Question

(Essay style) Describe the light dependent reactions of photosynthesis. Your answer should discuss their components, the cellular localisation of these, and their products.

Answer 1

Answer=

The light dependent reactions of photosynthesis are as follows:

The light dependent reactions convert light energy into chemical energy in the form of ATP & NADH. This chemical energy will be used by the calvin cycle.These light dependent reactions begins in a grouping of pigment molecules and proteins called photosystem.

Photosystems exist in the membranes of thylakoids.A pigment molecule in the photosystem absorbs one photon,a quantity or "packet"of light energy,at a time.

Photosystems are the functional and structural units of protein complexes involved in photosynthesis.

A photosystem consists of - a light harvesting complex and reaction center.

pigments in the light harvesting complex pass light energy to two special chlorophyll a molecules in the reaction center.The light excites an electron from the cholorophyll a pair ;which passes to the primary electron acceptor.the excited electron must then be replaced. In photosystem II,the electrons come from the splitting of water,which releases oxygen as a waste product.

In photosystem I electrons comes from the chloroplast electron transport chain.

Both photosystems have the same basic structure;a number of antenna proteins to which the cholorophyll molecules are bound surround the reaction center,where photochemistry takes place.

Each photosystem consists of light harvesting complex,which passes energy from sunlight to the reaction center; it consists of many antenna proteins.