Inquiry into Life Twelfth Edition Chapter 7 Lecture PowerPoint to accompany Sylvia S. Mader Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

7.1 Metabolism

Catabolism: Breaking down of molecules

7.1 Metabolism Catabolism: Breaking down of molecules Anabolism: Building up of molecules (ATP is the energy currency used by these reactions)

Metabolism

7.1 Metabolism Catabolism –Food contains three nutrients that are used as energy sources –These nutrients can be broken down into smaller molecules Carbohydrates Glucose Fats Glycerol and Fatty Acids Proteins Amino Acids

7.1 Metabolism Anabolism –Many of the building blocks of larger molecules come directly from our food. Glucose Glycogen Amino Acids Proteins

7.1 Metabolism Cellular Respiration –Release of energy from glucose (usually) coupled to ATP synthesis –An aerobic process that requires O 2 and releases CO 2

Cellular Respiration

7.2 Overview of Cellular Respiration This is hard. You must learn it. So – Get it done

7.2 Overview of Cellular Respiration Metabolic pathways allow energy within glucose to be released Release of energy does happen all at once As glucose is broken down, ATP is built up Breakdown of glucose results in 36 or 38 ATP molecules The energy released is by the removal of a phosphate group

7.2 Overview of Cellular Respiration NAD + and FAD Two coenzymes of oxidation and reduction that are active during cellular respiration They carry electrons from the cytoplasm or the mitochondrial matrix and carry them to the cristae of the mitochondria NAD + and FAD each carry two electrons and two hydrogen atoms

The NAD + Cycle

7.2 Overview of Cellular Respiration Phases of Cellular Respiration –Glycolysis –Preparatory Reaction –Citric Acid Cycle –Electron Transport Chain –We will simplify: Glycolysis, Krebs cycle, electron transport

Phases of Glucose Breakdown

7.2 Overview of Cellular Respiration Glycolysis –Breakdown of glucose to 2 molecules of pyruvate –Oxidation by removal of hydrogens releases enough energy to make 2 ATP

7.2 Overview of Cellular Respiration Glycolysis –Breakdown of glucose to 2 molecules of pyruvate –Oxidation by removal of hydrogens releases enough energy to make 2 ATP

7.2 Overview of Cellular Respiration Glycolysis –Breakdown of glucose to 2 molecules of pyruvate –Oxidation by removal of hydrogens releases enough energy to make 2 ATP

7.2 Overview of Cellular Respiration Preparatory Reaction –Pyruvate oxidized to acetyl CoA and carbon dioxide is removed –Prep reaction occurs twice because glycolysis produces 2 pyruvates

7.2 Overview of Cellular Respiration Citric Acid Cycle –Acetyl CoA is converted to citric acid and enters the cycle –Cyclical series of oxidation reactions that produces 1 ATP and carbon dioxide –Citric acid cycle turns twice because 2 acetyl CoA’s are produced per glucose

7.2 Overview of Cellular Respiration Electron Transport Chain –Series of electron carrier molecules –Electrons passed from one carrier to another –As the electrons move from a higher energy state to a lower one, energy is released to make ATP –Under aerobic conditions ATP per glucose molecule can be produced

7.2 Overview of Cellular Respiration Electron Transport Chain –Series of electron carrier molecules –Electrons passed from one carrier to another –As the electrons move from a higher energy state to a lower one, energy is released to make ATP –Under aerobic conditions ATP per glucose molecule can be produced

7.2 Overview of Cellular Respiration Pyruvate –Pivotal metabolite in cellular respiration –If no oxygen is available, pyruvate is reduced to lactate (in animals) or alcohol and carbon dioxide (in plants) in a process called fermentation –Fermentation results in a net gain of 2 ATP/glucose

7.3 Outside the Mitochondria: Gycolysis

Energy-Investment Steps –Energy from 2 ATP is used to activate glucose –Glucose is split into two 3-carbon G3P molecules

7.3 Outside the Mitochondria: Gycolysis Energy-Harvesting Steps –Oxidation of G3P by removal of hydrogens –Hydrogen’s are picked up by NAD + to form NADH –Oxidation of G3P and further substrates yields enough energy to produce 4 ATP by direct substrate phosphorylation

Glycolysis: Inputs and Outputs

7.4 Inside the Mitochondria Preparatory Reaction –Produces the molecule that will enter the citric acid cycle –3C pyruvate is converted to 2C acetyl CoA –Carbon dioxide is produced –Hydrogen atoms are removed from pyruvate and picked up to form NADH –This reaction occurs twice per glucose

The Preparatory Reaction

7.4 Inside the Mitochondria Citric Acid Cycle –C 2 acetyl group from prep reaction combines with a C 4 molecule to produce C 6 citrate –Oxidation of citrate by removal of hydrogens –Produces 3 NADH and 1 FADH 2 –Produces 1 ATP by direct substrate phosphorylation –Cycle turns twice per glucose

Citric Acid Cycle: Inputs and Outputs

Citric Acid Cycle

7.4 Inside the Mitochondria Electron Transport Chain –2 electrons per NADH and FADH 2 enter the electron transport chain –Electrons are passed to series of electron carriers called cytochromes –Energy is captured and stored as a hydrogen ion concentration gradient –For each NADH enough energy is released to form 3 ATP –For each FADH 2 there are 2 ATP produced

7.4 Inside the Mitochondria Electron Transport Chain –The final electron acceptor is oxygen –After receiving electrons oxygen combines with hydrogen ions to form water as an end product ½ O e- + 2H+  H 2 O –NAD + and FAD recycle back to pick up more electrons from glycolysis, prep reaction, and citric acid cycle

Electron Transport Chain

7.4 Inside the Mitochondria Organization of Cristae –Electron carriers are arranged along the cristae As electrons are passed, energy is used to pump H + into the intermembrane space of mitochondrion As H + moves back into matrix energy is released and captured to form ATP by ATP synthase complexes –Process is called chemiosmosis

Organization of Cristae

Energy Yield per Glucose Molecule

7.4 Inside the Mitochondria

Efficiency of Cellular Respiration –The difference in energy content of reactants (glucose and oxygen) and products (carbon dioxide and water) is 686 kcal –ATP phosphate bond has 7.3 kcal of energy –36 ATP are produced in respiration 36 X 7.3 = 263 kcal –263/686 = 39% efficiency of energy capture –The rest of the energy is lost as heat

7.5 Fermentation Fermentation –Occurs when O 2 is not available –Animal cells convert pyruvate to lactate –Other organisms convert pyruvate to alcohol and CO 2 –Fermentation regenerates NAD + which keeps glycolysis going

7.5 Fermentation Advantages and Disadvantages of Fermentation –Provides a rapid burst of ATP –Provides a low but continuous supply of ATP when oxygen is limited and only glycolysis can function –Lactate is potentially toxic to muscles, lowering pH and causing fatigue

Fermentation: Inputs and Outputs

Fermentation