3.5.1 Photosynthesis, LDR and LIR (C11) Flashcards
Describe how NADP+ is reduced in the LDR of photosynthesis.
2e- from electron carrier protein (originally from chlorophyll) are gained.
H+ is gained from stroma.
What are the products of the light dependent reactions of photosynthesis?
ATP
NADPH (Reduced NADP)
Oxygen
Identify the labels.
Identify the labels.
Why is ATP sometimes referred ot as an immediate energy source of energy?
Because only one bond needs ot be broken to release energy.
ATP is rapidly resynthesised.
In biology what is meant by OXIDATION?
The loss of electrons
The loss of hydrogen
The gain of oxygen
For what are the products of the light dependent reactions used for?
NADPH and ATP are required in the light independent reacitons of photosynthesis (Calvin cycle)
Oxygen is used in respiraiton or exits the plant via the stomata.
Why does the plant need to carry out the respiration if the light dependent reactions produce ATP?
Not enough ATP is produced.
ATP is difficult to transport around the plant.
So ATP can be produced in the dark.
Not all plant cells contain chlorophyll
ATP is not a stable store of energy.
Identify the labels.
In biology, what is meant by REDUCTION?
The gain of electrons.
The gain of hydrogen.
The loss of oxygen.
Describe the Light Dependent Reactions of photosynthesis.
In photoionisation, light excites the electrons in chlorophyll II and they move to carrier proteins in the thylakoid membrane.
The electrons are replaced by the e- produced by splitting water (photolysis), which also produces oxygen and H+.
Electrons move along carrier proteins in a series of redox reactions losing energy as they go. This is used to pump H+ into the thylakoid space creating a chemiosmotic gradient.
H+ move down the gradient through ATP synthase during photophosphorylation producing ATP from ADP+Pi
The electrons are donated to chlorophyll I and more are excited by light, travelling along another ETC until they reduce NADP to NADPH with H+ from photolysis.
Identify the labels.
Identify the labels.
What does the diagram show?
The thylakoid membrane of a chloroplast.
Where the light dependent reactions of photosynthesis take place.
What is NADP?
A coenzyme/cofactor that works alongside an enzyme, in this case it is a hydrogen carrier and electron acceptor.
How can we measure the rate of the light dependent reactions of photosynthesis?
Measure the volume of oxygen produced.
Over time.
In the light-dependent reaction of photosynthesis, light energy generates ATP. Describe how. (5 marks)
- Light (energy) excites / raises energy level of electrons in chlorophyll;
- Electrons pass down electron transfer chain;
- (Electrons) reduce carriers / passage involves redox reactions;
- Electron transfer chain / role of chain associated with chloroplast
membranes / in thylakoids / grana; - Energy released / carriers at decreasing energy levels;
- ATP generated from ADP and phosphate / Pi / phosphorylation of ATP;
When investigating how light intensity affects plant growth what variables should you control?
temperature
concentration carbon dioxide
volume of water
concentation of ions in soil
pH of soil
Describe the light independent reaction
CO2 is fixed, combining with RuBP using the enzyme Rubisco
This produces two glycerate-3-phosphate (GP)
GP is reduced to Triose phosphate (TP)
Using energy from ATP and reduced NADP
TP can be regenerated to RuBP using energy from ATP,
1C from TP is converted into organic molecules e.g. glucose, amino acids, glycerol
How many carbon atoms in Ribulose Bisphosphate (RuBP)?
5
Name the enzyme that catalyses the fixation of carbon dioxde into RuBP to produce glycerate-3-phosphate.
Rubisco
How many turns of the calvin cycle take place to produce 1 molecule of glucose?
6
How many carbon atoms in glycerate-3-phosphate?
3
What are the products of every 6 turns of the carbon cycle?
1 x glucose molecule/carbon containing molecule
5 x RuBP
What are the products of the LIR
Organic compounds e.g. glucose, amino acids, lipids
RuBP (Ribulose Bisphosphate)
How many carbon atoms in triose phosphate?
3
Does the Calvin Cycle require light to function?
No
BUT
The reactions will stop eventually in the absence of light because essential ATP and NADPH from light reactions will run out.
During the light-independent reaction of photosynthesis, carbon dioxide is converted into organic substances. Describe how. (6 marks)
- Carbon dioxide combines with ribulose bisphosphate / RuBP;
- Produces two glycerate-3-phosphate / GP;
- GP reduced to triose phosphate / TP;
- Using reduced NADP; and…
- …Using energy from ATP;
- Triose phosphate converted to glucose / RuBP / ribulose bisphosphate
Heat stress decreases the LDR - why does this lead to a decrease in the LIDR?
Less ATP
Less reduced NADP
A decrease in the activity of the enzyme rubisco would limit photosynthesis - why?
Less carbon dioxide reacts with RuBP
so
Less GP
where is rubisco found?
stroma (of chloroplast)
