Overview of Biology Unit 2

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  • Created by: Uma
  • Created on: 12-12-10 16:16

Specialised Cells

Root Hair Cell (Plant): 1. Large surface area so can absorb more water and mineral ions

                                 2. Very few cell organelles allowing them to store water and ions

Palisade or leaf Cell: 1. Well loads of chloroplasts so photosynthesis happens more 

                               2. Long and thin so more of them

Sperm Cell: 1. Well loads of mitochondria so able to release well loads of glucose

                  2. Enzymes on its head so can break into egg easileh

Fat Cell (Human): 1. Can expand 1000x its size to hold fat

                           2. Contain few mitochondria cause they don't need the energy


Reactions inside cells can be controlled by enzymes. Examples are photosynthesis, protein synthesis and respiration.

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What do cells contain?

All cells have: - Nucleus which controls activities in cell

                     - Cytoplasm where chemical reactions take place

                     - Mitochondria where respiration takes place

                     - Cell Membrane which controls what goes in and out of the cell

                     - Ribosomes where protein synthesis occurs


But oh poopy hold your horses. Because plant cells also have:

                     - Cell Wall which prevents cell from filling up with too much water

                     - Chloroplasts which are (funnily enough) filled with chlorophyll to make                              glucose in photosynthesis

                     - Vacuole which is filled with cell sap. It stores glucose and supports cell.

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Diffusion & Osmosis

DIFFUSION - The movement of a substance (gas or dissolved solid) from a region where it is in high concentration to a region where it is in low concentration

The greater the difference in concentration between the two regions, the faster it happens. 

Active transport is just the opposite (where it goes for low concentration to high concentration). 


Osmosis - The movement of water from a dilute solution to a more concentrated solution through a partially permeable membrane, which is a membrane that allow some molecules through but not some - discrimination I tell you. 

Plants use osmosis to gain water through their roots.

Active transport is the opposite of diffusion. It involves movement of a dissolved substance from an area of low concentration to an area of high concentration. 


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Carbon Dioxide + Water (+Light Energy) ----> Glucose + Oxygen

1) Energy from UV light hits chloroplasts inside palisade cells. It is absorbed by chlorophyll enzymes inside the chloroplasts. 

2) The chlorophyll enzymes are activated when they absorb the UV light an are able to join together the molecules of carbon dioxide with molecules of water.

3) The result of this is the production of glucose and oxygen.

The glucose produced is used for various things. Some is delivered straight to the cells, where it is used for respiration. This allows the plant to grow/repair itself etc. Any glucose not needed by the plant immediately can be stored in the vacuoles. In the vacuoles, glucose is joined together to produce starch. Starch is insoluble so becomes trapped inside the vacuole of the cell, until it is needed.

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What do plants need to keep healthy?

Apart from glucose, plants need a good supply of mineral ions which they absorb from the soil via a process called active transport.

Nitrates are used by a plant to produce amino acids, which are turned into proteins. Proteins are vital in plant growth. If a plant cannot get nitrates, the growth of the plant is stunted as the plant cannot make the protein it needs to grow.

Magnesium is needed for the production of chlorophyll, which is an enzyme involved in photosynthesis. If the plant cannot get magnesium, the leaves will turn yellow, as fewer chlorophyll (which are green) can be produced.

Things such as temperature, amount of UV light, amount of carbon dioxide and amount of water all limit the rate of photosynthesis. Think about it. If the temp gets too hot or too cold, then the chlorophyll will get denatured. If there is too little carbon dioxide or water, then the plant cannot photosynthesise because these are the raw materials needed for it. If there is a shortage of UV light, the chlorophyll cannot be activated.

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This is unfinished guys



:S this looks confusing .... we are doing our unit 3 in january and unit 2 in june ... hope you have it finished for june for me :D x



haa, oh yeah fingers crossed i will have it done for january

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