Chapter 6 Energy Flow in the Life of a Cell Chapter 6 Energy Flow in the Life of a Cell

Chapter 6 Outline 6.1 What Is Energy? 6.2 How Does Energy Flow in Chemical Reactions? 6.3 How Is Cellular Energy Carried Between Coupled Reactions? 6.4 How Do Cells Control Their Metabolic Reactions?

6.1 What Is Energy? Energy is the ____________________ Work is a force acting on an object that causes the object to _________ _________________ is the energy that powers life –The objects that move are __________, which reposition during chemical reactions

The Laws of Thermodynamics The two fundamental types of energy –Kinetic energy is the energy of __________ e.g. light, heat, electricity, moving objects –Potential energy is _____________ energy e.g. chemical energy in bonds, electrical charge in a battery, a rock at the top of a hill

The Laws of Thermodynamics The laws of thermodynamics describe the availability and usefulness of energy –________________________________ (first law of thermodynamics) –The total amount of energy within a given system remains __________ unless energy is added or removed from the system

The Laws of Thermodynamics Availability and usefulness of energy: –The amount of useful energy __________ when energy is converted from one form to another (second law of thermodynamics) –Entropy (disorder) ______________

Energy of Sunlight Living Things Use the Energy of Sunlight to Create the _____________ Conditions Characteristic of Life __________________ organisms use external solar energy to maintain orderly structure ____________________ organisms use stored chemical energy in other living things to counter increasing entropy

Section 6.2 Outline 6.2 How Does Energy Flow in Chemical Reactions? –The Nature of Chemical Reactions –Exergonic Reactions ___________ Energy –Endergonic Reactions ___________ an Input of Energy –Coupled Reactions _______Exergonic and Endergonic Reactions

Chemical Reactions Chemical reactions are processes that ____________________________ between atoms Chemical reactions convert _________ to products Reactants Products

Chemical Reactions Reactions can be categorized as exergonic or endergonic based on energy gain or loss

Exergonic Reactions Exergonic reactions __________ energy Reactants contain _______ energy than products in exergonic reactions

Exergonic Reactions Exergonic reaction example: the burning of glucose

Exergonic Reactions All chemical reactions require an initial energy input (____________________) to get started –Molecules need to be moving with sufficient collision speed –The electrons of an atom repel other atoms and inhibit bond formation

Endergonic Reactions Endergonic reactions are _______________ ___________________________ of energy Products contain _______ energy than reactants in endergonic reactions

Endergonic Reactions Endergonic reaction example: photosynthesis

Coupled Reactions ______________ reactions drive _____________ reactions –The product of an energy-yielding reaction fuels an energy-requiring reaction in a _________________

Coupled Reactions The exergonic and endergonic parts of coupled reactions often occur at different places within the cell ___________________________ are used to transfer the energy within cells

Section 6.3 Outline 6.3 How Is Cellular Energy Carried Between Coupled Reactions? –Energy Carrier Molecules –______ Is the Principal Energy Carrier in Cells –____________________ Also Transport Energy Within Cells

Energy Carrier Molecules Food energy cannot be used _______ to power energy-requiring reactions (e.g. muscle contraction) Energy carrier molecules act as ______________ to carry energy between __________ and _____________ reactions Energy carrier molecules are only used within cells because they are ________

ATP ______________________ (ATP) is the most common energy carrying molecule ATP is composed of an adenosine molecule and ______ phosphates

ATP Energy is stored in the high-energy bond extending to the _________________ Heat is given off when ATP breaks into _____ (adenosine diphosphate) and ___ (phosphate)

ATP The energy released when ATP is broken down into ADP + P is transferred to ______________ reactions through coupling

Electron Carriers Energy can be transferred to __________ in glucose metabolism and photosynthesis Electron _________ transport high- energy electrons Two common electron carriers 1.Nicotinamide adenine dinucleotide ______ 2.Flavin adenine dinucleotide _______

Section 6.4 Outline 6.4 How Do Cells Control Their Metabolic Reactions? –Overview of Metabolism –At Body Temperatures, Spontaneous Reactions Proceed Too ________to Sustain Life –Catalysts __________ Activation Energy –Enzymes Are Biological ______________ –Cells Regulate Metabolism by __________ Enzymes –Poisons, Drugs, and Environmental Conditions Influence ___________________

Overview of Metabolism The sum of all the chemical reactions inside a cell is its __________________ Many cellular reactions are linked through metabolic _______________

Overview of Metabolism Metabolic pathways proceed smoothly for three reasons: 1.Endergonic reactions are _______ with exergonic reactions 2.Energy-carrier molecules capture energy and ____________ between endergonic and exergonic reactions 3.Chemical reactions are regulated through protein _______________

Spontaneous Reactions At body temperatures, spontaneous reactions proceed too _________ to sustain life Reaction speed is generally determined by the activation energy required –Reactions with low activation energies proceed _________ at body temperature –Reactions with high activation energies (e.g. sugar breakdown) move very _______ at body temperature, even if exergonic overall

Spontaneous Reactions Enzyme molecules are employed to ___________(speed up) chemical reactions in cells Catalysts ________________ of a chemical reaction without themselves being used up

Catalysts Reduce Activation Energy Catalytic converters in cars facilitate the conversion of carbon monoxide to carbon dioxide Octane + oxygen carbon dioxide + water + energy + carbon monoxide (poisonous) Catalyst in catalytic converter speeds carbon monoxide conversion Carbon monoxide + oxygen carbon dioxide + energy

Catalysts Reduce Activation Energy Catalysts speed up spontaneous reactions by ____________________________

Enzymes Are Biological Catalysts Enzymes __________________________ molecules in the process of lowering activation energy Enzymes (proteins) differ from non-biological catalysts because: 1.Enzymes are very ___________ for the molecules they catalyze 2.Enzyme activity is often ____________________ by their reactants or products Some enzymes require helper ___________ molecules to function (e.g. certain B vitamins)

Enzyme Structure Enzymes have a pocket called an _________ Reactants (_________) bind to the active site –Distinctive shape of active site is complementary and specific to the substrate –Active site amino acids bind to the substrate and distort bonds to facilitate a reaction

Enzyme Structure Three steps of enzyme catalysis 1.Substrates enter the _________ in a specific orientation 2.Upon binding, the substrates and enzyme _____________ to promote a reaction 3.Products of the reaction ________ the active site, leaving the enzyme ready for another catalysis

Cells Regulate Metabolism A given enzyme usually catalyzes a single step in a chain of metabolic reactions Metabolic pathways are controlled in several ways 1.Control of _____________________ regulates availability 2.Some enzymes are inactive when synthesized and must be _____________ __________________

Cells Regulate Metabolism Metabolic pathways are controlled in several ways (continued) 3.Small organic molecules can bind to enzymes and ___________________ activity (allosteric regulation)

Cells Regulate Metabolism Metabolic pathways are controlled in several ways (continued) 4.Adequate amounts of formed product inhibit enzyme activity ___________________

Drugs and Poisons Drugs and poisons often inhibit enzymes by ____________ with the natural substrate for the active site This process is known as _______________________ Some inhibitors bind permanently to the enzyme

Environmental Conditions Three-dimensional structure of an enzyme is sensitive to ______________________ ______________________________ Most enzymes function optimally only within a very narrow range of these conditions

Environmental Conditions Enzyme structure is _________ and function is destroyed when pH is _________ _____________ Salts in an enzyme’s environment can also destroy function by altering ___________

Environmental Conditions Temperature also affects enzyme activity –Low temperatures ______________ molecular movement –High temperatures cause ___________ to be altered, destroying function