Key Concept Prt2 - Biology Tpc1

Key Concept Prt2 - Biology Tpc1

1. Enzymes

   • Enzymes are catalyst produced by living things
     • living things have thousands of different chemical reactions
     • These reactions - need to be carefully controlled.
   • Enzymes have special shapes so they can catalyse reactions
     • The substrate is the molecule changed in this reaction.
     • Every enzyme has an active site where the reaction takes place.
     • They usually only work with one substrate - they usually have a high specifity for that one only - this is for the reaction to work correctly
       • This is for the reaction to work correctly the substrate has to fit in the active site. If the substrates shape doesn't match the reaction wont be catalysed.
         • Lock + Key
   • Temperature + pH + Substrate Concentration Affect the Rate Of Reaction
     • Changing the temperature changes the rate of an enzyme catalysed reaction.
       • Like any reaction; a higher temperature increases the rate of reaction at first then if it gets too hot the bonds holding the enzyme together break, which changes the the shape of the active site, so the substrate wont fit any more, the enzyme is then said to be denatured.
     • The pH also affects the enzymes. If its too high or too low; the pH interferes with the bonds holding the enzyme site together. This changes the shape of the active site and denatures the enzyme.
     • Substrate concentration also affects the rate of reaction - the higher the concentration - the faster the reaction. This is because its more likely the enzyme will meet up and react with a substrate molecule. This is only true up to a point tho - after this there are only so many that the enzyme can react with - which can make the active site full; after this thee is no difference.

2. Rate Of Reaction

   • Rate = 1000/time.
   • Rate is a measure of how much something changes over time.

3. Enzymes in breakdown and synthesis

   • Enzymes break down big molecules
     • Proteins, lipids and some carbs are big molecules.
       • Enzymes called carbohydrase’s convert carbohydrates into simple sugars. Amylase is an example of carbohydrase. It breaks down starch.
       • Proteases convert proteins into amino acids. Lipases convert lipids into glycerol and fatty acids.
   • Some enzymes join molecules together
     • Carbohydrates can be synthesised by joining together a simple sugars. Glycogen synthase is an enzyme that joins together lots of chains of glucose molecules to make glycogen. Proteins are made by joining amino acids together, enzymes catalyse the reactions needed to do this. Lots of enzymes are also involved in the synthesis of lipids from fatty acids and glycerol.

4. Testing for biological molecules

   • You can test for sugars using benedict's reagent.
     • The higher the concentration of reducing sugar the colour will change from blue to brick red.
   • Starch is tested iodine
     • colour will change if present from browny orange --> blue-black colour.
   • Use the emulsion test for lipids.
     • Shake test with ethanol; then pour the solution into water.
     • If lipids are present they will precipitate out of the liquid and show up as a milky solution - the more milky the more lipids.
   • The biuret test is used for proteins.

5. Energy in food

   • Test + then:
     • Energy in food (J) = Mass of water (in g) x Temperature change of water x 4.2

6. Transport:

   • Diffusion is the net (overall) movement of particles from area of higher concentration to an area of lower concentration.
   • Osmosis is the net movement of water molecules across a partially permeable membrane from a region of higher water concentration to to a a region of lower water concentration.
   • Active transport is the movement of particles across a membrane against a concentration gradient using energy transferred during respiration.