Respiration..... It ain't just breathin' anymore!!

How Do Organisms Supply Themselves With Energy?

Key Questions How do organisms supply themselves with energy? How do organisms extract energy from glucose? How is the energy in glucose used to make ATP?

How Do Organisms Supply Themselves With Energy? All organisms need energy Ultimate source of energy on the Earth is the sun Autotrophs make their own food; examples: plants, some bacteria Heterotrophs obtain chemical energy from other organisms Examples?

Energy Currency Adenosine Triphosphate or ATP Cellular respiration produces ATP Aerobic versus anaerobic

Cellular Respiration

Steps of Cellular Respiration Step 1: glycolysis Step 2: acetyl-CoA formation Step 3: citric acid cycle Step 4: electron transport and oxidative phosphorylation

Cellular Respiration — Chemical Equation C6H12O6 + 6O2 Glucose Oxygen 6CO2 + 6H2O + ATP Carbon Water Energy Dioxide

What Is Oxidation? Oxidizing agent or electron acceptor accepts an electron Reducing agent or electron donor donates an electron Oxidation and reduction always go hand in hand Examples of acceptors: O2, NAD+, FAD

Step 1: Glycolysis Occurs in Cytoplasm Part 1: 6 carbons are split into 3-carbon molecules and are phosphorylated; uses ATP Part 2: Phosphates and electrons are removed; electrons added to NAD+ to make NADH; produces 2 ATP

Step 1: Glycolysis Cont. Part 3: More electrons and phosphates are removed from the 3-carbon molecules; phosphates are added to ADP to make ATP

Glycolysis Overview Breaks glucose into 2 molecules of pyruvate, generating 2 molecules of ATP and 2 molecules of NADH Aerobic or anaerobic? The pyruvate enters a cell’s ______. When compounds are reduced, they ___ electrons. When compounds are oxidized, they ___ electrons. Which molecules/coenzymes from Glycolysis accept electrons? ANAEROBIC MITOCHONDRIA DONATE ACCEPT NAD+

Step 2: Acetyl CoA Occurs in ______ MITOCHONDRIA Oxygen needed for this reaction; aerobic Pyruvate loses a carbon and 2 oxygens in the form of CO2 Enzymes link coenzyme A to the acetate CoA synthesizes fatty acids.

Step 3: Citric Acid Cycle Overview High energy electrons are captured in the form of NADH and FAD Occurs in the matrix of the mitochondria With each turn of the cycle, citrate loses a total of 8 electrons to electron acceptors such as NAD+

Step 3: Citric Acid Cycle 3 parts Part 1: 6-carbon citrate and isocitrate formation Part 2: conversion of isocitrate into a 4-carbon compound Part 3: production of another molecule of OAA, which starts the cycle over again

Citric Acid Cycle

What If There Is No Oxygen? After glycolysis, if there is no oxygen, fermentation will occur Cells must regenerate more NAD+ from NADH Yeast — form ethanol (terminal reaction produces CO2 ) Animals — form lactic acid (ouch)

Biochemical Pathway Intersections Figure 6-7 Catabolism — breakdown of complex molecules such as food; produces energy, involves oxidation Anabolism — synthesis of complex molecules; uses energy

How Do Other Food Molecules Enter Metabolism? Fat, carbohydrates and proteins enter the cellular respiration pathway at different points The most likely point is at acetyl CoA

Electron Transport Chain

Step 4: Electron Transport & Oxidative Phosphorylation The pathway of electrons from one carrier to another is called ____ ____ _____; Each electron carrier passes its electrons to the next carrier (bucket brigade) Most of the electrons to the electron transport chain are received from what cycle? A reduced carrier becomes oxidized when it gives up its electrons (forms ATP from ADP) Oxygen accepts electrons ELECTRON TRANSPORT CHAIN KREB’S

How Do Cells Harvest Energy? Proton gradient — flow of electrons through the electron transport chain creates this gradient (ATP is made from this gradient) Chemiosmosis — harnessing of the energy stored in the chemical gradient; some machinery in the membrane must do this process

Generating a Proton Gradient Mitochondria — inner and outer membrane Intermembrane space — space between 2 membranes Matrix — space within the inner membrane; makes up about 2/3 of the volume; ETC is embedded in this inner membrane

Pumping Protons pH & cytochromes assist w/ transport of electrons. Gradient is produced when…..

ATP Synthase Proton complex Protons flow through these channels back into the matrix Works like a turbine Uses energy to make ATP

Key Concepts Cellular respiration converts the chemical energy of food molecules into the chemical energy of ATP Most cells can use glycolysis to obtain energy ATP production from cellular respiration depends on oxidative phosphorylation