Photosynthesis Flashcards
What is ATP hydrolase?
Enzyme that hydrolyses the terminal high energy bond of ATP releasing Pi and energy
What is ATP synthase?
Enzyme that forms high-energy bond through condensation between Pi and ADP
ATP is useful in many biological processes. Explain why. (4)
- Releases energy in small/ manageable amounts
- Broken down in one step / single bond broken
- Immediate energy compound / makes energy available rapidly
- Phosphorylates / adds phosphate
- Makes (phosphorylated substances) more reactive / lowers activation energy
- Reformed / made again
Contrast the structures of ATP and a nucleotide found in DNA to give two differences (2)
1) ATP has ribose sugar BUT DNA nucleotides have deoxyribose sugars
2) ATP has three phosphate groups BUT DNA nucleotides have only one phosphate group
3) ATP nitrogen-containing base is always adenine BUT DNA nucleotide base can vary (adenine, guanine, cytoside or thymine)
Give two ways in which the hydrolysis of ATP is used in cells. (2)
- Active transport (using carrier proteins)
- Muscle contraction
- Protein synthesis (transcription and translation)
- DNA replication
- Secretion of enzyme / hormones (exocytosis)
Describe the light dependent reaction
1) Chlorophyll absorbs light energy & excites e-
2) e- removed via photoionisation
3) e- move along carriers/ e- transport chain releasing energy
4) energy released by e- used to form proton gradient
5) H+ ions move through ATP synthase
6) providing energy to join ADP + Pi to form ATP
7) photolysis of water produces 2 Protons+2e- +1/2 O2
8) NADP reduced by e- / protons + e- / Hydrogen
Name TWO products of the light dependent reaction that are required for light independent reaction
1) ATP
2) reduced NADP
Where precisely is rubisco found in a cell ?
1) Stroma
Describe the effect of introducing a herbicide/inhibitor on the electron transport chain (4)
• Reduced transfer of protons across thylakoid membrane
OR
• Reduced electrochemical 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;
Suggest why most of the Triose Phophate is converted back into RuBP (3)
1) Two triose phosphate are needed to synthesise glucose, leaving ten triose phosphate (from six cycles) to regenerate 6x RuBP using ATP
2) Each RuBP is involved in fixing 1x CO2 molecules catalysed by ——RUBISCO to make two GP which are reduced to make 2xTP.
3) Allowing the cycle of light independent reactions to continue in stroma
How is the chloroplast adapted to maximising the rate of photosynthesis in the stroma? (5)
1) Thylakoid membranes provide large surface area for MORE chlorophyll pigments (to absorb red and blue light)
2) MORE photoionisation to establish electrochemical gradient
3) MORE photophosphorylation to make ATP (ADP + Pi by ATP synthase)
4) MORE NADPH formed
5) Both ATP and NADPH are needed in LIR (MORE reduction GP to TP)
