B4

Carbon dioxide + water --> glucose + oxygen

6CO2 + 6H2O --> C6H12O6 +6O2

• An enzyme is a protein that acts as a catalyst.
• Cells make enzymes according to instructions carried in genes
• It contains an active site that has a complimentary fit with a substrate of two molecules.
• When the substrate fits the active site it weakens and causes the bond between the molecules to break so the products can diffuse away seperately.

• PH factor ( the optimun is 7.5)
• Temperature

A change in either of these cab cause the shape of the active site to change and become denatures

denatured= chnaged shape- means it doesn't work

A low temperature equals low enzyme activity because substrate molecules are moving slowly and therefore have a decreased chance of colliding with the active site.

Increasing temperature increases the rate of reaction up to the optimun ( about 37.5 degrees which is body temperature). After the optimum the enzyme becomes denatured

Osmosis ( a specific case of diffusion) is the overall movement of water from a dilute to a more concentrated solution through a partially permeable membrane

Osmosis occurs in plants through the cell membrane. The water molecules are attracted to the glucose molecules so travel through the membrane because they are small. However all other molecules are kept in/out.

The movement of water into plant roots- from the soil, across the roots- occur by osmosis

Active transport goes against diffusion so requires energy from respiration.

Nitrogen compounds from the fertiliser are added into the soil. Nitrates are normally in a higher concentration in plant cells than the soil, so root cells cannot take up nitrates by diffusion. The nitates randomly collide with carrier molecules on the membranes which take the nitates into the plant. These nitrates combine with the porducts of photosynthsis to create amino acids which are assembled into proteins.

Glucose is a product of photosynthesis. Light energy from the sun is absorbed by a green chemical called cholrophyll which is found in chloroplasts. This energy drives the reaction between carbon dioxide and water to make glucose.

Uses of glucose

• cellulose for cell walls
• proteins for growth
• to make chlorophyll
• respired to release energy
• starch for energy storage

Nucleus- Contains DNA which stores genetic code - found in animal cells, plant cells, yeast cells and bacteria have no nucleus but their circular DNA is in the cytoplasm.

Cytoplasm- A thick solution where most chemical reactions take place - found in all animal, plant and microorganism

Cell membrane- Surrounds the cell and controls what enters and leaves the cell - found in all animal, plant and microorganism cells

Mitochondria- Found in the cytoplasm. Contains enzymes reuired for the release of energy by aerobic respiration - found in animal cells, plant cells, and yeat cells

Cell wall- Lets water and other chemicals pass through freely and provides structure to the cell - found in plant cells and microorganisms

Vacuole- A membrane bound sac containing molecules such as glucose dissolved in water - found in plant cells

Ribosomes- Found in cytoplasm, used for protein synthesis - found in plant cells

Respiration is needed for energy to:

• movement
• synthesis of large molecules - such as sythethis of polymers like starch or syntheis of amino acids 
• active transport

Aerobic repiration: Respiration using oxygen is called aerobic repiration and it produces more energy per glucose molecule than anaerobic repiration. The word and symbol equations are:

glucose + oxygen --> carbon dioxide + water   C6H12O6 + 6O2 --> 6CO2 + 6H2O

Anaerobic repiration: Some organisms can still get energy when oxygen is low or absent by anaerobic repiration. It can occur in plant roots in watterlogged soil and with bacteria in deep puncture wounds and human cells in vigerous exercise.

In animal cells the reaction is: glucose --> latic acid

In plant cells the reaction is: glucose --> ethonal + carbon dioxide

Photosynthesis= A series of chemical reactions that use energy from sunlight to build large food molecules in plant cells and some mircoorganisms

Diffusion is the passive overall movement of chemicals from a high to low concentration which does not use any energy.

eg. the movement of oxygen and carbon dioxide in and out of leaves during photosynthesis

• Temperature
• Carbon dioxide
• Light intensity

Some micro organisms, including yeast, produce alcohol (ethanol) by fermentation. This is important in the production of alcoholic drinks and bread. Bubbles of carbon dioxide makes bread rise, and alcoholic drinks sparkle. In bread alchol is evaportaed off as it cooks.

It is also important for biogas. On a larger scale  yeast, water, sugar and some other nutrients bioethanol can be made that can be used as a fuel.