Question

The most difficult concept of photosynthesis is arguably active transport and facilitated diffusion. Why? What is a fundamental property of the membrane that is necessary for photosynthesis to occur?

Answer 1

Active transport is the movement of molecules from an area of high concentration to the area of low concentration across a membrane. Energy is required for this movement which comes from cellular processes. Energy is required in active transport as the movement of molecules are against the concentration gradient. There are 2 types of active transport- primary and secondary , out of which primary active transport takes place during photosynthesis. During photosynthesis, proteins use the photon energy to generate a proton gradient across the thylakoid membrane which helps in pumping of H+ ions.

Facilitated diffusion is the opposite of active transport. It is the passive spontaneous movements of molecules along the concentration gradient. The molecules and ions move across a biological membrane with the help of certain integral proteins. Since the movement is down the concentration gradient direct energy is not required from ATP molecules.

The photosynthetic membranes are called thylakoids. The light reactions take place here. The thylakoids are made up of many proteins, pigments, chlorophyll and lipid membranes. There are two photosystems present namely photosystem 1 and photosystem 2. Because of this complex structure if carries out the function of electron transport and ATP synthesis in addition to absorbing light.