B2 Revision

B2 Revision

Cell Organelles
1. Nucleus - controls activities of the cell
2. Cell Membrane - controls activity/passages in and out of the cell
3. Cytoplasm - where chemical reactions take place
4. Ribosomes - protein synthesis of molecules
5. Mitochondria - where respiration occurs
6. Cell Wall - supports the cell
7. Vacuole - contains cell sap
8. Chloroplasts - absorb light energy to be used in photosynthesis
Other Cells
1. Yeast
  1. single-celled, no cellulose, cannot photosynthesis because it has no chloroplasts
2. Bacteria
  1. no nucleus - floating DNA
3. Algae
  1. similar to plant cells
4. Viruses
  1. sphere of protein
Diffusion
1. spreading of particles from high to low concentrations
  1. oxygen diffuses
  2. larger concentration gradient = faster diffusion
Tissues
1. Muscular
  1. predominantly needed for movement - lots of mitochondria in cells, used in respiration for contraction
2. Glandular
  1. cells secrete enzymes and hormones from vesicles
3. Multi-cellular
  1. many different cells; specialised
Plant Features
1. Xylem - carries water from root to leaf
2. Phloem - transport of sugars
3. Epidermal Tissue has holes (stomata) which allows gases to diffuse
4. Limiting Factors - Light, CO2, Temperature
Enzymes
1. Amylase - breaks down starch into simple sugars
  1. Produced in pancreas and salivary glands
    1. Used in sugar syrup - starch changed to sugar by adding amylase ( carbohydrase )
2. Protease - breaks down proteins into amino acids
  1. Produced in pancreas, stomach and small intestine
    1. Used in baby food to break down large proteins into amino acids, so that babies can absorb the AA at ease.
3. Lipase - breaks down fats and lipids into fatty acids and glycerol
  1. Produced in pancreas and small intestine
4. Isomerase used to turn glucose into fructose - sweeter, so less is needed and is consequently used in slimming foods.
Aerobic Respiration
1. oxygen+glucose=carbon dioxide+water+(energy)
2. Glycogen stores are broken down into glucose for respiration
  1. respiration releases energy which increases body temperature
  2. amino acids can be made from nitrate and sugar ions
3. Anaerobic Respiration
  1. glucose=lactic acid+(little energy)
  2. Carried out when insufficient oxygen supplies
  3. Oxygen debt removes lactic acid build up
Mitosis - cell division into TWO
1. provides cells for growth/repair
2. Copies made, particles then line up at the middle of the cell, identical copies then split moving to opposite sides of the cell. 2 new daughter cells are made. Chromosomes form 2 nuclei, alongside new cell membranes forming.
3. 1 division, 2 cells made, same number of chromosomes as original, creates new body cells, all body parts
Meiosis
1. Copies made, cell division happens twice creating 4 daughter cells. Therefore, new cells are only provided with half the original number of chromosomes.
2. 2 divisons, 4 cells made, 1/2 number of chromosomes as original, gametes, testes and ovaries
3. homologous pairs
Stem Cells
1. have the ability to develop into any type of cell
2. most cells differentiate, forming specialised cells
  1. In plants, cells can differentiate at any time
Genes
1. have different forms
  1. Alleles
    1. Mendel worked with allele factors in his pea pollination
2. humans have 2 sets of chromosomes in each cell
3. DNA is always different
Fossils
1. Bones and teeth do not easily decay
2. Some parts of organisms do not decay because conditions are not suitable for this to happen
3. Parts of organisms may be replaced by other materials such as hard minerals as they decay
4. Traces of an organism may be preserved in rocks as prints
Extinction
1. Change in environment
2. New predators
3. New diseases
4. More succesful competitors
New species/Speciation
1. 1. Geographical isolation
  1. Few lizards drift away from the mainland on floating logs and end up on an island. Isolated from rest of species.
2. 2. Genetic Variation
  1. In both mainland and island lizards, different alleles of genes which lead to variation.
3. 3. Natural Selection
  1. Environment, predators etc on mainland are dif from those on island. Natural selection takes place and dif features are selected.
4. 4. Speciation
  1. Over time, more and more difs build up between two populations until they are no longer the same species

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	Criado por georgialennon mais de 9 anos atrás