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YEAR 12- biology a-level > mass transport in plants > Flashcards

mass transport in plants Flashcards

1
Q

how are leaves adapted for effective gas exchange?

A

they have a large surface area which absorbs lots of sunlight
many stomata
Guard cells to close stomata
Thin for a short diffusion pathway
Concentration gradient from phloem and Xylon

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2
Q

What is the gas exchange system in plants?

A

surface of the mesophyll cells

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3
Q

describe gas exchange through the movements of guard cells and stomata

A

gas enters and leaves the leaf through the stomata
The opening and closing of the stomata is controlled by the guard cells
In light guard cells swell with water and become turgid so stomata opens
In dark, they shrivel to prevent water loss as stomata closes

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4
Q

what are xerophyte plants

A

plants which live in extreme environments

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5
Q

how are xerophyte plants adapted for extreme environments

A

They have stomata sunken in pits
layers of hairs on epidermis
curled leaves with stomata inside
Reduced number of stomata
Waxy, cuticle

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6
Q

how is xerophytes having stomata sunken in pits beneficial to reduce gas exchange

A

trap moist air and collect water and reduces concentration gradient

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7
Q

how is xerophytes having lots of hairs on epidermis beneficial

A

traps moisture

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8
Q

how is xerophytes having curled leaves with stomata inside beneficial

A

protects them from wind so there’s less water loss from transpiration

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9
Q

how is xerophytes having reduced number of stomata beneficial?

A

less water loss

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10
Q

how is xerophytes having a waxy cuticle beneficial?

A

reduce water loss from transpiration/ evaporation

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11
Q

Word equation for photosynthesis

A

carbon dioxide + water > (light/ chloroplasts)> oxygen + glucose + ATP

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12
Q

Why do plants do photosynthesis?

A

To convert carbon dioxide and water into oxygen and glucose for aerobic respiration to produce energy

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13
Q

what are plants use their glucose from photosynthesis to make or do?

A

ATP
Cellulose
Respiration
Starch
Fats and oils
Combines with nitrates in soil to make proteins

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14
Q

What is the function of the the leaf?

A

Allow water to diffuse out of stomata and is the area of photosynthesis

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15
Q

What is the function of roots?

A

Absorb water and mineral ions

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16
Q

What is the function of the stem?

A

transport water and mineral ions up the xylem to leaf and phloem

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17
Q

what is transpiration?

A

Water evaporating out of leaves through the stomata

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18
Q

What are the factors which affect rate of transpiration?

A

humidity
Wind speed
Light intensity
Temperature

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19
Q

How does humidity affect the rate of transpiration?

A

Low humidity creates a steeper concentration gradient so there is more evaporation

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20
Q

How does windspeed affect the rate of transpiration?

A

loses more water with high speed
Water that has been evaporated is blown away which maintains concentration gradient between the leaf and air

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21
Q

how does light intensity affect the rate of transpiration?

A

Highlight intensity results in more photosynthesis so stomata is open for carbon dioxide and more water escapes

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22
Q

How does temperature affect the rate of transpiration?

A

higher temperature means water has more kinetic energy and evaporates faster

23
Q

What does a potometer do

A

Estimate rate of transpiration and uptake of water in the shoot of a plant

24
Q

How is a plant adapted to mass transport?

A

transpiration- transport of water through xylem
Translocation -transport of food/sugars through phloem

25
features and function of the xylem
One way transport of water and mineral ions no end cell walls between cells so there is an uninterrupted tube for water Strengthened with lignin Made of deadcells
26
what is the cohesion tension theory?
Movement of water through xylem
27
What happens in the cohesion tension theory?
water evaporate through the leaves at the top of the xylem via transpiration This creates tension pulling more water into the leaf Since water molecules are cohesive when some are pulled into the leaf the other molecules follow Therefore, the whole column of water in the Xylem moves upwards Water then enters the stem from the roots
28
what is the function of the phloem tissue
transport organic solute ,mainly sucrose ,around plants
29
Describe the structure of the phloem
sieve cells has end cell walls supported by companion cells
30
How are sieve cells adapted for easier mass flow of organic solute
they have little cytoplasm Hollow Few/no organelles Large space Thick walls no nuclei perforated and walls accompanied by companion cells as they provide the organelles needed - mitochondria
31
why are sieve cells supported by companion cells?
they provide energy for active transport of solutes and carry out the living function for sieve cells as they contain ribosomes to produce proteins linked to transport and it is an active process which needs energy
32
which direction are organic solutes transported through the phloem
Two way transport
33
what is translocation?
The movement of solutes/ assimilates such as amino acids or sucrose to where they are needed in a plant solutes sources to sinks through a two-way flow which requires energy
34
what is the first step of mass flow hypothesis? source
At the source assimilates are actively transported from companion cells to sieve cells in the phloem. water potential inside sieve tubes lowers so water enters the tubes by osmosis from the Xylem and companion cells, creating a high-pressure inside the sieve tubes at the source end of the phloem
35
What is the second step of the mass flow hypothesis? sink
at the sink end solutes are removed from the phloem to be used up. This increases the water potential inside the sieve tubes so water also leaves the tubes by osmosis. This lowers the pressure inside the sieve tubes.
36
what is the third step of the mass flow hypothesis? Flow
this results in a pressure gradient from the source end to the sink end this gradient pushes solutes along the sieve tube towards the sink to be used in respiration or stored as starch the higher concentration of sucrose at the source creates a higher rate of translocation
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40
what is the function of the phloem
transport organic solutes/ assimilates- mainly sucrose- around the plant
41
describe the structure of the phloem
no end cell walls living made up of sieve cells sieve plates supported by companion cells two way transport system to transport dissolved food molecules
42
what are the adaptations of sieve cells for mass transport
few organelles/ no nuclei/ little cytoplasm/ hollow/ large space/ thick walls/ perforated cell walls/ accompanied by companion cells for the easier flow and active transport of organic solutes
43
what are the adaptations of companion cells for the mass transport of assimilates
contain organelles such as mitochondria for energy release for the active transport of organic solutes contain ribosomes/ RER for the production of proteins linked to transport
44
what is translocation
movement of solutes such as amino acids or sucrose to where they are needed in a plant (2 way flow) moving solutes from sources to sinks- requires energy
45
what is the mass flow hypothesis
shows how the he solutes are transported from source to sink by translocation
46
what is the first step of the mass flow hypothesis (source) and explain what happens
at the source, assimilates are actively transported from companion cells to sieve cells in the phloem water potential inside the sieve tubes lowers so water enters the tubes by osmosis from the xylem and companion cells creates a high pressure inside the sieve tubes at the source end of phloem
47
what is the second step of mass flow hypothesis (sink) and explain what happens
at the sink end, solutes are removed from the phloem to be used up, causing an increase in water potential in sieve tubes causing water to leave the tubes by osmosis lowering the pressure in sieve tubes
48
what is the third step of mass flow hypothesis (flow) and explain what happens
the previous steps results in a pressure gradient from the source end to the sink end. the gradient pushes solutes along the sieve tubes towards the sink to be used during respiration or to be stored as starch higher concentration of sucrose= higher rate of translocation
49
how does a higher concentration of sucrose affect the rate of translocation
increases
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YEAR 12- biology a-level (13 decks)

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