SB6 - Plant Structures and their Functions ✓ Flashcards
SB6a - What is the equation for photosynthesis?
Carbon dioxide + Water -> Glucose + Oxygen
SB6a - What is the equation for respiration?
Glucose + Oxygen -> Carbon dioxide + Water
SB6a - What does photsynthesis do?
It traps energy from the sunlight and converts it to glucose
SB6a - Where does photosynthesis occur?
In the chloroplasts of the plant cell
SB6a - What type of reaction is photsynthesis?
Endothermic. The products have more enrgy than the reactants. This means they have taken in energy from the surroundings during the reactions
SB6a - Why is glucose necessary?
Glucose molecules are joined together to form a polymer of starch. After photosynthesis stops, this is broken down to simple molecules which are used to form sucrose. Sucrose is used to make:
- Starch (In a storage organ such as a potato)
- other molecules for the plant (cellulose, lipids etc.)
- Glucose for respiration (to release energy)
SB6a - How are leaves adapted for their purpose?
- They have a broad flat shape giving them a large surface area for photsynthesis
- There are lots of palisade cells near the top which are packed with chloroplasts to absorb light
- Stomata allow carbon dioxide to diffuse in for photosynthesis
- When there is light (during day) water flows into guard cells making them rigid and when there is less light (nighttime) The water flows out making it loose its rigidity
- When it is rigid, it is open so it is only open when there is light
- This means it will only allow carbon dioxide to diffuse when there is also light to conduct photsynthesis
- Leaves are thin meaning carbon dioxide doesn’t have far to diffuse
SB6a - Tomayto, tomahto?
Stomayto, stomatoh
SB6a - Why are the stomata an example of a gas exchange system?
They let carbon dioxide diffuse in and let oxygen diffuse out
SB6b - What are the three main limiting factors that affect photosynthesis?
- Carbon dioxide CONCENTRATION
- Light INTENSITY
- Temperature
SB6b - Why are plants less likely to grow higher up on a mountain?
Higher up, the air pressure is lower meaining the carbon dioxide concentration is lower
SB6b - A graph showing how increasing rate of light intensity affects rate of photosynthesis eventually levels out. Why can’t it get any higher despite light intensity increasing?
As the graph curves, light intensity is the limiting factor. Once it levels out, something else is the limiting factor.
SB6b - Once the rate of photosynthesis can’t increase anymore (due to light intensity in this case) how would you increase the rate of photosynthesis?
Something else is the limiting factor.. Increasing the CO2 concentration or increasing the temperature will allow the rate of photosynthesis to continue to increase. Eventually it will level out again as something else has become the limiting factor.
SB6b - Why is it that even if temperature is the limiting factor, you’ll get to a point where increasing it won’t increase the rate of photosynthesis?
At a temperature that is too high, the enzymes in the plant become denatured. They can no longer bind to their substrate and therefore processes can’t occur anymore
SB6b - What is the inverse square law, and where does it apply to?
The inverse square law is used to find out how light intensity chages ith distance from the source.
I - light intensity d -distance
I(original) x d(original)² = I(new) x d(new)²
light intensity is inversely proportionate to the square of the distance
SB6b CP - Describe a method, using algae balls and hydrogen carbonate indicator, to investigate rates of photosynthesis at differing light intensities.
- Add 20 algae balls and the same amount of indicator to as many glass bottles as you need
- Compare the colour of the bottle at the start to a key to work out its starting pH (they should all be the same)
- Place a tank of water between the light and the first glass to absorb the heat given off by the light
- Cover one with foil so it is in the dark and place it next to the one closest to the lamp
- Measure out the distances you place all of the bottles
- Turn on the light and wait till you see noticable changes in the pH
- Once you’ve decided to stop, work out the pH again by comparing to a key
- Work out the change in pH/hour to be your rate of reaction
- Plot a graph of rate of reaction vs distance from light
SB6c - Why do plants need to take in water?
To be used in/to:
- Carrying dissolved mineral ions
- Keeping cells rigid so plants don’t wilt (droop)
- Cooling leaves (when it evapourates)
- Photosynthesis
SB6c - How are roots adapted to absorb water?
Roots have root hair cells The hairs make the surface area larger meaing there is more area for mineral ions to be quickly absorbed through water
SB6c - What is a concentration gradient and what can it cause to occur?
When two areas are connected in some way and having differing levels of concentration of a substance, they have a concentration gradient
If this is in a fluid, diffusion can occur, where the substance moves from the area of higher to lower concentration
SB6c - What do root hair cells and root cells have between them and why?
They have a little tube allowing diffusion of fluids between cells
SB6c - How can some water enter the root hair cells if not through openings?
The root hair cells have a semi-permeable membrane meaning that osmosis can take place with the water moving down the concentration gradient into the cytoplasm of the cell
SB6c - How do plants take in mineral ions?
Through the water they absorb. However as there is a higher concentration of these in the plant than in the soil, they can’t absorb it through diffusion but rather through active transport which takes up energy
SB6d - Describe the process of transpiration
- The flow of water into a root, up the stem and out the leaves
- As water on the leaves’ surface evapourates, a concentration gradient is created
- This prompts water to be drawn out from the inside of the leaves through the stomata through diffusion and osmosis
- They travel through the xylem down the concentration gradient
- This is aided by the cohesion between the H2O molecues due to hydrogen bonds and adhesion to the walls of the xylem cell
- At the root hair cells, as water moves up the xylem, water is also taken in due to the concentration gradient
SB6d - Describe the process of translocation
- The transport of sucrose around a plant
- The source is the leaf where glucose is created by photosynthesis
- Glucose monomers join together to from a sucrose polymer (as onyl polymers can be transported this way)
- The sucrose is actively transported into the phloem through a companion cell
- At the top of the phloem there is a low concentration of water. So water from the xylem difuses through pores in the cells
- This water then has a high pressure so moves down the phloem taking the sucrose with it
- It will then be actively transported through a companion cell to whatever cell it is needed in
