Biology unit 2 last min revision!

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  • Created by: Emma
  • Created on: 25-05-11 20:36

EUKARYOTIC CELLS: membrane bounded organelles, such as: nucleus, mitochondrian and chloroplasts. whilst PROKARYOTIC cells lack much of the structure of Ecells, and do not have membrane bound nucleus. they have a nucleoid. and addtional bits in the cell called plasmids. respiration takes place in the mesosome which is found in the prokaryotic cells.

Endoplasmic Reticulum: spreads through the whole cytoplasm. bounded by membranes. the site of synthesis, and it makes up a large part of the transport system.

Rough and smooth endoplasmic reticulum: covered in ribosomes. makes proteins, and isolates, transports these proteins once they have been made. has a large surface area to synthesize all proteins.

Smooth endoplasmic reticulum: also involved in sythnesis and transport, but in the case of fatty molecules: steriods and lipids. the amount and type of ER in a cell give an idea of what type of job the cell deoes.

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Lysosomes: the breaking down of food

 that is not needed anymore. appear in the cytoplasm. contain digestive enzymes. A lysosome will fuse with the outer cell membrane to release its enzymes outsidde the cell as extracelluar enzymes. e.g to destroy bacteria and prevent indigestion.

Budding: involves mitotic cell division. it is the outgrowth from the parent organism, which produces a smaller but identical indivudual. this bud eventually becomes detached from the parent and has an independent exsitance.

Vegeatative propagation is a version of reproductive budding, a plant forms a structure which develops into a fully differentitated plant. identical to the parent, and eventually becomes independent.

Discontinous varation is shown by features that are either present or not, such as blood groups or sex. the environment does not have effect. discontinous variation are characteristics such as weight and height. or number of leaves on a plant, factors like these are determined by the number of genes. height and weight are polygenic features.  but are also affected by the environment. when looking at continous varation you need to gain a large sample from all regions.

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in a plant cell you will find: cytoplasm, nucleus, RER, and SER and golgi bodies.

the plant cells: regualar and uniform shape, bounded by a cell wall. the cell wall is made up of cellulose. - b glucouse, 1-4 glycosidic bonds. hydrogen bonds. long straight chains. in a cell wall the cellulose molecules form microfibrils. - can only be seen under a electron mircoscope. the cellulose fibrils are laid down in layers held together by a matrix.

the plant cell wall consists of many layers: 1) middle lamella. made of pectin. the matrix and mircofibrils build up on the sides of the middle lamella. within the structure of a plant there are many long cells with cellulose cell walls which have been heavly lignified. these are known as plant fibres. Intercelluar exchanges take place through cytoplasmic brigdes between the cells plasodesmata. plasodesmata is produced as cells divide.

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