Calvin Cycle and Light-Dependent Reactions Flashcards
How do light-dependent reactions work?
Photon of light hits photosystem II and is absorbed by chlorophyll, it’s energy gets passed from pigment molecule to pigment molecule until it hits the reaction center that boosts the electron to a high energy level, it gets passed to an acceptor molecule that keeps transferring down the electron transport chain (this energy drives the pumping of protons), protons get pumped from the stroma into they thylakoid lumen (leads to a high concentration of protons in the thylakoid lumen), electron was given up by the reaction center and needs to be replaced, water donates an electron to the reaction center by splitting water into oxygen and hydrogen, this leads to another photon of light being absorbed by photosystem I. The same electron process happens in photosystem I, but this time, an electron is donated to an electron carrier (NADP+) and is transferred through the electron transport chain to the electron carrier to produce NADPH. The protons in the lumen want to flow down their gradient into the stroma, and that drives ATP synthase to generate ATP by adding a phosphate group onto ADP to produce ATP
Electrons at a ground state occupies orbital closest to the nucleus, gets excited by a photon of light, kicking the electron in the pigment molecule up to an excited state
The electron moves to the outer orbital away from the nucleus (higher energy orbital)
Less stable than electron closer to the nucleus
Wants to get rid of excited electron so it transfers its excited electron to the neighbouring molecule
How does the carbon fixation of the Calvin cycle work?
plants are taking carbon dioxide from the atmosphere and converting it into a biologically usable form (creates G3P)
Takes atmospheric carbon dioxide and combines it with an enzyme called Rubisco, creating a 6 carbon intermediate (unstable) that immediately splits apart to generate two 3 carbon molecules called 3PGA
How does the reduction step work in the Calvin Cycle?
NADPH donates electrons to make a carbon-based intermediate
ATP transfers a phosphate group to make ADP in the creation of the 3 carbon intermediate, NADPH transfers carbons to form NADP+ to create G3P
ADP goes back to stroma as does NADP+
ADP is used as a substrate for ATP synthase
NADP+ is an electron carrier that transfers electrons from electron transport chain back to fuel the Calvin cycle
How does regeneration work in the Calvin Cycle?
Some G3P serves as a substrate for sugar synthesis (glucose in animal cells), glucose gets broken down for cellular respiration
G3P needs to get recycled as well, so it requires an input of ATP, and G3P gets regenerated into the original 5 carbon molecule RuBP
