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Higher Biology > 3.1B Plant Growth and Productivity > Flashcards

3.1B Plant Growth and Productivity Flashcards

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1
Q

What is photosynthesis/

A

photosynthesis is the way in which plants use light energy to make carbohydrate in the form of glucose

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2
Q

What are the three fates of light striking a leaf?

A

reflected - bounced off the surface of the leaf
absorbed - some used for photosynthesis, most lost as heat
transmitted - passes straight through the leaf

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3
Q

Most of the light striking the leaf is…

A

absorbed
very little of the energy is used for photosynthesis (converted into chemical energy)
most is converted to heat energy and lost by radiation or transpiration

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4
Q

TOPTIP

A

ART

absorption reflection transmission

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5
Q

What are pigments?

A

plants contain coloured chemical compounds called pigments

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6
Q

Where are these photosynthetic pigments found?

A

in the granum of the chloroplast

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7
Q

What makes up the visible spectrum?

A

each pigment absorbs different colours and wavelengths of light which creates the visible spectrum

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8
Q

what are the five features in the structure of a chloroplast?

A 
double unit membrane
granum
stroma
lamella 
starch grains
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9
Q

What are the functions of the five features of a chloroplast?

A

double unit membrane - enclose contents
granum - site of light dependent phase contain photosynthetic pigments
stroma - site of carbon fixation contain enzymes and starch grains
lamella - connects grana contains no pigments
starch grains - food store

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10
Q

Name the five organelles in a chloroplast?

what is the function of these organelles?

A 
outer membrane
inner membrane
stroma
granum
thylakoid membrane

these organelles capture light energy from the sun and use it to fix carbon.

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11
Q

What are the 4 main photosynthetic pigments in a green plant?

A

chlorophyll a
chlorophyll b
xanthophyll (carotenoid)
carotene (carotenoid)

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12
Q

What is the function of these pigments?

A

these are chemicals which absorb light energy and convert it to make chemical energy

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13
Q

what is chlorophyll a?

A

chlorophyll a is a complex molecule containing magnesium

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14
Q

What is the function of an accessory pigment?

CATCHPHRASE ANSWER

A

they broaden the spectrum of absorption so that more energy is available for photosynthesis

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15
Q

White light is a mixture of what?

A

a mix of coloured light of different wavelengths

by passing white light through a prism of glass (or a raindrop) the individual colours are separated to form a spectrum

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16
Q

What is a prism?

A

a prism is a specifically shaped piece of glass that can split white light into its component colours

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17
Q

Explain the colours blue and red on the spectrum?

A

light at the blue end of the spectrum has a shorter wavelength and higher energy.
light at the red end of the spectrum has a longer wavelength and lower energy

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18
Q

What does an action spectrum graph show?

A

shows how good each colour of absorbed light is at ‘driving’ photosynthesis
the rate of photosynthesis is highest in blue and red light, the ends of the spectrum where most light is absorbed by green plants
there is little photosynthesis activity in the yellow and orange parts of the spectrum due to some absorption of these wavelengths of light by the carotenoid pigments

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19
Q

What is the correlation between absorption and action spectra?

A

If an absorption spectrum graph and an action spectrum graph follow a similar pattern, then we could conclude that the light being absorbed by the pigment is actually being used for photosynthesis

If the graphs do not follow a similar pattern, then it is likely that other pigments are involved in absorbing different wavelengths of light

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20
Q

TOPTIP

A

remember that the ‘action’ referred to in the action spectrum is photosynthesis

21
Q

Definition of absorption spectrum?

A

a graph showing the level of light absorbed by a pigment at different wavelengths of light

22
Q

definition of action spectrum?

A

a graph showing the rate of photosynthesis at different wavelengths of light

23
Q

Explain the energy capture by pigments?

A

when pigments absorb light, the energy excites electrons in the pigment molecules.
these high energy electrons move through a series of electron carrier proteins attached to the membranes of chloroplasts, releasing their energy which is then used by ATP synthase to regenerate ATP from ADP and Pi

24
Q

TOPTIP

A

photosynthesis occurs in two stages

  1. light dependent stage
  2. carbon fixation
25
Q

What are the two main reactions in the light dependent stage of photosynthesis?

A
  1. photophosphorylation (ATP production)

2. photolysis (splitting water)

26
Q

Explain fully the steps of light dependent stage?

A

absorbed light energy causes electrons within pigment molecules to reach a high energy state
Some high energy electrons flow along the electron transport chain, rotating the enzyme molecule ATP, located in the plasmid membrane of the granum, generating a molecule of ATP from ADP and Pi
Other high electrons break the chemical bonds between hydrogen and oxygen atoms in a molecule of water
Oxygen and hydrogen are released
Oxygen moves through the plant cells and exits the leaf through the stomata
hydrogen is picked up by the coenzyme NADP to form NADPH
Both NADPH and ATP produced during the light dependent stage are essential for the next stage carbon fixation in the calvin cycle

27
Q

TOPTIP

A

NADP is the hydrogen acceptor in photosynthesis - dont get it confused with NAD in respiration

28
Q

TOPTIP

A

Both hydrogen and ATP are used in the next stage of photosynthesis… carbon fixation in the calvin cycle

29
Q

What is the calvin cycle and where does it occur?

A

the calvin cycle is the light independent
the calvin cycle occurs in the stroma of the chloroplast and is dependent upon NADPH and ATP being produced during the light dependent stage

30
Q

Explain the stages of the calvin cycle?

A

carbon dioxide enters the leaf through the stomata and moves by diffusion into the chloroplast
carbon dioxide combines with RuBP (ribulose biphosphate) catalysed by the enzyme RuBPisCO (ribulose biphosphate carboxylase oxygenase)
3-phosphoglycerate is produced and using the ATP and NADPH from the light dependent stage is converted into glyceraldehyde-3-phosphate (G3P)
G3P has two possible fates - some is used to regenerate RuBP which is continually being used up and some is used to make glucose.

31
Q

What are the fates of glucose?

A

some will be converted to starch (a storage carbohydrate)
some will be converted to cellulose for cell walls (a natural structural carbohydrate)
some is used to produce energy in respiration
some passes to other biosynthetic pathways

32
Q

PLANT PRODUCTIVITY

what is productivity?

A

the rate of production of new plant biomass per unit area per unit of time

33
Q

what is assimilation?

A

the increase in mass of plant due to its production of glucose and starch during photosynthesis

34
Q

what is net assimilation?

A

the increase in mass due to photosynthesis minus the loss in mass due to respiration

35
Q

what is biological yield?

A

total biomass produced

36
Q

what is economic yield?

A

mass of desired product produced

37
Q

what is the harvest index?

A

dry mass of economic yield
divided by
dry mass of biological yield

38
Q

How can the rate of photosynthesis be measured as?

A

volume of carbon dioxide absorbed
volume of oxygen released
increase in dry mass of the plant

all measured over a period of time e.g. oxygen bubbles/minute

39
Q

Elodea bubbler experiment?

A

to alter light intensity the light source is placed at different distances from the elodea
to alter carbon dioxide concentration the concentration of sodium hydrogen carbonate is changed
to alter the temperature, the apparatus is placed in the water bath set at different temperatures
the rate of photosynthesis is measured as the volume of oxygen per unit time.

40
Q

What is a limiting factor?

A

factors which if in short supply slow down the rate of photosynthesis

41
Q

What are these limiting factors?

A

temperature
light intensity
carbon dioxide concentration

42
Q

Explain temperature as a limiting factor?

A

enzymes of carbon fixation work slowly at low temperatures and so limit the rate of photosynthesis
enzymes of carbon fixation are denatured at high temperatures, stopping photosynthesis

43
Q

Explain light intensity as a limiting factor?

A

the graph below shows the effect of increasing light intensity on the rate of photosynthesis.
XX check notes XX

44
Q

State what happens to light that strikes a green leaf?

A

absorbed
reflected
transmitted

45
Q

Explain the difference between the absorption spectrum of a pigment and the action spectrum of a green plant?

A

absorption spectrum shows wavelength of light absorbed by one pigment whereas the action spectrum shows the level of photosynthesis carried out at each wavelength of light.

46
Q

Explain the part played by carotenoid pigments in photosynthesis?

A

carotenoid pigments extend the range of wavelengths of light absorbed for photosynthesis and pass the energy trapped onto chlorophyll

47
Q

describe the fates of glucose produced by photosynthesis?

A

used in respiration; converted to starch for storage; converted to cellulose to form cell walls; passed to other biosynthetic pathways

48
Q

State what is meant by

i) biological yield
ii) economic yield

A

i) total plant biomass produced

ii) biomass of desired crop

49
Q

State how the harvest index is calculated?

A

divide the dry mass of the economic yield with the dry mass of the biological yield

Higher Biology (26 decks)

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