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Biology > SB6 Plant Structures and their Functions > Flashcards

SB6 Plant Structures and their Functions Flashcards

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1
Q

Define Photosynthesis

A

A chemical process used by plants to make glucose and oxygen from carbon dioxide and water. It is an endothermic reaction

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2
Q

Define biomass

A

The materials in an organism

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3
Q

State the photosynthesis word equation

A

carbon dioxide + water –> glucose + oxygen

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4
Q

What chemical do plants contain which aids them to trap light for photosynthesis?

A

Chlorophyll contained in chloroplasts

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5
Q

What polymer do glucose molecules make?

A

Starch

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6
Q

What is the symbol equation for photosnythesis?

A

6Co2 + 6H20–> C6H12O6 + 6O2

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7
Q

Where does photosynthesis take place?

A

Plant leaves

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8
Q

What can starch be broken down into and what other molecules can be made?

A

Sucrose, which can be used to make cellulose, lipids or proteins

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9
Q

What are some adaptations of a leaf and what do they do?

A
  • broad and flat (large surface area)
  • thin (allows easy gas exchange)
  • a network of veins (to support the leaf and transport mineral ions, water and sucrose)
  • stomata (again allows gas exchange)
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10
Q

What are the parts of the leaf?

A
  • spongy mesophyll
  • cuticle
  • veins
  • guard cell
  • stomata
  • epidermis
  • palisade
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11
Q

What is the role of the spongy mesophyll?

A

Layer with air spaces to increase surface area for gas exchange

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12
Q

What is the role of the cuticle?

A
  • Waxy layer that prevents loss of water
  • allows light through
  • prevent infection from occuring
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13
Q

What is the role of the veins?

A

Made of tubes that carry water, minerals and sucrose in a plant

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14
Q

What is the role of the guard cell?

A

Controls the opening and closing of the stomata

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15
Q

What is the role of the stomata?

A

Pores in leaf that allow gases in and out

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16
Q

What is the role of the epidermis?

A
  • A protective layer of cells that allows light through
  • is thin and transparent
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17
Q

What is the role of the palisade?

A

Layer of cells with chloroplasts for photosynthesis

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18
Q

Define limiting factor

A

A factor that prevents a rate increasing

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19
Q

What are the limiting factors for photosynthesis?

A
  • carbon dioxide concentration
  • temperature
  • light intensity
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20
Q

What equation is used to link distance and light intensity together?

A

light intensity is directly proportional to 1/distance^2

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21
Q

How does temperature affect photosynthesis?

A
  • the reaction is controlled by enzymes so the temperature will continue to quicken the rate of reaction
  • until the enzymes denature and the rate of reaction begins to decrease
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22
Q

How does light intensity affect photosynthesis?

A
  • as there is more light to continue the reaction, more co2 and water can be made into glucose and oxygen
  • so the rate of reaction increases
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23
Q

How does carbon dioxide concentration affect photosynthesis?

A
  • also needed to make glucose, so if one of the products increases, so will the output
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24
Q

What is the water absorbed by plant roots used for?

A
  • carrying dissolved mineral ions
  • keeping cells rigid
  • leaves cool due to evaporation
  • photosynthesis
25
Q

What are the adaptations of a root cell?

A
  • Large surface area for water and mineral ions absorption
  • thin cell walls so water can flow into cells easily
  • lots of mitochondria as active transport has to take place for root hair cells to consume mineral ions
  • found in tips of roots
26
Q

What are root hair cells specialised for?

A

To take up water by osmosis and mineral ions through active transport

27
Q

Define osmosis

A

When solvent molecules such as water diffuse through a semi-permeable membrane

28
Q

What do plants need mineral ions for?

A

To produce new substances

29
Q

Why do root hair cells need to use active transport to take in mineral ions from the soil?

A
  • there is a larger concentration of mineral ions inside the root hair cells as compared to the soil
  • so diffusion can’t occur into the root hair cell
  • therefore energy has to be used to bring in more ions
30
Q

Define transpiration

A

The flow of water into a root, up the stem, and out of the leaves; is an unavoidable side effect of photosynthesis

31
Q

What happens during transpiration?

A
  • plant opens its stomata to let in carbon dioxide
  • water on the cell surfaces of the spongy mesophyll and the palisade mesophyll evaporate
  • and diffuse out of the leaf
  • as water molecules are attracted to each other when some molecules leave the plant the rest are pulled up through the xylem
  • this results in more water uptake from the soil
  • forming a continuous stream of water within the xylem vessels
32
Q

What are xylem vessels and what is transported in them?

A
  • tiny continuous pipes leading from a plant’s roots up to its stem
  • transports water and mineral ions
33
Q

What are the adaptations of xylem vessels?

A
  • made up of ‘dead’ cells (hollow, no cytoplasm)
  • lignin deposited in spirals which helps the cells withstand the pressure from the upwards movement of water
  • cells that make up the xylem lose their end walls to form one continuous long tube
  • lack of cell walls means the water speed remains unaffected
  • tiny pores allow water and mineral ions to enter and leave
34
Q

What is the purpose of transpiration?

A
  • provides water for photosynthesis
  • transports mineral ions
  • cools the leaf as water evaporates
  • provides water which keeps the cells turgid, supporting herbaceous plants
35
Q

What factors affect transpiration?

A
  • temperature
  • air movement
  • humidity
  • light intensity
36
Q

How does temperature affect the rate of transpiration?

A
  • increases the rate
  • increases molecular movement, which means that more water molecules evaporate from cell surfaces
    –> The rate of diffusion from water molecules is increased
37
Q

How does humidity affect the rate of transpiration?

A
  • decreases the rate
  • if humidity is high
  • there will be a reduced concentration gradient between the water inside and outside the leaf
  • which means the rate of diffusion slows down
38
Q

How does air movement affect the rate of transpiration?

A
  • increases the rate
  • removes water vapour from surfaces of leaves
  • forms a high concentration gradient
39
Q

How does light intensity affect the rate of transpiration?

A
  • increases the rate
  • increases the rate of photosynthesis which means that the stomata are open for longer
  • and water diffuses out of the leaf
40
Q

Define translocation

A

The transportation of other minerals such as sucrose, it is an active process

41
Q

Where does translocation occur?

A

Phloem cells

42
Q

What are the cells that make up a phloem cell?

A
  • sieve cells
  • companion cells
43
Q

What are the adaptations of a sieve cell?

A
  • no nuclei for more space
  • has a perforated end so one cytoplasm connects to the next
  • only have some cytoplasm for space, therefore these cells are alive
44
Q

What is the role of a companion cell?

A
  • provides energy to the sieve cells
  • pumps sucrose in and out of sieve cells
45
Q

What adaptations do plants have for dry weather?

A
  • rolled leaf, leaf hairs, stomata in pits: traps water vapour close to leaves which increases humidity + reduces water loss
  • spines instead of leaves: less surface area for water loss
  • thick cuticle: less water loss
  • stomata open at night: less water loss through evaporation
46
Q

What adaptations do plants have for cold weather?

A
  • losing leaves: less water loss where the ground frozen
  • needle-shaped leaves: same as above
47
Q

What adaptations do plants have for tropical weather?

A
  • large leaves: more surface area for photosynthesis
  • tall plants: to obtain more sunlight
48
Q

What adaptations do plants have for waterlogged conditions?

A
  • no air spaces in soil: lack of oxygen
  • more spongy tissue in root to store oxygen
49
Q

Define stimulus

A

A change in the environment which causes a response by the organism

50
Q

Define tropism

A

Responding to a stimulus by growing towards or away from it

51
Q

What are the two main types of tropisms?

A
  • positive tropism: plant grows towards the stimulus
  • negative tropism: plant grows away from the tropism
52
Q

What is the difference between gravitropism and phototropism

A
  • phototropism: response to light
  • gravitropism: responds to gravity
53
Q

What are auxins?

A

Plant hormones which are used to respond to a stimulus, mainly made in the tips of roots and shoots but can diffuse to any place they are required

54
Q

How do auxins respond to phototropism?

A
  • positively
  • when the plant is exposed to light on one side of the plant
  • the auxins move to the shaded sides
  • and stimulates the cells to grow there
  • which makes the plant appear to bend towards the light
  • since the plant receives more light, faster photosynthesis can occur
55
Q

How do auxins in the shoots of plants respond to gravitropism?

A
  • negatively
  • if a shoot is horizontal:
  • auxins move to the lower side
  • the cells of the auxins grow more on the side with more auxins so more cells grow
  • which makes the plant grow away from the ground
  • this is beneficial because it allows the plant to gain more light for photosynthesis
56
Q

How do auxins in the roots of plants respond to gravitropism?

A
  • positively
  • if a root is horizontal
  • auxin moves to the lower side
  • cells of the root grow more on the side with less auxins so it stimulates cells to grow on the upper side
  • which makes the root bend and go downwards
  • beneficial as more water may be available and helps roots to anchor the plant
57
Q

How do auxins in the roots differ from those in the shoots?

A
  • in the shoots, wherever the auxins go they cause elongation of the cells
  • whereas in the roots they stop cell elongation
58
Q

How are artificial auxins used?

A
  • selective weedkillers: can kill weeds with broad leaves, which are the majority of them
  • rooting powder: increase the development of roots in cuttings
  • gibberellins (released during seed germination) can trigger artificial germination
  • ethene is a plant hormone which can be sprayed to prevent early ripening

Biology (18 decks)

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