Ch 4: Cellular Metabolism, Part 1Ch 4: Cellular Metabolism, Part 1Ch 4: Cellular Metabolism, Part 1Ch 4: Cellular Metabolism, Part 1
EnergyEnergy as it relates to Biology as it relates to Biology Energy for synthesis and movement Energy transformation
EnzymesEnzymes and how they speed reactions
MetabolismMetabolism and metabolic pathways and metabolic pathways Catabolism (ATP production)Catabolism (ATP production) Anabolism (Anabolism (Synthesis of biologically
important molecules))
Energy in Biol. Systems:Energy in Biol. Systems: General definition of energy: General definition of energy:
Capacity to do workCapacity to do work Chemical, transport, movementChemical, transport, movement
First Law of Thermodynamics: First Law of Thermodynamics: Energy can neither be created Energy can neither be created nor destroyednor destroyed
Ultimate source of energy: Sun!Ultimate source of energy: Sun!
Fig 4-2
2 types of energy:2 types of energy:
Kinetic energyKinetic energy = motion = motionexamples ?
Potential energyPotential energy = stored energy = stored energyexamples ?
Energy (E) Transfer OverviewEnergy (E) Transfer Overview
Figure 4-1
Potential Energy
Kinetic Energy
WORK
heatheat (~ 70% of energyused in physical exercise)
Bioenergetics =Bioenergetics = study of energy flow
through biol. systems
Chemical reactions transfer energyChemical reactions transfer energy
A + B A + B C + DC + D
Substratesor reactants
Products
Speed of reaction = Reaction rateInitial force = Activation Energy
Potential Energy Stored in Chemical Potential Energy Stored in Chemical Bonds of Substrate can be . . .Bonds of Substrate can be . . .
1.1. transferred to the chemical bonds of transferred to the chemical bonds of the productthe product
2.2. released as heat (usually waste)released as heat (usually waste)
3.3. used to do work (used to do work (= = free energy)free energy)
Chemical Reactions Chemical Reactions p 93p 93
Activation energy
Endergonic vs. exergonic reactions reactions
Coupled reactionsCoupled reactionsDirect coupling vs. indirect couplingDirect coupling vs. indirect coupling
Reversible vs. irreversible reactionsReversible vs. irreversible reactions
Activation EnergyActivation Energy
Fig 4-3
Endo- and Exergonic ReactionsEndo- and Exergonic Reactions
Which is which??
ATP + H2O ADP + Pi + H+ + Energy
Enzyme (= Biol. Catalyst)Enzyme (= Biol. Catalyst)
1.1. Enzymes are proteinsEnzymes are proteins
2.2. rate of chemical reaction by lowering activation rate of chemical reaction by lowering activation energyenergy
3.3. is is not changed itself itself
1.1. It may change DURING the reactionIt may change DURING the reaction
4.4. does not change the nature of the reaction nor the does not change the nature of the reaction nor the resultresult
5.5. is specificis specific
Some important characteristics of an enzyme:
Fig 4-6
Enzymes lower activation energy:Enzymes lower activation energy:All chemical reactions in body must be conducted at body temp.!!
How do enzymes lower activation energy ?
Some more characteristics of Some more characteristics of enzymes:enzymes:
Usually end in –aseUsually end in –ase Inactive form: -ogenInactive form: -ogen in few cases RNA has enzymatic in few cases RNA has enzymatic
activity activity (eg: rRNA (eg: rRNA peptide bond) peptide bond) Isoenzymes may be produced in different Isoenzymes may be produced in different
areas of the bodyareas of the body E.g., LDHE.g., LDH
Small region of the complex Small region of the complex 3D structure is active (or 3D structure is active (or
binding) site.binding) site.
Enzymes bind to substrateEnzymes bind to substrate
Active Site:Active Site:
Old: Lock-and-key model / New: Induced-fit model
Enzyme-substrate interaction: Enzyme-substrate interaction: The old and the new modelThe old and the new model
Lock and Key:
Induced fit:
Naming of EnzymesNaming of Enzymes
KinaseKinase
PhosphatasePhosphatase
PeptidasePeptidase
DehydrogenaseDehydrogenase
mostly suffix mostly suffix -ase-asefirst part gives info on functionfirst part gives info on function
examples
Isoenzymes = Isoenzymes = different models of same different models of same
enzyme (differ in 1 or few aa)enzyme (differ in 1 or few aa)
Examples:Examples:
1.1. AmylaseAmylase
2.2. LDH → LDH → importance in diagnostics
Catalyze same reaction but under different Catalyze same reaction but under different conditions and in different tissues/organsconditions and in different tissues/organs
Enzyme Activity Enzyme Activity depends on depends on
1. Proteolytic activation (for some)(for some)
2.2. Cofactors & coenzymes Cofactors & coenzymes (for some)(for some)
3.3. TemperatureTemperature
4.4. pHpH
5.5. Other molecules interacting with enzymeOther molecules interacting with enzyme
1.1. Competitive inhibitorsCompetitive inhibitors
2.2. Allosteric modulatorsAllosteric modulators
1) Proteolytic 1) Proteolytic Activation Activation
Also 1. Pepsinogen Pepsin2. Trypsinogen Trypsin
2) Cofactors & Coenzymes2) Cofactors & Coenzymes
structure:Inorganic molecules (?)
function:conformational change of active site
structure:Organic molecules (vitamin derivatives, FADH2 ....)
function:act as receptors & carriers for atoms or functional groups that are removed from substrate
3)
4) Molecules interacting with enzyme4) Molecules interacting with enzyme
Competitive inhibitorsCompetitive inhibitors: : bind to active sitebind to active site
block active siteblock active site
E.g.: Penicillin binds covalently (= irreversiblyto important bacterial enzyme active site)
Fig 4-13
4)4) Molecules interacting with enzyme, cont’dMolecules interacting with enzyme, cont’d
Allosteric modulatorsAllosteric modulators (fig 4-14)(fig 4-14):: bind to enzyme bind to enzyme away from active siteaway from active site change shape change shape of active site (for better or for worse)of active site (for better or for worse)
= end product inhibitionSpecial case:
Allosteric Modulation
Reaction Rate Depends on Enzyme Reaction Rate Depends on Enzyme & Substrate Concentration& Substrate Concentration
Reversible Reactions follow the Reversible Reactions follow the Law of Mass ActionLaw of Mass Action
Three Major Types of Enzymatic Three Major Types of Enzymatic Reactions:Reactions:
1.1. Oxydation - Reduction reactionsOxydation - Reduction reactions(transfer of electrons or protons (H(transfer of electrons or protons (H++))))
2.2. Hydrolysis - Dehydration reactionsHydrolysis - Dehydration reactions(breakdown & synthesis of water)(breakdown & synthesis of water)
3.3. Addition-Subtraction-Exchange (of a Addition-Subtraction-Exchange (of a functional group) reactionsfunctional group) reactions
?
MetabolismMetabolism
Catabolism Anabolism