cell structure and transport

• what is the function of the nucleus?


  controls cells activities and contains genes on chromosomes that carry instructions for making proteins needed to build new cells/organisms.
• what is the function of the cell membrane?

  controls what enters and leaves the cell (mineral ions and glucose)
• what is the function of the cytoplasm?


  a liquid gel where all of the chemical reactions take place.
• what is the function of mitochondria ?


  structures in the cytoplasm where aerobic respiration takes place to release energy.
• what is the function of ribosomes?


  they make all the proteins that are needed in the cell.
• what is the function of the chloroplast?


  the site of photosynthesis, contains a strong light absorbing pigment
• what is the purpose of the cell wall?


  made of cellulose; used for support.
• what is the function of the permanent vacuole?

  contains cell sap and is important for keeping the cell rigid to give support.
• what is chlorophyll used for?


  a light absorbing green pigment found in chloroplasts.
• compare the structure of a plant and animal cell

  the plant cell has chloroplasts, chlorophyll, (for photosynthesis) a cell wall, a permanent vacuole while the animal cell has none of these. they both have a cell membrane, nucleus, cytoplasm, ribosomes and mitochondria.
• what is a eukaryotic cell?


  1. all animal and plant cells
  2. have a cell membrane, cytoplasm and genetic material enclosed in a nucleus
  3. have DNA
• what is a prokaryotic cell?


  1. bacteria - single celled organisms
  2. have a cytoplasm, cell membrane surrounded by a cell wall, plasmids, slime capsule, flagella.
  3. genetic material is not enclosed in a nucleus - bacterial chromosome is a single DNA loop found free in the cytoplasm
• what are the parts of a prokaryote ?


  plasmid - extra small rings of DNA that code for specific features such as antibiotic resistance

  flagella - a long protein that lashes about, aiding them to move

  slime capsule - protects from phagocytosis
• key adaptations of nerve cells?


  1. lots of dendrites to make connections to other nerve cells
  2. an axon to carry impulses
  3. synapses adapted impulses to other cells using transmitter chemicals.
• how are muscle cells adapted?


  1. contain special proteins that slide over eachother
  2. they contain many mitochondria to transfer energy needed for chemical reactions as cells contract and relax
  3. store glycogen, broken down and used in cellular respiration by mitochondria
• how are sperm cells adapted?


  1. a long tail that whips from side to side to help move sperm through female reproductive system
  2. middle section is full of mitochondria - transfer energy for tail to work
  3. acrosome stores digestive enzymes for breaking down outer layer of egg
  4. large nucleus contains genetic information
• how are root hair cells adapted?


  1. greatly increase the SA available for water to move into the cell
  2. a large permanent vacuole that speeds up movement of water by osmosis
  3. many mitochondria to transfer energy needed for active transport of mineral ions into root hair cells
• how are photosynthetic cells adapted?


  1. specialised green structures (chloroplasts) containing chlorophyll that trap light for photosynthesis
  2. positioned in continuous layers in the leaves so they can absorb asm much light as possible
  3. large permanent vacuole - keep cell rigid as a result of osmosis
• how are xylem cells adapted?


  1. have lignin spirals in cell walls so that water and mineral ions can move easily through them
  2. spirals of lignin make them strong so that they can withstand the pressure of water moving up the plant
• how are phloem cells adapted?


  1. cell walls between the cells break down to form sieve plates so that water and dissolved food can travel throughout the tubes
  2. are supported by companion cells to keep they alive - mitochondria transfer energy to move dissolved food up and down.
• what is diffusion?


  The net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient.
• factors affecting rate of diffusion?

  1. concentration gradient
  2. temperature
  3. surface area of the membrane
• how is the small intestine adapted for exchanging materials?


  1. millions of villi line the small intestine which increase the SA
  2. single layer of cells with a good blood supply
• how are the lungs adapted for diffusion?


  1. alveoli have a large SA
  2. moist lining
  3. thin walls
  4. good blood supply
• how do gills aid diffusion for fish?


  1. large SA for gas exchange
  2. oxygen is transported from the water to the blood by diffusion
  3. gills have gill filaments and lamellae - large SA
  4. thin surface layer and capillaries for good blood supply
• how are plants adapted for gas exchange?


  1. SA of leaf is flattened to increase SA for more diffusion and gas exchange
  2. oxygen and water diffuse out of the stomata.
  3. guard cells control water loss.
• what is a stem cell?


  an undifferentiated cell of an organism which can give rise to many more cells of the same type, and from which, certain other cells can arise from differentiation
• how to calculate magnification?


  magnification = size of image x size of real object
• how is the effectiveness of an exchange surface increased?


  1. large SA
  2. thin membrane for a short diffusion pathway
  3. efficient blood supply
  4. ventilation for gaseous exchange
• what is osmosis?


  The movement of water molecules from an area of high concentration to an area of low concentration across a semi-permeable membrane.
• what is an isotonic solution?


  if the c concentration of solutes in the solution outside the cell is the same as the internal concentration, the solution is isotonic to the cell.
• what is a hypertonic solution?


  if the concentration of solutes in the solution outside the cell is higher than the internal concentration, the solution is hypertonic to the cell.
• what is a hypotonic solution?


  if the concentration of solutes in the solution outside the cell is lower than the internal concentration, the solution is hypotonic to the cell.
• how does osmosis work in animal cells?


  1. cytoplasm becomes more concentrated
  2. surrounding fluid is hypotonic and more water moves in
  3. cytoplasm becomes dilute because water is made in chemical reactions
  4. surrounding fluid becomes hypertonic and water leaves the cell by osmosis.
• how does osmosis work in plants?


  1. water moving into plant cells causes vacuole to swell
  2. pressure builds up between cytoplasm and cell wall and no more water can enter - turgor.
  3. cells become hard and rigid
• why is it important that plant cells stay turgid?


  1. cells are turgid when solution is hypotonic to thew cytoplasm
  2. water moves in right direction and cells are turgid
  3. if solution is hypertonic, water will leave the cells
  4. cells become flaccid - turgor doesn't support the plant tissues.
• when do cells become plasmolysed?


  if more water is lost by osmosis, the cell membrane pulls away from the cell wall - cell is plasmolyse.
• what is active transport?


  the movement of substances from a dilute solution to a concentrated solution against a concentration gradient using energy.
• why is active transport important?


  plants use active transport to absorb mineral ions and nitrate ions in the soil which are found in dilute solutions so they can travel against a concentration gradient into the plant.
• what is differentiation?


  the process by which a cell changes to become specialised for a specific function.