Absorption of specific wavelengths of light by photosynthetic pigments

Primary photosynthetic pigments

Chlorophyll a

Chlorophyll b

Carotenoids

Photosynthetic pigments

specialised molecules that absorb light energy and convert it into chemical energy during photosynthesis

What is the role of chlorophyll in photosynthesis?

Chlorophyll absorbs specific wavelengths of light, which excites electrons and convert light energy into chemical energy.

What happens to electrons when light is absorbed by a pigment?

energy of the photons is transferred to the electrons, causing them to become excited and move to a higher energy state.

Two main parts of a photosystem

Antenna Complex

Reaction center

Antenna Complex

A collection of pigments that absorb light and transfer energy

Reaction Center:

A pair of chlorophyll molecules that release excited electrons

What are photosystems located?

thylakoid membranes of chloroplasts

function of the antenna complex in a photosystem?

to absorb light and transfer energy to the reaction center

What occurs to excited electrons in the reaction center

They are transferred to an electron transport chain

How does the electron transport chain contribute to ATP production

As electrons move through the chain, their energy is used to pump protons, creating a gradient that drives ATP synthesis through chemiosmosis

Why do photosynthetic pigments only absorb certain wavelengths of light?

They can only absorb photons with energies that match the energy level of their electrons

What wavelengths does chlorophyll a absord most efficiently

Blue and red regions

Why do plants appear green?

reflect green light which chlorophyll A does not absord

Relationship between a pigment’s absorption spectrum and its role in photosynthesis

Wavelengths that are absorbed most efficiently by the pigment drive and the highest rates of photosynthesis.

first step in converting light energy to chemical energy

excitation of an electron within a pigment molecule when it absorbs a photon

Why is it beneficial for plants to reflect some wavelengths of light?

Reflecting certain wavelengths helps prevent overheating and damage from excessive light absorption.

List the absorption ranges for chlorophyll a, chlorophyll b, and carotenoids.

- Chlorophyll a: Red (~680 nm) and blue-violet (~450 nm)
- Chlorophyll b: Blue (~455 nm) and red-orange (~675 nm)
- Carotenoids: Blue-green (400–500 nm)