Photosynthesis
Overview-
Photosynthesis is the process by which organisms use solar energy to make sugar and oxygen (nutrient molecules) from carbon dioxide and water (PimaCommunityCollege).
The chemical equation of this process is: carbon dioxide + water =light energy=> glucose + oxygen
6CO2 + 6H2O =light energy=> C6H12O6 + 6O2, or
Six molecules of carbon dioxide plus six molecules of water produce one molecule of sugar plus six molecules of oxygen.
The two stages of photosynthesis:
The two stages of the photosynthetic process are Light Reactions and Dark Reactions, also referred to some cases as “Calvin Cycle Reactions.”
In the Light Reaction, light hits reactions centers of chlorophyll, found in chloroplasts, and vibrates which causes a breaking apart of the water. Oxygen is released into the air, while hydrogen stays in the chloroplast, attached to NADPH (Nicotinamide adenine dinucleotide phosphate)(California Department of Education).
In light reactions, electron transport chains generate ATP (adenosine triphosphate), NADPH (Nicotinamide adenine dinucleotide phosphate), and O2. Two connected photosystems collect photons of light and transfer the energy to chlorophyll electrons, and then electrons are passed to electron transport chains from the primary electron acceptor. This energy ends up in ATP and NADPH.The electron transport chains are arranged with the photosystems in the thylakoid membranes and pump H+ through that membrane. The flow of H+ back through the membrane is harnessed by ATP synthase to make ATP. In the stroma, the H+ ions combine with NADP+ to form NADPH (CreativeCommons).
The Dark Reaction, also known as the “Calvin Cycle,” happens when C02 is joined from the atmosphere to hydrogen from water molecules (NADPH) in order to form glucose (Nave&Nave):
CO2 is added to the 5-Carbonmolecule, RuBP by the enzyme rubisco, or RuBP carboxylase.This 6-Carbonmolecule splits to two 3-Carbon molecules of PGA or 3-phosphoglyceric acid. PGA is converted to Glyceraldehyde 3-phosphate (G3P), two of which bond to form glucose.G3P is the 3-Carbon sugar formed by three turns of the cycle. From a G3P molecule, plants can suffice all the molecules they need, crediting them with much biochemical capability (Mader&Windelspecht).
Where does photosynthesis occur?
Photosynthesis occurs in chloroplasts, usually in the leaves. Chloroplast contains a fluid called stroma and stacks of thylakoid (contain chlorophyll), known as grana. Chlorophyll is what captures light for photosynthesis, and accounts for the green pigment (Mader&Windelspecht).
Types of photosynthesis
C3
C3Photosynthesis: C3 plants- in this form of photosynthesis, CO2 is initially incorporated into a 3-carbon compound (Mader&Windelspecht).
Features of C3 plants can include: open stomata during the day; the enzyme involved in the uptake of CO2 is RUBISCO, which is the enzyme involved in photosynthesis; most all plants are C3;C3 plants are found to be more efficient than C4 and CAM plants when subject to cool and moist conditions, and also under normal light because this requires less machinery (fewer enzymes and no specialized anatomy) (PimaCommunityCollege). C4
C4 Photosynthesis: C4 plants- in this form of photosynthesis, CO2 is initially incorporated into a 4-carbon compound (Mader&Windelspecht).
Features of C4 plants can include: Open stomata during the day; The enzyme involved in the uptake of CO2 is PEP Carboxylase, which allows CO2 to quickly enter up into the plant, which is then able to deliver the CO2 directly to RUBISCO for the process of photosynthesis; Photosynthesis is C4 plants takes place in the inner cells; C4 plants deliver CO2 directly to RUBISCO, which prevents it from grabbing oxygen and being able to undergo photorespiration, because it photosynthesizes faster than C3 plants under the conditions of high light intensity and high temperatures (PimaCommunityCollege). CAM
CAM Photosynthesis: CAM plants- CAM, or Crassulacean