AQA Biology Unit 2 (B2)
Key facts on AQA's Unit 2 specification in Biology!
- Created by: Triciaaa
- Created on: 04-01-13 13:46
B2.1 Cells and Cell Structure
Animal cells
- Cell membrane = controls movement of substances in and out of cell
- Cytoplasm = gel like substance where chemical reactions take place
- Mitochondria = site of aerobic respiration
- Ribosomes = site of proteinsynthesis (chain of amino acids)
- Nucleus = controls protein production and contains genetic material
Plant cells
(have everything animal cells have but MORE)
- Cell wall = made of cellulose fibres that supports and strengthens cell
- Chloroplasts = contain chlorophyll for photosynthesis
- Vacuole = cell sap (sugary substances)
(OTHER CELLS - yeast cell, bacteria cell etc.)
Diffusion - the net movement of particles from an area of high concentration to an area of low concentration (usually through the cell membrane)
Cells > Tissues > Organs > Organ system
Epithelial cell > Epithelial Tissue > Stomach > Digestive system
B2.2 Plants obtaining food and growth
Photosynthesis equation
CARBON DIOXIDE + WATER ---> GLUCOSE + OXYGEN (+energy)
Limiting factors
Temperature, Light intensity, Carbon dioxide
Uses of glucose
Respiration > converts glucose to other useful substances
Cell wall > glucose makes cellulose thats useful for cell walls (strengthens)
Proteins > glucose + nitrate ions = amino acids to make proteins
Seeds > glucose makes lipids stored in seeds
Starch > glucose can be stored as starch (in roots, stems and leaves) its insoluble.
Greenhouses | Ideal conditions
Parafin heaters = release c02 as well as heat
Artificial lighting
Ventilators = cools down house
Blinds = to reduce light intensity if too much
B2.3 Ecology
Distribution of organisms depend on several environmental factors:
- temperature
- availability of water
- availability of oxygen + CO2
- availability of nutrients
- amount of light
Collecting data
- Quadrats = square frames enclosing known area to measure how COMMON (to meaure the mean = total/no. of quadrats
- Transects = measuring the DISTRIBUTION of organisms along a area
Reliablity relies on sample size, random samples to improve reproducibility
Validity relies on control variable and whether it supports the question (hypothesis maybe)
B2.4 Proteins and their functions
Enzymes are biological catalysts. They are not used up or changed in the reaction!
Its important to have the right temperature and pH to avoid DENATURATION
Enzyme + substrate --> enzyme substrate complex (active site) ---> enzyme + product
Digestive enzymes (all located in the SMALL INTESTINE and PANCREAS)
- Amylase - starch to glucose (alkaline)
- Protease - proteins to amino acids (acid and alkaline)
- Lipase - lipids to glycerol and fatty acids (alkaline)
Bile is extremely alkaline that is located in the liver to neutralise the stomach acid
Enzyme uses
Industry - protease = pre-digest protein in baby food, isomerase = convert glucose into fructorse, carbohydrase = starch into sugar syrup
Home - biological detergents
B2.5 Energy from respiration
Aerobic respiration - glucose + oxygen --> carbon dioxide + water + energy
Anaerobic respiration - glucose --> lactic acid + energy
Changes during exercise
Increase in heart rate = more oxygen and glucose travel to the muscles therefore releasing more energy from glucose (aerobic respiration) AND carbon dioxide and lactic acid are removed from the muscles meaning the prevention of oxygen debt.
B2.6 Patterns of inheritance
Cell division
Mitosis - when a cell reproduces itself by splitting to form two identical offspring
Meisosis - produces cells that have half the normal number of chromosomes
Differentiated cells
Embryonic stem cells - turn into ANY type of celll
Can cure many DISEASES e.g. blood diseases treated by bone marrow transplants
Mendel's work
1) characteristics in pea plants are determined by heriditary units
2) heriditary units are passes on from both parents
3) heriditary units can be dominant or recessive
Genetic disorders
Polydactaly - dominant
Cystic fibrosis - recessive
B2.7 Organisms changing through time
Fossil evidence
-Gradual replacement
-Casts and impressions
-Preservation
Causes of extinction
-Environmental changes
-New predators
-New disease
-Competition for food
-Catastrophic event e.g. volcano
-New species
Speciation (development of new species)
*4, 5, 6 (explanation of natural selection)
1. similar organisms reproduce to give fertile offspring
2. physical barrier/ geological barrier e.g. mountains
3. causes isolation
4. each area show variation due to a wide range of alleles
5. selective advantage (survival of the fittest)
6. best alleles passed onto new generation
7. unable to interbreed and give fertile offspring
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