cell transport

• name 5 examples of exchange surfaces

  • alveoli in lungs
  • fish gills
  • small intestine (villi and microvilli)
  • plant leaves
  • plant roots
• what are adaptations of plant roots as an exhange surface?

  • tiny hairs - increase surface area
  • made of root hair cells which have long thin shape to further increase surface area, and contain lots of mitochondria for cellular respiration, to release energy for active transport of mineral ions
• what are the adaptations of plant leaves as exchange surfaces?

  • stomata
  • guard cells
  • flat shape
  • walls of cells
• what substances are exchanged at plant roots?

  mineral ions
• what substances are exchanged at plant leaves?

  • out of stomata - oxygen and water vapour
  • in - co2 diffuses into leaf, then cells
• what substances are exchanged at fish gills?

  oxygen and co2
• why are substances in fish gills exchanged in opposite direction?

  to maintain large concentration gradient between water and blood
• what are the adaptations of fish gills as exchange surfaces?

  • made up of stacks of thin filaments to give large surface area, each with rich blood supply
  • operculum = flap to pump water to maintain concentration gradient needed for gas exchange
  • lamellae = tiny structures that cover filaments to increase surface area
  • concentration of oxygen in water is always higher than in the blood so as much oxygen as possible diffuses into blood
• what substances are exchanged in villi in small intestines?

  digested food exchanged into blood
• what are adaptations of villi as exchange surfaces?

  • single layer of surface cells
  • good blood supply so quick absorption
  • increase surface area
• what substances are exchanged in alveoli in lungs

  oxygen and co2
• adaptations of alveoli?

  • big surface area
  • moist lining for dissolving gases
  • very thin walls
  • good blood supply
• when the total volume is bigger, the surface area to volume ratio is.....


  smaller
• exchange surfaces are needed when...

  the rate of diffusion isn't fast enough because the surface area to volume ratio is too small
• shapes with larger surface area to volume ratio will have ...... rates of diffusion

  faster
• opposite of osmosis?

  active transport
• why does active transport require energy?

  to go against concentration gradient
• define diffusion

  net movement of particles of a gas or solute from an area of higher concentration to an area of lower concentration down a concentration gradient
• what 4 factors affect diffusion?

  • temperature
  • surface area
  • concentration gradient
  • distance
• in pure water, plant cells become....

  turgid
• in pure water, animal cells....

  under goes lysis ( pops)
• in concentrated salt solution, both animal and plant cells....

  becomes plasmolysed (shrink and shrivel due to water loss)
• define osmosis

  the movement of water from an area of higher water potential to an area of lower water potential through a partially permeable membrane
• define active transport

  the movement of a substance from an area of lower concentration to an area of higher concentration against a concentration gradient, across a membrane, using energy
• define translocation

  The transport of dissolved material within a plant

  occurs in phloem

  includes sugars, produced by photosynthesis to be used in respiration
• is diffusion an active or passive process?

  passive as it requires no energy
• is active transport an active or passive process?

  active as it requires energy
• what membrane can smaller particles diffuse through?

  partially-permeable membrane
• when does water move into a cell through osmosis?

  when the concentration of water molecules is higher outside
• why does water diffuse through osmosis?

  to balance the concentrations of solution inside and outside of the cell. water must move as the larger molecules cannot fit through the partially permeable membrane.
• how to increase the rate of diffusion?

  • increase surface area
  • increase temperature
  • increase difference in concentrations
• what does active transport require?

  carrier proteins, which require energy
• in the osmosis practical, how can we use the graph to deduce the concentration in the potato?

  interpolate using line of best fit

  the concentration at which there would be no change in mass must be same as concentration inside potato
• shape of red blood cell?

  biconcave shape
• where does active transport always take place?

  across a membrane
• where does the energy for active transport always come from?

  cellular respiration
• how are magnesium ions used to plants?

  to produce chlorophyll
• how do plants use nitrate ions?

  to produce proteins
• why can't root hair cells absorb mineral ions by diffusion?

  the ions are at a higher concentration inside the cells than in the soil

  so require energy, so use active transport
• the higher the concentration gradient, the...

  higher the rate of diffusion