Edexcel AS BiologyThere 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

Edexcel A2 BiologyThere 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

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.

Membranes

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

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.

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

PhospholipidsLipids formed when 2 fatty acids, a phosphate group and glycerol are joined together.

Hydro – waterPhillic – loves

Hydro – waterPhobic – hates

Due to the negative charges on the phosphate group

The long hydrocarbon chains do not have any charged groups

Fatty acid tails- Hates water

Phosphate head- Likes water so turned towards water

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.

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.

The fluid mosaic model of the plasma membrane:

Temperature affects the fluidity of the membrane.

HOW?

To be investigated......

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.