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 CO2 into organic compounds

Factors Affecting Photosynthesis

• Rate of photosynthesis increases as light intensity increases

• Concentration of CO2 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 O2

• 2 types of fermentation– Lactic acid (sore muscles)

– Alcoholic (baking - yeast)

Respiration

QuickTime™ and aSorenson Video 3 decompressorare needed to see this picture.