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Life and Cells

PLANT and ANIMALS have a nucleus, cytoplasms, cell membranes, mitochondria and ribosomes. PLANTS however have a cell wall, chloroplasts and a permanent vacuole. 

PALISIDE LEAF CELLS are adapted for PHOTOSYNTHESIS because they are packed with chloroplasts.Their tall shapes means they have more surface area to absorb CO2.

GUARD CELLS are adapted to OPEN AND CLOSE PORES because they have a special kidney shape, when the cells are filled with water they go plump and turgid, which makes the stomata open so gases can be released and when the cell isnt full with water the stomata closes to save water vapour escaping.

RED BLOOD CELLS are adapted to carry oxygen because they havea big surface area(increased by having no nucleus), and have a concave shape to carry the oxyhaemoglobin. 

SPERM AND EGG CELLS are adapted for REPRODUCTION because the sperm has a streamlined body to be able to swim through the womans ovaries, the eggs membrane changes when fused with the sperm to stop other sperm swimming in, the sperm contains mitochondria to provide energy to swim and the sperm also contains enzymes to be able to break down the eggs membrane. 

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Diffusion and Osmosis

DIFFUSION is the movement of particles from an area of high concentration to an area of low concentration. OSMOSIS is the movement of water molecules across a partially permable membrane from an area of high water concentration to an area of low water concentration. 

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PHOTOSYNTHESIS is the process that provides food to plants, in other cases GLUCOSE. It happens in leaves of all green plants, inside the CHLOROPLASTS. This is made up of a substance called chlorophyll, which absorbs sunlight and uses the energy to make glucose. 

4 Things needed for Photosynthesis;

  • Light (Usually from the sun)
  • Chlorophyll (the substance that makes leaves green, absorbs the solar energy)
  • Water (comes from the soil and diffused into the root hair cells using osmosis)
  • Carbon Dioxide (Enters the leaf from the air around)

LIMITING FACTORS of Photosynthesis:

  • Environmental Conditions; at night there is no light, in winter there is no sun
  • Too little Carbon Dioxide
  • Temperature
  • Light
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How Plants Use Glucose

  • For Respiration - Glucose releases energy which enables them to convert the rest of the glucose into other useful substances in which they can bulld new cells and grow. 
  • Making Fruits - Glucose and Fructose is turned into sucrose for storing in fruits. Fruits taste nice so that animals will eat them and spread seeds.
  • Making Cell Walls - Glucose is converted into cellulose for making cell walls
  • Making Proteins - Glucose is combined into nitrates to make amino acids, which are then made into proteins. 
  • Storing Seeds - Glucose is turned into fats and oils for storing in seeds. Sunflower seeds contain a lot of oil and seeds also store starch.
  • Stored as starch - Glucose is turned into starch and stored in roots, stems and leaves, ready for use when photosynthesis isnt happening, like in winter. Starch is insoluble which makes it much better for storing, because it doesnt bloat the storage cells by osmosis.
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Minerals for Healthy Growth

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Minerals for Healthy Growth

  • NITRATES - Used for making amino acids, and are then used for making proteins.
  • MAGNESIUM - Needed to make chorophyll, which is needed for photosynthesis.


  • Lack of nitrates - The plant starts to show stunted growth and wont reach normal size. This is because proteins are needed for new growth.
  • Lack of magnesium - The leaves of the plant start to turn yellow. This is because magnesium is needed to make chlorophyll, which turns the leaves green. 
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Pyramids of Number and Biomass

Each bar on a pyramid of biomass shows the mass of living material at that stage of the food chain - bascially how much all the organisms at each level would weigh if you put them all together.

The big bar along the bottom of the pyramid always represents the producer. The next bar will always be the primary consumer( the animal that eats the plant), and then the secondary consumer.

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Energy Transfer Cycle

  • LIVING THINGS are made of materials they take from the world around them.
  • PLANTS take elements such as CARBON, OXYGEN, HYDROGEN and NITROGEN from the soil or air. They turn these elements into the complex compounds(carboydrates, proteins and fats) that make up living organisms, and then these pass through the food chain. 
  • These elements are then returned to the environment in waste products produced by the organisms, or when the organisms die. These materials decay because they are BROKEN DOWN by MICROORGANISMS-thats how they get put back into the soil.
  • Microorganisms work best in warm, moist conditions. Many microorganisms also break down material faster when theres plenty of oxygen avaliable.
  • All important elements are then RECYCLED-they return to the soil, ready to be used by new plants and put back into the food chain. 
  • In a stable community, the materials are TAKEN OUT of the soil and used are balanced by those that are put BACK IN. 
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Carbon Cycle

1) CO2 is removed from the atmosphere by green plants and used to make CARBOYDRATES, FATS and PROTEINS in the plants.

2) Some of the CO2 is returned to the atmosphere when the plants RESPIRE.

3) Some of the carbon becomes part of the compounds in the AMINALS when PLANTS are eaten. The carbon then moves through the FOOD CHAIN.

4) When plants and animals die, other animals and microorgasnisms feed on their remains. When these organisms respire, CO2 is returned to the atmosphere.

5) Animals also produce waste, and this too is broken down by other animals and microorganisms feeding on their remains.

7) So the cabon is constantly being CYCLED from the aqir, through food chains and back out into the air again.

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Biological Catalysts - Enzymes

CATALYST - Speeds up the rate of reactions

ENZYME - A chemical made inside, and released from, the living cell in order to speed up the rate of reaction by diffusion. An enzyme is a biological catalyst.

  • For every body reaction, there is a different enzyme. 
  • The active site match the type of substrate 
  • For example, Protease is fitted to protein enzymes. 


The enzyme is released from the genetic DNA and folded into a 3D figure. The enzyme is released from the living cell and breaks down proteins to find the correct substrate or 'lock'. The active site draws in the substrate and the bonds in the substrate are weakened. The substrate is then released from the enzyme and is broken into products.

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Enzymes and Factors Affecting

Enyzmes are made up of PROTEINS and they speed up chemical reactions. 

ACTIVATION ENERGY - The amount of energy needed to start a reaction, The activation energy is lowered when the enzyme breaks down a molecule to speed up a reaction,


Enzymes in the HUMAN BODY work at around 37 degrees. 

The pH also affects enzymes. If its too high or too low, the pH intereferes with the bonds holding the enzyme together. This changes the shape and denatures the enzyme. 

OPTIMUM pH - the best pH the enzymes work at.

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