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Biology > Module 5.5 - Photosynthesis > Flashcards

Module 5.5 - Photosynthesis Flashcards

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1
Q

Why do living things need energy? (2)

A
  • Animals/plants need energy for photosynthesis, muscle contraction, maintenance of body temperature, active transport, DNA replication, cell division and protein synthesis
  • Without energy, these biological processes would stop and the plant or animal would die
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2
Q

What is photosynthesis? (4)

A
  • Storage of energy in glucose
  • Energy is stored in glucose until its respired for energy
  • The process where the light energy is converted to chemical energy in the form of glucose
  • 6H2O + 6CO2 → C6H1206 (glucose) + 6O2
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3
Q

Types of respiration? (2)

A
  • Aerobic respiration: respiration using oxygen
  • Anaerobic respiration: respiration without oxygen
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4
Q

Aerobic respiration? (1)

A
  • C6H1206 (glucose) + 6O2 → 6H2O + 6CO2 + energy
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5
Q

Metabolic pathway? (2)

A
  • Series of small enzyme-controlled reactions
  • Respiration and photosynthesis
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6
Q

Phosphorylation? (2)

A
  • Adding phosphate to a molecule
  • ADP is phosphorylated to ATP
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7
Q

Photophosphorylation? (1)

A
  • Adding phosphate to a molecule using light
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8
Q

Photolysis? (1)

A
  • The splitting (lysis) of a molecule using light (photo) energy
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9
Q

Hydrolysis? (1)

A
  • The splitting (lysis) of a molecule using water (hydro)
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10
Q

Decarboxylation?(1)

A
  • The removal of carbon dioxide from a molecule
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11
Q

Dehydrogenation? (1)

A
  • The removal of hydrogen from a molecule
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12
Q

Redox reactions? (2)

A
  • Reactions that involve oxidation and reduction
  • OILRIG
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13
Q

Coenzyme? (2)

A
  • A molecule that aids the function of an enzyme
  • Work by transferring a chemical group from one molecule to another
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14
Q

Coenzyme involved in photosynthesis? (3)

A
  • NADP
  • Transfers hydrogen from one molecule to another
  • NADP can reduce or oxidise a molecule
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15
Q

Coenzymes used in respiration? (3)

A
  • NAD
  • Coenzyme A
  • FAD
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16
Q

NAD and FAD? (2)

A
  • Transfer hydrogen from one molecule to another this means
  • They can reduce or oxidise a molecule
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17
Q

What is also transferred when hydrogen is transferred? (1)

A
  • Electrons are transferred
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18
Q

Coenzyme A? (1)

A
  • Transfers acetate between molecules
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19
Q

Where does photosynthesis take place? (1)

A
  • Chloroplasts
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20
Q

Chloroplasts? (4)

A
  • Small, flattened organelles found in plant cells
  • Double membraned (chloroplast envelope)
  • Thylakoids are stacked up into structures called grana
  • Grana are linked together by bits of thylakoid membrane called lamellae
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21
Q

Photosynthetic pigments? (3)

A
  • Chlorophyll a, chlorophyll b and carotene
  • Are coloured substances that absorb the light energy needed for photosynthesis
  • Found in the thylakoid membranes & are attached to proteins
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22
Q

Photosystem? (4)

A
  • Protein and pigment
  • Used to capture light
  • Photosystem I (or PSI) absorbs light at 700 nm
  • Photosystem II (PSII) absorbs light at 680 nm
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23
Q

Types of photosynthetic pigments in a photosystem? (2)

A
  • Primary pigments
  • Accessory pigments
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24
Q

Primary pigments? (1)

A
  • Reaction centres where electrons get excited during the light-dependent reaction
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25
Q

Accessory pigments? (2)

A
  • Make-up light-harvesting systems which surround reaction centres
  • And transfer light energy to them to boost the energy available for electron excitement to take place
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26
Q

Stroma? (3)

A
  • Gel-like substance
  • Contained within the inner membrane of the chloroplast and surrounds the thylakoids
  • Chloroplasts’ circular DNA found here
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27
Q

What does the inner membrane of the chloroplast contain? (1)

A
  • Enzymes, sugars and organic acids
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28
Q

Starch grains? (1)

A
  • Carbohydrates produced by photosynthesis are stored as starch grains in the stroma
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29
Q

Stages of photosynthesis(2)

A
  • The Light-Dependent Reaction
  • The Light-Independent Reaction
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30
Q

The light-dependent reaction? (6)

A
  • Reaction needs light energy
  • Takes place in thylakoid membranes of chloroplasts
  • Light energy is absorbed by photosynthetic pigments in photosystems
  • ATP transfers energy to the light-independent reaction
  • Reduced NADP transfers hydrogen to the light-independent reaction
  • During the process H2O is oxidised to O2
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31
Q

What happens to light energy after being absorbed by pigments? (3)

A
  • Light energy is converted to chemical energy
  • Light energy is used to add a phosphate group to ADP to form ATP
  • Light energy is used to reduce NADP to form reduced NADP
32
Q

Reduced NADP?(2)

A
  • An energy-rich molecule
  • It can transfer hydrogen/electrons to other molecules
33
Q

The Light-Independent Reaction? (4)

A
  • Calvin cycle
  • Doesn’t use light energy directly but relies on the products of the light-dependent reaction
  • Takes place in the stroma of the chloroplasts
  • ATP and reduced NADP supply the energy and hydrogen to make glucose from CO2
34
Q

Photophosphorylation? (2)

A
  • In the light-dependent reaction ATP is Made
  • Light energy absorbed by the photosystems is used for three things
35
Q

What is the light energy absorbed by the photosystems used for? (3)

A
  • Photophosphorylation
  • Making NADPH from NADP
  • Photolysis
36
Q

How are photosystems linked together? (3)

A
  • By electron carriers
  • Electron carriers are proteins that transfer electrons
  • The photosystems and electron carriers form
37
Q

Electron transport chain? (1)

A
  • A chain of proteins through which excited electrons flow
38
Q

Types of photophosphorylation? (2)

A
  • Non-cyclic
  • Cyclic
39
Q

Non-cyclic photophosphorylation (1)

A
  • Produces ATP, NADPH and O2
40
Q

How do high-energy electrons move from PSII to PSI? (5)

A
  • Light energy is absorbed by PSII
  • Light energy excites electrons in chlorophyll
  • Electrons move to higher energy level
  • Electrons have more energy
  • High-energy electrons move along the electron transport chain to PSI
41
Q

What happens to PSII when excited electrons leave? (3)

A
  • Excited electrons are replaced
  • Light energy splits water into protons (H+), electrons and oxygen
  • H2O → 2H+ + ½O2
42
Q

Proton concentration gradient? (5)

A
  • Excited electrons lose energy as they move along electron transport chain
  • The energy lost is used to transport protons into the thylakoid via proton pumps
  • Thylakoid has a higher concentration of protons than the stroma
  • This forms a proton gradient across membrane
  • Protons move down concentration gradient into stroma
43
Q

Proton pumps? (1)

A
  • Membrane proteins
44
Q

How do protons move down the proton concentration gradient? (2)

A
  • Via an enzyme called ATP synthase
  • Energy from movement combines ADP and inorganic phosphate (Pi) to form ATP
45
Q

How is NADPH generated? (4)

A
  • Light energy is absorbed by PSI
  • Excites electrons again to an even higher energy level
  • Electrons & H+ (from stroma) are transferred to NADP
  • NADP is reduced to NADPH
46
Q

Chemiosmosis/ chemiosmotic theory? (2)

A
  • Process of electrons flowing down the electron transport chain
  • Creating a proton gradient across the membrane to drive ATP synthesis
47
Q

Cyclic photophosphorylation? (2)

A
  • Only produces ATP
  • Only uses PSI
48
Q

Why is cyclic photophosphorylation called cyclic? (5)

A
  • Electrons from the chlorophyll molecule aren’t passed onto NADP
  • Electrons are passed back to PSI via electron carriers
  • Electrons are recycled and can repeatedly flow through PSI
  • Cyclic photophosphorylation doesn’t produce NADPH or O2
  • Cyclic photophosphorylation produces small amounts of ATP
49
Q

Calvin cycle? (5)

A
  • Takes place in the stroma of the chloroplast
  • Also known as carbon dioxide fixation
  • Turns CO2 + RuBP into TP
  • Needs ATP and H+
  • RuBP is regenerated
50
Q

Carbon fixation? (1)

A
  • Carbon from CO2, is fixed into an organic molecule
51
Q

RuBP? (2)

A
  • Ribulose bisphosphate
  • A 5-carbon compound
52
Q

TP? (2)

A
  • Triose phosphate
  • Can make glucose and other useful organic substances
53
Q

How is GP generated? (4)

A
  • CO2 enters leaf through the stomata
  • CO2 diffuses into stroma
  • CO2 dioxide + RuBP form unstable 6-carbon compound
  • 6-carbon compound bread down into two molecules of glycerate 3-phosphate (GP)
54
Q

RuBisCO? (1)

A
  • Ribulose bisphosphate carboxylase catalyses the reaction between CO2 + RuBP
55
Q

How is TP generated? (4)

A
  • ATP energy to turn GP into TP
  • Requires H+ NADPH
  • NADPH is recycled to NADP
  • TP is converted into many organic compounds
56
Q

Why is NADPH recycled to NADP? (1)

A
  • To be re-used in the light-dependent stage
57
Q

How is RuBP regenerated? (2)

A
  • Five out of every six molecules of TP produced is used to regenerate RuBP
  • Regenerating RuBP uses the rest of the ATP produced by the light-dependent reaction
58
Q

What are TP and GP used to make? (3)

A
  • Carbohydrates
  • Lipids
  • Amino acids
59
Q

How are carbohydrates made? (2)

A
  • Hexose sugars from two TP molecules
  • Larger carbohydrates from combining hexose sugars
60
Q

How are lipids made? (2)

A
  • Glycerol - which is synthesised from TP
  • Fatty acids - which is synthesised from GP
61
Q

What are some amino acids made? (1)

A
  • GP
62
Q

How does the Calvin cycle make one hexose sugar? (7)

A
  • For every 1 of CO2 used 2 of TP is formed
  • 3 turns of cycle produces 6 of TP
  • 5 out of 6 of TP are used to regenerate RuBP
  • To make a hexose sugar, 3 turns of the cycle produces only one of TP
  • Two of TP are needed to form 1 of hexose
  • Cycle must turn six times
  • Six turns need 18 ATP +12 reduced NADP
63
Q

Optimum conditions for photosynthesis in temperate climates? (3)

A
  • High light intensity of a certain wavelength
  • Temperature around 25 °C
  • Carbon dioxide at 0.4%
64
Q

High light intensity of a certain wavelength? (5)

A
  • Light is needed to provide energy for light-dependent reactions
  • Higher the intensity of light, the more energy it provides
  • Certain wavelengths of light are used for photosynthesis
  • Photosynthetic pigments absorb red and blue light
  • Green light is reflected, which is why plants look green
65
Q

Temperature’s effect on enzymes? (3)

A
  • Photosynthesis involves enzymes
  • If the temperature falls below 10 °C the enzymes become inactive
  • If the temperature is more than 45 °C they may start to denature
66
Q

High temperature’s effect on stomata? (2)

A
  • Stomata close to avoid losing too much water
  • Causes photosynthesis to slow down because less CO2 entering the leaf
67
Q

Stomatal aperture? (1)

A
  • The width of the opening of stomata
68
Q

High temperature’s effect on thylakoid membranes? (3)

A
  • Membranes may be damaged
  • Number of sites available for electron transfer reduces
  • Reduce the rate of light-dependent stage reactions
69
Q

High temperature’s effect on membranes around chloroplasts? (3)

A
  • Membranes around the chloroplasts could be damaged
  • Enzymes important in the Calvin cycle will be released into the cell and not to the stroma
  • Reduce the rate of the light-independent stage reactions
70
Q

High temperature’s effect on chlorophyll? (3)

A
  • Chlorophyll could be damaged
  • Reduce the amount of pigment that can absorb light energy
  • Reduce the rate of the light-dependent stage reactions
71
Q

Carbon dioxide at 0.4%? (3)

A
  • Carbon dioxide makes up 0.04% of the gases in the atmosphere.
  • Increasing this to 0.4% gives a higher rate of photosynthesis
  • But any higher and the stomata start to close
72
Q

Light, Temperature and CO2 as limiting factors of photosynthesis? (3)

A
  • All three have to be at the right level for photosynthesis to happen quickly as possible
  • If any of these factors is too low or too high, it will limit photosynthesis
  • These factors could become the limiting factor based on the environmental conditions
73
Q

Saturation point? (2)

A
  • When a factor is no longer limiting the reaction
  • Something else has become the limiting factor
74
Q

How can water stress affect photosynthesis? (4)

A
  • Plants don’t have enough water
  • Stomata will close to preserve water they do have
  • Less CO2 enters the leaf for the Calvin cycle
  • Photosynthesis slows down
75
Q

Light intensity’s effect on the levels of GP, RuBP and TP in the Calvin cycle? (2)

A
  • At low light intensity the products of the light-dependent stage will be in short supply
  • Conversion of GP to TP and RuBP is slow
76
Q

Temperature’s effect on the levels of GP, RuBP and TP in the Calvin cycle? (4)

A
  • All reactions in Calvin cycle are catalysed by enzymes
  • At low temperatures all reactions will be slower as enzymes work more slowly
  • Levels of RuBP, GP and TP will fall
  • GP, TP and RuBP are affected the same way at high temperatures as enzymes will denature
77
Q

Carbon Dioxide concentration’s effect on the levels of GP, RuBP and TP in the Calvin cycle? (2)

A
  • At low CO2 concentrations conversion of RuBP to GP is slow
  • As less CO2 entering the leaf to combine with RuBP

Biology (10 decks)

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