Unit 5 - Energy transfers in and between organisms Flashcards
What are the two reactions in photosynthesis?
light-dependent reaction, light-independent reaction
Where does the light-dependent reaction take place?
in the thylakoid membrane
Where does the light-independent reaction take place?
in the stroma
Which chemicals are needed for the light-independent reaction?
NADP, ADP, Pi and water
What happens during photoionisation?
chlorophyll absorbs light and electrons are lost
How does the light-dependent reaction generate ATP?
Chlorophyll absorbs light energy which excites the electrons
Electrons pass down the electron transport chain in the thylakoid membrane and lose energy
Energy used to pump H+ into thylakoid lumen from stroma
Chemiosmosis - H+ moves down the electrochemical gradient by facilitated diffusion through ATP synthase
ADP + Pi –> ATP
How is NADPH made in the light-dependent reaction of photosynthesis?
light energy is absorbed by chlorophyll
excites electrons
electrons pass down electron transport chain
electrons lose energy
electrons accepted by chlorophyll
light energy excites electrons
electron accepted by NADP —–> NADPH
What is photolysis?
splitting of water using light energy
2H2O —-> O2 + 4H+ +4e-
Describe the light-independent reaction of photosynthesis? (Calvin cycle)
CO2 and RuBP binds to Rubisco enzyme
2x GP is produced
GP is reduced to Triose phosphate using reduced NADP and energy from ATP
2x triose phosphate forms hexose sugars
triose phosphate is used to regenerate RuBP using energy from ATP
What are the properties of ATP?
- stores or releases only a small amount of energy so no energy wasted as heat
- small, soluble molecule so easily transported around the cell
- easily broken down so energy can be released instantly
- it can be quickly remade
- can make other molecules more reactive by phosphorylation
- can’t pass out of the cell so the cell always has an energy supply
What are the stages of aerobic respiration?
glycolysis, link reaction, kreb’s cycle, oxidative phosphorylation and the electron transport chain
What happens during glycolysis?
phosphorylation of glucose using ATP, phosphorylate glucose is converted to 2x triose phosphate, oxidation of triose phosphate to pyruvate, net gain of ATP, NAD reduced
Where does glycolysis take place?
cytoplasm
What happens during the Link reaction?
pyruvate actively transported from the cytoplasm into the matrix of mitochondria
pyruvate is oxidised to acetate
NAD reduced and CO2 lost
acetate and co-enzyme A combine to form acetyl co-enzyme A
What happens during the Kreb’s cycle?
Acetyl CoA combines with a 4 carbon compound called oxaloacetate. This reaction releases the CoA enzyme allowing it to be re-used. The now 6 carbon compound (citric acid) releases Co2 leaving a 5 carbon compound. This reaction also produces NADH, reduced FAD and ATP
