photosynthesis Flashcards
Describe the light dependent reaction
• Chlorophyll absorbs light energy & Excites electrons
• electrons removed (Oxidation of chlorophyll) via photoionisation;
• Electrons move along carriers/electron transport chain releasing energy (Series of REDOX reactions)
• Energy released (by electrons) used to form proton gradient;
• H+ ions move through ATP synthase;
• providing energy to join ADP and Pi to form ATP;
• Photolysis of water produces 2 protons, 2 electrons and ½ oxygen;
• NADP reduced by electrons / electrons and protons / hydrogen;
Describe the light independent reaction
• Carbon dioxide combines with ribulose bisphosphate/RuBP;
• Produces two glycerate (3-)phosphate/GP;
• GP reduced to triose phosphate;
• Using reduced NADP;
• Using energy from ATP;
• Triose phosphate converted to glucose/hexose/RuBP/ named organic substance;
ATP is produced in the light dependant reaction, suggest why this is not their (plants) only source of ATP.
• Plants don’t photosynthesis in the dark;
• Not all the parts of the plants photosynthesise;
• Plants require more ATP than is produced in the light dependant reaction;
• ATP used in Active Transport (accept other named processes)
Describe the effect of introducing a herbicide/inhibitor on the electron transport chain (4)
• Reduced transfer of protons across thylakoid membrane
OR
• Reduced chemiosmotic gradient/proton gradient across thylakoid membrane;
• (So) less ATP produced;
• (So) less reduced NADP produced;
• (So) light-independent reaction slows/stops
OR
• Less reduction of GP to triose phosphate;
Describe what happens during photoionisation in the light dependent reaction.
• Chlorophyll absorbs light
OR
Light excites/moves electrons in chlorophyll;
• Electron/s are lost
OR
(Chlorophyll) becomes positively charged;
Accept electrons go to electron transport/carrier chain for ‘electrons lost’.
When producing a chromatogram explain why the origin is marked using a pencil rather than ink.
• Ink and (leaf) pigments would mix
OR
• (With ink) origin/line in different position
OR
• (With pencil) origin/line in same position
OR
• (With pencil) origin/line still visible;
While making a chromatogram, describe the method used to separate the pigments after the solution of pigment had been applied to the origin.
Level of solvent below origin/line;
• Remove/stop before (solvent) reaches top/end;
Suggest and explain the advantage to plants of having different colour pigments in leaves.
• Absorb different/more wavelengths of light for photosynthesis;
ATP is useful in many biological processes. Explain why (5)
- Releases energy in small amounts
- Broken down in one step / single bond broken
- Immediate energy compound
- Phosphorylates
- Makes more reactive / lowers Ea
- Can be reformed / made again
Contrast the structures of ATP and a nucleotide found in DNA to give two differences (2)
- ATP has ribose sugar whereas DNA nucleotides have deoxyribose sugar
- ATP has 3 phosphate groups whereas DNA nucleotides have only 1 phosphate groups
- ATP nitrogen-containing base is always adenine whereas DNA nucleotide base can differ (adenine, thymine, guanine, cytosine)
Give two ways in which the hydrolysis of ATP is used in cells
(2)
- Active transport of Nat
- Phosphorylates other compound making them more reactive
- Releases small amounts of energy for protein synthesis
- DNA replication
- Secretion of enzyme / hormones
Where does the light-dependent reaction occur? (1)
Granum
Where does the light - independent reaction occur? (1)
Stroma
Name the two products of the light - dependent reaction that are required in the light - independent reaction? (2)
- ATP
- NADPH
What are the reactants and products of the light
- dependent reaction? (2)
- REACTANTS - Light, Water
- PRODUCTS - Oxygen, ATP, NADPH
