AQA 9-1 B1 Cell Structure and Transport

B1.1 The world of the microscope
1. Using Units
  1. 1km = 1000m
  2. 1m = 100cm
  3. 1cm = 10mm
  4. 1mm = 1000 micrometres(um)
  5. 1um = 1000nm (nanometers)
2. Calculating Size
  1. magnification = size of image / size of real object
  2. magnification = objective lens x eyepiece lens
3. Microscopes
  1. Electron Microscope
    1. magnify up to 2,000,000x
    2. resolving power of 0.2nm
    3. 2D images high magnification and resolution
    4. large, expensive, kept in special temperature, humidity and pressure rooms
  2. Light Microscope
    1. Magnify up to 2000x
    2. resolving power of 200nm
    3. Cheap, can be used anywhere, magnifies live specimens
    4. School microscopes only magnify several hundred times
B1.2 Animal and Plant Cells
1. Cells
  1. Ribosomes : where protein synthesis takes place
  2. Nucleus : controls cell activities, contains genes to create new cell
  3. Cytoplasm : liquid gel, where chemical reactions needed for life take place
  4. Cell Membrane : controls passage and movement of substances
  5. Mitochondria : where aerobic respiration takes place, releasing energy for cell
2. Plant Cells
  1. Cellulose Cell Wall : strengthens and supports cell
  2. Chloroplasts : contain chlorophyll to create food and photosynthesise ROOT CELLS DO NOT CONTAIN CHLOROPLASTS AS THEY ARE UNDERGROUND
  3. Permanent Vacuole : contains cell sap to keep cell rigid
B1.3 Eukaryotic Cells and Prokaryotic Cells
1. Eukaryotic Cells
  1. All contain Cell Membrane; Cytoplasm and Genetic Material contained within a Nucleus
  2. All animals (including humans), plants, fungi and protista are eukaryotes
2. Prokaryotic Cells
  1. Bacteria is an example of prokaryote
    1. Flagellum (Flaggela) : long protein strand which bacteria uses to move
  2. Prokaryotes contain : Cytoplasm and a cell membrane surrounded by a cell wall
    1. Plasmids are small rings of DNA
B1.4 Specialisation in Animal Cells
1. Nerve Cells : Specialised to carry electric impulses around the body of an animal
  1. Denditried to make connections to other cells
  2. Axon which carries nerve impluse from one place to another
  3. Nerve ending/synapses adapted to pass impulses to different cells, needs mitochondria to provide energy needed
2. Sperm Cells : Specialised to fertilise egg
  1. Long tail to help sperm cell move through female reproductive system
  2. Middle section is full of mitochondria which transfers energy needed for tail to work
  3. Acrosome store digestive enzymes needed to break down outer layers of egg
  4. Large nucleus containing genetic information to pass on
3. Muscle Cells
  1. Special proteins which slide over eachother causing them to contract
  2. Contains many mitochondria to transfer energy needed for chemical reactions to take place as cells contract and relax
  3. Can store glycogen, a chemical which can be broken down and used in cellular respiration
B1.5 Specialisation in Plant Cells
1. Root Hair Cells
  1. Increase surface area for water to move into the cell
  2. Large permanent vacuole which speeds up movement of water by osmosis from soil across root hair cell
  3. Many mitochondria which transfers energy needed for active transport of mineral ions
2. Phloem Cell
  1. Cell walls between cells break down to for special sieve plates. Means that water carrying dissolved food can move up tubes freely
  2. Phloem cells lose alot of internal structure however are supported by companion cells which aid in keeping them alive
    1. Mitochondria of companion cells transfer energy needed to move dissolved food up and down plant in phloem
3. Photosynthetic Cells
  1. Contain specialised green structures called chloroplasts containing chlorophyll which trap light needed for photosynthesis
  2. Usually positioned in continuous layers of leaves and outer stem to absorb as much sunlight as possible
  3. Large permanent vacuole to help keep cell rigid. This also spreads leaf out so it can absorb as much sunlight as possible
4. Xylem Cells
  1. Xylem cells are alive when first formed. A chemical called lignin builds up in sprials in the cell wall which kills the xylem cell however leaves a hollow tube for water and mineral ions to easily pass through them
  2. Spirals and rings of lignin make the xylem very strong and help them withstand pressure when water is moving up the plant. This also supports the stem of plant
B1.6 Diffusion
1. The spreading of particles of any substance, in a solution or gas
  1. Results in a net movement from an area of high concentration to an area of lower concentration, via a concentration gradient
2. Factors which affect rate of diffusion:
  1. concentration difference
  2. temperature
  3. avaliable surface area
3. Cells adapt for diffusion by folding membrane, which gives more surface area for faster rate of diffusion
B1.7 Osmosis
1. Osmosis is a special type of diffusion, movement of a water from dilute, to a more concentrated solute solution across a partially permeable membrane
2. Cell states
  1. If concentration of solutes in solution outside of cell is equal to the internal concentration. the solution is isotonic to the cell
  2. If concentration of solutes in solution outside of cell is lower than the internal concentration. the solution is hypotonic to the cell
    1. This can cause the cell to swell and burst
  3. If concentration of solutes in solution outside of cell is higher than the internal concentration. the solution is hypertonic to the cell
    1. This can cause water to move out of the cell via osmosis and the cell will shrivel up and can no longer survive
B1.8 Osmosis in Plants
1. Plants rely on osmosis as water will fill vacuole which causes it to swell and press cytoplasm against cell wall which keeps the cell hard and rigid, which in turn keeps the leaves and stem of plant rigid and firm
2. Plants need the fluid surrounding the cell to be hypotonic to cytoplasm, this leads to a turgid cell.
  1. If solution is hypertonic, the cell becomes flaccid and weak which leads plants to wilt.
B1.9 Active Transport
1. Moves substances from a more dilute solution to a more concentrated solution against a concentration gradient
  1. This process uses the energy which is released from food in respiration to provide energy required
  2. This process allows root hair cells to absorb mineral ions which is required for healthy growth from very dilute solutions in the soil against a concentration gradient
  3. Enables sugar molecules which are used for cellular respiration to be absorbed from lower concentrations in gut, into the blood where sugar concentration is higher
B1.10 Exchanging Materials
1. Surface Area to Volume Ratio :
  1. To find surface area: length x width x sides
  2. To find volume : length x width x height
  3. SA : V (simplify if possible) 5:1 you cannot simplify, however, 54:27 -> 2:1
2. Single celled organisms often have large volume to surface area ratios whereas multicellular organism have a smaller ratio so instead, these organisms are specialised for different types of exchanges
3. Exchange surfaces usually have a large surface area and thin walls, which leads to shorter diffusion distance.
  1. In animals, exchange surfaces have an efficient blood supply or, for gaseous exchange, be ventilated

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AQA 9-1 B1 Cell Structure and Transport

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