2.11 describe experiments to investigate how enzyme activity can be affected by changes in temperature.

• Put starch into a test tube; either heat or cool it.
• Add amylase
• With this mixture on white tiles, add iodine
• Time how long it takes for the iodine to stop being blue black
• Repeat at different temperatures and compare

When the iodine stops being blue/black there is no starch present, so it must have been digested by the enzymes.

2.10 understand how the functioning of enzymes can be affected by changes in active site caused by changes in pH

Change in PH can denature enzymes by breaking the bonds that  hold the structure in place. So the active site no longer fits with the the substrate it is meant to be breaking down. The PH at which this happens is different for different enzymes, but generally an extreme PH will denature any enzyme.

2.8 understand the role of enzymes as biological catalysts in metabolic reactions

Enzymes lower the activation energy of a reaction- making it faster- and they are unchanged from begining to end of a reaction. These two things mean its a catalyst.

For information on enzymes this is a great source: http://www.abpischools.org.uk/page/modules/enzymes/enzymes5.cfm?coSiteNavigation_allTopic=1

2.9 understand how the functioning of enzymes can be affected by changes in temperature, including changes due to change in active site

As heat increases kinetic energy increases, this means enzymes and substrates more around more so they are more likely to 'bump into' one another (collide) and bind. This means that as heat increases so does the amount of reactions an enzyme catalyses.

However if the temperatures are too high it will denature enzymes, so they can't function. Because the energy breaks the bonds that hold the shape of the enzyme: without these the structure will be distorted, which will mean the active site won't be able to bind with the substrate to break it down.

Note the active site is the area on an enzyme that binds with a substrate to break it down; it is the lock in the lock and key theory.

Optimum temperature is in between these two scenarios, where there is lots of energy from heat but not enough to denature the enzyme. It is different for different enzymes.

2.7 describe the tests for glucose and starch

Test for glucose
Heat object with Benedict’s or Fehling’s Reagent.
if it turns from blue to orange then glucose is present.

The starch test
Apply iodine to the object you are testing,
if it turns from red to blue/black then there is starch.
Note: in an exam you are safest saying blue/black instead of blue or black.

2.6 describe the structure of carbohydrates, proteins and lipids

as large molecules made up from smaller basic units

Carbohydrates

Simple sugars- monosaccharides-such as glucose are the basic carbohydrates

They join together to make more complex disaccharides and polysaccharides: 

Proteins

are made up of amino acids

amino acids differ depending on what the 'r' (rest) is:

Lipids

are made from combining glycerol and three fatty acids:

The following video is quite good to watch, but it has a lot of extra content: http://www.youtube.com/watch?v=H8WJ2KENlK0

2.5 identify the chemical elements present in carbohydrates, proteins and lipids

Carbohydrates and lipids (fats and oils) are both made up of:

• Carbon

• Hydrogen

• Oxygen

Proteines consist of:

• Carbon

• Hydrogen

• Oxygen

• Sulphur

• Phosphorous

• Nitrogen