glycogen involves the making and breaking of glycosidic bonds. Glucose is C6H12O6. it can be drawn in either a chain or ring structure, and has slightly different arrangements which cause different properties.

Two alpha glucoses=maltose. Three or more glucose molecules=amylose. (1-4). Long chains of amylose coil into a spring because of the shape of the glucose molecule and the formation of the glycosidic bonds. Makes it compact.
Starch=amylose and amylopectin. Long and branched chains, stored in chloroplasts and elsewhere in the plant in starch grains. Starch can be broken down into glucose molecules. They don't dissolve so the stored glucose does not affect the water potential of the cell. Hold glucose molecules in chains so they can easily be broken off from the ends to provide glucose.
Glycogen=amylose and more amylopectin, animal starch, more branched than starch. They don't dissolve so the stored glucose does not affect the water potential of the cell. Hold glucose molecules in chains so they can easily be broken off from the ends to provide glucose.

Many beta glucoses=cellulose. Arranged to form plant cells. Many hydrogen bonds form between them, bundles of microfibrils which then become macro fibrils. They have great mechanical strength, polysaccharide glue called pectin forms the cell walls.

Amino acid-amino group, acid group, r group.


All amino acids are joined in exactly the same way. A condensation reaction between the acid group of one amino acid group and one amino group of another forms a peptide bond. The new molecule produced is called a dipeptide.

PRIMARY STRUCTURE-the specific amino acid sequence that makes up the protein.

SECONDARY STRUCTURE-refers to coiling and pleating of parts of the polypeptide molecule. Hydrogen bonding holds the alpha helix or beta sheets in place.

TERTIARY STRUCTURE-the overall 3D structure of the final polypeptide or protein molecule. When the coils and pleats themselves fold. This is held in place by a number of different bonds and interactions-disulfide bonds-where two molecules with S atoms on are close together, these bonds formed e.g. cysteine. Ionic bonds-r groups sometimes carry a charge. Where oppositely charged amino acids are found close to each other they form an ionic bond. Hydrogen bonds-where slightly…


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