photosynthesis

Question 1

what is photosynthesis?

Answer 1

process by which photosynthetic organisms convert light energy to chemical energy to fix CO2 and produce sugar

light dependant and independent reactions

Question 2

light dependant reaction

Answer 2

converts light energy into chemical energy

require light in visible range of spectrum
produces ATP and NADPH
produce oxygen as byproduct

occurs on thylakoid membrane

Question 3

light independent reaction

Answer 3

carbon fixation

must be preceded by light dependant
uses ATP and NADPH from dependant

carbon is fixed
sugar/carbohydrates produced

occurs in stroma

Question 4

chloroplast structure

Answer 4

thylakoid discs stacked into granum
each surround by a thylakoid membrane
membrane can extend between grana creating a thylakoid lamellae
surrounded by storm containing metabolites and enzymes

2 membranes
envelope surrounding stroma and
inner membrane impermeable to most molecules
has many transporter proteins

Question 5

structure of chlorophyll

Answer 5

tetraphytol ring
- nitrogen atoms surrounding magnesium atom
- required for chlorophyll to capture light

phytol tail
- hydrocarbon tail
- allows molecule to embed itself into thylakoid membrane

different chlorophylls have different functional groups

form complexes called antennae
one chlorophyll acts as a reaction centre
antennae embedded in large protein complexes in thylakoid membrane
create complexes called photosystems

Question 6

chlorophyll and light

Answer 6

absorb light at the extremes of the visible spectrum
chla and b exhibit two absorption maxima at the extremes

maximal are where most light is absorbed
- at blue and red part of spectrum

Question 7

photosystem 1

Answer 7

reaction centre = chla
P700

primary electron acceptor = Fe-S protein
final electron acceptor = ferredoxin

responsible for photo reduction

Question 8

photosystem 2

Answer 8

reaction centre = chla and chlb
P680

primary electron acceptor = pheophytin
final electron acceptor = plastocyanin

responsbile for photo-oxidation (photolysis) and photophosphorylation

Question 9

what is redox potential?

Answer 9

measure of the tendency (how easy) of a molecule to loose or acquire electrons
- measured in volts

drives electrons in electron transport chain

more positive = greater the affinity for electrons
accepts electrons
therefore becomes reduced

more negative = lower affinity
easily donate electrons and become oxidised
donates to molecule with more positive potential

electrons move from molecules with more negative to more positive potential

Question 10

reductants vs oxidants

Answer 10

reductants
- easily donate electrons to another with more positive potential
become oxidised
electron acceptor becomes reduced

oxidants
- easily accepts electrons
becomes reduced
acceptor becomes oxidised

lose electrons = oxidised
gain electrons = reduced

Question 11

redox potential in the electron transport chain

Answer 11

electrons flow from more negative to more positive electrode potential

allows flow of electrons along chain
redox gets increasingly positive

eventually ends at reaction centre of P700
becomes excited and gives electrons to primary electrons acceptor at photosystem 1