Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Fireflies use light to signal to potential mates attract males of other species — as meals Cool “Fires” Attract Mates and Meals luciferin-luciferase system

What is energy? Why do we need it? How do chemical reactions use or produce energy? How does ATP transfer energy? How do enzymes affect rates of chemical reactions? Energy and cells

Energy is the capacity to perform work

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Chemical energy is due to the arrangement of atoms in molecules Rearrangement of atoms will either store or release energy chemical reaction = rearrangement of atoms

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –Endergonic reactions absorb energy and yield products rich in potential energy Figure 5.3A Reactants Potential energy of molecules Products Amount of energy INPUT

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings –Exergonic reactions release energy and yield products that contain less potential energy than their reactants Figure 5.3B Reactants Potential energy of molecules Products Amount of energy OUTPUT

Energy content of common chemicals (foods) Energy used in activities

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In cellular respiration, some energy is stored in ATP molecules ATP powers nearly all forms of cellular work ATP is key to energy coupling ATP shuttles chemical energy within the cell

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings This reaction supplies energy for cellular work: Figure 5.4A Phosphate groups Adenine Ribose Adenosine triphosphate Hydrolysis Adenosine diphosphate (ADP) Energy

How is ATP’s chemical energy used to do work in a cell?

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings For a chemical reaction to begin, reactants must absorb some energy –energy of activation (EA) = energy barrier Enzymes lower energy barriers How do enzymes work?

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings enzymes can decrease the energy barrier E A barrier Reactants 1Products2 Enzyme Figure 5.5A

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Enzyme (sucrase) Active site Substrate (sucrose) Enzyme available with empty active site Substrate binds to enzyme with induced fit Substrate is converted to products 4 Products are released GlucoseFructose enzyme is unchanged and can repeat the process Figure 5.6 A specific enzyme catalyzes each cellular reaction

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Enzyme activity is influenced by –temperature –salt concentration –pH Reaction rate is affected by amount of substrate Allosteric regulation by other factors The cellular environment affects enzyme activity

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Some enzymes require nonprotein cofactors Ex. zinc, iron coenzymes = cofactors that are organic molecules Ex. vitamins

A. Cellular respiration 1.Glycolysis 1.Kreb cycle 1.Electron transport chain B. Fermentation

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Cellular respiration breaks down glucose molecules and banks their energy in ATP –uses O 2 and releases CO 2 and H 2 O GlucoseOxygen gas Carbon dioxide WaterEnergy

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Glucose gives up energy as it is oxidized oxidation = loss of H Oxygen is reduced (gains H) Loss of hydrogen atoms Glucose Gain of hydrogen atoms Energy Figure 6.4 Redox reactions are linked oxidations and reductions

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An overview of cellular respiration Figure 6.8 High-energy electrons carried by NADH GLYCOLYSIS GlucosePyruvic acid KREBS CYCLE ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS Mitochondrion Cytoplasmic fluid

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Glycolysis harvests chemical energy by oxidizing glucose to pyruvic acid Figure 6.9A GlucosePyruvic acid

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Each pyruvic acid molecule is broken down to form CO 2 and a two-carbon acetyl group, which enters the Kreb cycle Pyruvic acid is chemically groomed for the Kreb cycle Figure 6.10 Pyruvic acid CO 2 Acetyl CoA (acetyl coenzyme A)

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings enzymes strip away electrons and H + from each acetyl group, generating many NADH and FADH 2 molecules The Krebs cycle completes the oxidation of organic fuel Figure 6.11A Acetyl CoA KREBS CYCLE 2 CO 2

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Steps in the Electron Transport System Figure 3.28

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Electron Transport System and chemiosmosis in the mitochondrion Figure 6.12 Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Protein complex Electron carrier Electron flow ELECTRON TRANSPORT CHAIN ATP SYNTHASE

cell inner membrane outer membrane mitochondrion

glycolysis Krebs cycle outer membrane inner membrane electron transport chain inner compartment H2OH2O O2O2 H+H+ e-e- outer compartment H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Certain poisons interrupt critical events in cellular respiration Figure 6.13 Rotenone Cyanide, carbon monoxide Oligomycin ELECTRON TRANSPORT CHAIN ATP SYNTHASE

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings An overview of cellular respiration Figure 6.8 High-energy electrons carried by NADH GLYCOLYSIS GlucosePyruvic acid KREBS CYCLE ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS Mitochondrion Cytoplasmic fluid

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Without oxygen, cells can use glycolysis alone to produce small amounts of ATP –But a cell must replenish NAD+ Fermentation is an anaerobic alternative to aerobic respiration GlucosePyruvic acid

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In alcoholic fermentation, pyruvic acid is converted to CO 2 and ethanol –This recycles NAD + to keep glycolysis working GLYCOLYSIS 2 Pyruvic acid released 2 Ethanol Glucose Figure 6.15C FERMENTATION

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings In lactic acid fermentation, pyruvic acid is converted to lactic acid –NAD + is recycled Produces cheese and yogurt GLYCOLYSIS 2 Pyruvic acid 2 Lactic acid Glucose Figure 6.15B

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Polysaccharides monosaccharides glucose for glycolysis Proteins amino acids Krebs cycle Fats acetyl-Co A Krebs cycle Cells use many kinds of organic molecules as fuel for cellular respiration

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Pathways of molecular breakdown Figure 6.16 Food, such as peanuts PolysaccharidesFatsProteins SugarsGlycerolFatty acidsAmino acids Amino groups GlucoseG3P Pyruvic acid GLYCOLYSIS Acetyl CoA KREBS CYCLE ELECTRON TRANSPORT CHAIN AND CHEMIOSMOSIS

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings cells need raw materials for growth and repair –Some directly from food –Others made from intermediates in glycolysis and the Krebs cycle Biosynthesis uses ATP (endergonic) Food molecules provide raw materials for biosynthesis

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Biosynthesis of macromolecules from intermediates in cellular respiration Figure 6.17 ATP needed to drive biosynthesis PolysaccharidesFatsProteins KREBS CYCLE Acetyl CoA Pyruvic acid G3PGlucose GLUCOSE SYNTHESIS Amino groups Amino acidsFatty acidsGlycerolSugars Cells, tissues, organisms