Photosynthesis
Light-Dependent Reactions: Light-dependent reactions happen in the thylakoids of chloroplasts.
Light Independent reactions: Plants use ATP and NADPH to make high-energy sugars out of the carbon dioxide in the air. Light independent reactions do not need light and these reactions occur in the cell's stroma.
What is Photosynthesis?
Making NADPH
ATP and ADP
Electron Transport Chain
ATP synthase
The H+ ions inside the thylakoid cause the exterior of the thylakoid to become more negatively charged the interior of the thylakoid. This reaction is what powers the ATP creation process. Since the H+ ions cannot cross through the membrane, they have to go through a protien called ATP synthase. ATP synthase is a protein that creates an energy storage system. ADP is turned into ATP by adding on that extra phosphate group.
In plant cells, carrier molecules are used to transport high energy electrons from chlorophyll to other locations in the cell. One of the molecules used is called Nicotinamide Adenine Dinucleotide phosphate or NADP+. The NADP+ carries electrons to the other parts of the cell, and the process of transporting these electrons changes NADP+ into NADPH. The now transported electrons are used to help build helpful molecules, such as sugars. Energy from sunlight, hydrogen ions from water, and electrons are used go help make ATP and NADPH.
Adenosine Triphosphate (ATP) is made up of adenine, ribose (a sugar), and three phosphate groups. The bonds of the phosphate groups are where energy is stored, and when the bonds are broken, the energy is released.
The electron transport chain is a group of carrier proteins. Energy is used from electrons by these proteins to help circulate H+ ions in the thylakoid. When light comes into contact with chlorophyll, the amount of electrons that enter the electron transport chain is increased.
Calvin cycle
The Calvin cycle is a light independent reaction that produces high energy sugars. These sugars are stable so energy is able to be stored in them for a long time. A protein joins the carbon dioxide molecules from the air along with the pre-existing molecules in the cell. This cycle produces energy-rich carbohydrates by using ATP and NADPH. C4 plants have a special chemical pathway that incorporates carbon into the Calvin cycle even at times where there is not a lot of carbon dioxide availabe.
Photosynthesis is a process that takes place in chloroplasts of plant cells. The product of this process is energy in the form of glucose. This product is produced by capturing carbon dioxide, water, and sunlight and chemically processing it and turning it into energy.
Adenosine Diphosphate (ADP) is similar to ATP in the sense that it is also made up of adenine, ribose, and phosphate, but the key difference is the fact that ADP has one less phosphate group than ATP. This means that, while ADP can still store and release energy, it stores less energy than ATP because it has one less phosphate bond.
A good way of remembering the key difference between ATP and ADP is thinking about them as batteries. ADP is more of a half full battery which is able to store and release lower amounts of energy, than ATP which is a fuller battery and is able to release higher amounts of energy.
Photosystems
Photosystem II
Photosystem I
The pigments in this photosystem take in energy from light and release high energy electrons. These high energy electrons are moved through the electron transport chain and go through the cycles explained above.
Electrons in photosystem II lose their energy as they are circulated through the membrane. In photosystem I, after these electrons come into contact with light, they regain their energy. After, they continue through yet another transport chain where their sole function is to turn NADP+ into NADPH.