Announcements ● Tutoring Center SCI I, 407 M 12-3, 5:30-6:30; W 8-9, 5:30-6:30, Th 8-12, 6-7; F 8-9 ● MasteringBiology Assignment due Thursday 4/28

Producers and Consumers Autotrophs (self-feeders): Make their own organic matter from inorganic nutrients. Heterotrophs (other-feeders): Organisms that cannot make organic molecules from inorganic ones.

Energy Flow and Chemical Cycling in the Biosphere Sunlight energy enters ecosystem Photosynthesis Cellular respiration drives cellular work Heat energy exits ecosystem ATP C 6 H 12 O 6 (Glucose) + O 2 (Oxygen) CO 2 (Carbon dioxide) + H 2 O (water)

Cellular Respiration – Cellular respiration is: The main way that chemical energy is harvested from food and converted to ATP An aerobic process—it requires oxygen Organic + Oxygen Carbon + Water + Energy Compounds Dioxide Summary equations:

Breathing Cellular respiration Muscle cells Lungs CO 2 O2O2 O2O2 Cellular respiration and breathing are closely related. Cellular respiration requires a cell to exchange gases with its surroundings. Breathing exchanges these same gases between the blood and outside air. Cellular Respiration and Breathing

Cellular Respiration C 6 H 12 O 6 CO 2 O2O2 H2OH2O GlucoseOxygenCarbon dioxide Water  6 6 Reduction Oxidation Oxygen gains electrons (and hydrogens) Glucose loses electrons (and hydrogens) By oxidizing glucose, energy is taken out of “storage” and made available for ATP synthesis

Cytoplasm Animal cellPlant cell Mitochondrion High-energy electrons carried by NADH High-energy electrons carried mainly by NADH Citric Acid Cycle Electron Transport Glycolysis Glucose 2 Pyruvic acid ATP Figure 6.6 Cytoplasm Animal cell Plant cell Mitochondrion High-energy electrons carried by NADH High-energy electrons carried mainly by NADH Citric Acid Cycle Electron Transport Glycolysis ATP

Cytoplasm Animal cellPlant cell Mitochondrion High-energy electrons carried by NADH High-energy electrons carried mainly by NADH Citric Acid Cycle Electron Transport Glycolysis Glucose 2 Pyruvic acid ATP Figure 6.6 Cytoplasm Animal cell Plant cell Mitochondrion High-energy electrons carried by NADH High-energy electrons carried mainly by NADH Citric Acid Cycle Electron Transport Glycolysis ATP 2 2 ~34 ~38 ATP per glucose

Versatility of Cellular Respiration Food PolysaccharidesFats Proteins Sugars Glycerol Fatty acids Amino acids Glycolysis Acetyl CoA Citric Acid Cycle Electron Transport ATP – In addition to glucose, cellular respiration can “burn”: Diverse types of carbohydrates Fats Proteins

Fermentation aerobic anaerobic

Photosynthesis: Is used by plants, some protists, and some bacteria Transforms light energy into chemical energy Uses carbon dioxide and water as starting materials Photosynthesis Carbon dioxide 6 O 2 6 CO 2 6 H 2 O C 6 H 12 O 6 Water Glucose Photo- synthesis Oxygen gas Light energy

Photosynthesis – Organisms that use photosynthesis are: Photosynthetic autotrophs The producers for most ecosystems Plants (mostly on land) Photosynthetic Protists (aquatic) PHOTOSYNTHETIC AUTOTROPHS Photosynthetic Bacteria (aquatic) Micrograph of cyanobacteriaKelp, a large alga Forest plants LM

found b/w lower and upper epidermis Photosynthesis

Light H2OH2O O2O2 Chloroplast Light reactions NADPH ATP Calvin cycle CO 2 NADP + ADP P Sugar (C 6 H 12 O 6 ) Photosynthesis

Why Green? Light Chloroplast Reflected light Absorbed light Transmitted light

Alternative Pathways Sugar C 4 Pathway (example: sugarcane) C 4 plant CAM plant Sugar Calvin cycle Calvin cycle Day Cell type 1 Four-carbon compound Night Four-carbon compound Cell type 2 CAM Pathway (example: pineapple) ALTERNATIVE PHOTOSYNTHETIC PATHWAYS CO 2