13.3 Photosynthesis Flashcards
What does ATP stand for?
Adenosine Triphosphate
What makes up ATP?
A ribose sugar
3 phosphate groups
Nitrogenous base (adenine)
Name the 2 uses of ATP
Provides energy for active transport/muscle contraction/protein synthesis
Phosphorylation
What its phosphorylation?
When a phosphate molecule binds to an enzyme to lower the activation energy and increase the reactivity by altering the tertiary structure
How is ATP formed?
via ADP and phosphate group (Pi)
Why is ATP easily broken?
The bond between the second and third phosphate group is easily broken and releases small amounts of energy
Why is ATP useful?
- Releases small amounts of energy
- Easily reformed
- Single step process
- Immediate release of energy
- Phosphorylates to make enzyme more reactive
Contrast the structure of ATP and DNA
DNA has a deoxyribose sugar whereas ATP has a ribose sugar
DNA has 1 phosphate molecule whereas ATP has 3
ATP always has adenine as its base whereas DNA either has cytosine, thymine, guanine or adenine
What does NADP stand for?
Nicotinamide Adenine Dinucleotide Phosphate
What does NADP act as?
Hydrogen acceptor
What is NADPH?
Reducing agent
What happens when NADPH loses a hydrogen?
Becomes oxidised to NADP
What is NADP?
Coenzyme
- molecule that binds to support the function of an enzyme
Name all the components of a chloroplast
Granum
Thylakoid
Thylakoid membrain
Stroma
Free DNA
70s ribosomes
Starch grains
Inner and outer membrane
What is the word equation for photosynthesis?
Carbon dioxide + water –> Glucose + oxygen
What is the number equation for photosynthesis?
6CO2 + 6H2O –> C6H12O6 + 6O2
What are the two stages of photosynthesis?
Light dependent reaction
Light independent reaction
Photoionisation definition
When light energy excites energy levels of electrons in chlorophyll
Photolysis definition
The splitting up of water with light to produce 2 protons, 2 electrons and 1/2 oxygen
Phosphorylation definition
Where does LDR take place?
In the thylakoid membrane
what does the LDR result in?
Production of ATP and NADPH
Describe the light dependent reaction
- Chlorophyll absorbs light energy via photoionisation
- Excites electrons to a higher energy level, the chlorophyll is oxidised
- The electrons travel down an electron transport chains, releasing energy
- Energy is released by the electrons used to form the proton gradient
- H+ ions diffuse through ATP synthase (photophosphorylation)
- This provides energy too join ADP and Pi, to form ATP
- Photolysis of the water produces 2 protons, 2 electrons and 1/2 oxygen molecules
- NADP reduced by electrons and protons
Photolysis equation
2H2O –> 2H+ + 2e- + 1/2O2
What are the two essential things needed for the LDR?
NADPH
ATP
Chemiosmotic theory definition
The movement of ions (protons) across a membrane down an electrochemical gradient (usually established through redox reactions and activation of proton pumps)
What does weed killer do?
Stop electrons being released from the chlorophyll
Less ATP
No reduced NADP can be formed
What does the use of fluorescence do?
Electron transport chain not available for excited electron
Electron cannot leave chlorophyll and lose energy via the electron transport chain
This releases energy as light or heat
In plants, ATP is produced in the LDR, suggest why this is not the plants only source of ATP?
Plants doing photosynthesise in the dark
Not all parts of the plant photosynthesise (roots)
Plants require more ATP than is produced in the LDR
ATP is used in active transport
Describe the effect of introducing a herbicide on the electron transport chain
Reduced transport of protons across thylakoid membrane
Reduced chemiosmotic gradient
Reduced ATP produced
Reduced NADP produced
Slower LDR
What are the three stages of the light independent reaction?
Carbon fixation
Reduction
Regeneration
Describe the light independent reaction
Carbon dioxide combines with RuBP with the enzyme ribisco to form 2 GP molecules. hey are reduced to two ribose phosphate molecules with the energ from ATP and reduced NADP. Some triose phosphate molecules are converted into amino acids, or starch or cellulose. Most triose phosphate molecules are regenerated into RuBP via the phosphate from AP
How is the Calvin cycle controlled?
Enzymes
Describe fixation in the Calvin cycle
RuBP acts as a carbon dioxide acceptor and is catalysed by the enzyme rubisco. he CO2 reacts with the RuBP to form two molecules of GP.
Describe reduction in the Calvin cycle
The two GP molecules are reduced to 2 triose phosphate molecules, this required NADP and the energy from ATP. Some of the triose phosphate molecules are converted into useful organic compounds - carbohydrates,amino acids and triglycerides
Describe the regeneration stage of the Calvin cycle
Most triose phosphate molecules are used to regenerate RuBP using phosphate from ATP
How is the chloroplast adapted to maximising the rate of photosynthesis in the stroma?
The chloroplast has its own DNA to transcribe and translate its own proteins needed in the light independent reaction
It also has a large surface area to allow as much light as possible to be absorbed, this increases the rate of the light dependent reaction and therefore photosynthesis.
What are the three factors affecting the rate of photosynthesis?
- Temperature
- Carbon dioxide concentration
- Light intensity and wavelength
