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Task 1 :A/S GROUP 2007-2008, Read the section on microscopy. All of you should aim to post me a least one comment before next lesson! In your comments answer the two following questions:

1. Explain why a scanning electron microscope produces more detailed images of cells than a light microscope.
2. Give two disadvantages of using a transmission electron microscope.
   

For a comprehensive revision list check out the AQA Biology B specification

MODULE 1 CORE PRINCIPLES
Please check out and make revision notes from the following webpages.
Carbohydrates
Proteins
Lipids
Enzymes
Eukaryotic Cells Structure
Prokaryotic Cell Structure
Comparing the two
Test on Cells
Transport
Diffusion, Osmosis, Active Transport
Microscopy



Task 2 : Post me a comment, answering the next section of questions:

1. How does the structure of glycogen differ from starch and cellulose [3]
2. Give two ways in which starch is an ideal sorage compound in plants. [2]
3. How could you test some onion cells to see if they contained starch? [2]
4. How are cellulose molecules arranged in cell walls of plants? [3]
   

Task 3: Answer these questions on Enzymes.

1. What is meant by the 'specficity of enzymes'? [1]
2. How does the lock and key hypothesis account for the specificity of enzymes? [3]
3. How does the induced fit hypothesis differ from the lock and key hypothesis? [2]
4. Explain the effect of increasing the temperature above the optimum on enzyme activity [4]
5. Explain how enzymes are able to catalyse biological reactions. [2]
6. Describe how a non-competitive inhibitor prevents enzyme activity. [3]
   

Module 3 Physiology and Transport

Transport in plants

Xylem and Transpiration
Phloem and Translocation
Mass Flow Hypothesis - experimental evidence (ringing and autoradiographs)

Task: In a maximum of 100 words summarise how sugars are transported from source to sink

Plant vasular Systems (the basics)

A/S notes on plant transport

Module 2 Genes and Genetics

DNA
You need to know the structure of DNA. Questions may ask you to label a diagram or name the parts of DNA.
You may have to work out the percentage of one base given the percentage of other bases.

DNA Relpication.
The semi-conservative method.
You will have to recall the name of the enzyme involved.

PCR
Task: compare and contrast DNA relpication and PCR

Protein Synthesis
Read and learn the steps involved in protein synthesis
Common questions involve you working out the amino acid sequence given either the DNA sense (or nonsense) strand or the mRNA sequence.




A/S Guru

DNA and RNA structure

Protein Synthesis

Protein Synthesis (this site is very good for module 1 too)







Applications of gene technology
In recent years we have progressed from the study of genes and genetics to taking a more active role. We now have the ability to identify genes and find out what they do. We can also cut them out and insert them into other organsims, forming Transgenic organisms.

There are two essential types of enzymes used in genetic engineering:

1. restriction endonucleases which cut DNA at precise points called recognition sites. Many of these enzymes produce staggered cuts known as sticky ends.
2. DNA ligases that stick DNA together.

Genetically engineering

For example: genetically modifying bacteria to make a valuable product e.g. Insulin

Gene therapy

The example you have to know about is for the tratment of cystic fibrosis.

Cystic fibrosis (CF) is an inherited disease in which the sufferer's lungs get clogged up with a sticky mucus that makes breathing less efficient and cause sufferer's to have many lung infections. CF is inherited when both parents have a faulty allele that codes for a protein called CFTR. In CF the CFTR protein differs in just one of its 1480 amino acids as a result of substitution. This causes the protein not to work. What it should do is pass ions across cell membranes, causing water to follow, hence the mucus is watery. The faulty protein can't, so the resulting mucus is thick and sticky!

Gene therapy is used to replace faulty genes with healthy ones.

The treatment is temporary and involves:

1. Isolation of the healthy CFTR gene, use PCR to clone it.
2. Encapsulate the gene into a vector that will carry it into a human lung cell e.g. a liposome (spheres of phospholipids) or a harmless virus.
3. Inhale the vector in an aerosol spray.
4. The epithelial cells take in the healthy gene, incorporaring it into their DNA and express the gene to make the healthy protein.
5. Symptoms are alleviated, but is not permanent.

Life cycles : Mitosis and Meiosis

The diploid number of chromosomes for a species is often described as 2n, e.g. For humans the diploid number is 46. All somatic cells will contain the diploid number. They have this because during mitosis the chromosomes are relpicated - Interphase.

Sex cells or gametes are made through a different type of cell division called meiosis. This reduces the diplod number, 2n, to the haploid number, n, in gametes. Each gamete produced by meiosis gets chromosomes from each homologous pair. When the gametes fuse in fertilisation the zygote will have the diplod number.

So when answering questions where you have to fill in the chromosome number in a life cycle of an organism, remember to halve the number of chromosomes a cell contains after meiosis e.g in the gametes (sperm and ova) and to use the full number of chromososmes after fertiliasation has taken place. Don't panic if thequestion is about an organism that has adults which may have haploid adults like the water flea!

Module 3 Physiology and Transport

The Heart

There are only so many questions they can ask you about the heart.
1. Structure.
2. The Cardiac Cycle, including reference to graphs.
3. How the cardiac cycle is controlled.
4. How heart rate is modified.

Read about all these areas by using the links.

The Cardiac Cycle

The Heart Quiz (use this site mainly for it's aniamation)

The Structure of the Heart

More on the heart

Exam practice June 2005 Answers June 2005

Exam practice 2004 Answers June 2004

Advanced Level Biology

A2 Research Assignment

Module 5a Environment

Human activites can impose far-reaching effects on the environment.

In groups you will research one of the following aspects.

• Ecological impact of farming - impact of monoculture, removal of hedgerows, organic wastes from farmland, eutrophication.
• Pesticide toxicity- Bioaccumulation of pesticides. Biological control methods.
• Problems caused by the fishing industry-Bycatch, Ghost nets, Overfishing.

Your task will be to produce a revision booklet on your given area of research, which will include revision notes, past exam questions and answers, revision tips, bibliography. I will photocopy these to ensure all of you have the information.

You will also have to complete a short presentation - this could include a poster and / or a powerpoint.

GOOD LUCK - you have 2 weeks to complete this work!

This website has been produced to help you with your revision.
Try all the links, making revision notes and attempting all the quizzes.
If you have any questions or need any help please add comments.

GOOD LUCK