photosynthesis and respiration Flashcards
Describe the light DEPENDANT stage
Occurs in thylakoid membrane
Makes ATP, NADPH (oxygen released)
Chlorophyll absorbs light energy
Excites electrons in chlorophyll
Electrons move along electron transfer chain
Energy from electrons released
Energy used to transport H+ ions into thylakoid space H+ ions diffuse through ATP synthase to make ATP ADP and Pi condense to form ATP
H+ ions combine with NADP to form NADPH
Photolysis of water produces protons, electrons and oxygen NADP reduced by electrons and protons
Oxygen released as a waste gas
Describe the light INDEPENDENT stage
Occurs in stroma
Makes more RuBP and organic substances
Light independent reaction fixes CO2
CO2 fixed to ribulose bisphosphate (5c)
to make 2 molecules of glycerate-3-phosphate (3c)
The enzyme rubisco catalyses this reaction
Glycerate-3-phosphate becomes reduced.
to form 2 molecules of triose phosphate
using NADPH from the light dependent reaction
using ATP from the light dependent reaction
5/6 of the triose phosphate is converted into ribulose bisphosphate.
1/6 of the triose phosphate is converted into organic substances eg glucose.
Describe glycolysis
Glycolysis takes place in cytoplasm
Glucose phosphorylated
- using 2 phosphates from 2 ATP molecules
Hydrolysed to form 2 triose phosphate
Triose phosphate oxidised (removal of hydrogen)
Hydrogen transferred to NAD to form NADH
2 pyruvate molecules made
Substrate level phosphorylation produces 2 ATP
Describe link reaction
Pyruvate is oxidised and decarboxylated
to form acetate
Hydrogen removed is attached to NAD to form NADH
CO2 released
Acetate is bound to Coenzyme A
Describe Krebs cycle
Occurs in the matrix of mitochondria
acetylcoenzyme A reacts with 4c molecule
- coenzyme A released (back to link)
= 6c molecule
decarboxylated and oxidised
- releases CO2 and reduces NAD to NADH
= 5c molecule
decarboxylated and oxidised again
- releases CO2 and reduces NAD to NADH
= 4c molecule
oxidised
- ATP released by substrate level phosphorylation
- NAD reduced to NADH
- FAD reduced to FADH
= 4c molecule again
Describe oxidative phosphorylation
Krebs cycle / link reaction produces NADH and FADH
happens in matrix and intermembrane space (space between inner and outer membrane)
chemiosmosis
- NADH and FADH oxidised into NAD and FAD
- Releases hydrogen atoms - split into protons and electrons - Electrons released pass along electron transport chain (made of electron carriers)
- electrons lose energy at each carrier, released
- energy used to pump protons from matrix to intermembrane space
- concentration of protons now higher in intermembrane space
- forms electrochemical gradient - protons move down gradient into matrix through ATP synthase
- synthesises ATP from ADP and Pi
electrons protons and oxygen left in matrix make water
Anaerobic respiration in animals (+ bacteria)
Forms lactate and NAD
- Glycolysis
- Pyruvate converted to lactate
Uses NADH —> NAD oxidised
Production of NAD means glycolysis can continue in low oxygen
Small amount of ATP can be produced
Anaerobic respiration in plants and yeast
Forms ethanol and NAD
- glycolysis
- Pyruvate converted to ethanal (releases CO2)
- ethanal converted to ethanol (oxidises NADH to NAD)
chemiosmosis
production of ATP from movement of H+ ions (protons) across a membrane, due to electrons in transport chain
products of glycolysis
2 ATP
2 NADH
2 pyruvate
products of link reaction
NADH
CO2 released
Acetyl CoA
no ATP
products of Krebs cycle
coenzyme A - used in link
NADH
FADH
used in OP
ATP
CO2
products of oxidative phosphorylation
NAD
FAD
ATP
3 respiratory substrates
Glucose
Amino acids
Glycerol and fatty acids from lipids
How are amino acids used as respiratory substrates?
Deaminated
= Pyruvate
Creates 4/5c compounds used in Krebs cycle
