Unit 6- Cell Energy- Photosynthesis & Cellular Respiration 6b- Cellular Respiration

Bellwork Explain the Calvin Cycle using these words: CO2 , RuBP, PGA, ATP & NADPH, PGAL. How is it a cycle? What is the final product of the Calvin Cycle? Where does it occur? What three factors affect the rate of photosynthesis?

Bellwork 1) CO2 combines with RuBP, new molecule splits into PGA. PGA combines with ATP/NADPH to become PGAL. PGAL makes glucose, leftover PGAL becomes RuBP to start cycle again. 2) Final product= glucose! 3) Occurs in the stroma. 4) Temperature, amount of CO2, amount of sunlight.

Cellular Respiration Goal of Cellular Respiration: to convert the chemical energy in food to chemical energy stored in adenosine triphosphate (ATP) ATP can then release the energy for cellular metabolic processes, such as active transport, protein synthesis, & muscle contraction Any organic molecule can be broken down into smaller molecules & then used as a source of energy to produce ATP molecules. Occurs in both autotrophs & heterotrophs

Stages of Cellular Respiration The process is generally represented using a balanced chemical equation… C6H12O6 + 6O2  6CO2 + 6H2O + energy (ATP) However, to transfer the energy stored in glucose to ATP, a cell must break down glucose slowly in a series of steps and capture the energy in stages. 2 Stages (when oxygen is present) Glycolysis Anaerobic – does not require oxygen Aerobic Respiration Aerobic- requires oxygen

Glycolysis Glycolysis- A series of reactions catalyzed by enzymes Occurs in the cytoplasm of the cell Anaerobic- Does not require oxygen In the process of glycolysis, a glucose molecule is broken down into pyruvic acid molecules and two ATP molecules Glucose pyruvic acid + ATP (small amount) Many texts use pyruvic acid and pyruvate interchangeably. Pyruvic acid is a pyruvate molecule that has combined with a hydrogen ion Requires 2 ATP and produces 4…so net gain of 2 ATP per glucose molecule

Aerobic Respiration If oxygen is available, the 2-stage process of aerobic respiration occurs after glycolysis. The two aerobic reactions are the Krebs Cycle (aka Citric Acid Cycle) the Electron Transport Chain Occurs in the mitochondria of the cell

Krebs Cycle (Citric Acid Cycle) The pyruvic acid, produced by glycolysis, travels to the mitochondria where it is broken down in a cycle of chemical reactions Occurs in the mitochondrial matrix- space inside mitochondria Produces carbon dioxide, ATP, & electron carriers (NADH & FADH2) Pyruvic acid  CO2 + ATP (small amount) + electron carriers CoA- coenzyme A

Krebs Cycle CO2 is released Pyruvic acid from Glycolysis fuels the cycle CO2 is released Electron carriers are released ATP is released

Electron Transport Chain A series of chemical reactions in which energy is transferred to form a large number of ATP molecules Located in the inner membrane of the mitochondria Uses the electron carriers (NADH and FADH2) to pass electrons down the protein chain & slowly release energy that is used to form ATP

Electron Transport Chain At the end of the chain oxygen combines with hydrogen & the electrons to form water. Why is oxygen required? ATP can only be synthesized if electrons continue to move along the ETC. The last molecule in the chain must pass the electrons to a final electron acceptor. Otherwise, the process would stop.

Checkpoint: try to fill in the blank! The steps of Cellular respiration: Glycolysis Produces what? Needs or does not need oxygen? Aerobic Respiration: What does it use in the Krebs cycle? What does it produce in the Krebs cycle? After the Krebs Cycle, the Electron Transport Chain. What is produced?

Electron Transport Chain Cellular Respiration 2 ATP Glycolysis 1 Glucose 2 Pyruvic Acid CO2 Citric Acid Cycle (Krebs Cycle) 2 Pyruvic Acid 2 ATP NADH and FADH2 Actual number of ATP varies from cell to cell. Most eukaryotic cells have to actively transport NADH into the mitochondria so the max net ATP is 36; also depends on the conditions within the cell NADH and FADH2 Electron Transport Chain Water 34 ATP Oxygen

Cellular Respiration Equation C6H12O6 + 6O2 6CO2 + 6H2O + energy Carbon Dioxide – waste product of the Krebs cycle Water – released from Electron Transport Chain Glucose made in photosynthesis by plants or consumed by animals Used in Glycolysis ATP released from Glycolysis, Krebs Cycle, & Electron Transport Chain Oxygen from the atmosphere Used in Electron Transport Chain Up to 38 ATP molecules are made from the breakdown of one glucose molecule: 2 from glycolysis & up to 36 from aerobic respiration. Most of the energy released by respiration, that is not used to make ATP, is released in the form of heat.