(c) biological molecules

chemical elements + structure of carbohydrates (2.7)

made up of carbon, hydrogen, oxygen (in ratio 1:2:1); important source of energy

simple carbohydrate → quick release of energy e.g. sugar

• single sugar (monosaccharide) — glucose, fructose, galactose

• two sugars (disaccharide) — maltose (glucose-glucose), sucrose (glucose-fructose), lactose (glucose-galatose)

complex carbohydrate → slow release of energy e.g. bread

• plants — starch (energy) and cellulose (cell walls#)

• animals — glycogen (energy store)

chemical elements + structure of proteins (2.7)

organic compounds compose of one or more long chains (polymers) of amino acids; always contain carbon, hydrogen, oxygen and nitrogen; meat, fish, dairy, beans, nuts and eggs are rich in protein

functions:

• muscle + bone growth

• making up hair, skin, cell membranes, red blood cells, antibodies, enzymes

chemical elements + structure of lipids (2.7)

made up of carbon, hydrogen and oxygen; when solid, a lipid is fat, when liquid, a lipid is oil

properties:

• insoluble in water + hydrophobic // waterproof

• insulates heat

• buoyancy

• long term energy store

• protect organs, shock absorption

• cell membranes are made of lipids

• vitamins transported with fats

• broken down to water e.g. camels

• triglycerides

  • saturated (solids → fat)

    • single C-C bonds, max hydrogen

    • solid, very energy dense, animal fats, unhealthy in large amounts

  • monounsaturated (liquids → oils)

    • some C=C double bonds, less hydrogen

    • oil, less energy dense, animal + plant fats, healthier

  • polyunsaturated

    • many C=C double bonds, least amount of hydrogen

    • oils, fish + plants

    • least energy dense

    • most healthy

practical investigating food samples for glucose, starch, protein and fat (2.8 / 2.9)

glucose:

• benedicts solution, heat to 85°C

  • blue → no glucose

  • green → low concentration

  • orange → medium concentration

  • red → high concentration

starch:

• iodine solution

  • brown → low concentration

  • blue black → high concentration

protein:

• sample + biuret solution

  • if protein is present, the colour will change from blue to purple

fat:

• crush food sample, add ethanol, add water, shake

  • cloudy white emulsion → lipids present

role of enzymes as biological catalysts in metabolic reactions (2.10)

enzymes help to speed up rates of metabolic reactions without being used up.

they do this by lowering the activation energy needed for the reaction to occur. activation energy is the term for the extra energy needed to be given to the reactants to break bonds within them to allow the product molecules to be formed. enzymes provide an alternate reaction pathway that has a lower activation energy. this means that under any conditions a higher proportion of the reactant molecule will have sufficient energy to overcome the activation energy barrier and so more reactants will be turned into products.

temperature effects on enzyme function (2.11)

practical investigating how enzyme activity can be affected by changes in temperature (2.12)

pH effects on enzyme function (2.13)

practical investigating how enzyme activity can be affected by changes in pH (2.14B)