GCSE B2 Full Revision Notes

Detailed revision notes for GCSE B2 exam-Good luck

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  • Created on: 10-05-13 14:24
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B2 Notes
Light microscopes: Magnify 100s of times
Electron Microscopes: Magnify 100,000s of times
Both Have:
-Nucleus: Contains genetic material and controls cell activity
-Cytoplasm: Contains enzymes that control chemical reactions
-Cell Membrane: Controls what substances go in or out of cell
-Mitochondria: Where respiration occurs to release energy for cell activity
-Ribosomes: Where protein synthesis takes place
ONLY Plants Have:
-Cell Wall: Made up of Cellulose, supports and strengthens cell
-Permanent Vacuole: Contains Cell Sap, supports cell and contains weak salt and sugar solution
-Chloroplasts: Have Chlorophyll, Photosynthesis
-Single Celled Micro-organisms
-Contain: Nucleus
Cell Membrane
Cell Wall

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Specialised Cells:
-The cell structure of a specialised cell is adapted to suit its particular function
-They look different from typical animal/plant cells
-Some cells become so specialised they only have one job/function
Specialised Cell Adapted for/to... Adaptions
Sperm and Egg Cells Reproduction Egg cells
-When sperm fuses with egg, egg membrane
changes structure to stop any more sperms
entering; this makes sure each offspring has the
right amount of DNA.
Sperm cells
-Have long tail and stream lined head to help
them swim.…read more

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Cell Organisation
Multicellular Organisms:
-Specialised cells are formed through a process known as Differentiation.
-Differentiation occurs during the development of Multicellular Organism.
-Specialised cells form Tissues, which form Organs, which Organ Systems.
-In Large multicellular organisms these organ systems are used to transport and exchange materials.…read more

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What happens during Photosynthesis?
Photosynthesis produces glucose using sunlight and releases oxygen as by product.
1. Sunlight provides energy for process
2. Chlorophyll absorbs light energy
3. Water reaches cell via xylem
4. Carbon dioxide diffuses into the leaf
5. Photosynthesis occurs
6. Oxygen is given off as by product
Leaf Structure: Main organ for Photosynthesis
Epidermis protects the leaf and is
transparent to let light through.
Palisade mesophyll cells are tall and closely packed to absorb maximum light. They contain many
chloroplasts.…read more

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The Rate of Photosynthesis
Affected by:
-Intensity of light
-Volume of Carbon dioxide
3 Important Graphs for Rate of Photosynthesis
Not enough LIGHT:
-Slows down photosynthesis as light provides energy for photosynthesis
-As the light increases so will the rate of photosynthesis but only to a certain point
-After that either carbon dioxide or temperature will be the limiting factors
-Slows down photosynthesis as carbon dioxide is the raw material needed for
- As the carbon dioxide levels…read more

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Distribution of Organisms
Affected By
-Availability of water
-Availability of carbon dioxide and oxygen
-Availability of nutrients
-Amount of light
Recording distribution of organisms:
-Used to study distribution of small organisms
-Are placed randomly
- look at the results from several quadrats in an area to reduce the effect of an unusual
- results are more reliable when you look at the results from many quadrats
-quadrats may also be used for slow moving animals such as snails/slugs
-Population Size = Mean…read more

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H Level
Enzymes work best at their optimum pH.…read more

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Anaerobic Respiration
-Without oxygen
-Less efficient than aerobic
-Glucose Energy + Lactic Acid (what causes stitches etc)
Oxygen Debt- When lungs, heart and blood couldn't keep up with oxygen demand
-Not enough oxygen results in panting, panting leads to more oxygen entering the body,
therefore oxidising the lactic acid, releasing carbon dioxide and water.…read more

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- Chromosomes consist of long strands of DNA
-DNA contain bases (different combinations of GC and AT)
-The bases make up the genetic code for a particular gene
-A gene is a unit of inheritance
Cell Division
Mitosis- When a cell reproduces itself by splitting to two form two identical offspring's
-Used by plants and animals to replace damaged cells
- Occurs in asexual reproduction (e.g. strawberry plants form runners which become new
strawberry plants)
-Produces identical cells (offspring's) with no variation
1.…read more

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Occurs in two divisions
First Division
1. Before cell division , cell duplicates DNA
2.Chromosomes pairs line up in cell centre
3.Pairs pulled apart forming 2 new cells, both with a mixture of male and female chromosomes
Second Division
4.New cell chromosomes line up again and are pulled apart
5.End result is 4 gametes each with single sets of chromosomes
After fertilisation gametes join and cells reproduce repeatedly diving via mitosis.…read more


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