Photosynthesis & Respiration

Chapter Sections Section 1 - Energy and Living Things Section 2 - Photosynthesis Section 3 - Cellular Respiration

Energy and Living Things Directly or indirectly, almost all energy in living systems needed for metabolism comes from the sun Metabolism - involves using energy to build molecules or breaking down molecules in which energy is stored During Photosynthesis autotrophs convert light energy to chemical energy During C. Respiration heterotrophs release much of the energy in food to make ATP ATP delivers energy wherever it is needed in the cell

Photosynthesis Process that provides energy for almost all life. Occurs in the chloroplasts of the cell Photosynthesis: 3 stages –Capture sunlight –Light energy converted to chemical energy –Chem. Energy in ATP and NADPH powers formation of organic compounds

Stages of Photosynthesis Stage 1: Absorption of Light Energy - plants have pigments that absorb light (chlorophyll- absorbs blue/red & reflect green/yellow) (carotenoids produce yellow and orange fall leaf color) Stage 2: Conversion of Light Energy - Excited electrons that leave the chlorophyll are used to produce ATP, NADPH, and other molecules Stage 3: Storage of Energy - Carbon dioxide fixation- transfer of CO 2 into organic compounds

Factors Affecting Photosynthesis Rate of photosynthesis increases as light intensity increases Concentration of CO 2 affects photosynthesis Temperature can affect photosynthesis –Unfavorable temperatures may inactivate certain enzymes

Photosynthesis

Cellular Respiration Cellular respiration transfers the energy in organic compounds (glucose) to ATP Aerobic respiration requires oxygen Anaerobic respiration do not require oxygen Most respiration occurs in the mitochondria

Two Stages of Cellular Respiration Stage 1: Breakdown Glucose Carbohydrates (starches, sucrose) are broken down for energy (fats too) Glycolysis - breaking down of glucose in the cytoplasm Stage 2: Production of ATP When oxygen is present, more ATP is produced than w/o oxygen When oxygen is absent, small amounts of ATP are produced by fermentation.

Respiration without Oxygen Fermentation uses hydrogen to make ATP instead of O 2 2 types of fermentation –Lactic acid (sore muscles) –Alcoholic (baking - yeast)

Respiration