Biological Molecules

• Water is a solvent - substances can dissolve in it 
• Water transports substances

Structure of water related to transportation

• Shared electrons pulled closer to the oxygen atom than hydrogen atoms

• (this makes it) dipolar

• Good solvent for other polar molecules

• Substances can be transported more easily when dissolved into water

• Water is cohesive (due to dipolar nature) - helps water to flow

Monosaccharides ---> Disaccharide ---> Polysaccharide

Made from long chains of monosaccharides. Joined by Glycosidic bonds in condensation reaction (H2O removed)

Monosaccharides;

• e.g. glucose, fructose, galactose

Disaccharide

• e.g. sucrose, lactose, maltose
• Made of two monosaccharides

Polysaccharide

• e.g. amylose, amylopectin, glycogen
• Made of more than two monosaccharides

• Energy store in plants - get energy from glucose
• Store excess glucose as starch - breaks starch down to release glucose
• Mixture of two polysaccharides of alpha - glucose:
• Insoluble

Amylose

• 1-4 glycosidic bond

• Long, coiled, unbranched 

• Compact - good for storage

Amylopectin

• 1-4 + 1-6 glycosidic bonds

• Long, branched

• Side brances allow enzymes to break bonds easily to release glucose

• Energy store in animals

• Store excess glucose as glycogen

• 1-4 + 1-6 glycosidic bonds

• Side branches - release energy quicker

• Compact - good for storage

• Insoluble - cells don't swell by osmosis

• Large molecule - store more energy

• Triglycerides - one glycerol + three fatty acids - joined by ester bonds
• Fatty acids have long tails made of hydrocarbons
• Tails are hydrophobic - make lipids insoluble

Saturated

• Animal fats (e.g. butter)

• NO double bonds between carbon atoms

Unsaturated

• Plants (e.g. olive oil)

• Has double bonds between carbon atoms

• Melt at lower temperatures

• Made from long chains of amino acids (monomers)
• Dipeptide - two amino acids
• Polypeptide - two or more amino acids
• Joined by peptide bonds

Structure of Amino Acids

• Carboxyl group (-COOH)

• Amino group (-NH2)

• Carbon atom (C)

• Variable group (R)

Biological Catalysts - speeds up chemical reactions

e.g. digestion, respiration

Globular proteins

Have active site - specific shape for substrate molecules to bind to

Specific - catalyse one reaction

Lowers activation energy - speeds reaction up

Lock & Key Method

Substrate fits enzyme

Induced Fit Method

Substrate has to be right shape 

Makes active site change shape