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Photosynthesis & Cellular Respiration. Chapter 9. Chemical Energy. Energy: the ability to do work In cells, energy is in the chemical form The stored chemical energy in cells is called ATP , or adenosine triphosphate Energy is released when ATP is converted into ADP + a phosphate group.
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Photosynthesis & Cellular Respiration Chapter 9
Chemical Energy • Energy: the ability to do work • In cells, energy is in the chemical form • The stored chemical energy in cells is called ATP, or adenosine triphosphate • Energy is released when ATP is converted into ADP + a phosphate group
Plants and animals obtain energy in different ways: • Plants ONLY: make their own energy through the process of photosynthesis • Plants and Animals: get ATP by breaking down organic compounds (proteins, carbs, etc.) through the process of cellular respiration
Photosynthesis Overview • Photosynthesis:the conversion of light energy into chemical energy • Occurs in chloroplasts • Reactants (IN): CO2, H2O, and energy • Products (OUT): O2 and glucose (C6H12O6) • 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
Phases of Photosynthesis • 1) Light Reactions (“photo”) • Occurs in thylakoid • Light from sun excites electrons • O2 is released • 2) Calvin Cycle (“synthesis”) • Occurs in stroma • CO2 is used to make glucose (C6H12O6)
Cellular Respiration Overview • Plant and animal cells make ATP by breaking down organic molecules (sugars, fats, etc.) • This process is called Cellular Respiration • Occurs in the mitochondria • Reactants (IN): C6H12O6 (glucose) & O2 • Products (OUT): CO2 & H2O & ATP (energy) • C6H12O6 + 6O2 → 6CO2 + 6 H2O + 36 ATP
Cell Respiration Overview • Begins with Glycolysis • 1 molecule glucose is split in half into 2 pyruvate molecules • If O2 is present → Citric Acid (Kreb’s) Cycle & Electron Transport Chain • If O2 is NOT present → Fermentation
Fermentation • Occurs when no O2 is present • 2 Types: • 1. Lactic Acid Fermentation: Converts pyruvate → lactic acid • Helps make yogurt & cheese • Creates burning sensation in muscles during exercise • 2. Alcoholic Fermentation: Converts pyruvate → ethyl alcohol • Helps make bread, wine & beer
Citric Acid (Kreb’s) Cycle & Electron Transport Chain • Occurs when O2 is present • Breaks down pyruvate molecules (from glycolysis) into smaller molecules • As chemical bonds form and break, electrons get moved around & CO2 is released • This releases energy, thus making ATP!