5.1 Photosynthesis Flashcards
What do the genes in a chloroplast DNA code for
Photosynthetic enzymes
What is the name of the chloroplast cytoplasm
Stroma
What do the thylakoids contain
Chlorophyll
What is the name of the enzyme we need to know that’s involved in photosynthesis
Rubisco
What is the chemical GCSE equation for photosynthesis
6CO2 + 6H2O -> C6H12O6 + 6O2
What is the name of the 2 stages in photosynthesis
- Light dependent stage
- Light independent stage
Where does the light dependent stage occur
In the thylakoid membrane
Where do the light independent stage occur
In the stroma
What are the 2 things that the light dependent stage requires
- Light
- Chlorophyll
In the light dependent stage what does the photosynthetic pigment absorb
Energy
What is the reactant for the light dependent stage
Water
What is the photosynthetic product of the light dependent stage
Oxygen
During the light dependent stage, how does NADP become reduced
By the addition of the hydrogen that is released from the water
What is the chemical formula of reduced NADP
NADPH2
What is the reactant for the light independent stage
Carbon dioxide
What is the product from the light independent stage/ what is the name of the carbohydrate formed
CHO , triose phosphate
In terms of hydrogen, what is oxidation
Remove of hydrogen
In terms of hydrogen, what is reduction
The add of hydrogen
In the light dependent stage, what is oxidised
Water
In the light dependent stage, what is reduced
NADP
In the light independent stage, what is oxidised
Carbon dioxide
What is the overall equation in the light dependent stage
H2O + NADP -> NADPH2 + O2
If NADP is removed from the light dependent stage, will oxygen still be produced
NO
When light energy is absorbed by the chlorophyll, what does this excite
2 electrons
In the light dependent stage, what happens to the 2 excited electrons
They leave the chlorophyll and pass to an electron acceptor
What is the name of the process by which 2 electrons get excited and leave the chlorophyll
Photoionisation of chlorophyll
Once the excited electrons leave the chlorophyll what are they passed along
A series of electron carriers
What happens to the electrons in the light dependent stage as they pass along a series of electron carriers
They lose energy
What is the energy that is released from the electrons as they move along a series of electron carriers used to produce
ATP from ADP and Pi by chemiosmosis
What is the name of the process by which the energy that the electrons lose as they move along the series of electron carriers is used toe produced ATP from ADP and Pi
Chemiosmosis
What is the name of the process where a water molecule is split
Photolysis
What is the equation of photolysis of water
2H2O -> 4H+ + 4e- + O2
Where do the electrons that replace those that are lost from the chlorophyll come from
The photolysis of water
What is the name of the process where a water molecule splits
Photolysis of water
What is the photolysis of water equation
2H2O -> 4H+ + 4e- + O2
Where do the electrons that replace those lost from the chlorophyll come from
The photolysis of water
What are the protons produced from the photolysis of water used for
They reduce NADP
What is the by-product of water photolysis
Oxygen
Where do the electrons for reduction of NADP come from
The photoionisation of chlorophyll
Where do the protons for the reduction of NADP come from
The photolysis of water
In the chemiosmosis theory, what happens to the high energy electrons
They pass along a series of electron carriers
In the chemiosmosis theory, what happens to the high energy electrons as they pass along the series of electron carriers
They lose energy
In the chemiosmosis theory, what is the energy that is lost from the electrons used for
Used to pump protons, H+
In the chemiosmosis theory, where are the protons pumped from and where are they pumped to
Pumped from the stroma into the thylakoid space
After the protons are pumped into the thylakoid space in the chemiosmosis theory, what is produced and why
A concentration gradient is produced since the protons accumulate
Once a concentration gradient of protons has been established in the chemiosmosis theory, what happens to the protons
They diffuse back into the stroma via ATP synthase.
What provides the energy to form ATP from ADP and Pi
ATP synthase which is associated with the channel protein in the thylakoid membrane
What does the ATP synthase associated with the channel protein in chemiosmosis essentially act as
A molecular motor
How can the reduction of NADP be demostrated experimentally
Using an artificial hydrogen acceptor like DCPIP
What is DCPIP
An artificial hydrogen acceptor
What is the reaction called when the reduction of NADP is demostrated experimentally using an artificial hydrogen acceptor
Hill Reaction
What is the colour of oxidised DCPIP
Blue
What is the colour of reduced DCPIP
Colourless
What happens to DCPIP when it is added to a suspension of isolated chloroplasts
It’ll be reduced under certain conditions
In the Hill Reaction, what type of solution is added to all 4 test tubes
Cold, isotonic and buffered solution
In the Hill reaction, why does on test tube only contain chloroplasts and the solution but no DCPIP
To act as the colour standard
In the Hill reaction, what does the test tube with only the solution and DCPIP act as
The control because it has no chloroplasts inside - so it’s evidence that the reduction of DCPIP is down to chloroplasts being present
In the Hill reaction, why is one of the test tubes with chloroplasts, solution and DCPIP put in a dark space while the other test tube is put beneath a lamp
The light dependent reaction in the chloroplasts will only occur in the test tube under the lamp and without the light dependent reaction there is no reduction of NADP since no photoionisation nor photolysis of water so no reduction of DCPIP
In the Hill reaction, which on the 2 test tubes with chloroplasts, solution and DCPIP inside becomesc the colour of the test tube with only chloroplasts and solution
The test tube that was placed under light e.g. a lamp so the test tube where the light dependent reaction occured so NADP was reduced so DCPIP was also reduced
Explain how the chemicals which inhibit the decolourisation of DCPIP could slow the growth of weeds ( 2 marks)
- Less/ no ATP produced
- Less/ no NADPH2 produced
Where does the light independent reaction occur
In the stroma
What are the 4 requirements for the light independent reaction
- Carbon dioxide
- ATP
- NADPH2
- Rubisco
What are the 3 products of the light independent reaction
- Triose phosphate
- ADP and Pi
- NADP
What is the name of the cycle in the light independent reaction
Calvin cycle
How many carbons are in RuBP
5 carbons
What is added to the calvin cycle that reacts with RuBP
Carbon dioxide
What does RuBP and CO2 produce in the calvin cycle
GP (Glycerate-3-phosphate)
How many G-3-P molecules are produced from one RuBP molecule
2
What is the name of the enzyme in the calvin cycle
Rubisco
What type of reaction converts G-3-P into Triose phosphate
Reduction
When G-3-P is reduced into triose phosphate, what is oxidised
NADPH2 to NADP
When G-3-P is reduced into triose phosphate, what is needed and where is this provided from
Energy is needed from ATP being hydrolysed into ADP and Pi
What is needed to convert triose phosphate into RuBP
ATP
Why is ATP needed to convert triose phosphate into RuBP
Since the Pi phosphorylates the molecule - essentially add another phosphate group to the molecule to produce RuBP
What are the 3 molecules that the triose phosphate that left the cycle can be converted into
- Glucose
- Amino acids
- Glycerol and fatty acids
If 6 RuBP molecules are used in the cycle along with 6CO2, how many G-3-P are made
12
If 12 G-3-P molecules are produced, how many triose phosphate can be formed after the reduction
12
Of the 12 triose phosphate molecules made in the calvin cycle how many remain in the cycle
10 triose phosphates and get converts into RuBP
Of the 12 triose phosphate molecules produced, how many leave the cycle to be converted into biological molecules
2
What would happen to the concentration of G-3-P if the plant was placed in the dark
The concentration would increase but eventually flatten out
Why would the concentration of G-3-P increase if the plant was placed in the dark
Since RuBP and CO2 will still be able to form G-3-P however without the products from the light dependent reaction G-3-P cannot be reduced into triose phosphate so the concentration of G-3-P builds up
What happens to the concentration of RuBP if the plant was placed in the dark
The concentration will fall until it eventually reaches zero
Why does the RuBP concentration fall when the plant is placed in the dark
Since the RuBP is being used to make G-3-P and less RuBP is being made compared to what is being used to make other molecules since there is less triose phosphate so eventually the triose phosphate will run out so no more RuBP will be synthesised hence why the concentration will drop
State one measurement that could be taken to determine the rate of photosynthesis
Change in pH or the volume of oxygen produced
What is the explanation that explains why the factor on the x-axis is the limiting factor initally
As the x-axis factor increases so does the rate of photosynthesis and then when the graph plateus another factor becomes the limiting factor
Why can the rate of photosynthesis increase when carbon dioxide is leaving the plant instead of being absorbed
Since carbon dioxide is produced via aerobic respiration
When the temperature increases, why does the rate of photosynthesis increase
Since the kinetic energy increases so the enzymes involved in photosynthesis gain kinetic energy, so more enzyme-substrate complexes form
After the optimum temperature and the temperature still rises why does the rate of photosynthesis decreases
The enzymes for photosynthesis denature
Describe the role of thylakoid membranes in the synthesis of ATP
- The thylakoid membranes provide a large surface area for the attachment of chlorophyll electron carriers, and ATP synthase, maintaining ATP production
- The thylakoid membranes contain electron carrier that transfer electrons through a series of redox reactions, releaing energy
- Energy from the electron transfer chain is used to pump protons into the thylakoid lumen, /creating a proton gradient across the membrane
- Protons diffuse back into the stroma through ATP synthase, driving the phosphorylation of ADP to ATP
Explain the importance of the formation of ATP and NADH2 in the LDR
- ATP is used for the synthesis of carbohydrates in the Calvin cycle
- NADPH2 provides hydrogen for the reduction of G-3-P to triose phosphate in the Calvin cycle
- ATP provides the energy for this redox rea/ction and the energy needed to regenerate RuBP
Describe the light-independent reaction of photosynthesis (6 marks)
- Carbon dioxide
combines/reacts with ribulose
bisphosphate/RuBP; - Produces two glycerate (3-
)phosphate/GP using
(enzyme) Rubisco; - GP reduced to triose
phosphate; - Using reduced NADP;
- Using energy from ATP;
- Triose phosphate converted to
glucose/hexose/RuBP/ribulose
bisphosphate/named organic
substance;
