17.3 Photosynthesis Flashcards
(80 cards)
1
Q
What is photosynthesis?
A
The process in which energy in the form of light from the sun, is used to build large complex organic molecules, such as glucose.
2
Q
What happens in photosynthesis?
2 points
A
- light energy is transformed into chemical energy.
- Trapped in the bonds of the complex organic molecules produced.
3
Q
What are autotrophic organisms?
A
Organisms that can photosynthesis.
4
Q
How do heterotrophs obtain organic molecules?
A
They obtain complex organic molecules by eating other autotrophic and heterotrophic organisms.
5
Q
How are the network of membranes present in chloroplasts suitable for their role?
2 points
A
- Provide large surface area
- To maximise absorption of light essential for the first set of photosynthesis.
6
Q
In chloroplast what is light absorbed by and where is it found?
2 points
A
- Chlorophyll (complex of pigments)
- Embedded within thylakoid membranes.
7
Q
What is the stroma?
A
The site of many chemical reactions resulting in the formation of complex organic molecules.
8
Q
What do pigment molecules do?
A
Absorb specific wavelengths (colours) of light and reflect others.
9
Q
Why do different pigments have different colours?
A
Different pigments absorb and reflect different wavelengths of light.
10
Q
What is the primary pigment in photosynthesis?
A
Chlorophyll a
11
Q
What does chlorophyll absorb and reflect?
A
- absorbs red and blue light.
- reflects green light.
12
Q
Why are there different shades and colours of leaves?
A
-Different combination of pigments.
13
Q
Where are other pigments(accessory pigments) other than chlorophyll a ?
A
-Chlorophyll b, carotenoids and xanthophyll are embedded in thylakoid membranes.
14
Q
What is light harvesting system also known as?
A
Antennae complex
15
Q
What is the role of light harvesting system?
2 points
A
- Absorb or harvest light energy.
- of different wavelengths, and transfer quickly and efficiently to reaction centre.
16
Q
Where is chlorophyll a located?
A
Reaction centre
17
Q
What is the reaction centre primary reaction centre?
A
Where the reactions involved in photosynthesis take place.
18
Q
What forms light harvesting systems?
A
Pigments like, carotenoids,xanthophylls, chlorophyll b and proteins.
19
Q
What is the photo system? And what structure is it?
A
What the light harvesting system and reaction centre is collectively known as.
Funnel-shaped
20
Q
What is a feature of photo systems that-maximises absorption of light?
A
The reaction centre is surrounded by the light harvesting system.
21
Q
What is chromatography used for in photosynthesis?
A
To separate different pigments in plant extracts.
22
Q
What is the mobile phase?
A
The solution containing a mixture of pigments.
23
Q
What is the stationary phase?
A
A thin layer of silica gel applied to glass.
24
Q
Due to the pigment moving at different rates what happens?
A
This results in the pigments being separated, as they move through silica gel.
25
What is the retention value equation?
Distance travelled by component./distance travelled by solvent.
26
List the apparatus you would use, and outline the process you would follow to separate a mixture of plant pigments.
9 points
- Small strip of TLC plate.
- Grind leaves with organic solvent(Propanone).
- Apply drop of extract to TLC near to one end.
- Repeat until concentrated spot produced.
- Place TLC strip in test tube.
- Put solvent into test tube, so level of solvent below spot.
- Ensure strip not touching sides of tube.
- Leave solvent to run up strip
- Remove TLC strip before solvent reaches top of strip.
27
Describe what happens in light dependent stage in photosynthesis?
2 points
- Energy from sunlight is absorbed and used to form ATP.
| - Hydrogen from water is used to reduce coenzyme NADP to reduced NADP.
28
Describe what happens in light independent stage?
-Hydrogen from reduced NADP and CO2, used to build organic molecules (glucose, lipids, amino acids).
29
What supplies energy for light independent reaction?
ATP
30
Which photo system absorbs light at higher wavelength?
2 points
- Photosystem 1(700nm)
| - Whereas for photosystem 2 it’s (680nm)
31
What happens first at PS2?
3 points
- The light absorbed excites electrons at the reaction centre of photo systems.
- The excited electrons are released from reaction centre of PS2 and are passed to an electron transport chain.
- ATP produced by process of chemiosmosis.
32
What replaces electrons lost from photosystem 2?
Replaced from photolysis of water molecules, broken down using energy from sun. (Chapter 17.4)
33
What happens in PS1
2 points
- Excited electrons released from reaction centre and passed to another electron transport chain.
- ATP is again produced by chemiosmosis.
34
What replaces electrons lost from PSI?
The electrons that have just traveled along the first electron transport chain, after being released from PS11.
35
What happens to the electrons leaving the electron transport chain following PS1?
2 points
- They are accepted along with a hydrogen by the coenzyme NADP.
- Forming reduced NADP.
36
What is the need for reduced NADP?
2 points
- Provides hydrogen/reducing power in production of organic molecules. (E.g glucose)
- In light independent stage
37
What is photolysis?
When water is split into hydrogen ions, electrons and oxygen molecules using energy from the sun.
38
What catalyses photolysis the breakdown of water?
The oxygen-evolving complex present in PS2.
39
Photolysis reaction equation?
H20= 2H+ + 2e- + 1/2 O2
40
Why is water along with light and CO2 a raw material of photosynthesis?
The electrons released from photolysis replaces electrons lost from reaction centre in PS2.
41
What is the byproduct of photolysis?
Oxygen gas
42
What happens to the protons produced in photolysis?
4 points
- Protons released into lumen of thylakoids increasing concentration along membranes.
- They move back through membrane down concentration gradient and electrochemical gradient.
- This drives formation of more ATP.
- Once hydrogen ions return to stroma , they combine with NADP and an electron from PS1 to form reduced NADP.
43
Why is this process useful? Other than the production of reduced NADP.
2 points
- Removes hydrogen ions from stroma.
| - Helps to maintain the proton gradient across thylakoid membranes.
44
Describe cyclic photophosphorylation in PS1.
3 points
- Electrons leaving transport chain after PS1 can be returned to PS1.
- Instead of being used to form reduced NADP.
- This means PS1 can still lead to production of ATP, without any electrons being supplied from PS2.
45
Where does light independent stage of photosynthesis take place?
-In stroma of chloroplast.
46
What is the raw material used in light independent stage of photosynthesis? And what else from products of light dependent stage is required?
3 points
- Co2
- Reduced NADP
- ATP
47
Describe what happens in Calvin cycle concisely?
2 points
-Organic molecules like glucose produced.
In a series of reactions collectively known as Calvin cycle.
48
What are the 3 stages of the Calvin cycle?
- Fixation-Co2 fixed(Incorporated into organic molecule)
- Reduced-GP to To by addition of hydrogen from reduced NADP, using energy from ATP.
- Regeneration-RuBp regenerated from recycled TP.
49
How does CO2 enter the stroma?
- Enters intercellular spaces within spongy mesophyll , of leaves by diffusion.
- From atmosphere through stomata.
- It diffuses into cells, and into the stroma of chloroplast.
50
What happens in fixation?
- Co2 combines with 5-carbon molecule(Ribulose biphosphate).
- Carbon is fixed which means incorporated into organic molecule.
- Unstable 6 carbon intermediate produced.
51
What catalyses fixation?
- Ribulose bisphosphate carboxylasee (RuBIsCo).
| - Unstable 6 carbon intermediate produced.
52
Why is RuBIsCo seen as inefficient? (The most abundant enzyme and is key enzyme of photosynthesis.)
- Competitively inhibited by oxygen.
| - So a lot needed to carry out photosynthesis successfully.
53
How is GP produced?
- Unstable 6-carbon intermediate formed immediately breaks down.
- Forming GPx2 molecules (glycerate 3-phosphate) 2 3 carbon molecules.
54
What happens in reduction?
- GP reduced into another 3-carbon molecule TP.
| - Using hydrogen atom from reduced NADP and energy supplied by ATP.
55
What do you know about triose phosphate?
- 3 carbon sugar
- Majority recycled to regenerate RuBp so Calvin cycle can continue.
- Starting point for synthesis of many complex biological molecules.
56
What happens in regeneration of RuBp?
- For one glucose molecule to be produced 6CO2 molecules have to enter Calvin cycle,so full turns of cycle.
- 2 TP molecules removed to make glucose molecule.
-10 TP molecules used to regenerate six RuBp.
(Used in 6 turns of cycle.)
-Energy supplies by ATP.
57
Explain why photorespiration is not something commercial producers would encourage?
- less carbon fixed
- Less Organic molecules synthesised.
- Reduced yield
58
Suggest why plants evolved with such important enzyme RuBisCo vein inhibited by oxygen?
- Photosynthesis produces oxygen.
| - No oxygen in atmosphere when plants begun to evolve.
59
Describe photorespiration?
- Low humidity+high temperature= high transpiration(too much water lost.)
- Stomata closes and photosynthesis still happens.
- O2 produced and co2 concentrations decrease.
- O2 is competitive inhibitor of RuBIsCo producing phosphoglycolate.
- Phosphoglycolate- toxic 2-carbon molecule, converted into other organic molecule, energy from ATP needed.
- 25 percent of products of Calvin cycle lost in photorespiration.
60
Define photophosphorylation?
- Synthesis of ATP./Addition of phosphate to ADP.
| - Using energy from light.
61
Explain why photosynthesis stops when pants exposed to green light only?
- Green light reflected.
- No energy for light independent stage.
- No ATP and reduced NADP for light independent stage.
62
What is meant by the term fixation?
- Inorganic carbon
| - Added to organic molecule.
63
Where does light independent stage of photosynthesis take place?
-In stroma of chloroplast.
64
What is the raw material used in light independent stage of photosynthesis? And what else from products of light dependent stage is required?
3 points
- Co2
- Reduced NADP
- ATP
65
Describe what happens in Calvin cycle concisely?
2 points
-Organic molecules like glucose produced.
In a series of reactions collectively known as Calvin cycle.
66
What are the 3 stages of the Calvin cycle?
- Fixation-Co2 fixed(Incorporated into organic molecule)
- Reduced-GP to To by addition of hydrogen from reduced NADP, using energy from ATP.
- Regeneration-RuBp regenerated from recycled TP.
67
How does CO2 enter the stroma?
- Enters intercellular spaces within spongy mesophyll , of leaves by diffusion.
- From atmosphere through stomata.
- It diffuses into cells, and into the stroma of chloroplast.
68
What happens in fixation?
- Co2 combines with 5-carbon molecule(Ribulose biphosphate).
- Carbon is fixed which means incorporated into organic molecule.
- Unstable 6 carbon intermediate produced.
69
What catalyses fixation?
- Ribulose bisphosphate carboxylasee (RuBIsCo).
| - Unstable 6 carbon intermediate produced.
70
Why is RuBIsCo seen as inefficient? (The most abundant enzyme and is key enzyme of photosynthesis.)
- Competitively inhibited by oxygen.
| - So a lot needed to carry out photosynthesis successfully.
71
How is GP produced?
- Unstable 6-carbon intermediate formed immediately breaks down.
- Forming GPx2 molecules (glycerate 3-phosphate) 2 3 carbon molecules.
72
What happens in reduction?
- GP reduced into another 3-carbon molecule TP.
| - Using hydrogen atom from reduced NADP and energy supplied by ATP.
73
What do you know about triose phosphate?
- 3 carbon sugar
- Majority recycled to regenerate RuBp so Calvin cycle can continue.
- Starting point for synthesis of many complex biological molecules.
74
What happens in regeneration of RuBp?
- For one glucose molecule to be produced 6CO2 molecules have to enter Calvin cycle,so full turns of cycle.
- 2 TP molecules removed to make glucose molecule.
-10 TP molecules used to regenerate six RuBp.
(Used in 6 turns of cycle.)
-Energy supplies by ATP.
75
Explain why photorespiration is not something commercial producers would encourage?
- less carbon fixed
- Less Organic molecules synthesised.
- Reduced yield
76
Suggest why plants evolved with such important enzyme RuBisCo vein inhibited by oxygen?
- Photosynthesis produces oxygen.
| - No oxygen in atmosphere when plants begun to evolve.
77
Describe photorespiration?
- Low humidity+high temperature= high transpiration(too much water lost.)
- Stomata closes and photosynthesis still happens.
- O2 produced and co2 concentrations decrease.
- O2 is competitive inhibitor of RuBIsCo producing phosphoglycolate.
- Phosphoglycolate- toxic 2-carbon molecule, converted into other organic molecule, energy from ATP needed.
- 25 percent of products of Calvin cycle lost in photorespiration.
78
Define photophosphorylation?
- Synthesis of ATP./Addition of phosphate to ADP.
| - Using energy from light.
79
Explain why photosynthesis stops when pants exposed to green light only?
- Green light reflected.
- No energy for light independent stage.
- No ATP and reduced NADP for light independent stage.
80
What is meant by the term fixation?
- Inorganic carbon
| - Added to organic molecule.
