Photosystem: General Biology 1 PDF

PHOTOSYSTEM General Biology 1  PHOTOSYSTEM An aggregate of pigments and proteins in the thylakoid membrane Responsible for the absorption of photons (a quantity or “packet” of light energy) and the transfer of energy and  PHOTOSYSTEM It is composed of Light-har...

PHOTOSYSTEM General Biology 1  PHOTOSYSTEM An aggregate of pigments and proteins in the thylakoid membrane Responsible for the absorption of photons (a quantity or “packet” of light energy) and the transfer of energy and  PHOTOSYSTEM It is composed of Light-harvesting complex and Reaction-center complex. LIGHT-HARVESTING COMPLEX Antenna complex Consists of several different pigments (Chlorophyll a, chlorophyll b, carotenoids) bounded with proteins LIGHT-HARVESTING COMPLEX When a pigment molecule absorbs a photon, energy is passed on from one pigment molecule to another pigment molecule until the energy reaches the REACTION-CENTER COMPLEX composed of a pair of chlorophyll a and a primary electron acceptor. The primary electron acceptor is a specialized molecule that is able to accept electrons from REACTION-CENTER COMPLEX The pair of chlorophyll a in the reaction-center is also specialized because they are capable of transferring an electron to the primary electron acceptor and not just boosting the electron to  TWO TYPES OF PHOTOSYSTEM  TWO TYPES OF PHOTOSYSTEM  PHOTOSYSTEM II discovered later after the discovery of Photosystem I. functions first in the light reaction of photosynthesis. The chlorophyll a in the reaction-center of Photosystem II effectively absorbs light with a wavelength of 680nm and thus called P680.  PHOTOSYSTEM II 1. Light energy is trapped and boosts electron to a higher level. 2. The electrons are received by an electron acceptor  PHOTOSYSTEM II 3. The electrons are passed from one acceptor (plastoquinone and cytochrome) to the next to photosystem I. 4. Energy lost reduces  PHOTOSYSTEM I was discovered first. Its reaction-center has a chlorophyll a called P700 because it is effective in absorbing light with a wavelength of 700nm.  PHOTOSYSTEM I 1. The electrons from photosystem II lost energy when they pumped H+ across the membrane. 2. The light gives electrons energy again combines with proton from the split of water to reduce NADP.  PHOTOSYSTEM I 3. It goes through electron transport chain (ETC). 4. It produces NADPH to be used on the next set of reactions.