Lecture 2 - Beth Dyson Flashcards
What is photosynthesis? [1]
Photosynthesis is how plants make ‘food’ from light.
What % of life on Earth does photosynthesis provide energy for? [2]
99% of life acquires its energy from photosynthesis.
How many Gt of carbon dioxide is taken up by plants per year?
120Gt of CO2 is taken up by plants each year.
How much CO2 is released as part of anthropogenic emissions?
9Gt of CO2 is released as part of anthropogenic emissions.
How old is photosynthesis in deep time?
3800Ma
What other compounds can be used for photosynthesis? [2]
Sulphur compounds and hydrogen can be used in some forms of photosynthesis.
What type of photosynthesis led to mass divergence and when? [2]
Oxygenic photosynthesis in cyanobacteria back 2400Ma.
Give two similarities of photosynthesis and respiration. [2]
They both involve production of ATP via phosphorylation and an electron transport chain.
Give two differences between photosynthesis and respiration. [2]
Photosynthesis is anabolic while respiration is catabolic.
Photosynthesis uses light to split water and build sugars, while respiration breaks down sugars and produces water as a waste product.
Name five features of the chloroplast. [5]
Double membraned. Stroma Thylakoids Granum Lamella
What is the stroma and what does it contain? [3]
The stroma is a colourless fluid within chloroplast.
It also has a suitable pH for Calvin Cycle and contains lots of enzymes
What are granum? [1]
Granum are flat membrane stacks.
This is good for an increased surface area:volume ratio.
What are lamella? [1]
Lamella connect and separate thylakoid stacks.
What are thylakoids? [1]
Thylakoids are the location for light-dependant reactions.
Where light absorption occurs.
Where does the Calvin Cycle happen? [1]
In the stroma.
What do light dependant reactions produce? [2]
NADPH and ATP
What do light independent reactions produce? [1]
Sugars.
What’s the ‘basic’ idea of the ETC? [1]
The basic idea of the ETC is that some energy is lost in each step.
This energy can be used by the plant.
Name in order the six parts of the Electron Transport Chain. [6]
PSII Pheophytin Plastoquinone Cytochrome b6f Plastocyanin PS1
Where is Photosystem II located? [1]
PSII is located in grana within the thylakoid membrane.
What is the composition of Photosystem II in terms of subunits and cofactors? [2]
PSII is a protein complex, with 20 subunits and 99 + co-factors (35 chlorophylls, 12 β-carotenes).
What two complexes exist within Photosystem II? [2]
PSII contains:
Light harvesting complexes.
A P680-containing reaction centre complex.
What happens when light hits PSII? [3]
Light initially hits at the chlorophyll-filled LHC.
This energy is funnelled along many LHC until it reaches the P680 dimer in the RCC.
P680 then passes It to pheophytin.
How does PSII regain the electron lost to pheophytin? [1]
It splits water via photolysis.
Two photons are needed to split H2O, while a full O2 molecule requires four photons to be created.
What does pheophytin do? [1]
Pheophytin passes an electron to plastoquinone.
Where is plastoquinone located?
Plastoquinone is in the chloroplast membrane.
What does plastoquinone do? [2]
Plastoquinone passes an electron to cytochrome b6f.
Excess energy moves a H+ ion to the lumen.
What does cytochrome b6f do? [2]
Cytochrome b6f passes an electron to plastocyanin.
Excess energy moves a H+ ion to the lumen.
What does plastocyanin do?
Plastocyanin passes an electron to Photosystem I.
How does Photosystem I differ from Photosystem II? [3]
PSI is a far larger complex with PSII.
PSI’s LHC contains P700, rather than P680.
pigments.
PSI takes its electron from plastocyanin not water.
What does Photosystem I do?
It takes light in from plastocyanin and through P700 passes it to ferredoxin.
What does Ferredoxin do? [1]
Ferredoxin provides energy, allowing FNR to make NADPH (reducing NADP+ with the extra electron).
What is the Z scheme? [1]
The ETC pathway of energy transfer.
It has two ‘peaks’ when P680 and P700 gain an electron, but between them energy is reduced at each step.
Where is ATP synthase located? [1]
ATP synthase is located in the thylakoid membrane.
What ‘drives’ ATP synthase? [1]
H+ ions released in the lumen, from Plastoquinone and Cytochrome b6f.
What does ATP synthase do? [2]
ATP synthase acts as a ‘motor’.
Protons pass through the enzyme and they’re used to form ATP (from ADP) and NADPH (form NADP+)
What is cyclic electron transport? [2]
In CET, ferredoxin passes its electron back to Cytochrome b6f, which pumps more H+ ions through the membrane.
The extra H+ is good for producing ATP.
