1. Metabolism The chemical reactions that take place in living organisms.
2 general categories of metabolic reactions
Anabolic Catabolic
Reactions Reactions

2. Metabolism The chemical reactions that take place in living organisms.
2 general categories of metabolic reactions
Anabolic Catabolic
Reactions Reactions

3. 2 general categories of metabolic reactions
Anabolic Catabolic
Reactions Reactions
Build up large Break down
molecules large molecules
from smaller ones into smaller ones
E.g. Photosynthesis E.g. Respiration

4. Types of biological molecule
Water
Carbohydrate – energy source, energy store or structural material
Protein – functional role (enzymes, hormones etc.) or structural role ( keratin, collagen etc.)
Lipid – energy store; insulation; membranes
Nucleic Acids (DNA & RNA) – genetic material

5. Biological elements and compounds in the human body
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6. Covalent bonding in water
Compounds can contain more than one covalent bond.
Oxygen (2.6) needs 2 more electrons, but hydrogen [1] only needs 1 more. How can these three elements be joined by covalent bonding? H O
The oxygen atom shares 1 electron with 1 hydrogen atom, and a second electron with another hydrogen atom.

7. The Importance of Water
As a transport medium

8. PROPERTIES OF WATER

11. Solvent properties The dipoles on water make it an excellent solvent
Any substance that is fairly small molecules with charges on them, or that can separate into ion, can dissolve in water
They are known as hydrophillic (water loving)
How it helps in transport?
Blood plasma is mainly water and carries many substances in solution, including glucose, oxygen and ions such as sodium.

12. WATER IS A GOOD SOLVENT: NaCl dissolving in water

13. Thermal Properties Fact
The specific heat capacity of water, the amount of energy in joules required to raise the temperature of 1ml water by 10C ,is very high.
WHY ?
Water requires a large amount of energy to break the hydrogen bonds.
Consequence
A large input of energy causes only a small increase in temperature, so water warms up and cools down slowly.
How this helps with transport?
Avoid rapid changes in internal temperature – maintain a steady temp even when external surroundings varies. Cell contents are unlikely to freeze.

14. Liquid at room temperature
Fact
Water is a small molecule but is liquid at room temp unlike others like Carbon dioxide
WHY?
Hydrogen bonds between molecules: these hold the water molecules together and more energy required to vaporise
Consequence
Water stays as a liquid at the temperatures inside the body and can flow
How this helps with transport?
Water remains as a liquid solvent, many polar molecules can dissolve in it and it can move them all over the body.

15. Low viscosity
Water will flow through very small spaces and capillaries

19. PROPERTIES OF WATER
Good solvent for charged and uncharged molecules: water molecules are attracted to ions and polar molecules like glucose
High specific heat capacity: a lot of heat energy is required to warm water up. Eg.: helps body to prevent temperature change
Good coolant: a lot of heat (thermal) energy is used to change water into vapour. Eg.: loss of heat when sweating
High cohesion: water molecules “stick” together by hydrogen bonds. Eg.: water drawn up in the xylem.
Can be reactive with various substances. Eg.: Hydrolysis and photosynthesis reactions
Can not be compressed: water molecules are pulled closely together by H-bonds, so it is relatively dense. eg: earthworm have an hydrostatic skeleton, and plant get their turgidity from water.