1

BIOENERGETICBIOENERGETICSS

Energy Flow

2

What is Bioenergetics?

The study of energyenergy in living systemsliving systems (environments) and the organismsorganisms (plants and animals) that utilize them

3

Energy Required by

all organisms

May be Kinetic or Potential energy

4

Kinetic Energy Energy of

Motion Heat and

light energy are examples

5

Potential Energy EnergyEnergy of of

positionposition Includes Includes

energy energy stored in stored in chemical chemical bondsbonds

6

Two Types of Energy Reactions

7

Endergonic Reactions

Chemical reactionChemical reaction that requires a net input of energyenergy.

Absorbs free energy and stores it

PhotosynthesisPhotosynthesis

6CO2+ 6H2O C6H12O6 + 6O2

SUNphotonsphotons

LightEnergy

(glucose)(glucose)

8

Exergonic Reactions Chemical reactionsChemical reactions that

releases energyreleases energy Cellular Respiration

C6H12O6 + 6O2 6CO2 + 6H2O+ATP(glucose)(glucose)

EnergyEnergy

9

Metabolic Reactions of

Cells

10

What is Metabolism?

The sum totalsum total of the chemical chemical activitiesactivities of all cellscells.

Managing the material and energy resources of the cell

11

Two Types of Metabolism

CataboliCatabolic c PathwayPathwayss

Anabolic Anabolic PathwayPathwayss

12

Catabolic PathwayCatabolic Pathway Metabolic reactionsMetabolic reactions which

release energyrelease energy (exergonic)(exergonic) by breaking downbreaking down complex molecules in simpler compounds

Hydrolysis = add a water molecule to break apart chemical bonds

Cellular RespirationCellular Respiration C6H12O6 + 6O2 6CO2 + 6H2O +

ATP(glucose)(glucose)

energy

13

Anabolic PathwayAnabolic Pathway Metabolic reactions,Metabolic reactions, which

consume energyconsume energy (endergonic),(endergonic), to buildbuild complicated molecules from simpler compounds.

Dehydration synthesis = removal of a water molecule to bond compounds together

PhotosynthesisPhotosynthesis

6CO2 + 6H2O C6H12O6 + 6O2

SUN lightlightenergyenergy

(glucose)(glucose)

14

Energy CouplingEnergy Coupling The transfer of energy from catabolism to anabolism

Energy from exergonic reactions drive endergonic reactions and vice versa

EX. Photosynthesis – cellular respiration cycle

15

Energy TransformationEnergy Transformation Governed by the Laws of

Thermodynamics.

16

1st Law of 1st Law of ThermodynamicsThermodynamics Energy can be transferred and

transformed, but it cannot be created or destroyed.

Also known as the law of Conservation of Energy.

17

2nd Law of 2nd Law of ThermodynamicsThermodynamics Each energy transfer or

transformation increases the entropy of the universe.

Entropy = a measure of disorder or randomness

HEAT is energy in its most random state.

18

SummarySummary The quantity of energy in the

universe is constant, but its quality is not.

19

Free EnergyFree Energy The portion of a system's energy

that can perform work.

G = H - TSG = H - TS G = free energy of a system H = total energy of a system T = temperature in oK S = entropy of a system

20

Free Energy of a Free Energy of a SystemSystem

If the system has: more free energy it is less stable It has greater work capacity

Metabolic equilibrium = zero free energy so it can do no work DEAD CELL

Metabolic disequilibrium = produces free energy to do work

More unstable produces more free energy EX. Greater concentration/ temperature differences

21

Free Energy Changes

22

Spontaneous Process If the system is unstable, it has a

greater tendency to change spontaneously to a more stable state.

This change provides free energy for work.

23

Chemical Reactions Are the source of energy for living

systems. Are based on free energy changes.

Exergonic: chemical reactions with a net release of free energy.Endergonic: chemical reactions that absorb free energy from the surroundings.

Reaction Types

24

Exergonic/Endergonic

25

3 main kinds of cellular 3 main kinds of cellular workwork Mechanical - muscle contractions Transport - pumping across

membranes Chemical - making polymers

All cellular work is powered by

ATP

26

Cell EnergyCell Energy Couples an exergonic process to

drive an endergonic one. ATP is used to couple the

reactions together.

27

Cellular Energy - Cellular Energy - ATPATP

28

ATPATP Components:Components:

1. adenine: nitrogenous 1. adenine: nitrogenous basebase

2. ribose:2. ribose: five carbon five carbon sugarsugar

3.phosphate group: chain 3.phosphate group: chain of 3of 3

riboseribose

adenineadenine

P P P

phosphate groupphosphate group

29

Adenosine Adenosine TriphosphateTriphosphate

Three Three phosphate phosphate groups-groups-(two(two with with high energy bondshigh energy bonds

Last phosphateLast phosphate group (POgroup (PO44) ) contains the contains the MOST MOST energyenergy

All three All three phosphate groups phosphate groups are are negatively negatively chargedcharged (repel (repel each other making each other making it very it very unstableunstable))

30

Breaking the Bonds of Breaking the Bonds of ATPATP Occurs continually in cells Enzyme ATP-aseATP-ase can

weaken & break last POlast PO44 bondbond releasing energy & free PO4

Phosphorylated Phosphorylated = a phosphate group attaches to other molecules making them more unstable and more reactive (energy boost to do work)

31

How does ATP How does ATP work ?work ? Organisms use enzymesenzymes

to break down energy-rich energy-rich glucoseglucose to release its potential energy

This energy is trapped and stored in the form of adenosine adenosine triphosphate(ATP)triphosphate(ATP)

32

How Much ATP Do Cells How Much ATP Do Cells Use?Use?

It is estimated that each celleach cell will generate and consume approximately 10,000,000 10,000,000 molecules of molecules of ATP ATP per per secondsecond

33

Coupled Reaction - Coupled Reaction - ATPATP The exergonic exergonic

hydrolysishydrolysis of ATPATP is coupled with the endergonic endergonic dehydration dehydration processprocess by transferringtransferring a phosphate groupphosphate group to another molecule.

HH22OO

HH22OO

34

Hydrolysis ofHydrolysis of ATP ATPATP + H2O ADP + P (exergonic)

HydrolysisHydrolysis(add water)(add water)

P P P

Adenosine triphosphate (ATP)Adenosine triphosphate (ATP)

P P P++

Adenosine diphosphate (ADP)Adenosine diphosphate (ADP)

35

Hyrolysis is ExergonicHyrolysis is Exergonic

EnergEnergy y

Used Used by by

CellsCells

36

Dehydration ofDehydration of ATP ATPADP + ADP + P P ATPATP + + HH22O O (endergonic(endergonic)

P P P

Adenosine triphosphate (ATP)Adenosine triphosphate (ATP)

P P P++

Adenosine diphosphate (ADP)Adenosine diphosphate (ADP)

DehydrationDehydration(Remove (Remove HH22OO

37

Dehydration is Dehydration is EndergonicEndergonic

Energy Energy is is restorerestored in d in ChemicChemical al BondsBonds

38

ATP in CellsATP in Cells A cell's ATP content is recycled

every minute. Humans use close to their body

weight in ATP daily.

No ATP production equals quick death.

39

What Are What Are Enzymes?Enzymes?

Most enzymes are Proteins Proteins ((tertiary and quaternary structures)

Act as CatalystCatalyst to accelerates a reaction

Not permanentlyNot permanently changed in the process

40

EnzymesEnzymes Are specific for

what they will catalyzecatalyze

Are ReusableReusable End in –asease

-Sucrase-Sucrase-Lactase-Lactase-Maltase-Maltase

41

How do enzymes Work?How do enzymes Work?

Enzymes work by weakening weakening bondsbonds which lowers owers activation energy

42

Activation EnergyActivation Energy Energy needed to convert

potential energy into kinetic energy.

Potential Energy

Activation Energy

43

EnzymesEnzymes

FreeEnergy

Progress of the reaction

Reactants

Products

Free energy of activationFree energy of activation

Without Enzyme

With Enzyme

44

45

46

Enzyme-Substrate Enzyme-Substrate ComplexComplex

The substancesubstance (reactant) an enzymeenzyme acts on is the substratesubstrate

EnzymeSubstrate Joins

47

Active SiteActive Site

A restricted regionrestricted region of an enzymeenzyme molecule which bindsbinds to the substratesubstrate.

Enzyme

Substrate

Active Site

48

49

Models of How Enzymes Models of How Enzymes WorkWork

1. Lock and Key model2. Induced Fit model

50

Lock and Key ModelLock and Key Model Substrate (key) fits to the active

site (lock) which provides a microenvironment for the specific reaction.

51

Induced FitInduced Fit A change in

the shapeshape of an enzyme’s active site

Induced Induced by the substrate

52

Induced Fit ModelInduced Fit Model Substrate “almost” fits into the

active site, causing a strain on the chemical bonds, allowing the reaction.

53

EnzymesEnzymes Usually specific to one substrate.

Each chemical reaction in a cell requires its own enzyme.

54

Factors that Affect Enzymes

Environment (Temperature & pH)

Cofactors Coenzymes Inhibitors Allosteric Sites

55

EnvironmentEnvironment Factors that change protein

structure will affect an enzyme. Examples:

pH shifts temperature salt concentrations

56

Temperature & pHTemperature & pH High temperaturesHigh temperatures denaturedenature

enzymes (Most enzymes like (Most enzymes like normal body temperaturesnormal body temperatures)

Most enzymes function near neutral pH (6 to 8)

Denatured (unfolded) by ionic ionic saltssalts

57

58

Cofactors Cofactors Inorganic substancesInorganic substances (zinc, iron, copper) (zinc, iron, copper)

are sometimes need for proper enzymatic enzymatic activityactivity.

Non-protein helpers can bond to the active site of enzymes to help in reactions

Example:Example: IronIron must be present in the

quaternary structure of hemoglobinhemoglobin in order for it to pick up oxygenoxygen.

59

CoenzymesCoenzymes Organic molecules that act as

cofactors which help enzymes. Examples:

vitamins

60

Two examples of Enzyme Two examples of Enzyme InhibitorsInhibitors

a. a. Competitive inhibitorsCompetitive inhibitors:: are chemicals that resembleresemble an enzyme’s normal substrateenzyme’s normal substrate and competecompete with it for the active active sitesite.

Enzyme

Competitive inhibitor

Substrate

61

InhibitorsInhibitorsb.b. Noncompetitive inhibitorsNoncompetitive inhibitors::

Inhibitors that do not enter thedo not enter the active active sitesite, but bind tobind to another partanother part of the enzymeenzyme causing the enzymeenzyme to change its change its shapeshape, which in turn alters the active sitealters the active site.

Enzymeactive site altered

NoncompetitiveInhibitor

Substrate

62

63

Control of MetabolismControl of Metabolism Is necessary if life is to function. Controlled by switching enzyme activity

"off" or "on” or separating the enzymes in time or space.

Types of Control1. Switching on or off the genes

that encode for specific enzyme production

2. Allosteric sites3. Feedback inhibition4. cooperativity

64

Allosteric RegulationAllosteric Regulation The control of an enzyme complex by the

binding of a regulatory molecule. Regulatory molecule may stimulate or inhibit

the enzyme complex.

Allosteric site is a specific receptor site on some part of the enzyme molecule away from the active site

When activated, this site changes the shape of the enzyme to inhibit it or to stimulate it

65

Allosteric RegulationAllosteric Regulation

66

Feedback InhibitionFeedback Inhibition When a metabolic pathway is

switched off by its end-product. End-product usually inhibits an

enzyme earlier in the pathway. Prevents the cell from wasting

chemical resources

67

68

CooperativityCooperativity One substrate molecule can

trigger the same favorable shape-change in all the other subunits of the enzyme

Amplifies the response of the enzymes to substrate

69

ReviewReview

70

How many high energy How many high energy phosphate bonds does ATP phosphate bonds does ATP have?have?

71

Which is true of Which is true of photosyntheis?photosyntheis?

Anabolic Anabolic or or CatabolicCatabolic

ExergonicExergonic OrOrEndergonicEndergonic

72

The breakdown of ATP is The breakdown of ATP is due to:due to:

DehydrationDehydration ororHydrolysisHydrolysis

HH22O addedO added oror HH22O removedO removed

73

Which Reactions are Which Reactions are often Coupled in often Coupled in

OrganismsOrganisms

HydrolysisHydrolysis or or DehydrationDehydration

AnabolismAnabolism or or CatabolismCatabolism

EndergonicEndergonic oror ExergonicExergonic

BOTHBOTH

BOTHBOTH

BOTHBOTH