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

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

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

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

Biological elements and compounds in the human body © Pearson Education Ltd 2008 This document may have been altered from the original

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.

The Importance of Water As a transport medium

PROPERTIES OF WATER

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. http://www.northland.cc.mn.us/biology/Biology1111/animations/hydrogenbonds.html

WATER IS A GOOD SOLVENT: NaCl dissolving in water

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.

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.

Low viscosity Water will flow through very small spaces and capillaries

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.