B4 - The Processes of Life

Animal cell:

Nucleus - contains DNA which contains the instructions for making proteins.

Cytoplasm - Enzymes made here

Cell membrane - Controls what goes in and out. Lets gases and water through while acting acting like a barrier to other chemicals.

Mitochondria - Enzymes are needed for aerobic respiration.

Plant cell:

Cell wall - Supports and strengthens cell.

Vacuole - Contains cell sap.

Chloroplasts - Photosynthesis takes place here. They contain chlorophyll and enzymes.

Yeast: Used to make bread and wine.

Different parts of a yeast cell: cell membrane, mitochondria, cytoplasm, nucleus and cell wall.

Bacteria:

Different parts of a bacterial cell: cell membrane, cell wall, cytoplasm and circular DNA molecule.

No nucleus. 

No mitochondria, but can still respire aerobically.

Living things have thousands of chemical reaction going on inside them.

These reactons need to be controlled carefully.

Living things produce enzymes: ENZYMES are proteins that SPEED UP CHEMICAL REACTIONS.

Instructions for making enzymes are found in a cell's genes.

Chemical reactions ausually involve things either being split apart or joined together.

A substrate is a molecule that is changed in a reaction.

Every enzyme has an active site - where a sunstrate joins on to the enzyme.

Enzymes usually speed up one reaction. For an enzyme to work, it has to fit in the active site. ('lock and key' model)

Enzymes need the right temperature to work at their optimum.

Changing the temperature changes the rate of reaction.

A higher temperature increases the rate at first.

If too hot the enzyme changes shape and so the substrate won't fit in the active site. (denatured)

Enzymes have an optimum pH. If the pH is oo high or too low it denatures.

RESPIRATION is a series of chemical reactions that RELEASE ENERGY by breaking down large FOOD MOLECULES. It happens in EVERY LIVING CELL.

The energy released is used to power some chemical reactions, e.g. the reactions involved in:

MOVEMENT - Energy is needed to make muscles contract.

ACTIVE TRANSPORT - This process uses energy to move some substances in and out of cells.

SYNTHESIS OF LARGE MOLECULES - Large molecules are made by small ones joining together. For example: Glucose is joined together to make startch and cellulose.

Glucose and nitrogen joined together to make amino scids. the acids are joined together to make proteins.

Aerobic = With oxygen

Releases more energy per glucose molecule than anaerobic respiration. 

Aerobic respiration takes place in animal and plant cells, and in some microorganisms. 

Glucose + Oxygen -> Carbon dioxide + Water (+ Energy Released)

Anaerobic = Without oxygen

Takes place in animal and plant cells and some microorganisms when there is very little or no oxygen. For example:

HUMAN CELLS - When you do vigorus exercise your body can't supply enough oxygen to your muscle cells - they start to respire anaerobically.

PLANT CELLS - If the soil becomes waterlogged there'll be no oxygen available for the roots - they will have to respire anaerobically. 

BACTERIAL CELLS - Bacteria can get under your skin through puncture wounds. There's very little oxygen under your skin - they have to respire anaerobically. 

Glucose -> Lactic Acid (+ Energy Released)

Glucose -> Ethanol + Carbon Dioxide (+ Energy Released)