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BIOLOGY PAPER 2 > Photosynthesis > Flashcards

Photosynthesis Flashcards

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1
Q

Process of light dependent reaction

A

-chlorophyll molecule absorbs light energy and a pair of e- is raised up energy level (excited) . e- leave chlorophyll - chlorophyll is ionised (photoionisation)
-excited e- passed from e- carrier to e- carrier in a series of redox reactions. series of e- carriers is located in the thylakoid membrane. each e- carrier is a lower energy level than previous one so e- loose energy
-the energy is used to pump H+ into the thylakoid space
-H+ move from high conc inside thylakoid to a lower conc in the stroma, through atp synthase.
Atp synthase comines ADP+Pi to form ATP
-H+ pass through ATP synthase and are taken up (along with e- bu NADP to form NADPH)
-Photolysis - splitting water with light provide e- to replace those lost from chlorophyll during photoionisation

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2
Q

How ATP is made during LDR

A

-chlorophyll molecule absorbs light energy and a pair of e- is raised up energy levels so e- leave chlorophyll
-exited e- passed from e- carrier to e- carrier in a series of redox reactions
-series of e- carriers are located in thylakoid membrane
-each e- carrier is a lower energy level than previous one so e- lose energy
-energy is used to pump h+ into thylakoid space
-h+ move from high conc inside thylakoid to a lower conc in the stroma through ATP synthase
-ATP synthase combines ADP+pi to from ATP

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3
Q

role of photolysis in LDR

A

-splitting water with light
-so provides e- to replace those lost from chlorophyll molecule during photoionisation
-h+ pass through atp synthase and are taken up (along with e-) by NADP to from NADPH

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4
Q

How chloroplasts adapted to carry out LDR

A

-thylakoid membrane has large SA > chlorophyll, e- carriers and enzymes to attach
-proteins in grana > hold chlorophyll in precise place for max absorption of light
-ATP synthase in thylakoid membrane > atp production

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5
Q

What does the LDR produce?

A

-reduced NADP (NADPH)
-ATP
-Oxygen (by-product)

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6
Q

What are the products of the LDR needed for?

A

LIR

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7
Q

What are the electrons produced in photolysis used for?

A

passed along chain of electron carrier proteins

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8
Q

What are the H+ ions produced in photolysis used for?

A

-picked up by NADP to make NADPH

-pumped to create electrochemical gradient and diffuse through ATP synthase (allowing ATP to be formed)

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9
Q

What causes chlorophyll to become ionised?

A

absorbs light energy, which raises energy level of electrons (excited state), causes them to leave chlorophyll

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10
Q

What happens to the electrons after they leave chlorophyll?

A

they are passed along an electron carrier chain in thylakoid membrane

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11
Q

What do the electrons passing through the chain do?

A

release/lose energy

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12
Q

What is the energy released by electrons passing through the electron carrier chain used for?

A

to pump H+ ions into the lumen of the thylakoid

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13
Q

What is created as H+ ions are pumped into the lumen of the thylakoid?

A

an electrochemical gradient

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14
Q

What are the 3 main steps of the LDR?

A

photoionisation
chemiosmosis
photolysis

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15
Q

How are electrons passed along the electron carrier proteins?

A

series of redox reactions

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16
Q

What are the electrons used for after being passed along the electron transfer chain?

A

accepted alongside H+ to form NADPH

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17
Q

What is the energy lost from the electrons used for?

A

pumping H+ ions against their electrochemical gradient

18
Q

What happens in photoionisation?

A

-light absorbed by chlorophyll
-raises electrons an energy level SO they are lost from the chlorophyl

19
Q

Why do plants benefit from having different coloured pigments?

A

absorb different/more wavelengths of light for the LDR

20
Q

Why might not all light be used in photosynthesis?

A

some could be reflected
some light is incorrect wavelength

21
Q

ATP produced by chemosmosis

A

-h+ pumped from stroma using hydrogen pump in the thylakoid membrane
-do this via the energy from e- released when water is split (photolysis) which also produces H+
-creates and maintains conc gradient of H+ across thylakoid membrane with high conc inside thylakoid space and low conc in stroma
-protons only cross thyalkoid membrane via ATP synthase
-as protons pass through ATP synthase they cause changes to structure of enzyme which then catalyses combination of ADP+Pi = ATP

22
Q

How co2 arrives in stroma of chloroplast

A

diffuse from atmosphere through stroma, spongy mesophyll and into palisade cell

23
Q

rubisco function

A

enzyme that catalyses reaction between RuBP and CO2

24
Q

Role of atp produced my LIR

A

convert GPP to TP to regenerate RuBP

25
Q

Fate of triose phosphate produced during calvin cycle

A

combined to form organic molecules including glucose. most is used to regenerate RuBP

26
Q

Explain how CO2 absorbed by plants is incorporated into organic molecule

A

-co2 enters stroma by diffusion and reacts with 5c ribulose biphosphate (RuBP) to form 2x molecules of 3C glycerate-3-phosphate (GP)
-reaction catalysed by rubisco

27
Q

Roles of ATP and NADH in LIR

A

-atp =hydrolyse to convert glycerate-3-phosphate (GP) into triose phosphate (TP) and TP back into RuBP

-NADH = convert GP into triose phosphate

28
Q

Describe events in calvin cycle

A

-CO2 and RuBP from 2x glycerate-3-phosphate in presence of rubisco
-GP converted to triose phosphate with ATP and NADH
-Some triose phosphate forms useful organic molecules eg glucose
-majority of triose phosphate recycled to RuBP and ATP

29
Q

What is used in the Calvin cycle?

A

-NADPH
-ATP
-CO2

30
Q

What is required in order to form triose phosphate molecules?

A

ATP and a H from reduced NADP

31
Q

Give 2 examples of what the glucose can be used to make?

A

glycerol used to make lipids
combine with nitrates to form amino acids
stored as starch
used in cell walls as cellulose

32
Q

How many times does the Calvin cycle need to happen before a hexose sugar (e.g glucose can be made)?

A

6

33
Q

Why is ATP needed for the second time in the Calvin cycle?

A

to regenerate the RuBP by joining a TP molecule to the molecule that donated it’s carbon atom for use in making organic molecules

34
Q

How many Carbon atoms leave the 2 x TP molecules to be used in organic molecules?

A

1

35
Q

What is GP reduced to form?

A

triose phosphate

36
Q

What is the role of the reduced NADP in the Calvin cycle?

A

donates H to reduce molecule GP

37
Q

Why won’t the LIR occur if the LDR doesn’t occur?

A

-no ATP
-no NADPH
-needed for LIR (converting GP to TP)

38
Q

Why will the rate of LIR decrease if rate of RuBisCo decreases?

A

-no CO2 reacts with RuBP
-so no GP

39
Q

Where is RuBisCo found in a cell?

A

stroma of chloroplasts

40
Q

LIR

A

1) Co2 enters stroma via diffusion and reacts with RuBP (5C)
- catalysed by rubisco
2) FoRMS 2x GP (3C)
3) NADPH from LDR used to reduce GPinto TP using energy from ATP
$)NADP is reformed and goes back to LDR to be reduced again by accepting more H+
5) some TP converted to useful organic substances eg glucose, strach, cellulose, nucleotides ect
6) most TP used to regenerate RuBP using ATP from LDR

BIOLOGY PAPER 2 (15 decks)

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