2.17 Describe the process of photosynthesis and understand its importance in the conservation of light energy to chemical energy

PHOTOSYNETHESIS:

• Process by which sunlight is used as energy to create oxygen and glucose from carbon dioxide and water
• The light energy is absorbed by chlorophyll in the plant leaves
• Using light energy to create chemical energy is conserving the energy from the sun as it is then passed up the food chain.

2.16 Describe simple experiments on diffusion and osmosis using living and non-living systems

DIFFUSION:

• Put a drop of food colouring into a glass of water
• Time how long it takes for the water to be all the same colour
• Make the independent variable temperature
• When the water is hotter, the particle will have more kinetic energy, therefore the dye will move through the water faster

OSMOSIS:

• Cut two pieces of potato the same size and write down their weights
• Put one in distilled water and the other in salt water
• After an hour weigh them again
• The one in distilled water would have gained weight because the water moves from an area of high density to an area of low density
• The one in the salt water will lose weight as the water in the potato will move to the more highly concentrated salt water

2.15 understand the factors that affect the rate of movement of substances into and out of cells, to include the effects of surface area to volume ratio, temperature and concentration gradient

SURFACE AREA:

• If there is a larger surface area, there is a larger surface area for the molecules to diffuse through, which increases the rate of movement

TEMPERATURE:

• Increasing the temperature increases the kinetic energy, which causes the molecules to collide with the partially permeable membrane, therefore making movement through it more frequent

CONCENTRATION GRADIENT:

• This is the difference in concentration between the inside of the cell and the outside of the cell.
• If the concentration gradient is bigger, the molecules will diffuse easier

2.14 Understand the importance in plants of turgid cells as a means of support

Cells in plants must be turgid because it increases the volume of the cytoplasm, therefore exerting pressure on the outside of the cell. This makes the cells stronger to support the plant to grow upwards

2.13 Understand that movement of substances into and out of cells can be by diffusion, osmosis and active transport

Diffusion, Osmosis and Active transport are all methods of moving substances into and out of cells

2.12 Recall simple definitions of diffusion, osmosis and active transport

DIFFUSION:

• The movement of molecules down a concentration gradient from an area of higher concentration to an area of lower concentration
• Occurs fastest in gasses and slowest in solutions

OSMOSIS:

• Involves water crossing a partially permeable membrane from an area of higher concentration to an area of lower concentration (moving down a concentration gradient)

ACTIVE TRANSPORT:

• The absorption of particles AGAINST a concentration gradient from an area of lower concentration to an area of higher concentration
• This requires energy in the form of ATP that cells release during respiration

2.11 Describe how to carry out simple controlled experiments to illustrate how enzyme activity can be affected by changes in temperature

ENZYME TEMPERATURE EXPERIMENT:

• Put starch into a test tube and heat it at a chosen temperature in a water bath
• Now put amylase into the solution, pour it onto a white tile and add iodine
• Then time how long it takes for the iodine to stop being blue/black
• When the solution is no longer blue/black it means the starch has been broken down by the enzymes into maltose
• Then repeat this experiment several times at different temperatures and compare them

2.10 Understand how the functioning of enzymes can be affected by changes in pH

Extreme pHs will denature the enzymes meaning the substrate can no longer fit into the active site of the enzyme

2.9 Understand how the functioning of enzymes can be effected by changes in temperature

INCREASING THE TEMPERATURE:

• Causes the kinetic energy to increase, therefore the enzyme and substrate collide more frequently per second so the reactions occur faster
• If the temperature goes above the optimum temperature (in Humans around 37 degrees) the enzymes can denature, meaning the bonds that hold the shape of the enzyme are broken
• This means the substrate will no longer fit into the active site and therefore cannot be broken down

DECREASING THE TEMPERATURE:

• Decreasing the temperature causes the kinetic energy to decrease meaning the enzyme and substrate collide less frequently per second so the reaction slows down

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

Enzymes lower the required activation energy, making the reaction occur faster and they remain unchanged throughout the reaction- This makes them a CATALYST