lec 14 slide 16

What is the central pigment in the light reactions of photosynthesis?

Chlorophyll

what does chlorophyll consist of that is similar to quinones

has a hydrophobic tail and behaves like a lipidd in the thylakoid membrane

what does chlorophyll consist of that is similar to cytochromes

a porphyrin ring that binds to MG which makes chlorophyll the characteristic green in color

What happens when light hits chlorophyll?

A delocalized electron in the porphyrin ring is excited to a higher energy state.

What are the three possible fates of the excited electron in chlorophyll?

• Energy released as heat or fluorescence

• Resonance energy transfer to another chlorophyll

• Electron transfer to another molecule → creates charge separation

What is fluorescence in chlorophyll?

When an excited electron returns to the ground state, energy is released as heat or light (longer wavelength than absorbed light).

What is resonance energy transfer?

Excited energy is transferred to another chlorophyll molecule, without transferring the electron itself.

What happens during electron transfer from chlorophyll?

• Chlorophyll loses an electron → becomes positively charged

• Positively charged chlorophyll extracts an electron from water → regenerates original state

• Creates charge separation, essential for photosynthesis

Where do energy and electron transfers occur in chlorophyll?

In chlorophyll bound to proteins in the thylakoid membrane.

Why is charge separation in chlorophyll critical?

It drives the light-driven reactions of photosynthesis, allowing water to be split and electrons to flow through the electron transport chain.