Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

A Level Biology > C1- Photosynthesis > Flashcards

C1- Photosynthesis Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

What are the two stages of photosynthesis?

A

The light dependent stage and light independent stage.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the overall equation for photosynthesis?

A

6CO2 + 6H2O → C6H12O6 + 6O2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Define photophosphorylation.

A

An endergonic reaction bonding a phosphate ion to a molecule of ADP using energy from light, making ATP.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Where does the light independent stage occur in a chloroplast?

A

In the stroma- a fluid filled interior bathing the thylakoids and grana.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Where does the light dependent stage occur in a chloroplast?

A

In the grana where the photosynthetic pigments are located.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are grana?

A
  • Chloroplasts have a double membrane.
  • The inner membranes folds inwards to make thylakoid lamellea.
  • These combine in stacks of up to 100 disc-shaped structures forming grana.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Why will starch grains appear white on electron micrographs?

A

The stain used osmium tetroxide binds to lipids but not carbohydrates.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Where are chloroplasts located in a plant and why?

A

They’re in the stem and leaves- mainly in the palisade mesophyll of the leaves, although they’re also found in the guard cells)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe how the structural features of a leaf are significant to photosynthesis.

A

check textbook

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe how the structural features of a leaf’s cells are significant to photosynthesis.

A

check textbook

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe how the structural features of chloroplasts are significant to photosynthesis.

A
  • large surface area- maximum light absorption
  • move with palisade cells- move towards the top of the cell on dull days for the maximum absorption of light and on dull days sink to the bottom to protect its pigments from bleaching.
  • rotate with the palisade cells- thylakoids maximise the absorption of light
  • pigments in the thylakoids are in a single layer at the surface of the thylakoid membrane- maximise absorption of light
  • five times as many in the palisade cells as the spongy mesophyll cells- palisade cells are at the top of the leaf so more exposed to light.
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Explain what is meant by chloroplasts being transducers.

A

A transducer changes energy from one form into another. Chloroplasts turn energy in photons of light into chemical energy, made available through ATP and incorporated into molecules such as glucose.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is a pigment?

A

A molecule that absorbs specific wavelengths of light.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Why are there different pigments within chlorophyl?

A

Allows for a large range of wavelengths to be absorbed and is consequently more useful than there was just one pigment present absorbing a small range of wavelengths.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the two main classes of pigment in flowering plants?

A
  • chlorophylls

- carotenoids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the two pigments in the chlorophylls class and what are their colours?

A
  • chlorophyll a- yellow-green

- chlorophyll b- blue-green

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What are the two pigments in the carotenoids class and what are their colours?

A

B-carotene- orange

xanthophyll- yellow

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is an absorption spectrum?

A

A graph showing how much light is absorbed at different wavelengths.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is an action spectrum?

A

A graph showing the rate of photosynthesis at different wavelengths.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What does a correlation between the action spectrum and absorption spectrum suggest?

A

The pigments are responsible for absorbing the light used in photosynthesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Where are photosystems located?

A

In the plane of the thylakoid membrane.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What two things is a photosystem comprised of?

A

An antenna complex and a reaction centre.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is an antenna complex?

A

An array of protein and pigment molecules in the thylakoid membranes of the grana that transfer energy from light of a range of wavelengths to a chlorophyll a, at the reaction centre.

24
Q

Describe the features of an antenna complex containing photosynthetic pigments in a photosystem.

A
  • Chlorophylls and carotenoids are anchored into the phospholipids of the thylakoid membrane.
  • They’re held together by protein molecules in clusters of up to 400 molecules.
  • Each cluster is called an antenna complex.
  • The combination of pigments allows light at a range of wavelengths to be absorbed.
25
Q

Describe the features of a reaction centre in a photosystem.

A
  • located within an antenna complex
  • contains two molecules of the primary pigment chlorophyll a.
  • when the chlorophyll a molecules absorb light, their excitation allows each one to emit an electron.
  • there are two types of reaction centres- PSI and PSII
26
Q

What are the two types of reaction centres?

A

Photosystem I (PSI):

  • arranged around a chlorophyll a molecule
  • absorption peak of 700nm
  • also called P700

Photosystem II (PSII):

  • discovered after PSI
  • arranged around a chlorophyll a molecule
  • absorption peak of 680nm
  • also called P680
27
Q

How are photons absorbed?

A
  • some are absorbed by chlorophyll a directly, but many are absorbed by chlorophyll b and the carotenoids which, are the accessory (or antenna) pigments.
  • the photons excite the accessory pigments and energy is passed through them to the reaction centre where electrons of chlorophyll a are excited and raised to a higher energy level.
28
Q

Why is chlorophyll a referred to as the primary or core pigment?

A

It is the most significant molecule of the reaction centre because it passes energy to the subsequent reactions of photosynthesis.

29
Q

What reaction uses light as an energy source and water?

A

The light dependent stage reactions

30
Q

What does the light dependent stage produce?

A
  • ATP- which provides chemical energy transducer from light energy
  • reduced NADP- which provides the reducing power to synthesise molecules such as glucose from carbon dioxide
  • oxygen- a by-product derived from water- it diffuses out of the leaf
31
Q

What light independent reactions occur and why are they known as this?

A
  • reactions using ATP and reduced NADP make molecules such as glucose occur in solution in the stroma
  • they can happen in light but do not require it so are described as light independent
  • they include a cycle of reactions called the Calvin cycle
32
Q

What is cyclic photophosphorylation?

A

ATP can be produced by electrons that take a cyclic pathway and are recycled back into the chlorophyll a in PSI.

33
Q

What is non-cyclic photophosphorylation?

A

ATP can be produced by electrons that take a linear pathway from water through PSII and PSI to NADP, which they then reduce.

34
Q

Describe cyclic photophosphorylation in detail.

A
  • PSI absorbs photons that excite electrons in the chlorophyll a molecules in its reaction centre.
  • The electrons are emitted and picked up by an electron acceptor, which passes them down a chain of electron carriers back to the PSI.
  • The energy released as they’re passed down the electron transport chain phosphorylates ADP to ATP.
35
Q

Describe non-cyclic photophosphorylation in detail.

A
  • electrons from PSI are transferred from the electron acceptors to oxidise NADP in the stroma, which protons from the photolysis of water reduce
  • the electrons are not returned to PSI so the chlorophyll is left with a positive charge.
  • the positive charge is neutralised by electrons from PSII which have been excited to a higher energy level by the absorption of light, picked up by an electron acceptor and passed down the electron transport chain to the PSI.
  • the electrons passage down the electron transport chain makes energy available for the phosphorylation of ADP to ATP.
  • the chlorophyll in PSII is left with a positive charge and is neutralised by the electrons released in the photolysis of water.
36
Q

Define photolysis.

A

The splitting of water molecules by light producing hydrogen ions, electrons and oxygen.

37
Q

Where does photolysis occur and why?

A

In the thylakoid spaces water molecules absorb light which indirectly causes them to dissociate into hydrogen, oxygen and electrons.

38
Q

Which stage of photosynthesis does non-cyclic photophosphorylation and cyclic photophosphorylation occur in?

A

the light dependent stage of photosynthesis

39
Q

What is the equation for the photolysis of water?

A

H2O → 2H^+ + 2e^- + 1/2O2

40
Q

What is photolysis enhanced by?

A

A protein complex in PSII, which is the only known enzyme that causes water to be oxidised.

41
Q

In photolysis where do each of the products go?

A
  • The electrons go to PSII to replace those lost to PSI
  • The protons from water and the electrons from PSI reduce NADP
  • Oxygen diffuses out of the chloroplast and cell, out through the stroma as a waste product.
42
Q

How is the oxygen plants released produced?

A

By the photolysis of water.

43
Q

Describe the passage of protons in the light dependent stage of photosynthesis.

A
  • electrons pass through the proton pump in the thylakoid membrane providing energy to pump protons from the stroma into the thylakoid space.
  • the protons join H^+ ions from the photolysis of water accumulating so that an electrochemical gradient is created- a source of potential energy
  • chemiosmosis then occurs- H^+ ions diffuse down their electrochemical gradient, through ATP synthetase in the thylakoid membrane into the stroma
  • this makes the energy from derived from light available as when they pass through ADP is phosphorylated to ATP.
  • Once in the stroma H^+ ions are passed to oxidised NADP reducing it.
  • The removal of H^+ ions in conjugation with the proton pump, contributes to maintaining the proton gradient across the thylakoid membrane.
44
Q

What is the Z-scheme?

A

The pathway taken by electrons in non-cyclic photophosphorylation.

45
Q

What is the equation for the reduction of NADP?

A

NADP + 2H^+ + e^- → reduced NADP

46
Q

What three factors maintain the proton gradient between the thylakoid space and stroma?

A
  • the proton pump associated with the electron transport chain pushing protons into the thylakoid space
  • the photolysis of water in the thylakoid space
  • the removal of protons from the stroma reducing NADP
47
Q

What is the overall equation for the light-dependent stage of photosynthesis?

A

NADP + H2O + 2ADP + 2Pi → reduced NADP + 1/2O2 + 2H2O + 2ATP

the 2H2O and 2ATP come from the condensation of 2ADP + 2Pi

48
Q

What are the similarities between cyclic and non-cyclic photophosphorylation?

A
  • PSI

- ATP production

49
Q

What are the differences between cyclic and non-cyclic photophosphorylation?

A
  • non-cyclic photophosphorylation uses PSII, but cyclic photophosphorylation doesn’t
  • the chlorophyll at the reaction centre in non-cyclic photophosphorylation is P680, but P700 for cyclic photophosphorylation
  • non-cyclic photophosphorylation is linear, but cyclic photophosphorylation is cyclic
  • non-cyclic photophosphorylation produces oxygen
  • non-cyclic photophosphorylation involves the reduction of NADP
  • non-cyclic photophosphorylation involves the photolysis of water
  • cyclic photophosphorylation is in all photosynthetic organisms, non-cyclic photophosphorylation is in plants, algae and cyanobacteria
50
Q

How does the light independent stage of photosynthesis relate to the light dependent stage?

A

It uses the products of the light dependent stage:

  • ATP is an energy source
  • reduced NADP is the source of the reducing power- reducing carbon dioxide
51
Q

Describe the Calvin cycle.

A
  • ribulose bisphosphate (5C) (RuBP) combines with carbon dioxide, catalysed by the enzyme rubisco
  • an unstable six carbon compound is formed
  • this immediately splits into two molecules of glycerate-3-phosphate (3C) (GP)
  • GP is reduced to triode phosphate by reduced NADP- this requires energy which is provided by ATP made in the light dependent stage
  • triose phosphate is the first carbohydrate made in photosynthesis
  • NADP is reformed
  • some triose phosphate is converted to glucose phosphate and then into starch by condensation
  • most triose phosphate goes through a series of reactions that regenerates RUBP so that the cycle can continue- ATP from the light dependent stage provides energy for this to occur.
52
Q

What enzyme catalyses the reaction of RuBP with carbon dioxide?

A

ribulose bisphosphate carboxylase- AKA rubisco

53
Q

Explain how the Calvin cycle was discovered.

A

pg 30 second year textbook

54
Q

How are carbohydrates produced within plants.

A
  • they’re produced from the triose phosphate
  • the first hexose made is fructose phosphate, which can be converted to glucose and combined with glucose to make sucrose for transport around a plant
  • the a-glucose molecules may be converted into starch for storage or B-glucose which is polymerised into cellulose for cell walls.
55
Q

How are fats produced within plants.

A
  • acetyl coenzyme A (AcCoA) can be synthesised from glycerate-3-phosphate in the calvin cycle and converted into fatty acids
  • triose phosphate can be converted directly into glycerol.
  • Fatty acids and glycerol undergo condensation reactions to form triglycerides
56
Q

How are proteins produced within plants.

A
  • glycerate-3-phosphate from the Calvin cycle can be converted into amino acids for protein synthesis
  • the amino acid group is derived from NH4^+ ions made from nitrate ions taken in at the roots and transported throughout the plant

A Level Biology (10 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions