Title of the first chapter in STPM Biology is Basic Chemistry of A Cell.

Let's go through the subtopic one by one.

C1 : Basic Chemistry of A Cell
1.1 Water
1.2 Carbohydrates
1.3 Lipids
1.4 Proteins
1.5 Nucleic Acid : DNA and RNA
1.6 Movement of substances across membrane
1.7 Technique of analysis

And yes, today, we are going to learn the first one, water.


As we all studied in SPM, water comes with its chemical formula :


But now in STPM, we need to learn in details. Not only we have to know it consists of 2 hydrogen atoms and 1 oxygen atom. We have to know more, how does the thing looks like?

Yea, the angle in between 2 hydrogen atoms is 104.5° . 

Apart from that, water is bipolar, this is due to uneven distribution of charge within the molecule.




Water molecules are linked through hydrogen bonds. A water molecule can form 4 hydrogen bonds with 4 other water molecules. Hydrogen bonds are weak bonds, not as strong as normal ionic bond or covalent bond.


Below are the importance of water.

1. As universal solvent.
- Can dissolve both ionic and polar substance.

2. Has high surface tension and cohesion.
- This is due to hydrogen bonding.
- By having high surface tension, small organism is able to walk on water surface.
- Besides, it helps in translocation of water through xylem in plants.

3. Has high specific heat capacity.
- 4.2kJ/kg/K.
- Large amount of heat energy is required to raise water temperature by 1 Kelvin.
- By having this properties, our body can maintain its own normal temperature constantly.

4. Has high latent heat of vaporisation.
- 2260J/kg.
- Allows vaporisation and cooling takes place.

5. Has high latent heat of fusion.
- 340kJ/kg.
- Our cells are less likely to freeze.

6. Density decreases when below 4°C.
- When water freezes, it can float on top and insulate below.
- Aquatic life below still can stay alive without getting further cooling and freezing.

7. Medium of chemical reaction.

8. One of reactants or products in chemical reaction.
- raw material in photosynthesis.

9. Lubricant.
- mucus helps in peristalsis.
- synovial fluid at joints. ; pericardial fluid for heart. ; pleural fluid for lungs.

10. Provides moist surface.
- substance can diffuse and dissolve.
- e.g alveoli in lungs

11. As medium of transport and removal of waste substances.
- transport nutrients, hormones, mineral salts.
- remove metabolic wastes like ammonia.

12. As medium of fertilisation.
- gametes that swim
- e.g sperms

13. As support.
- hydrostatic skeleton
- exerting pressure
- e.g earthworm

14. As dispersal agent for seeds
- e.g coconut tree

That's all for part 1. Do leave comments if encounter problem or found mistakes in our notes.

Check out our Part 2 soon.






Notes by WanQing
Images from Google

Labels: Biology, Notes, STPM