Biology - SB6

• What is the equation for photosynthesis?

  Carbon dioxide + water -> glucose + oxygen

  
• What type of reaction is photosynthesis?

  Endothermic reaction, meaning that it takes in more energy than it releases.
• What is sucrose used to make?

  - starch

  - other molecules from plants (eg lipids or proteins)

  - glucose for respiration
• What are the 3 factors that affect photosynthesis?

  Temperature, light intensity and carbon dioxide concentration
• How does temperature affect photosynthesis?

  As the temperature rises, the rate of photosynthesis increases as the reaction speeds up. As the reaction is controlled by enzymes this continues until the enzyme starts to denature.

  
• How does light intensity affect photosynthesis?

  Increased light intensity will increase the rate of photosynthesis

  
• How does carbon dioxide concentration affect photosynthesis?

  As concentration of carbon dioxide increases, the rate of photosynthesis also increases.

  
• What is meant by a limiting factor?

  a factor that prevents the rate from increasing.
• How do you calculate inverse square law?

  
• How is the practical carried out to measure photosynthesis indifferent light intensity?

  Decide on the different distances between the algae and the lamp you are going to use.

  For each distance you will need one clear glass bottle. You will also need one extra bottle.

  Add 20 of the algal balls to each bottle.

  Add the same amount of indicator solution to each bottle, and put on the bottle caps.

  Compare the colour in your tubes with this pH range to work out the pH at the start.

  Set up a tank of water between the lamp and the area where you will place your tubes. Take extreme care not to spill water near electrical apparatus (such as a lamp).

  Cover one bottle in kitchen foil, so that it is in the dark. Measure the different distances from the lamp. Place your bottles at those distances. Put the bottle covered in kitchen foil next to the bottle that is closest to the lamp.

  Turn on the lamp and wait until you can see obvious changes in the colours in your bottles. The longer you can wait, the more obvious your results are likely to be.

  Compare the colours of all your bottles with the pH range bottles. Write down the pH of the solutions in your bottles.

  For each bottle, calculate the change in pH/hour.

  Plot a suitable graph or chart of your results.
• Leaf adaptation: stomata?

  Able to minimise water loss and open to increase evaporation and transpiration They also allow gas exchange to occur when they are open.
• Leaf adaptation: chlorophyll?

  Chlorophyll is green, the most efficient colour for absorbing light. Meaning most light possible is absorbed.
• Leaf adaptation: thinness?

  They are very thin, meaning carbon dioxide only has a short distance to travel to enter the leaf (and work in photosynthesis) and oxygen only has a small distance to diffuse out.
• Leaf adaptation: large surface area?


  Large surface area means that the leaf can about more light at once, maximising the rate of photosynthesis.
• What is water absorbed by plants used for?

  - carrying dissolved minerals

  - keeping cells rigid (otherwise plants will wilt)

  - cooling the leaves (when it evaporates from them)

  - photosynthesis
• Adaptation of root hair cells?

  - large surface area due to root hairs, meaning more water and minerals can be absorbed quickly

  - thin cell walls so that the flow of water into cells is not slowed down
• What is meant by the term diffusion?

  Diffusion is the movement of particles from an area of higher concentration to an area of lower concentration.
• What is meant by the term transpiration?

  The loss of water of water vapour from the leaves and stem of the plant.
• What is the function of a xylem cell?

  Transport tissue for water and dissolved ions
• What is the adaptations of xylem cells?

  - No top and bottom walls between cells to form continuous hollow tubes through which water is drawn upwards towards the leaves by transpiration.

  - cells are dead, with without organelles or cytoplasm, to allow free passage of water. Other walls are thickened. with a substance called lignin, strengthening with tubes, which help support the plant.
• What is the function of a phloem cell?

  Transport of dissolved sugars and amino acids
• What is the adaptation of phloem cells?

  - many living cells which are supported by companion cells

  - cells are joined end-to-end and contain holes in the end cell walls (sieve plates) forming tubes which allow sugars and amino acids to flow easily through (by translocation)

  - cells also have very few subcellular structures to aid the flow of materials.
• What is meant by the term translocation?

  The movement of food substances made in the leaves up or down the phloem, for immediate use or storage.
• Plant adaptation: spongy cells?

  Creates air spaces, allowing gasses to diffuse easily inside a leaf
• Plant adaptation: epidermis cells?

  Transparent, allowing light to pass through them easily
• Plant adaptation: waxy cuticle?

  helps to prevent water loss and stops microorganisms and water entering the leaf.
• Adaptations of conifers(e.g pine tree)?

  Have needle-shaped leaves with a much smaller surface area and a very thick cuticle. This shape creates less wind resistance than broad leaves, allowing conifers to withstand high wind.
• What is tropism?

  Responding to a stimulus by growing towards or away from it
• What is phototropism?

  A plant's response to light
• What is gravitropism?

  A plant's response to gravity
• Where are auxins produced?

  tip of a shoot
• How do auxins work?


  more light reaches one side of the shoot, more auxin is sent down the shaded side of the suit shoot, this results in cells on the shaded side elongating more, the shoot, therefore, grows towards the light
• What does gibberellin do?

  It stimulates the seed to germinate and starts to grow shoots and roots.
• What does the ethene gas do?

  ripens fruit
• How are auxins helpful in selective weedkiller?

  It kills plants with broad leave but not those with narrow leaves
• How are auxins helpful in rooting powder?

  The auxins cause plant cutting to develop roots quickly. Large number of identical plants can be produced quickly using cutting, compared to growing plants form seed.