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What is Photosynthesis?


Photosynthesis is the process by which plants use energy from the sun to convert water and carbon dioxide into oxygen and high-energy carbohydrates like sugars.

Parts of a leaf

Cloroplast

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Thylakoid- A membrane-bound compartment inside a cloroplast. The site of light-dependant reactions during photosynthesis.

Granum- A stack of thylakoid disks, connected by lamellae. Cloroplasts can have from 10-100 grana.

Stroma- The thick fluid found inbetween grana inside the cloroplast. Where the carbohydrate formation reactions occur during photosynthesis.

Photosystems- Light capturing systems found on the thylakoid.

Calvin Cycle and Light Reactions

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Light Reactions

The light reactions are the first step in photosynthesis. In these reactions, light energy is converted
into chemical energy, in the form of ATP and NADPH. The light reactions take place on the thylakoid membrane,
and in the stroma. There are four major systems in the thylakoid membrane. Photosystems 1 and 2, ATP synthase, and Cytochrome
cf6 complex. These all work together to create ATP and NADPH.
Calvin Cycle
The calvin cycle, also known as dark reactions, or light-independent reactions, takes place int he stroma and it's goal is to make energy-containing sugars. It's reactants come from the ligth dependent reactions and are carbon dioxide, which provides carbon, and energy carries, which provides the energy. They produce sugar. The calvin cycle must occur twice for one molecule of sugar to be produced.

Energy Carriers



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Energy Carriers are used to store and release energy. One example of an energy carrier is Adenosine Triphosphate,
also known as ATP. ATP consists of adenine, a 5-carbon sugar called ribose, and three phosphate groups allow
ATP to store and release energy as is does.

Adenine Diphosphate, (ADP), is a compound that looks almost like ATP but with one less phosphate group, as it has 2 groups instead of three.
ADP is the key to the way living things store energy. When it has extra energy that it can store, a cell will store some of it
by adding a phosphate group to ADP, turning it into ATP. ADP could be compared to a half charged battery, and ATP to a fully charged battery.

Besides storing energy, energy carriers also have to release the energy when the cell needs it.
Releasing the energy is a simple process, and happens by just breaking the bond between the second and thrid phosphate groups.
The energy stored in ATP, once release, can power a variety of cellular activities, including muscle contraction and protein synthesis.