Paper 2- transport systems

• How are root hair cells adapted to aid the absorption of water and mineral ions?

  Root hair cells are adapted for absorption as follows:

  • They have a large surface area
  • They contain mitochondria which release energy for active transport
• how minerals move into RHCs


  Mineral ions move into root hair cells by active transport. Only water can move by osmosis.
• Why do root hair cells need energy from respiration?


  Root hair cells need energy to fuel the active transport of mineral ions from the soil against a concentration gradient.
• What causes water to move into root hair cells?


  Water moves into root hair cells by osmosis due to the water concentration gradient between the soil and the cell cytoplasm. Minerals, and other dissolved substances, in the cytoplasm of root hair cells lower the water concentration, so water moves into the cells by osmosis.
• transpiration


  Transpiration is the loss of water vapour from the leaves of plants by evaporation.
• What is the role of the spongy mesophyll cells in transpiration?


  The spongy mesophyll cells are involved in transpiration as follows: water vapour evaporates from the surface of spongy mesophyll cells and enters the leaf air spaces. From here water vapour diffuses out of the leaf.
• Guard cells- stomata 


  Guard cells can cause the stomata to close, preventing water vapour from exiting the leaf and stopping transpiration.
• transpiration- xylem 


  Transpiration involves the loss of water from the xylem of plants, so does not affect sucrose and amino acids, which are transported in the phloem.
• By what process does water vapour exit the leaf air spaces?

  Water vapour exits the leaf air spaces by the process of diffusion. 

  It is not osmosis because it does not cross a membrane.
• factors can affect the rate of transpiration in plants?

  • Humidity
  • Wind speed / air movement
  • Temperature
  • Light intensity
• What happens to transpiration rate as light intensity increases?

  As light intensity increases, the transpiration rate increases.
• transpiration- light intensity 


  Transpiration rate increases with light intensity because the stomata open at high light intensities to enable gas exchange for photosynthesis.
• What happens to transpiration rate as temperature decreases?

  As temperature decreases the transpiration rate decreases.
• trepidation- kinetic energy 


  At higher temperatures water molecules have more kinetic energy and are more likely to diffuse out via the stomata, so transpiration rate increases
• transpiration rate- wind


  As wind speed increases the transpiration rate increases.
• Why does transpiration occur faster on a windy day?


  Transpiration is faster on a windy day because wind blows water vapour away from the surface of leaves, maintaining a water vapour concentration gradient between the inside and the outside of leaves.
• How will putting a plant inside a plastic bag affect its rate of transpiration?

  Putting a plant inside a plastic bag will decrease its rate of transpiration. This is because the bag will trap water vapour and raise humidity levels, decreasing the water vapour concentration gradient between the leaf and the surrounding air.
• transpiration rate- humidity levels


  Increasing humidity levels will decrease the rate of transpiration.
• Define the term water vapour concentration gradient in the context of transpiration.


  The water vapour concentration gradient is the difference in water vapour concentration between the inside and the outside of a leaf.
• Practical: Factors Affecting Transpiration

  • We can investigate effect of different environmental conditions (such as temperature, humidity, light intensity+wind movement) on transpiration rate using a potometer
  • There are 2 types of potometer
  • A mass potometer measures a change in mass of a plant as a measure of the amount of water that has evaporated from the leaves and stem
  • A bubble potometer measures the uptake of water by a stem as a measure of the amount of water that is being lost by evaporation consequently pulling water up through the stem to replace it
• Investigating the effect of light intensity on transpiration using a bubble potometer

  Apparatus

  • Potometer (bubble or mass potometer)
  • Timer
  • Lamp
  • Ruler
  • Plant
• Method first half

  • Cut a shoot underwater
  • To prevent air entering the xylem and place in tube
  • Set up the apparatus as shown in the diagram and make sure it is airtight, using Vaseline to seal any gaps
  • Dry the leaves of the shoot
  • Wet leaves will affect the results
  • Remove the capillary tube from the beaker of water to allow a single air bubble to form and place the tube back into the water
  • Set up a lamp 10cm from the leaf
  • Allow the plant to adapt to the new environment for 5 minutes
  • Record the starting location of the air bubble
• method second half

  • Leave for 30 minutes
  • Record the end location of the air bubble
  • Change the light intensity
  • Reset the bubble by opening the tap below the reservoir
  • Repeat the experiment
  • Calculate the rate of transpiration by dividing the distance the bubble travelled by the time period
  • The further the bubble travels in the same time period, the greater the rate of transpiration
  • rate of transpiration= distance moved by air bubble (m)/ time (min)
• Other environmental factors can be investigated in the following ways:

  • Airflow: Set up a fan or hairdryer
  • Humidity: Spray water in a plastic bag and wrap around the plant
  • Temperature: Temperature of room (cold room or warm room)
• results

  • As light intensity increases, the rate of transpiration increases
  • This is shown by the bubble moving a greater distance in the 30 minute time period when the lamp was placed closer to the leaf
  • Transpiration rate increases with light intensity because more stomata tend to be open in bright light in order to maximise photosynthesis
  • The more stomata that are open, the more water can be lost by evaporation and diffusion through the stomatal pores
• Limitations

  • The potometer equipment has a leak
  • Solution: Ensure that all equipment fits together rightly around the rubber bungs and assemble underwater to help produce a good seal
  • The plant cutting has a blockage
  • Solution: Cut the stem underwater and assemble equipment underwater to minimise opportunities for air bubbles to enter the xylem
  • The potometer has shown no change during the experiment
  • Solution: Use the plant cuttings as soon as they have been cut, transpiration rates may slow down when the cuttings are no longer fresh
• CORMS

  • Change - We will change the intensity of the light
  • Organisms - The plants used in each repeat should be the same species, size, age, number of leaves
  • Repeat - We will repeat the investigation several times to ensure our results are reliable
  • Measurement 1 - We will measure the distance travelled by the bubble
  • Measurement 2 - ...in 30 minutes (calculate the rate of transpiration)
  • Same - We will control the temperature, wind speed and humidity of the environment
• What is the role of vaccines?


  Vaccines are used to induce immunity to infectious diseases by introducing harmless versions of pathogens into the body.
• How do scientists ensure that vaccines contain harmless pathogens?


  Scientists ensure that vaccines contain harmless pathogens by killing the pathogen, making it unable to grow or divide, or using fragments of pathogens rather than whole cells.
• What role do lymphocytes have once a vaccination enters the bloodstream?

  Lymphocytes recognise the antigens and produce specific antibodies to the antigen in the vaccine.
• How does vaccination lead to long-term immunity?

  Vaccination triggers a response where memory cells and antibodies remain in the bloodstream. Future infections by the same pathogen result in a faster immune response, preventing disease.
• What is the importance of vaccination beyond protecting the vaccinated individual?

  Vaccines also reduce the likelihood of infected individuals spreading the pathogen to others within the population, contributing to herd immunity.
• memory cell.


  Memory cells are produced after infection or vaccination and enable future antibody production to the same pathogen/antigen to occur sooner, faster and in greater quantity.
•  methods of administering vaccines.

  • orally (mouth)
  • nasally (nose)
  • injection
• role of platelets in the blood?


  Platelets are involved in helping the blood clot and forming scabs when the skin is broken or wounded.
• Why is blood clotting important?

  Blood clotting prevents significant blood loss from wounds and seals them with a scab, preventing entry of microorganismsthat could cause infection until new skin grows underneath.
• Define the term platelet.


  Platelets are fragments of cells that are involved in blood clotting and forming scabs where the skin has been cut or punctured.