Studied by 0 people
Where does the light-dependent reaction take place?
on thylakoid membrane in chloroplast
What is the first stage of the light-dependent reaction?
chlorophyll absorbs light energy → excites electrons to a higher energy level → released from chlorophyll = photoionisation
What is the second stage of the light-dependent reaction?
Production of ATP
electrons pass down ETC via redox reactions, losing energy at each step
energy; protons→stroma to thylakoid (a.t)
electrochemical gradient created across thylakoid membrane (higher in t)
protons down EC gradient (f.d) via ATP synthase in thylakoid membrane
ADP + Pi → ATP (photophosphorylation) - chemiosmotic theory
What is the third stage of the light-dependent reaction?
Production of reduced NADP
electrons excited + transferred to NADP to reduce NADP
What is the fourth stage of the light-dependent reaction?
Photolysis
splitting of water using light energy
produces protons, electrons + oxygen
What are the products of the LDR?
ATP for the LIDR
NADPH for the LIDR
oxygen for respiration
What is the light-independent reaction (Calvin Cycle)?
CO2 reacts with ribulose biphosphate (RuBP) catalysed by enzyme rubisco
produce 2x glycerine-3-phosphate (GP)
GP reduced to triose phosphate (TP)
using energy from hydrolysis of ATP and H+ from reduced NADP
some TP → useful organic substances, e.g glucose
TP used to regenerate RuBP (using ATP)
Why is temperature a limiting factor?
increases → increases rate
limits LIDR as rubisco is controlled
more KE → more ES complexes
H bonds break → a.s changes shape → enzyme denatures → fewer E-S complexes
Why is light intensity a limiting factor?
increases → increases rate
if reduced; ATP and NADPH reduced
LDR limited, less photoionisation of chlorophyll
LIDR slows, GP not reduced to TP, no TP to regenerate RuBP
Why is CO2 conc. a limiting factor?
increases → increases in rate
if reduced; limited LIDR reaction
less CO2 to combine with RuBP to form GP
less GP reduced to TP
less TP converted to organic substances + to regenerate RuBP
What agricultural practices overcome limiting factors?
artificial lighting
heating greenhouse
burning fuel
= photosynthesis increases
→ faster production of glucose → more respiration
→ more ATP - growth, e.g. cell division, protein-synthesis
→ higher yield = more profit
