Unit 5: Light Reactions

What are the 2 major stages of photosynthesis?

Light & Dark reactions

Stage 1: Light Reactions

starts with chlorophyll (which absorbs blue and red light) it reflects green light

Chlorophyll is…

amphipathic

Chlorophyll molecules…

reside in photosystems

Photosystems

allow the light energy absorbed by chlorophyll to be harnessed rather than wasted

Chlorophyll molecules have a…

“Special pair”

“Special pair” is when…

electrons get excited by getting passed down it takes an electron and hands it off completely to the electron acceptor

The special pair allows for…

electron transfer

Label image below with correct components (What is the whole image)

Photosystem

The ring around magnesium…

contains a lot of electrons that can be excited through light energy

How do we reset the special pair for continued reactions?

when electron carriers rip away electrons the chlorophyll is now missing electrons and it needs to be replaced. Something needs to replace the electron and that is water.

When light excited chlorophyll, where do the electrons go?

electrons are transferred through the electron transport chain within the thylakoid membranes of the chloroplast

1st stage of Photosystem II is when…

first e- is exicted

How does chlorophyll get its electron back?

redox cycling

Water splitting complex

splits apart water molecules H20 & 02 (main reason plants need water)

After Photosystem 2 an electron gets…

transferred down by photosystem chain

Plastoquinone

hands off electron to plastocyanin

Where does electron transfer occur?

in the thylakoid membrane (follow from left to right)

Electron that moves out of photosystem II is accepted by

plastoquinone

Photosystem I

2nd stage