Cancer

Causes
There are about 200 different types of cancer. They can start in any type of body tissue. What affects one body tissue may not affect another. For example, tobacco smoke that you breathe in may help to cause lung cancer. Overexposing your skin to the sun could cause a melanoma on your leg. But the sun won't give you lung cancer and smoking won't give you melanoma.

Apart from infectious diseases, most illnesses are 'multifactorial'. Cancer is no exception. Multifactorial means that there are many factors involved. In other words, there is no single cause for any one type of cancer.

Carcinogens
A 'carcinogen' is something that can help to cause cancer. Tobacco smoke is a powerful carcinogen. But not everyone who smokes gets lung cancer. So there must be other factors at work as well as carcinogens.

Age
Most types of cancer become more common as we get older. This is because the changes that make a cell become cancerous in the first place take a long time to develop. There have to be a number of changes to the genes within a cell before it turns into a cancer cell. These changes can happen by accident when the cell is dividing. Or they can happen because the cell has been damaged by carcinogens and the damage is then passed on to future 'daughter' cells when that cell divides. The longer we live, the more time there is for genetic mistakes to happen in our cells.

Genetic make-up
There need to be a number of genetic mutations within a cell before it becomes cancerous. Sometimes a person is born with one of these mutations already. This doesn't mean they will definitely get cancer. But with one mutation from the start, it makes it more likely statistically that they will develop cancer during their lifetime. Doctors call this 'genetic predisposition'.

The BRCA1 and BRCA2 breast cancer genes are examples of genetic predisposition. Women who carry one of these faulty genes have a higher chance of developing breast cancer than women who do not.

The BRCA genes are good examples for another reason. Most women with breast cancer do not have a mutated BRCA1 or BRCA 2 gene. Less than 5% of all breast cancer is due to these genes. So although women with one of these genes are individually more likely to get breast cancer, most breast cancer is not caused by a high risk inherited gene fault.

This is true of other common cancers where some people have a genetic predisposition - for example, colon (large bowel) cancer.

Researchers are looking at the genes of people with cancer in a study called SEARCH. They also hope to find out more about how other factors might interact with genes to increase the risk of cancer. Information about this study is on our clinical trials database.

The Immune System
People who have problems with their immune systems are more likely to get some types of cancer. This group includes people who

* Have had organ transplants and take drugs to suppress their immune systems to stop organ rejection
* Have HIV or AIDS
* Are born with rare medical syndromes which affect their immunity

The types of cancers that affect these groups of people fall into two, overlapping groups

* Cancers that are caused by viruses, such as cervical cancer and other cancers of the genital or anal area, some lymphomas, liver cancer and stomach cancer
* Lymphomas

Chronic infections or transplanted organs can continually stimulate cells to divide. This continual cell division means that immune cells are more likely to develop genetic faults and develop into lymphomas.

Bodyweight, diet and physical activity
Cancer experts estimate that maintaining a healthy bodyweight, making changes to our diet and taking regular physical activity could prevent about one in three deaths from cancer in the UK. In the western world, many of us eat too much red and processed meat and not enough fresh fruit and vegetables. This type of diet is known to increase the risk of cancer. Drinking alcohol can also increase the risk of developing some types of cancer. There is more information about this in the page on diet causing cancer.

Sometimes foods or food additives are blamed for directly causing cancer and described as 'carcinogenic'. This is often not really true. Sometimes a food is found to contain a substance that can cause cancer but in such small amounts that we could never eat enough of it to do any harm. And some additives may actually protect us. There is more about food additives in the page on diet causing cancer.

Day to day environment
By environmental causes we mean what is around you each day that may help to cause cancer. This could include

* Tobacco smoke
* The sun
* Natural and man made radiation
* Work place hazards
* Asbestos

Some of these are avoidable and some aren't. Most are only contributing factors to causing cancers - part of the jigsaw puzzle that scientists are still trying to put together. There is more about this in the page on causes of cancer in the environment.

Viruses
Viruses can help to cause some cancers. But this does not mean that these cancers can be caught like an infection. What happens is that the virus can cause genetic changes in cells that make them more likely to become cancerous.

These cancers and viruses are linked

* Cervical cancer, and other cancers of the genital and anal area, and the human papilloma virus (HPV)
* Primary liver cancer and the Hepatitis B and C viruses
* Lymphomas and the Epstein-Barr Virus
* T cell leukaemia in adults and the Human T cell leukaemia virus
* HPV also probably leads to oropharyngeal cancer and non melanoma skin cancers in some people

There will be people with primary liver cancer and with T cell leukaemia who haven't had the related virus. But infection increases their risk of getting that particular cancer. With cervical cancer, scientists now believe that everyone with an invasive cervical cancer has had an HPV infection beforehand.

Many people can be infected with a cancer causing virus, and never get cancer. The virus only causes cancer in certain situations. Many women get a high risk HPV infection, but never develop cervical cancer. Another example is Epstein-Barr virus (EBV). These are some facts about EBV

* It is very common - most people are infected with EBV
* People who catch it late in life get glandular fever and have an increased risk of lymphoma
* In sub-Saharan Africa, EBV infection and repeated attacks of malaria together cause a cancer called Burkitt's lymphoma in children
* In China, EBV infection (together with other unknown factors) causes nasopharyngeal cancer
* In people with AIDs and transplant patients EBV can cause lymphoma
* About 4 out of 10 cases of Hodgkin's lymphoma and a quarter of cases of Burkitt's lymphoma (a rare type of non Hodgkin's lymphoma) seem to be related to EBV infection.

Bacterial infection
Bacterial infections have not been thought of as cancer causing agents in the past. But studies have shown that people who have helicobacter pylori infection of their stomach develop inflammation of the stomach lining, which increases the risk of stomach cancer. Helicobacter pylori infection can be treated with a combination of antibiotics.

Research is also looking at whether substances produced by particular types of bacteria in the digestive system can increase the risk of bowel cancer or stomach lymphomas. Some researchers think that particular bacteria may produce cancer causing substances in some people. But research into this issue is at an early stage.

If bacteria do play a part in causing cancer this could be important in cancer prevention. Bacterial infections can often be cured with antibiotics, so getting rid of the infection could be a way to reduce the risk of these types of cancer.

P3 Answering Technique

Question 1
Observation
In 0.2M of sucrose solution, the final diameter of potato disc is 1.90 cm.
In 0.6M of sucrose solution, the final diameter of potato disc is 1.40 cm.
Your answer must be specific. Where do u get it?? From the title in the given table.

Inference
(At 0.2M of sucrose solution) water molecule diffuses into the potato disc by osmosis.
(At 0.6M of sucrose solution) water molecule diffuses out of the potato disc by osmosis.
You give reasons (why) based on your observation. But remember, inference 1 for observation 1 and inference 2 for observation 2. Jgn. silap, rugi....potong markah

Variables
Manipulated variable
Concentration of sucrose solution : Use five different concentrations of sucrose solutions

Responding variable
Final diameter of the potato disc : Measure and record the final diameter of potato disc by using a metre rule
The word record and the instrument used are important.
//
Percentage change in diameter of potato disc : Calculate the percentage change in diameter of potato disc
by using the formula :
(Final – Initial) diameter of potato disc x 100%
Initial diameter of potato disc
If you choose to write about the formula, must state clearly

Constant variable
Time taken to immerse the potato discs : Fix the time (to immerse the potato discs) at 20 minutes.
If the exact time or units are stated in the question, students must write them down. If not, telor ayam la....

Hypothesis
As the concentration of sucrose solution increases, the final diameter of potato disc / the percentage change in diameter decreases.
Just the MV + RV and the relationship(higher, lower); no need to explain further.
Majority of the students like to write `depends on', `affects', `influences'....style PMR.....1 mark only

Table
1. Title and units (must be correct)
No units will be given in the question. Students must refer the earlier page.
2. Apply readings from the table given earlier.(salin jer)
3. Some calculation.

Graph
1. Both axes with correct units and title
2. All points plotted correctly (don't simply add any readings on you own; eg. connect it to 0 ka...)
3. Smooth curve touching all points.

Relationship
The concentration of sucrose solution which is isotonic to the cell sap of potato disc is *0.49M. The percentage change in diameter is zero because
the rate of water that diffuses in and out of the cell is equal.
Must explain.

Prediction
Diameter (of potato disc) is more than 1.9 cm
Distilled water is hypotonic to the cell sap of potato disc
so more water diffuses into the potato (disc) by osmosis.
We predict more or less by referring to the data from the earlier page. Don't simply guess.

Operational definition (Give explanation based on the experiment; not theoretically. Normally combine CV,MV & RV)
Osmosis is the movement of water to / from potato disc through the plasma membrane (of potato) due to the difference concentration between sucrose solution and cell sap of potato cell that will result in changes / decrease / increase in diameter of potato disc.

We don't write osmosis is the movement of water molecules from the region of `high water concentration/low solute concentration' to the region of `low water concentration/high solute concentration' through the semi permeable membrane....as in the book (theory)

Classifying
Salin balik je...dlm kotak....kacang

Total : 33 marks

Question 2 (Latest format)
Eg.
Plan a laboratory experiment to investigate the percentage of vitamin C content in each fruit. DCPIP (dichlorophenolindophenol) 0.1% solution is used to test the presence of vitamin C in the fruit juices.
[Apple, Orange, Watermelon]

Problem statement (3 marks)
1. What is the percentage of vitamin C content in watermelon, orange and apple?/ fruits? //
2. Does apple/orange/watermelon contain more vitamin C than orange/watermelon/apple? //
3. Which fruit has more percentage of vitamin C?
(Remember, all must be in question form. Change the aim into a question form. (kacang). No question mark, deduce 1 mark)

Hypothesis (MV+RV+R) (3 marks)
Watermelon has highest content of vitamin C compare to other fruits.


Materials & Apparatus (3 marks)
DCPIP solution, Standard Ascorbic Acid, Fruit juices / watermelon juice/orange juice/apple juice, Conical flask /beaker, Syringe with needle, Specimen tube

Procedure (3 marks)
K1 : Steps to set up the apparatus & materials
K2 : Steps to handle the fixed variable
K3 : Steps to handle the manipulated variable
K4 : Steps to handle the responding variable
K5 : Precautionary steps / steps taken to get accurate results / readings
(Examiners will be looking for all these 5Ks to get 3 marks )

Eg.
K1 1. Three specimen tubes is labelled as A1, A2 and A3.
K2 2. Fill each specimen tubes with 1 ml of 0.1% DCPIP solution
K1 3 . Use a syringe to take 10 ml of standard ascorbic acid
K1 4 . Place the syringe needle into the DCPIP solution and release the ascorbic acid slowly into the DCPIP solution in A1
K4 5 Observe the change of DCPIP colour and stop releasing the ascorbic acid when the DCPIP become colourless/ no more blue traces
K4 6 Record the volume of ascorbic acid used to dicolourise the DCPIP solution.
K1/K5 7 Repeat steps 3 – 6 for A2 and A3 and calculate the average volume.
K1/K5 8 Juices from each of the fruits is obtained and kept fresh before used
K1/K2 9 Three specimen tubes is labelled as (B1, B2, B3, C1, C2, C3, D1, D2 and D3), and fill each specimen tubes with 1 ml of 0.1% DCPIP
K3 10 Repeat steps 2 – 7 by using fruit juices to replace the standard ascorbic acid.
K5 11 Do not shake the bottle to prevent from DCPIP is oxidated.
K4 12 Record the volume of watermelon juice, apple juice and orange juice that discolourise the DCPIP in the table and calculate the average volume
K4 13 Calculate the percentage of vitamin C in each of the fruit juice using the formula below:

Percentage of vitamin C in fruit juice =
volume of 0.1% ascorbic acid X 1.0 mgcm-1
volume of fruit juice

Tak payah tulis all the Ks in front. For reference only.

Presentation of Data (2 marks)

No data is required. Just the title and the correct units.
Total : 17 marks

Studying skills in Biology

1. Successful biology students study a minimum of 2 to 3 hours per day, 7 days a week, throughout the term.

2. Biology is hard work, so be aggressive. Take it as a challenge and give it your time and your energy.

3. Know and understand all your terminology. This is one of the keys to success in any field. This is the basis for many seemingly difficult terms. Study these roots. Make 3" x 5" flash cards to help you memorizse them and later do the same with your terminology.

4. Pay attention.

5. Make it a practice to read over the topic or chapter before going to your biology class.

6. Attend all classes and be an active listener. It is important to be alert and concentrate on what is said in class. Successful students take full and comprehensive notes, writing down about 66% of what is said in class, while failing students write half as much. It is most important to stay current. Do not allow yourself to miss classes and fall behind or the entire course will become an effort and a struggle for you.

7. After class go over the material as soon as possible and again 8 hours later. Studies have shown that you are more likely to remember the information later. Fill in all the missing words or incomplete explanations. Recite important concepts in your own words.

8. Always remember you have the right to ask questions before, during and after class. See your teachers during their office hours for help. Notice when you are beginning to get in trouble and seek help immediately.

9. Read and study all your textbook explanations. You may wish to use at least two or more books. These books are often available in the library. Each book has a different discussion and examples on your topic, and one of these is likely to be helpful to you.

10. Whenever possible explain aloud to another person what you are learning. Work with a classmate and explain terminology and concepts to each other.

11. Describe in your own words the similarities and differences between the different concepts you are learning. Do this aloud with someone else.

12. If biology is your most difficult subject, then always study it before all other subjects. You must study biology when you are most alert and fresh. Make sure to take 5 or 10 minute breaks every 20­40 minutes in order to clear your mind.

13. Write up summary sheets of biology terminology and concepts and review often. The more you review the more you'll remember. Also visually picture the terms in your minds eye. Visualising is a powerful technique for remembering terms. Break words into small chunks and picture each chunk until you can recall it. Then put the chunks together. Remember, the knowledge of roots can be extremely helpful.

14. Making up mnemonics memory techniques may be fun as well as beneficial. For example, if you need to remember the 12 cranial nerves you can take the first letter of each nerve and make up a sentence where each word begins with the first letter of each nerves.

15. Create sample tests for yourself and test yourself often.

16. Give yourself timed tests similar to those you expect in class. Time yourself with a kitchen timer or an alarm. Practice, practice, practice.

17. Review the types of errors you make and types of questions that cause you difficulty. Give yourself more practice in these areas of difficulty.

18. If possible, have a friend or family member quiz you on your notes and text information. Done regularly this commits more information to long­term memory.

Good luck.