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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

What is photosynthesis?

A

When plants/algae trap energy from the sun (transferred by light) which is then transferred to glucose molecules

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2
Q

What does glucose store?

A

Energy

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3
Q

What is biomass?

A

The materials in an organism

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4
Q

What is the word equation for photosynthesis?

A

Carbon dioxide + water ~> glucose + oxygen

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5
Q

Where does photosynthesis occur?

A

Chloroplasts

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6
Q

Is photosynthesis an endothermic or exothermic reaction?

A

Endothermic as energy enters from the surroundings and the products have more energy than the reactants

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7
Q

What happens as glucose molecules are made?

A

They link together to form a polymer called starch

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8
Q

What happens when photosynthesis stops?

A

Starch is broken down into simpler substances which are moved into the cytoplasm and used to make sucrose

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9
Q

What is sucrose?

A

A sugar molecule that is transported around the plant

It is used to make starch, other molecules for the plant (eg proteins) and glucose for respiration

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10
Q

What adaptations allow leaves to absorb a great deal of light?

A

They are broad and flat resulting in a large surface area

The palisade cells near the top of the leaf contain lots of chloroplasts

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11
Q

What do stomata do?

A

They allow carbon dioxide to diffuse into the leaf

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12
Q

How do the stomata allow diffusion?

A

They are opened and closed by specialised guard cells

In the light water flows into pairs of guard cells which makes them rigid and opens the stoma

At night water flows out of the guard cells which makes them lose their rigidness and the stoma shuts

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13
Q

How are leaves adapted for diffusion?

A

They are thin which means carbon dioxide does not have to diffuse far before reaching the cells that need it

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14
Q

Does photosynthesis happen quicker at higher or lower temperatures?

A

Higher

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15
Q

What is a limiting factor?

A

A factor that prevents a rate increasing

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16
Q

What are limiting factors of photosynthesis?

A

Carbon dioxide concentration

Temperature

Light intensity

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17
Q

What is water absorbed by plant roots used for?

A

Carrying dissolved mineral ions

Keeping cells rigid

Cooling the leaves

Photosynthesis

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18
Q

What are root hair cells and how are they adapted?

A

Extensions of the cell that provide a large surface area to absorb water and mineral ions quickly

They also have thin cell walls so the flow of water into the cells is not slowed down

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19
Q

How does water pass into the cytoplasm of root hair cells?

A

Osmosis

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20
Q

How do water particles travel towards the middle of the root?

A

Diffusion

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21
Q

How do mineral ions enter root hair cells?

A

Active transport

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22
Q

What is transpiration?

A

The flow of water into a root, up the stem and out of the leaves

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23
Q

What keeps plants cool?

A

The evaporation of water from leaves

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24
Q

What are xylem vessels?

A

Tiny continuous pipes from a plants roots to its leaves

25
Q

What is inside a xylem vessel?

A

An unbroken chain of water due to the weak forces of attraction between water molecules

26
Q

What happens in xylem vessels?

A

Water is pulled up the xylem vessels in the stem as water evaporates from the xylem vessels in the leaves

As the water vapour diffuses out of a leaf more water evaporates from the xylem inside the leaf

27
Q

What factors influence transpiration?

A

Any factor that reduces the concentration of water molecules outside the stomata

Eg:
Wind
Low humidity
Temperatures
Light intensity

28
Q

What happens during xylem cells development?

A

Xylem cells die and their top and bottom cell walls disintegrate which creates long empty vessels through which water can move easily

29
Q

Why are xylem vessels rigid?

A

They have thick side walls and rings of hard lignin so water pressure inside the vessels doesn’t burst or collapse them

It also helps to support the plants

30
Q

Where is sucrose transported to?

A

The sieve tubes of the phloem tissue

31
Q

How is sucrose transported in the sieve tubes of the phloem tissue?

A

The large central channel in each sieve cell is connected to its neighbours by holes which sucrose flows through

Companion cells actively pump sucrose into/out of the sieve cells that form the sieve tubes

As sucrose is pumped into sieve tubes the increased pressure causes the sucrose to flow up to growing shoots or down to storage organs

32
Q

What does chlorophyll do?

A

It traps energy transferred by light

33
Q

How do spongy cells allow diffusion?

A

They are irregularly shaped and do not fit together well which creates air spaces, allowing gases to diffuse easily inside a leaf

34
Q

What do epidermis cells do?

A

They form outer layers of a leaf holding the leaf together and protecting the cells inside

35
Q

How are epidermis cells adapted?

A

They are transparent to allow light to pass through them easily

They produce a waterproof waxy cuticle which prevents water loss and helps to stop microorganisms and water entering the leaf

36
Q

How are plants adapted to cold conditions?

A

Plants lose their leaves in winter to prevent water loss

Conifers have stomata in small pits to trap water vapour close to their leaves- slowing the rate of diffusion out of the leaves

Some plants use tiny hairs to trap water vapour

37
Q

How are plants adapted to dry conditions?

A

Cacti have spines instead of leaves to minimise the surface area of the plant and protect the stem from herbivores

Cacti stomata only open at night- carbon dioxide is taken in at night and stored for use during the day

Cacti stem store water

38
Q

What is a stimulus?

A

A change in the environment that causes a response by an organism

39
Q

What is a tropism?

A

Responding to a stimulus by growing towards or away from it

40
Q

What is a tropism caused by light?

A

Phototropism

41
Q

What is a positive tropism?

A

A tropism towards a stimulus

42
Q

What part of plants are positively phototropic?

A

Plant shoots

43
Q

What part of plants are negatively phototropic?

A

Plant roots

44
Q

What causes positive phototropism?

A

The plant hormones auxins

45
Q

Where are auxins produced?

A

The tips of a shoot

46
Q

What do auxins cause in shoots?

A

Elongation of the cells

47
Q

How do auxins work in shoots?

A

If a shoot is grown with light coming from only one direction, auxins move to the shaded side of the shoot

This makes the cells on the shaded side elongate more so the shoot grows towards the light

48
Q

Where are auxins found?

A

Plant shoot tips and root tips

49
Q

What do auxins cause in roots?

A

Cells to stop elongating- positive gravitropism

50
Q

What does positive gravitropism do?

A

Helps roots to anchor the plant in place and reach moisture underground

51
Q

What do gibberellins do?

A

Helps seeds to germinate and start to grow roots and shoots

52
Q

What does ethene gas do in terms of plants?

A

Helps fruit to ripen

53
Q

What do artificial auxins do?

A

Makes some plants grow uncontrollably which can kill them

54
Q

How do selective weedkillers work?

A

They contain artificial auxins to kill plants with broad leaves (like dandelions) but not those with narrow leaves (like wheat)

This allows farmers to kill weeds in a wheat farm without harming the wheat

55
Q

How do rooting powders work?

A

They contain auxins which cause plant cuttings to develop roots quickly

56
Q

What is photoperiodism?

A

The response of an organism to the number of daylight hours in a day

57
Q

What can gibberellins be used to do?

A

Override photoperiodism

Cause some plants to produce fruits without being pollinated which produces seedless fruits

Make plants produce bigger fruits

58
Q

How can fruit producers use ethene?

A

Pick unripe fruit which is easier to transport without damaging and then ripen it when needed with ethene gas

This ensures fruit reaches shops in just-ripened conditions

Biology (9 decks)

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