Photosynthesis Chapter 7 Mader: Biology 8th Ed.

Photosynthetic Pigments Photosynthesis Light Reactions Noncyclic Outline Flowering Plants Photosynthetic Pigments Photosynthesis Light Reactions Noncyclic Cyclic Calvin Cycle Reactions C4 CAM Mader: Biology 8th Ed.

Photosynthetic Organisms Photosynthesis transforms solar energy into the chemical energy of a carbohydrate. All organisms use organic molecules produced by photosynthesizers as a source of chemical energy. Mader: Biology 8th Ed.

Leaf of flowering plant contains mesophyll tissue. Flowering Plants The green portions of plants, particularly leaves, carry on photosynthesis. Leaf of flowering plant contains mesophyll tissue. Contains cells specialized to carry on photosynthesis. Mader: Biology 8th Ed.

CO2 enters leaf through stomata. Flowering Plants CO2 enters leaf through stomata. CO2 and water diffuse into chloroplasts. Double membrane surrounds fluid (stroma). Inner membrane system within stroma form flattened sacs (thylakoids). Often stacked to form grana. Chlorophyll and other pigments within thylakoid membranes are capable of absorbing solar energy. Mader: Biology 8th Ed.

Photosynthetic Pigments Most pigments absorb only some wavelengths of light and reflect or transmit the other wavelengths. Absorption Spectra Organic molecules and processes within organisms are chemically adapted to visible light. Mader: Biology 8th Ed.

Photosynthetic Pigments and Photosynthesis Mader: Biology 8th Ed.

Photosynthetic Reaction Light Reaction - Chlorophyll absorbs solar energy and energizes electrons. Electrons move down electron transport chain. Solar energy  ATP, NADPH Calvin Cycle Reaction - CO2 is taken up and reduced to a carbohydrate. Reduction requires ATP and NADPH. ATP, NADPH  Carbohydrate Mader: Biology 8th Ed.

Photosynthesis Overview Mader: Biology 8th Ed.

Light reactions consist of two electron pathways: Noncyclic electron pathway Cyclic electron pathway Both pathways produce ATP, but only the noncyclic pathway also produces NADPH. Mader: Biology 8th Ed.

Noncyclic Electron Pathway Electron flow can be traced from water to a molecule of NADPH. Uses two photosystems, PS I and PS II. Photosystem consists of pigment complex and electron acceptor molecules in the thylakoid membrane. Pigment complex helps gather solar energy. Mader: Biology 8th Ed.

Mader: Biology 8th Ed.

Cyclic Electron Pathway Cyclic pathway begins when PS I pigment complex absorbs solar energy and is passed from one pigment to another until it is concentrated in a reaction center. Pathway only results in ATP production. Mader: Biology 8th Ed.

Mader: Biology 8th Ed.

Thylakoid Organization Mader: Biology 8th Ed.

Calvin Cycle Reactions Calvin cycle is a series of reactions that produce carbohydrates before returning to the starting point again. Utilizes atmospheric carbon dioxide to produce carbohydrates. Includes: Carbon dioxide fixation Carbon dioxide reduction RuBP Regeneration Mader: Biology 8th Ed.

Mader: Biology 8th Ed.

Calvin Cycle Reactions Carbon Dioxide Fixation CO2 is attached to RuBP. The result is a 6-carbon molecule which splits into two 3-carbon molecules. Rubisco speeds up this reaction. Mader: Biology 8th Ed.

Calvin Cycle Reactions Reduction of Carbon Dioxide Mader: Biology 8th Ed.

Calvin Cycle Reactions Regeneration of RuBP Mader: Biology 8th Ed.

Importance of Calvin Cycle PGAL (glyceraldehyde-3-phosphate) is the product of the Calvin cycle that can be converted to a variety of organic molecules. A plant can utilize the hydrocarbon skeleton of PGAL to form fatty acids and glycerol, which are combined in plant oils. Mader: Biology 8th Ed.

Mader: Biology 8th Ed.

Avoid photorespiration C4 Photosynthesis In C4 leaf, bundle sheath cells and mesophyll cells contain chloroplasts. Mesophyll cells are arranged concentrically around the bundle sheath cells. In hot, dry climates, net photosynthetic rate of C4 plants is about 2-3 times that of C3 plants. Avoid photorespiration Mader: Biology 8th Ed.

C3 vs C4 Mader: Biology 8th Ed.

Carbon Dioxide Fixation in C3 and C4 Plants Mader: Biology 8th Ed.

Crassulacean-Acid Metabolism CAM Photosynthesis Crassulacean-Acid Metabolism C4 plants partition carbon fixation in space, while CAM partitions by time. During the night, CAM plants fix CO2, forming C4 molecules, which are stored in large vacuoles. C4 molecules release CO2 to Calvin cycle when NADPH and ATP are available. Water Conservation Mader: Biology 8th Ed.

Mader: Biology 8th Ed.

Photosynthetic Pigments Photosynthesis Light Reactions Noncyclic Review Flowering Plants Photosynthetic Pigments Photosynthesis Light Reactions Noncyclic Cyclic Calvin Cycle Reactions C4 CAM Mader: Biology 8th Ed.

Mader: Biology 8th Ed.