1. Edexcel AS Biology There are three units: Unit 1: Lifestyle, Transport, Genes and Health (40% AS 20% GCE) Exam: Jan 2013 Unit 2: Development, Plants and the Environment (40% AS 20% GCE) Exam: June 2013 Unit 3: Practical Biology and Research Skills (20% AS 10% GCE) 1500 - 2000 words report on into a biological topic – June 2013

2. Edexcel A2 Biology There are three units: Unit 4: The Natural Environment and Species Survival (40% A2 20% GCE) Exam: Jan 2013 Unit 5: Energy, Exercise and Coordination (40% A2 20% GCE) Exam: June 2013 Unit 6: Practical Biology and Research Skills (20% A2 10% GCE) Students will complete a written report of an experimental investigation

3. What is involved..... Skills: practical skills, fact learning, application of knowledge, mathematical skills, independent investigations- planning, implementing and writing up scientific reports, research papers. Topics: human biology, environmental biology, plant biology, immunology, genetics. Requirements: you need to be prepared to do lots of independent research and self study.

4. Membranes

5. Why do cells need membranes? Control entry and exit of substances Keep things in! Contain the cell contents and organelles; compartmentalise individual cell processes Communication with external environment Site of chemical reactions Allows cell to change shape Transport and packaging within a cell

6. What are cell membranes made of?  Mostly LIPIDS...... And so is impenetrable to water soluble substances  Some PROTEINS. These allow water-soluble substances and other molecules to pass across.

7. 3 main types of lipid - Phospholipids – most abundant - Cholesterol - helps to stabilise the membrane by partial immobilising of the fatty acid chains - Glycolipids - involved in cell to cell recognition and communication Membrane Structure

8. Phospholipids Lipids formed when 2 fatty acids, a phosphate group and glycerol are joined together.

9. Hydro – water Phillic – loves Hydro – water Phobic – hates Due to the negative charges on the phosphate group The long hydrocarbon chains do not have any charged groups

10. Fatty acid tails - Hates water Phosphate head - Likes water so turned towards water

11. This is the basic structure that forms all cell membranes. In water phospholipids tend to form into a double layer with the phosphate ‘heads’ in the water and the fatty acid ‘tails’ away from it.

12. The fluid mosaic model of the plasma membrane: The proteins and phospholipids can move in the layer. Small molecules can move in and out of the membrane.

13. The fluid mosaic model of the plasma membrane: Temperature affects the fluidity of the membrane. HOW? To be investigated......

14. Findings… As the temperature increases the % absorbency increases as more pigments are released from the vacuole into the surrounding water. The more pigment, the greater the light absorbed.