REVSION WORLD A LEVEL

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November 01, 2015

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Biology: Biological molecules- Water

What our body is made up of? Group name monomers polymers % dry mass Proteins amino acids polypeptides 50 nucleic acids nucleotides polynucleotides 18 carbohydrates monosaccharides polysaccharides 15 lipids fatty acids and glycerol Triglycerides 10 polarity density solvent capillary action adhesion cohesion surface tension Water: Water has a number of important properties essential for life. Many of the properties below are due to the hydrogen bonds in water. Here are some of the reasons why water is important for us: The unique properties of water: · Solvent . Because it is charged, water is a very good solvent . Charged or polar molecules such as salts, sugars, amino acids dissolve readily in water and so are called hydrophilic ("water loving"). Uncharged or non-polar molecules such as lipids do not di

Practical techniques in organic chemistry

Preparing a sample of an organic liquid: Quick fit apparatus: To carry out an organic preparation you will need to use Quick fit apparatus. It contains: - round bottom or pear shaped flask - Receiver - Screw tap adaptor - Condenser - Still head Heating under reflux: Many organic reactions occur slowly at room temperature. It is common for organic reactions to be heated to overcome the activation energy and increase the rate of reaction. Heating under reflux is a common procedure used to prepare an organic liquid without boiling off the solvent, reactants or products. To heat under reflux, you need the following pieces of apparatus: - round bottom or pear shaped flask - Condenser - Rubber tubing - Stand and clamp - Heat source For heating flammable liquids, a heating mantle can be used so that there is no naked flame present. This provides an added level of safety should any apparatus leak or crack. Anti bumping granule are added to the liquid before the flask is heated so that

Immunity

Non-specific immunity Ø Many pathogens cannot cause disease due to non specific barriers and cellular defences, that prevent them from entering the body Ø Physical barriers- prevent entry of pathogens and micro-organisms when they are in contact. (1st line of defence) o Tears o Eyelashes o Skin o Mucous o Ciliated cells Ø Skin- dry and strong, outer layers of cells are shed taking bacteria with them. Ø Eye lashes- respond to foreign bodies in the region of the eyes Ø Mucous- traps dirt and bacteria Ø Cilia- brushes the trapped dirt and bacteria away Ø Tears- lysosomes which destroy bacterial cells Ø HCL- present in stomach acid Ø Skin: o Secretes sebum which lowers the pH- inhibits pathogen growth o Sweat contains salts- hard for certain types of bacteria to survive Ø Tears and eye lashes: o Tears contain lysosomes which are enzymes that can destroy bacterial cells and prevents entry of pathogens in

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