Photosynthesis Introduction 2024 PDF

PHOTOSYNTHESIS Sustaining Life on Earth  Photosynthetic Organisms Plants, algae, cyanobacteria and some protists can all photosynthesize They are organisms that transform the sun’s radiant energy into chemical energy These organisms all contain the green coloured pigment...

PHOTOSYNTHESIS Sustaining Life on Earth  Photosynthetic Organisms Plants, algae, cyanobacteria and some protists can all photosynthesize They are organisms that transform the sun’s radiant energy into chemical energy These organisms all contain the green coloured pigment called chlorophyll plus other pigments  The Reaction The process of photosynthesis takes place within chloroplasts to produce sugars and oxygen. 6 CO2 + 6 H2O (sunlight) 🡪 C6H12O6 + 6 O2 Carbon Dioxide Water Glucose Oxygen Chloroplast  Chloroplast Chloroplasts are believed to have evolved from free-living photosynthetic prokaryotic cells which were absorbed by phagocytosis & became chloroplasts This is the theory of endosymbiosis  Chloroplast Just like current day bacteria, chloroplasts have – double membrane with inner membrane dotted with proteins which form an Electron Transport Chain (ETC) – Ribosomes so can make their own proteins – Circular DNA so can reproduce independently – Sequence of DNA bases closely matches bacterial DNA  Chloroplasts & Photosynthesis The 2 stages happen in the chloroplasts of palisade cells. Light Rx = thylakoids Dark Rx = stroma  Electromagnetic Spectrum Light from the sun is a mixture of photons of different energies When light is passed through a spectroscope, the photons of light are seperated into their different energies, forming an electromagnetic spectrum Most of the photons are invisible to humans, but a narrow band, ranging from about 380 nm (violet light) to 750 nm (red light) are wavelengths that make up the visible part of the spectrum  Photosystems Clusters of photosynthetic pigments, called photosystems, are embedded in the thylakoid membranes Pigments are chemical substances produced by plants which are able to absorb photons of a particular wavelength Plant Pigments  Absorption Spectrum Chlorophylls a and b absorb photons with energies in the blue-violet, and red regions, but reflect light in the green range which is why most photosynthesizing plants appear green Other pigments absorb in the ranges that chlorophylls a and b do not, so together, they cover almost the entire visible spectrum  Photosynthesis STAGE 1: LIGHT REACTION In the thylakoid membrane, light energy is captured by pigments which release electrons Water is broken down, releasing electrons and producing oxygen gas as a waste product The free electrons, travel through a series of membrane proteins (ETC) and in the process, ATP and NADPH are produced which travel to the 2nd stage = dark reaction or Calvin cycle  Photosynthesis: Light Reaction http://www.youtube.com/watch?v=v590JJV96lc &feature=related  Photosynthesis: Dark Reaction STAGE 2: Calvin Cycle In the stroma, NADPH, CO2, and the energy from ATP are used to make glucose  Uses of Products The glucose: The oxygen: can be used in cellular Is released as a waste respiration by the same product palisade cell Can be used in cellular Can be combined with respiration by the same another to form sucrose palisade cell which is how sugars move through the phloem in the plant. Can be joined into the polypeptide starch for storage