New Syllabus Notes

[saya]

Okay people, there are a lot of useful links on the net which help us revise almost every single subject...but the biology ones must be updated since the Syllabi changed last year. Our teacher teaches us the subject by giving us notes going by the Syllabus, so I thought it would be useful if I shared them with you...feel free (what's more, I obligue you) to comment on the notes, add, or substract any material. I don't trust my bio teacher that much, so please correct them where you feel correction is needed. I have made a domain in geocities, and most probably will put up the revised notes on it, so that everyone can access to them and study.

I hope this works out!!!

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TOPIC 2: CELLS [/size]

[size=3]2.1 Cell theory[/size]

[b]2.1.1 Outline the cell theory[/b]
*All living organism are composed of cells.
*Cells are the smallest unit of life and nothing smaller can survive independently.
*Cells come from pre-existing cells, by division, and therefore new cells cannot be constructed from non-living chemical substances.
*Cells contain hereditary information which is passed from cell to cell during cell division.
*All energy flow (metabolism & biochemistry) of life occurs within cells.
*All cells are basically the same in chemical composition.
*According to the number of cells, we classify the organism in the following:
-unicellular (amoeba)
-multi cellular
-in some organism, the body is made of cells with no partitions, resulting in the structure with many nuclear, these structures, are called multinuclear (e.g., muscle fibres in humans, Brain mall)

[b]2.1.2 Discuss the evidence for the cell theory[/b]
1. There are various types of organism which proves that all living organisms are composed of cells
2. In a foetus, from a single cell a foetus is formed, which proves cell division.
3. In an experiment with 2 different bottles of soup, one open and the other bottle is closed. The opened ones rots, which proves that life arises from previous cells.

[b]2.1.3 State that unicellular organisms carry out all the functions of life.[/b]
A unicellular organism is able to respond to
1. External stimulus
2. Respire by diffusion of gases in its surface area
3. Feed by food vacuole or by diffusion
4. Excrete by diffusion or by contractile vacuole
5. Reproduce by asexual reproduction (binary fusion)
7. Grow to a certain limit
8. Keep the internal environment constant (homeostasis)

[b]2.1.4 Compare the relative size of molecules cell membrane thickness, viruses, bacteria, organelles and cells, using the appropriate SI units.[/b]
molecules 1 nanometre
thickness of membrane 10 nanometre
virus 100 nanometre
bacteria 1 micrometer
organelles up to 10 micrometer

[b]2.1.5 Calculate the linear magnification of drawing and the actual size of specimen in images of known magnifications.[/b]
*we did a small exercise for this*

[b]2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size[/b]
*picture needs to be inserted to show how, with growth of size, surface are becomes smaller*
1. The size of a cell is limited by its need to exchange its material with the environment. If the cell becomes too large its diffusion system becomes too long to be efficient and the SA/VA becomes less.
2. The rate with which a cell produces heat, waste or consumes the resources is directly proportional to its volume. However, since all this takes place through the cell membrane, it is also proportional to its surface area.
3. Ways of dealing with this are to increase the surface area.
E.g. -protruding extensions like bile of small intestine
-increase in surface area like lungs
-reducing the diffusion distance like blood carrying material around the body

[b]2.1.7 State that multicellular organisms show emergent properties[/b]
Each level emerges from the level below (simplest of levels).
E.g. -the pumping of the heart emerges from interaction of tissues, chemicals and nerves
-individual neurons in the brain are not capable of thought but the communication and cooperation between neurons makes it possible for the brain to think
So, emerging property means that the organism can achieve then the sum of what each cell can achieve individually
It is important to study the organisms as a whole. The whole is greater than the sum of its parts.

[b]2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized functions by expressing some of their genes but no others[/b]
1- Differentiation of cells increases the efficiency in body functions. In multicellular organism all ells are genetically indicated (mitotic division of zygote)
Though all cells are generally identical they differ in the activity or expressivity of genes. Te factors that decide this are
a) the position of the cell with respect to other cells during embryonic development
b) the chemical compound present in the cell during embryonic development

[b]2.1.9. State that stem cells retain the capacity to divide and have the ability do differentiate along different pathways[/b]

[b]2.1.10 Outline one therapeutic use of stem cells.[/b]
Stem cells have been transplanted into injured spinal cords of experimental animals and there has been some recovery of mobility. This was due to the insulating myelin sheaths around neurons being repaired. However, side-effects have been observed, including stimuli that had previously been painless causing pain to the animal. (This is from the Course Companion)
1. There are various types of organism which proves that all living organisms are composed of cells
2. In a foetus, from a single cell a foetus is formed, which proves cell division.
3. In an experiment with 2 different bottles of soup, one open and the other bottle is closed. The opened ones rots, which proves that life arises from previous cells.