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GCSE Biology > Topic 6: Plant Structure & Function > Flashcards

Topic 6: Plant Structure & Function Flashcards

1
Q

What is photosynthesis?

A

An endothermic reaction that happens in plants and algae, in which energy is transferred to chloroplasts from the environment by light

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2
Q

What is the equation for photosynthesis?

A

Carbon + water —light—> glucose + oxygen

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3
Q

Is photosynthesis endothermic or exothermic?

A

Endothermic

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4
Q

Where does photosynthesis occur?

A

In the chloroplast

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5
Q

What do photosynthetic organisms make?

A

Biomass out of glucose

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6
Q

Who are the main producers of food for nearly all life on earth?

A

Photosynthetic organisms - they produce their own biomass

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7
Q

What is a limiting factor of photosynthesis?

A

A thing that stops photosynthesis happening faster

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8
Q

What are 3 limiting factors for photosynthesis?

A
  1. Temperature
  2. CO2 concentration
  3. Light intensity
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9
Q

How is temperature a limiting factor of photosynthesis?

A

Enzymes work slowly at low temperatures so photosynthesis slows down
High temperatures can also denature enzymes involved in photosynthesis

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10
Q

How are rate of photosynthesis and light intensity proportional?

A

Directly proportional

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11
Q

How are rate of distance from light source and light intensity proportional?

A

Inversely proportional

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12
Q

What is inverse square law?

A

Light intensity ∝ 1/distance²

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13
Q

In relation to the inverse square law, what happens if the distance from light source is doubled?

A

Light intensity becomes 4 times smaller

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14
Q

How does a light intensity limiting factor graph look like?

A

The line is straight and then plateaus

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15
Q

How does a CO2 concentration limiting factor graph look like?

A

The line is straight and then plateaus

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16
Q

How does a temperature limiting factor graph look like?

A

The line is not steep and is straight then curves and the rate decreases rapidly

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17
Q

What types of cells to plant root cells have?

A

Root hair cells

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18
Q

What are properties of root hair cells?

A

Large surface area - allows for more efficient absorption
Thin cell wall - allows for a short path for water and minerals
Many mitochondria - provides energy for active transport

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19
Q

What do root hair cells absorb, through what process?

A

Absorb mineral ions and water - through active transport

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20
Q

What are stomata?

A

Pores that let gases and water vapour escape from a plant

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21
Q

What are the role of the stomata?

A

Control gas exchange in the leaf
Limit evaporation and water loss

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22
Q

When does a stomata close?

A

When guard cells go flaccid

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23
Q

What are stomata surrounded by?

A

Guard cells

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24
Q

What do stomata do when they’re open?

A

They take in water through osmosis - changes in their shape

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25
Q

What controls the opening and closing of the stomata?

A

Guard cells

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26
Q

What is a xylem?

A

A tissue that carries water in the transpiration streams

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27
Q

What are properties of the xylem?

A

Walls are made of lignin - stops the xylem from bursting
Has no end walls - so water can travel up by capillary action in transpiration stream continuously
Made up of dead cells

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28
Q

Where does the xylem transport water from and to?

A

From: roots
To: stem and leaves

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29
Q

In the xylem, what direction does water flow?

A

ONLY up

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30
Q

In the phloem, what direction does sucrose and other food substances flow?

A

BOTH up and down

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31
Q

What does a xylem transport?

A

Water and mineral ions

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32
Q

What does a phloem transport?

A

Sucrose and other food substances

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33
Q

What are properties of the phloem?

A

They have small pores in end walls - to let substances through
They’re made up elongated living cells

34
Q

Where does the phloem transport sucrose from and to?

A

From: leaves
To: rest of the plant

35
Q

Why do plants carry out translocation through the phloem?

A

They need sugars like sucrose distributed throughout the plant for respiration

36
Q

When food molecules, like sucrose, are transported, what happens to them?

A

They can be used immediately or stored

37
Q

What is translocation?

A

The process in which food is moved through the phloem tubes, it requires energy

38
Q

What is transpiration?

A

The loss of water from a plant

39
Q

What is the process of transpiration?

A
  1. The water moves into the root by osmosis, up the stem through the xylem vessels to the leaves
  2. It then evaporates out of the leaf - done by capillary action
40
Q

Why is transpiration important?

A

Cools plant
Pumps water and minerals to the leaves for photosynthesis

41
Q

What are the 4 factors that increase the rate of transpiration?

A
  1. High light intensity
  2. Warm temperature
  3. Dry conditions (not humid)
  4. Good air flow
42
Q

How does high light intensity increase rate of transpiration?

A

Stomata is open when it’s light - water diffuses out of the leaf faster

43
Q

How does warm temperature increase rate of transpiration?

A

Water molecules have more kinetic energy - evaporation and diffusion rate increases

44
Q

How do dry conditions increase rate of transpiration?

A

Diffusion of water from the leaf increases - because the conditions outside the plants have a low concentration of water

45
Q

How does good air flow/wind increase rate of transpiration?

A

Fewer water molecules surround the leaves - so there’s a higher water concentration inside the leaf than outside and diffusion occurs faster

46
Q

What is a potometer?

A

A piece of equipment that measures the rate at which transpiration occurs

47
Q

How to calculate the rate of transpiration from a potometer?

A

Transpiration rate = distance moved by bubble/time taken

48
Q

How does a potometer work?

A
  1. Water flows through a capillary tube to a plant that takes up water
  2. Air is then taken and the air bubble within the potometer moves
  3. The distance this bubble travels can be used to estimate the rate
49
Q

What are the 8 adaptations of plants for photosynthesis and gas exchange?

A
  1. Cells in the upper epidermis
  2. Chloroplasts in the palisade mesophyll
  3. Air spaces in the spongy mesophyll
  4. Stomata in the lower epidermis
  5. Phloem
  6. Xylem
  7. Broad shape
  8. Waxy cuticle
50
Q

How are cells in the upper epidermis adapted for photosynthesis?

A

They’re transparent - let light through for photosynthesis

51
Q

How are chloroplasts in the palisade mesophyll adapted for photosynthesis?

A

There’s a lot of the chloroplasts - rate of photosynthesis increases as there’s lots of light in the palisade mesophyll

52
Q

How are air spaces in the spongy mesophyll adapted for gas exchange?

A

There are a lot of air spaces - allows for a faster diffusion of gases

53
Q

How are stomata in the lower epidermis adapted for gas exchange?

A

There’s a lot of them in the lower epidermis - allows gases to go in and out of the plant

54
Q

How is the broad shape of the leaf adapted for photosynthesis?

A

Broad shape - has a large surface area - allows for more exposure to light - increases rate of photosynthesis

55
Q

How is the waxy cuticle adapted for the leaf?

A

It reduces water loss

56
Q

What is a xerophyte?

A

A plant adapted to living in dry conditions

57
Q

Examples of xerophytes?

A

Cacti
Marram grass

58
Q

What are the 5 adaptations of xerophytes?

A
  1. Small leaves or spines
  2. Curled leaves or hairs on leaves
  3. Thick, waxy cuticle
  4. Stomata in pits
  5. Stomata only open at night and are shut during the day
59
Q

How do small leaves or spines on xerophytes help reduce water loss?

A

Reduces surface area - less water evaporates

60
Q

How do curled leaves or hairs on leaves on xerophytes help reduce water loss?

A

They trap water vapour - reducing diffusion from leaf to air

61
Q

How does a thick, waxy cuticle on xerophytes help reduce water loss?

A

Less water can evaporate as even more water is prevented from passing through the epidermis

62
Q

How do stomata being in pits in xerophytes help reduce water loss?

A

Reduce air flow near stomata - reducing diffusion of water vapour from the leaf to air

63
Q

How do stomata being closed during the day in xerophytes help reduce water loss?

A

It’s warmer in the day so more evaporation and transpiration will occur in the day - shutting stomata in day reduces this loss

64
Q

What is an auxin?

A

A plant hormone that controls growth near the tips of shoots and roots

65
Q

Are shoots positively or negatively phototropic? Describe process

A

Positively phototropic

  1. Shoot exposed to light
  2. Auxin accumulates on the shaded side
  3. Shoot bends towards the light
  4. Cells can grow faster on the shaded side because of this

CELL ELONGATION

66
Q

Are roots positively or negatively phototropic? Why?

A

Negatively phototropic - grow away from light

67
Q

What does positive phototropism mean?

A

Growing towards the direction of light

68
Q

What does negative phototropism mean?

A

Growing away from the direction light

69
Q

Are shoots positively or negatively gravitropic? Describe process

A

Negatively gravitropic

  1. Auxin accumulates on the lower side of the shoot
  2. Auxin makes the lower side of the shoot grow quickly
  3. Shoot bends upwards
70
Q

Are roots positively or negatively gravitropic? Describe process

A

Positively gravitropic

  1. Auxin accumulates on the lower side of the root
  2. Auxin inhibits the root growth on the lower side of the root
  3. Root bends downwards
71
Q

What is positive gravitropism?

A

Growing downwards in the direction of gravity (since gravity acts downwards)

72
Q

What is negative gravitropism?

A

Growing upwards against the direction of gravity (since gravity acts downwards)

73
Q

What are the 3 plants hormones that are commercially used?

A
  1. Auxins
  2. Ethene
  3. Gibberellins
74
Q

What are the commercial uses of auxins?

A

Developed to selectively kill weeds whilst crops remain untouched
Added to rooting powders to promote root growth in plant cuttings

75
Q

What are the commercial uses of ethene?

A

Speeds up the ripening of fruits - used in the transporting of fruits to shops

76
Q

What are the commercial uses of gibberellins?

A

Stimulates seed to germinate at any time of the year
Induces flowering without need for specific conditions
Reduces number of fruits produced - each fruit can grow larger
Can make un pollinated flowers produce seedless fruits

77
Q

EFFECT OF LIGHT INTENSITY ON RATE OF PHOTOSYNTHESIS CORE PRACTICAL: What are the steps to this experiment?

A
  1. Set up the apparatus: beaker with water and pondweed (photosynthesises and produces oxygen) in it that has a bung on it, a gas syringe connected to the beaker
  2. Have a light source 25cm away from the flask
  3. Measure the volume of oxygen produced in 2 minutes using a stop clock
  4. Repeat steps 2-3 again but bring the light source 5cm closer each time (USE A RULER TO MEASURE THIS DISTANCE)
78
Q

EFFECT OF LIGHT INTENSITY ON RATE OF PHOTOSYNTHESIS CORE PRACTICAL: How can the rate of photosynthesis be calculated from this experiment?

A

Rate = volume of oxygen produced/time

79
Q

EFFECT OF LIGHT INTENSITY ON RATE OF PHOTOSYNTHESIS CORE PRACTICAL: What is the conclusion of this experiment?

A

The higher the light intensity (closer the the light source to the pondweed), the faster rate of photosynthesis and thus faster rate of oxygen produced

80
Q

EFFECT OF LIGHT INTENSITY ON RATE OF PHOTOSYNTHESIS CORE PRACTICAL: What are the control, independent and dependent variables?

A

Control: the light source used, mass of pondweed, volume of water
Independent: distance of light source/light intensity
Dependent: volume of oxygen produced

GCSE Biology (9 decks)

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