Energy transfers Flashcards
Chloroplasts structure
Stacks of thylakoid membranes called grana
Proteins in grana hold chlorphyll
Double membrane
Selectively permeable
Contain DNA and ribosomes
LDR first step
Photons hit chlorophyll and electrons become excited
This causes photolysis
What is photolysis
4 photons split H2O into 4 e-, 4 H+ and 1 oxygen
O2 is either used in respiration or diffuses out the plant
Electrons replace those lost from chlorophyll
LDR step 2
Protons move into the stroma
Electrons move along a series of protein complexes in the thylakoid membrane (electron transfer chain) in a series of redox reactions
Electrons move to a higher energy level
Energy is released
LDR step 3
Energy released is used to pump H+ back into the thylakoid
Electron combines with H+ to produce H which is used to reduce NADP into NADPH
LDR step 4
H+ move back into the strima via ATP synthase
This phosphorylates ADP into ATP
Where does the LDR take place
granum/ thylakoid membranes
and stroma
What are the three stages of the light independent reaction
CO2 fixation
Reduction
Regeneration
Describe CO2 fixation
Rubisco converts 6CO2 into 2 3C molecules (glycerate-3-phosphate)
Describe reduction in the LIR
NADPH reduces 2 GP into 2 TP using ATP
NAD is formed
Rescribe regeneration in LIR
5 TP molecules regenerate 3RuBP
Using ATP
2 TP are combined to form a hexose sugar
which can be converted into glucose
Why is it necessary to synthesise a large amount of ATP
lots of energy is needed
ATP only releases a small amount of energy at a time
And it cannot be stored
Describe the role of the electron transport chain in photosynthesis
accepts excited electrons
from chlorophyll
electrons lose energy along the chain
ATP is produced from ADP and Pi
NADPH formed when electrons and H+ combine with NADP
Where does glycolysis occur
the cytoplasm
where does the link reaction occur
mitochondrial matrix
where does the Krebs cycle occur
mitochondrial matrix
where does oxidative phosphorylation occur
mitochondrial inner membrane
Describe glycolysis
substrate-level phosphorylation- glucose has 2 phosphate groups added to it from ATP
unstable glucose-2-phosphate splits into 2 TP
2 TP are oxidised to form 2 pyruvate
2 NAD are reduced to NADH
4 ATP are produced
Describe the link reaction
2 pyruvate are actively transported into the mitochondria
Decarboxylase removes one CO2 per pyruvate
NAD is reduced to NADH (1 per pyruvate)
Acetate formed combines with coenzyme A to form Acetyl CoA (2 per glucose molecule)
Describe the Kreb’s cycle
Acetyl CoA gives 2C acetate to a 4C molecule to form a 6C molecule (citrate)
Citrate loses H and CO2 is released
NADH and FADH are formed
ATP is formed
4C molecule is regenerated
Krebs turns twice per glucose
Describe oxidative phosphorylation
NADH binds to protein complex I forming NAD, H+ and e-
NAD returns to Krebs
FADH binds to protein complex II
Releases e- and H+
protons go to matrix
e- go to electron transport chain
e- go into a higher energy level as they move along the proteins
Energy released is used to pump H+ into the intermembrane space
e- is accepted by O2 (final electron acceptor)
Creating a H+ gradient
So H+ moves through the protein channel, providing energy for ATP synthesis
where does the LIR occur
stroma
where does anerobic respiration occur
cytoplasm
describe anerobic respiration in animals and plants
animals- pyruvate from glycolysis is reduced to form lactate and NAD
plants- pyruvate is reduced to form ethanol and CO2
NAD can be used again in glycolysis to keep a constant supply of ATP
