The Reactions of Photosynthesis

Photosynthesis is found in plants, bacteria, algae and protists. Photosynthesis happens in the Chloroplast Mesophyll cell- Cells in the middle of leafs that contain many chloroplast

Stomata – tiny holes on the epidermis of plants that control gas exchange. The chloroplast are made up of Thylakoid- Each individual pancake Granum- Stack of pancakes Stroma- Liquid in the chloroplast Pigment that help absorb light is Chlorophyll

Inside a Chloroplast In plants, photosynthesis takes place inside chloroplasts. The chloroplasts contain saclike photosynthetic membranes called thylakoids. Thylakoids are arranged in stacks called grana.

Inside a Chloroplast

Inside a Chloroplast Scientists describe the reactions of photosynthesis in two parts: The light dependent reactions (which occur within the thylakoid membranes) and… The light independent reactions or Calvin Cycle (which occur in the liquid spaces outside the thylakoid membranes called the stroma).

Electron Carriers When sunlight excites electrons in chlorophyll, the electrons gain a great deal of energy.

NADP+ This energy is carried by a special molecule known as NADP+ (nicotinamide adenine dinucleotide phosphate). This energy converts NADP+ to NADPH which is used to build a variety of molecules the cell needs including glucose.

Light Dependent Reactions When light strikes the chlorophyll molecule, energy is absorbed and used to split water into hydrogen and oxygen. The electrons that are released are passed down a series of proteins called the electron transport chain.

Light Dependent Reactions NADP+ transports these electrons and becomes NADPH. NADPH is used in the light independent reaction (Calvin Cycle) to form glucose

Light Dependent Reactions The left over positively charged hydrogens are used to power the process where a ADP is made into a ATP by adding a phosphorus.

Light Dependent Reactions

Light Independent Reactions – The Calvin Cycle ATP and NADPH made in the light dependent reactions contain a lot of chemical energy, but are not stable enough to store that energy for more than a few minutes. The Calvin Cycle uses ATP and NADPH from the light dependent reactions to produce high-energy sugars (glucose).

The Calvin Cycle The Calvin cycle, named after American scientist Melvin Calvin, is a complex series of reactions that do not require light.

The Calvin Cycle The cycle uses 6 molecules of CO2 to form a 6 carbon sugar (glucose)

The Calvin Cycle

Photosynthesis The two sets of photosynthetic reactions work together – the light dependent reaction traps the energy of sunlight in chemical form and the Calvin cycle converts this chemical energy into stable high-energy sugars from carbon dioxide and water. Oxygen is released as a by-product benefiting almost all life on Earth

Concept Map of Photosynthesis includes Light- dependent reactions Calvin cycle takes place in uses use take place in Thylakoid membranes Stroma NADPH ATP Energy from sunlight to produce of to produce ATP NADPH O2 Chloroplasts High-energy sugars

Factors Affecting Photosynthesis Many factors affect the rate of photosynthesis including: Amount of water Temperature Intensity of light