TEM & SEM advantages/disadvantages

Cell fractionation process

 

Before cell fractionation: Place tissue in isotonic buffered solution -low temperature reduces enzyme activity, which may break down the organelles -the isotonic solution prevents organelles bursting or shrinking as a result of osmotic gain or loss of water. The isotonic solution has the same water potential as the origional tissue. -the solution is buffered to maintain a constant pH.

Stage 1. Homogenation Cells are broken up by a homogeniser (blender), which releases the organelles from the cells. The resultant fluid (homogenate) is filtered to remove any complete cells and large debris. The filtrate (filtered homogenate) contains the organelles.

Stage 2. Ultracentrifugation A machine called a centrifuge separates the fragments in the filtrate into organelles. The filtrate is placed in a tube and the tube is placed into a centrifuge. The centrifuge spins the filtrate at a slow speed, which causes the heaviest organelles to sediment on the bottom- forms a pellet. The heavy organelles in the pellet are nuclei. The fluid (supernatant) is poured into another tube and spun at a faster speed. The next heaviest organelles are sedimented, which are mitochondria. This process is continued to produce pellets of organelles of varying sizes.

Cell fractionation video

http://www.youtube.com/watch?v=SjaFUJhzY9Q

20 strange things The Daily Mail say will cause cancer!

1.FACEBOOK: Social networking sites such as Facebook could raise your risk of serious health problems by reducing levels of face-to-face contact, a doctor claims.

2.  WINE: Drinking just a small glass of wine a day can more than double the risk of cancer, a study claims. It says that consuming just one 125ml glass of wine increases the chance of developing mouth and throat cancer by 168 per cent.

3. A COLD:  The common cold could be a major cause of childhood cancer, a new study claims. Researchers claim that an infection during pregnancy or in early childhood could leave children more susceptible to cancers like leukaemia or brain tumours.

4.  DEODORANT: New research suggests that the aluminium in many anti-perspirants has a potential link with breast cancer. Here, a leading breast cancer specialist explains why he explains why he suggests avoiding the products.

5.  CHIPS: Parents are being urged to stop giving their children chips amid fears they dramatically increase the risk of breast cancer. Serving under-fives chips just once a week raises their risk of breast cancer by 27 per cent, shocking new research has shown

6. ORAL SEX: Oral sex raises your risk of throat cancer scientists have warned. A new study found the sex act can pass on the human papillomavirus (HPV), which can trigger a specific type of throat cancer in both men and women

7. VITAMIN E: Vitamin E supplements may raise the risk of lung cancer, doctors have warned. A study of more than 77,000 people found that taking moderate to high doses of vitamin E led to a ’significant’ increase in risk of the cancer that kills on Briton every 15 minutes.

8. SAUSAGES AND BURGERS: A red dye used in sausages and burgers is being banned because it could cause cancer, the European Commission said today. The move will come into force within days

9.  SOUP: People who regularly have soup with a high salt content could be increasing their risk of stomach cancer, according to an expert.

10. HAIR DYE: Women who use permanent hair dye may be putting themselves at increased risk of bladder cancer. If you have used hair dye for at least 15 years, the risk is three times greater, says new research

11. MOUTHWASH: There is now ’sufficient evidence’ that mouthwashes containing alcohol contribute to the increased risk of cancer in the mouth, according to a scientist.

12. SUN CREAM: Sun creams could raise the risk of getting skin cancer, warn experts. Although they help prevent sunburn, lotions fail to block out the ultraviolet rays which can cause the disease

13. PRINGLES, HULA-HOOPS & PRINCE CHARLES’ ORGANIC CRISPS: An organic product sold under Prince Charles’s Duchy Originals brand has been found to contain elevated levels of a cancer causing chemical.

14. X-RAYS: Diagnostic X-rays are linked to a small raised risk of cancer, according to researchers. The radiation could be the cause of 700 cancer cases per year in Britain

15. TALCUM POWDER: Women who use talcum powder every day to keep fresh are 40 per cent more likely to develop ovarian cancer, according to alarming research.

16. MOISTURISERS: Moisturisers used by millions of women every day may be increasing their risk of skin cancer, scientists have warned.

17. MOBILE PHONES: Mobile phones can take as little as ten minutes to trigger changes in the brain associated with cancer, scientists claimed yesterday. They found even low levels of radiation from handsets interfere with the way brain cells divide

18. RED MEAT: Eating large amounts of red and processed meat leaves you at greater risk of cancer, a major report has warned. One in ten cases of both lung and bowel cancer could be prevented if people cut down on beef, lamb, pork, sausages, ham and bacon, scientists say

19.TOOTH WHITENER: Dentists are warning the public over the proposed sale of super-strength tooth whitener linked to cancer. Under European Commission plans, the limit on concentration levels of bleach in over-the-counter products will rise 60 times

20. CHOCOLATES AND BAGGED SNACKS: Chocolates and bagged snacks are being pulled from shop shelves after potential cancer-causing toxins were found in a batch of rice flour

Looking critically at data

1.Has the right factor been measured & have the correct questions been asked?

2.How were data gathered, were the methods reliable & was the right apparatus used?

3.Do those collecting the results have a vested interest in the outcome of the research? i.e. researcher bias

4.Has the study been repeated, with the same results & conclusions, by other people?

5.Are there still unanswered questions?

Welcome year 12!

Welcome to AS biology!
I will use this to post useful documents, revision materials, homework & useful stuff to help you on the course.
Enjoy!