Photosynthesis 5.6 Flashcards
1
Q
What is photophosphorylation? LD
A
Photophosphorylation id the generation of ATP using light energy from DP and Pi. It can be cyclic or non cyclic
2
Q
What are the two stages of photosynthesis?
A
Photosynthesis is the light dependant stage and then the light independent
3
Q
What are the 2 products of non cyclic photophosphorylation? LD
A
Non cyclic produces ATP and reduced NADP
4
Q
What is photolysis? LD
A
Photolysis is the splitting of water using light energy.
H2O —– 1/2 O2 + 2H+ +2e-
5
Q
What causes ATP synthase to turn? LD
A
ATP synthase turns as hydrogen ions diffuse through it
6
Q
What does the turning of ATP synthase do? LD
A
When ATP synthase turns it causes ADP and Pi to combine and create ATP
7
Q
What do the electron carriers have in? LD
A
The electron carriers contain iron 3+
8
Q
What happens to the electron carriers as electron pass in and out? LD
A
The electron carriers contain iron 3+. When electrons enter them they are reduced into iron 2+ and then when the electrons leave again they are oxidised back to iron 3+
9
Q
What is the energy released by movement of electrons used for? LD
A
Electrons passing through the electron carriers realises energy and this is used to pump hydrogen across the thylakoid membrane into the thylakoid lumen
10
Q
What does hydrogen ions getting pumped into the thylakoid lumen do? LD
A
When hydrogen ions are pumped into the thylakoid lumen it builds up a hydrogen ion gradient. Eventually as they accumulate they diffuse through ATP synthase
11
Q
What happens when electrons pass down electron carriers? LD
A
When electrons are passed down electron carriers they release energy
12
Q
What is ferredoxin? LD
A
Ferredoxin is a protein-iron-sulphur complex that accepts electrons and passes them to NADP in the stroma
13
Q
How do electrons get to the NADP in the stroma? LD
A
Electron get to NADP in the stroma by ferredoxin
14
Q
What order are the photosystems in? LD
A
First is photosystem 2 and then photosystem 1
15
Q
Briefly outline non cyclic photophosphorylation LD
A
Non cyclic photophosphorylation:
- Light energy excites 2 e- in PS2
- Electrons get passed down electron carriers which releases energy (reduces and oxidises). Electrons are replaced by those from photolysis
- energy released pumps H+ ions into thylakoid lumen , building up a proton gradient
- electron reaches ps1 and gets excited by light energy
- electrons pass to ferredoxin and then to the NADP in stroma
- H+ diffuse through ATP synthase, turning it forming ATP from ADP and Pi
- NADP reduced by 2 electron sand 2 hydrogen ions by NADP reductase
16
Q
How is NADP reduced? LD
A
NADP is reduced by adding 2 electrons and 2 hydrogen ions. NADP reductase catalyses this
17
Q
How are electrons in either photosystem 1 or 2 excited? LD
A
Electrons in photosystem 1 or 2 are excited by light energy
18
Q
What is the Z scheme? LD
A
The z scheme is a sketch of the pathways of enzyme and component of photophosphorylation against a Y axis measuring the energy of electrons at every stage
19
Q
What is cyclic photophosphorylation? LD
A
Cyclic photophosphorylation is where electrons are excited at photosystem 1 then back to the electron carrier chain. It only makes ATP and only uses photosystem 1
20
Q
What are the differences between non cyclic and cyclic phosphorylation? LD
A
cyclic photophosphorylation:
- only uses photosystem 1, non uses both
- ATP is the only product, non also makes reduced NADP
- no photolysis
21
Q
What cells is cyclic photophosphorylation used by? LD
A
Guard cells only have photosystem 1 so only make ATP. They use this ATP to actively move potassium ions into the guard cells, reducing their water potential. So water then ,moves in by osmosis causing the cells to swell until they push apart and therefore open the stoma
22
Q
What is the brief passage of electrons in the light dependent stage?
A
Photosystem 2 Electron carrier system photosystem 1 ferredoxin NADP reductase
23
Q
At what stage of photosynthesis does cyclic and non cyclic photophosphorylation occur?
A
These occur at the light dependent stage
24
Q
Where in photophosphorylation does energy get released and how is it used? LD
A
Energy I released from movement of electrons along the electron carrier chain. It is used to pump hydrogen ions into the thylakoid lumen, building a gradient until they diffuse into the stroma via ATP synthase to generate ATP production
25
Where does the reduction of NADP occur? LD
Reduction of NADP occurs in the stroma
26
Where does the 2 electrons and 2 hydrogen ions come from in the reduction of NADP? LD
The 2 electron come from the ferredoxin
| The 2 hydrogen ions come from photolysis of water
27
Where does the light independent stage happen?
The light independent stage occurs in the stroma of chloroplasts
28
What happens in the light independent stage?
In the light independent stage carbon dioxide gets converted to organic compounds in the calvin cycle
29
How does CO2 enter the stroma? LI
CO2 comes through the stoma and then diffuse into the spongy mesophyll cells then into a palisade cell where it enters the stroma of the chloroplasts
30
What does TP stand for? LI
TP= triose phosphate
31
What does GP stand for? LI
GP = glycerate 3 phosphate
32
What does RuBP stand for? LI
RuBP = ribulose bisphosphate
33
What is the CO2 concentration like in the stroma? Why is this important? LI
In the stroma CO2 concentration is kept low as it gets fixed in the celvin cycle. This means there is a bug concentration gradient outside and inside the stroma meaning CO2 keeps diffusing in enabling the calvin cycle to continue
34
What time conditions does the light independent stage happen in?
The light independent stage only happens in daylight
35
Why would the light independent stage cease without day light?
Despite being light independent it would cease without day light because it needs ATP which is made in the light dependent stage
36
How many turns does the calvin cycle need to do? Why? LI
The calvin cycle needs to turn 6 times in order to make the 2 TP needed to make glucose and the 10 needed to go back into RuBP production
37
Overall how many TP are needed to be produced? LI
12 TP are needed as 10 go to RuBP and 2 into the production of glucose
38
How many carbons are in:
- TP
- GP
- RuBP
- CO2
- intermediate product
```
TP = 3C
GP = 3C
RuBP = 5C
CO2 = 1C
intermediate product = 6C
```
39
What are the uses of TP? LI
uses of TP:
- glucose ---- starch and cellulose
- amino acids
- glycerol
- fatty acids
40
Outline the calvin cycle LI?
Calvin Cycle:
1. CO2 combines with RuBP catalysed by RuBisCO
2. 6C intermediate compound forms because the RuBP is carboxylated and immediately breaks down
3. 2 GP (3C) are formed
4. 2 ATP broken down to ADP and Pi +2 reduced NADP becomes 2 NADP
5. GP reduced (by the hydrogen from reduced NADP) into 2 TP (3C)
6. some TP go into synthesising organic compounds
7. Regeneration of RuBP by some TP requires phosphates so ATP is used breaking it down to ADP and Pi
41
Why does reduced NADP get turned back to NADP? LI
When reduced NADP gets turned back to NADP it loses hydrogen ions and these hydrogen ions are needed to turn GP into TP as it needs to be reduced
42
How many points does ATP get broken down in the Calvin cycle? LI
ATP is broken down into ADP and Pi :
- Turning GP into TP
- Turning TP to RuBP to give the reaction phosphates
43
In plants what is the glucose turned into from TP? LI
Glucose is used for starch and cellulose production
44
Why does the light independent stage only occur in day light?
In daylight:
- ATP and reduced NADP made in light
- light dependent stage raises the stroma pH as H+ get pumped out of it, this pH is the optimum for RuBisCO
- concentration of Mg2+ increases in stroma and these act as co factors for RuBisCO, activating it by attaching to its active site
- ferredoxin gets reduced in the light dependent stage and this ferredoxin activates enzymes in Calvin cycle
45
What happens to magnesium ions in daylight? LI
magnesium ion concentration increases in the stroma in daylight and these act as cofactors to activate RubisCO by attaching to it active site.
46
Why is it important in light independent stage that stroma pH increases?
In the light dependent stage hydrogen ions are pumped out of stroma. This raises pH to 8 which is the optimum temperature for RubisCO, it works best in these conditions
47
What is ferredoxins role in the light independent stage?
Ferredoxin activates enzymes in the calvin cycle.
48
How many ATP (at separate points) and reduced NADP are used in one turn of the calvin cycle?
- 2 ATP broken down into 2 ADP and Pi
- 2 reduced NADP into 2 NADP
- 1 ATP into 1 ADP and Pi
49
What is the general equation for photosynthesis?
Photosynthesis =
| 6CO2 + 6H2O+ ENERGY -----C6H1206 + 6O2
50
What is photosynthesis?
Photosynthesis is a physiological process that converts light energy from sunlight to chemical energy
51
What can organisms use this chemical energy from photosynthesis for?
Chemical energy is used by organisms to synthesise large molecules which form the building blocks of organic cells
52
What is autotrophic nutrition?
Autotrophic nutrition is where organisms make their own nutrients
53
What is a photon?
A photon is a particle of energy
54
What are organisms called when they can photosynthesise?
Organisms that can photosynthesise are called photoautotrophs (because they use light as an energy source or autotrophic nutrition). Also known as producers
55
Is carbon fixation endothermic or exothermic?
Carbon fixation is endothermic as it requires energy
56
What are heterotrophs?
Heterotrophs obtain energy by digesting complex organic molecules of food to smaller molecules that they can use as respiratory substrates
57
Is respiration endothermic or exothermic?
Respiration is exothermic as it releases chemical energy
58
How do photosynthesis and respiration interrelate?
The products of one are the raw materials for the other. Aerobic respiration removes oxygen from the atmosphere and photosynthesis adds oxygen to the atmosphere
59
What is the general equation for respiration?
Respiration=
| C6H12O6 + 6O2 ----- 6H2O + 6CO2 + ENERGY
60
Difference in when respiration and photosynthesis occur?
Plants respire all the time but only photosynthesise during day light
61
What is the compensation point?
Compensation point is where photosynthesis and respiration occur at the same rate so that there is no net loss or net gain of carbohydrate
62
What is the compensation period?
Compensation period is the time a plant takes to reach the compensation point
63
What is the difference between compensation point and period in sun versus shade plants?
Shade plants reach their compensation point sooner so have a shorter compensation period because they utilise light at a lower intensity
Sun plants take longer to reach compensation point as they require a higher light intensity take longer before able to photosynthesise well
64
Does photosynthetic bacteria have chloroplasts?
Photosynthetic bacteria do not have chloroplasts
65
Discuss the membrane of chloroplasts?
Chloroplasts have an envelope made up of two membranes; an inner and an outer. Between these two there is an intermembrane space. The outer membrane is highly permeable. They have a third membrane called the thylakoid membrane which is folded inside
66
What are the two distinct regions within the chloroplast s?
In chloroplasts there is:
- The stroma (fluid filled matrix)
- grana consisting of stacks of thylakoids
67
How are thylakoids from different grana connected?
A thylakoid of one grana may be connected to a thylakoid of a different grana by intergranal lamellae.
68
What is the single for grana?
Grana is plural for granum
69
How is the thylakoid membrane folded?
The thylakoid membrane is folded into flattened disc like sacs called thylakoids
70
What is a stack of thylakoids called?
A stack of thylakoids is a granum
71
What is the inside of a thylakoid referred to?
The inside of a thylakoid is called the thylakoid lumen or thylakoid space
72
Why is it good that the grana are surrounded by stroma ?
Grana are surrounded by stroma so the products of the light dependent stage can easily pass into the stroma for the light independent stage
73
Why is there a huge surface area in chloroplasts/by chloroplasts?
There are many grana in every chloroplast and many chloroplasts in each photosynthetic cell making a huge surface area for:
- distribution of photosystems that contain photosynthetic pigments
- electron carriers and ATP synthase enzymes needed to convert light energy into ATP
74
What is in the stroma?
The stroma contains
- enzymes for LI stage
- starch grains
- oil droplets
- small ribosomes
- DNA
75
What does the loop of DNA in the stroma of chloroplasts do?
This loop of DNA codes for some of the proteins needed for photosynthesis. These are assembled at chloroplast ribosomes
76
What are photosystems?
Photosystems are funnel shaped structures embedded in the thylakoid membrane held by proteins. they contain photosynthetic pigments. They have a primary reaction centre consisting of p680 or p700 chlorophyll
77
What are photosynthetic pigments?
Photosynthetic pigments absorb light of a particular wavelength and reflects another colour which is what we see.
78
What are the two types of chlorophyll a and where are they found?
Chlorophyll A
- p700 found in photosystem 1
- p680 found din photosystem 2
79
What colour do they absorb and reflect?
- chlorophyll a
- chlorophyll b
Chlorophyll a absorbs red and some blue and reflect blue green
Chlorophyll b absorbs 400-500nm and 640nm and it reflects yellow green
80
What are 2 accessory pigments?
Accessory pigments:
- carotenoids reflect orange and yellow and absorb 400-500nm
- Xanthrophylls reflect yellow and absorb 375nm-550nm
81
discuss the term limiting factor?
Limiting factors are present tin the least favourable amounts.
The rate of a metabolic process that depends on a number of factors, is limited by he factor present in the least favourable level
82
What happens when you increase/decrease light intensity on rate of photosynthesis?
Increasing light intensity = faster rate of photosynthesis
| Decreasing light intensity = slower rate of photosynthesis
83
Why does light affect rate of photosynthesis?
Light affects the rate of photosynthesis because the first stage of photosynthesis is dependent on light and therefore the second stage is also then affected because it needs products made in the first stage to continue
84
How does light intensity affect stoma and what does this do?
Light causes stoma to open so CO2 can diffuse in and transpiration can occur leading ti the uptake of water
85
What are the effects of having no/dim light on the calvin cycle?
```
Dim light on calvin cycle
No ATP or reduced NADP will be made in the light dependent stage so:
-no TP made as no ATP or reduced NADP
-accumulation of GP as not becoming TP
-No RuBP as no ATP
```
86
What are the effects of having bright light on the calvin cycle?
Bright light on the Calvin cycle
This means ATP and reduced NADP are being made in the light dependent stage so:
-high RuBP as there is ATP
-high TP as there is ATP and reduced NADP
-low GP as it gets made into TP
87
What is CO2 role in the calvin cycle?
In the calvin cycle CO2 gets fixed
88
What happens if CO2 concentrations fall below 0.01%?
If CO2 levels fall below 0.01% then RuBP cannot accept in and become GP so
- RuBP accumulates
- GP drops as no CO2
- TP drops as no GP
89
What happens if the temperature is 30 degrees or lower?
At 30 degrees or lower, assuming light intensity, water and carbon dioxide are sufficient then photosynthesis increases as temperature increases
90
What happens of the temperature raises above 30 degrees?
When the temperature is above 30 degrees growth rates reduce due to photo respiration.
Photo respiration is where oxygen competes with carbon dioxide to enter RuBisCOs active site, and it favours the oxygen.
-initial accumulation of RuBP then gradually declines
-Decrease in GP and TP
91
What happens when temperature is above 45 degrees?
When the temperature is above 45 degrees enzymes denature so rate of photosynthesis slows down
92
What are 3 reasons why water is important other than it being a reactant?
Waters importance:
- cooling effect on the plant
- maintains turgidity
- turgid guard cells keep stoma open for gaseous exchange
93
What are 3 effects when the plant does not have enough water? Including rate of photosynthesis
Not enough water:
- plasmolysis, flaccid tissues and wilting
- roots start to produce absicisic acid which causes stomata to close therefore reducing gaseous exchange
- Rate of photosynthesis reduces
94
What are two ways would could measure the rate of photosynthesis?
You can measure the rate of photosynthesis by:
- CO2 uptake
- O2 production
95
What are the limitations of measuring rate of photosynthesis with O2 production?
O2 production:
- Some of the oxygen will be used in respiration so the a mount you measure will be an underestimate
- Some nitrogen gas may be in what you collect
96
What equipment do you use to measure the oxygen production from the plant?
To measure oxygen production you use a photosynthometer (audus microburette)
97
What is a photosynthometer also known as?
A photosynthomenter is also known as an audus microburette
98
How do you set up the experiment for measuring oxygen production?
- thermometer
- elodea plant in pond water/sodium hydrogen carbonate solution
- water bath
- capillary tube with funneled end
- syringe attached to tubing to moVVe bubble
- scale/ruler to measure bubble
99
What happens in the experiment for oxygen production?
1. bubbles of gas collect at the funnel and goes up capillary tube
2. experimenter manipulates bubble, moving it with a syringe
3. measure the length of the bubble
4. work out the volume of gas ( length x pi r squared)
100
What are 4 things you have to do for an experiment?
- control variables like co2 concentrations, light
- write a plan
- write a prediction
- work out IV and DV
