Light Reactions

Photophosphorylation

Attaching a phosphate group to a protein / molecule

• uses ETC and chemiosmosis to make ATP

thylakoid membrane

Light reactions occur on the ?

ATP, NADPH

Products of light reactions that are used in the dark reactions

Photosystem

Cluster of pigments around reaction center

• harvest light energy and convert it to chemical energy

700nm

PSI absorbs wavelengths at

680nm

PSII absorbs wavelengths at

Photolysis / Hydrolysis

water splitting due to an enzyme associated with PSII

Sunlight

680 nm Photons from the ? hit PSII and bounce around the photosystem

2 electrons

Once the photons hit the reaction center in PSII, it’ll release ?

primary electron acceptor

the 2 electrons released from PSII get picked up by a ?

electron transport chain

the primary electron acceptor takes the 2 electrons from PSII to the ?

Electron Transport Chain (ETC)

a series of proteins that pass around electrons from PSII, releasing energy with each bounce

• the electrons are used to fill up PSI

• the energy released at each bounce helps push H⁺ against its gradient into the cell

PSI

the 2 electrons from PSII get passed around the ETC, releasing energy at each bounce, until it is used to fill the holes in ?

lumen, ATP Synthase, NADP⁺

the 2H⁺ from photolysis gets pumped into ?, out through the ?, then picked up by the ?

PSII, ETC, PSI, NADP⁺

The 2 electrons from photolysis refill ?, then go to ?, to ?, then picked up by ?

waste product

The ½ O₂ from photolysis becomes a ?

NADP⁺

700 nm photons from the sunlight hit the PSI, exciting electrons that get picked up by ?

Electron Carriers

Molecules that can be both oxidized and reduced

• NADH, NADPH, FADH₂

ATP Synthase

Channel protein on membrane that is also an enzyme

• found in mitochondrial and chloroplast membranes

  • permeable to H⁺

  • H⁺ flows down concentration gradient (facilitated diffusion)

  • flows like a water wheel

shape, P_i

As H⁺ leaves the lumen with ATP Synthase’s help, it changes the ? of ATP Synthase and powers the bonding of ? to ADP

linear electron flow

The light reactions of photosynthesis are considered ? since electrons flow in one direction