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1[GCSE Biology]1 > SB6 - Plant Structures and their Functions ✓ > Flashcards

SB6 - Plant Structures and their Functions ✓ Flashcards

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1
Q

SB6a - What is the equation for photosynthesis?

A

Carbon dioxide + Water -> Glucose + Oxygen

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2
Q

SB6a - What is the equation for respiration?

A

Glucose + Oxygen -> Carbon dioxide + Water

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3
Q

SB6a - What does photsynthesis do?

A

It traps energy from the sunlight and converts it to glucose

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4
Q

SB6a - Where does photosynthesis occur?

A

In the chloroplasts of the plant cell

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5
Q

SB6a - What type of reaction is photsynthesis?

A

Endothermic. The products have more enrgy than the reactants. This means they have taken in energy from the surroundings during the reactions

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6
Q

SB6a - Why is glucose necessary?

A

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)
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7
Q

SB6a - How are leaves adapted for their purpose?

A
  • 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
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8
Q

SB6a - Tomayto, tomahto?

A

Stomayto, stomatoh

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9
Q

SB6a - Why are the stomata an example of a gas exchange system?

A

They let carbon dioxide diffuse in and let oxygen diffuse out

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10
Q

SB6b - What are the three main limiting factors that affect photosynthesis?

A
  • Carbon dioxide CONCENTRATION
  • Light INTENSITY
  • Temperature
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11
Q

SB6b - Why are plants less likely to grow higher up on a mountain?

A

Higher up, the air pressure is lower meaining the carbon dioxide concentration is lower

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12
Q

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?

A

As the graph curves, light intensity is the limiting factor. Once it levels out, something else is the limiting factor.

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13
Q

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?

A

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.

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14
Q

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?

A

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

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15
Q

SB6b - What is the inverse square law, and where does it apply to?

A

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

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16
Q

SB6b CP - Describe a method, using algae balls and hydrogen carbonate indicator, to investigate rates of photosynthesis at differing light intensities.

A
  • 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
17
Q

SB6c - Why do plants need to take in water?

A

To be used in/to:

  • Carrying dissolved mineral ions
  • Keeping cells rigid so plants don’t wilt (droop)
  • Cooling leaves (when it evapourates)
  • Photosynthesis
18
Q

SB6c - How are roots adapted to absorb water?

A

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

19
Q

SB6c - What is a concentration gradient and what can it cause to occur?

A

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

20
Q

SB6c - What do root hair cells and root cells have between them and why?

A

They have a little tube allowing diffusion of fluids between cells

21
Q

SB6c - How can some water enter the root hair cells if not through openings?

A

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

22
Q

SB6c - How do plants take in mineral ions?

A

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

23
Q

SB6d - Describe the process of transpiration

A
  • 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
24
Q

SB6d - Describe the process of translocation

A
  • 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
25
Q

SB6d - Describe the adaptations of the xylem

A
  • Multiple pores to allow water and mineral ions to enter and leave
  • dead cells, no cytoplasm and no cell walls to allow flow of water through it
  • rings made of lignin and thick side walls to keep the water inside
26
Q

SB6d - Describe the adaptations of the phloem

A
  • Holes in cell walls to allow liquids to flow
  • No nucleus or cytoplasm as they aren’t needed and would be a waste of energy
  • Companion cells to pump have many mitochondria so they have energy to actively transport sucrose
27
Q

SB6d - Describe how you can investigate rates of transpiration

A

A potometer is used for this. It involves using a plant attached to a rubber stopper connected to a reservoir of water and a capillary tube. The capillary tube should have at least one bubble in it and should have a scale . As the plant uses up water it will draw water from the tube moving the air bubble. The speed of the bubble will allow you to calculate the rate of transpiration

28
Q

SB6e - How is the structure of a leaf adapted for photosynthesis and gas exchange?

A

Leaves are broad and flat which gives them a large surface area. Palisade cells near the top of the leaf are packed with chloroplasts to allow large amounts of light absorption. Spongy cells create air spaces so gasses can diffuse in and out.

29
Q

SB6e - Why do some plant have needle shaped leaves?

A

Small leaves result in a reduced surface area so transpiration happens more slowly. A thick cuticle protects them from infection. The smaller leaves helps them to withstand strong winds and a lack of water

30
Q

SB6e - How do plants reduce water loss?

A
  • Having stomata located inside small pits
  • By losing leaves in winter
  • By closing stomata at night
31
Q

SB6f - What are the names of some plant hormones?

A
  • Auxins: promote growth
  • Gibberellins: cause germination
  • Ethene: cause fruit ripening
32
Q

SB6f - What are positive and negative phototropism and gravitropism?

A
  • Positive = towards
  • Negative = away
  • Phototropism = a response to light
  • Gravitropism = a response to gravity
33
Q

SB6f - How does phototropism occur?

A
  • Auxins a produced in the tip of the shoot
  • As the shoot is exposed to light, auxins move to the shaded side of the root (the side away from the sun)
  • Here they cause the cells to elongate causing the shoot to point towards the sun
34
Q

SB6g - How are auxins used by plant growers?

A

Selective weedkillers contain artificial auxins to kill plants with broad leaves. Auxins are also used in rooting powders which cause plant cuttings to grow roots rather quickly

35
Q

SB6g - What are the uses of gibberellins?

A
  • Produce seedless fruits
  • Promote flowering
  • Increase fruit size
  • Germinate seeds
36
Q

SB6g - How do farmers ripen fruits once they have been removed from a tree?

A
  • Use ethene gas
37
Q

SB6d - Describe the factors that affect transpiration.

A
  • Light intensity: stomata opens wider allowing wate rin quicker
  • Temperature: More evapuration means a greater concentration gradient on the leaf surface
  • Wind speed: Less water on leaf surface steenpens the concentration gradient
  • Fall in humidity: As the air becomes less satured, water vapour evapourates more easily steepening the concentration gradient
38
Q

SB6f - How does gravitropism occur?

A
  • Auxins in the root are pulled down by gravity.
  • They inhibit cell elongation here causing the root to grow downwards
  • Auxins in the shoot are also pulled down by gravity but here they cause cell elongation making the shoot grow upwards
39
Q

SB6f - Describe Darwin’s experiments with auxin and what can be concluded from the results.

A
  • Three intact shoots exposed to light. One covered with a black cap, one with a transparent cap and one normal
  • The one with the black cap didn’t ben towards the light while the other two did
  • This shows that auxins are dependant on light to work
  • One where the tip was removed didn’t bend towards the light.
  • This showed that auxins are produced in the tip of the shoot
  • A tip was also placed on a permeable and and impermeable base (removed from the plant)
  • The one on the permeable base (agar block) bent towards the light but the other didn’t
  • This shows that auxins need to travel further down in the plant to work

1[GCSE Biology]1 (23 decks)

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