catabolism (breakdown) + anabolism (building)energy sources, carbon sources, electron sources --->precursor metabolites--->monomers and other building blocks ---> macromolecules ---> cells
overview of metabolism-2 components
1) chemical2) transport3) mechanical
3 types of cellular work
-represents all 5 nutritional types (evolutionary success) ^ see diagram-key in element cycling (ex: nitrogen cycle)-industry/medicine (antibiotic production)-important symbiotic relationships (ex: termites, main source of food is wood, have a microbe in gut to digest cellulose)
importance of microbial metabolism
thermodynamics = analysis of energy changes in a system-everything else = surroundings
thermodynamics
-conservation of energy-total energy in universe: constant^energy is redistributed: within system or between system and surroundings
first law of thermodynamics
entropy increases --> chemical and physical processes proceed such that entropy increases^ order => disorderentropy of any system can increase, decrease, or remain unchanged
second law of thermodynamics
free energy = amt of energy in a system -measured by delta G for rxn A => B, delta G= Gb-Ga
free energy-how is it measured?
-positive delta G-Gb > Ga-energetically unfavorable-increases "order"-ex: compressing a spring-non spontaneous
endergonic rxn
-negative delta G-Gb < Ga-energetically favorable-decreases "order" aka more disorder-ex: releasing a spring-spontaneous
exergonic rxn
cellular energy currency: ATP-energy from "generating" systems => "work" systems
role of ATP as energy provider
most biological rxns are endergonicex: biosynthesis (needs energy)-exergonic: ATP => ADP + Pi^coupled with many endergonic rxns so they can take place (see diagrams)
most biological reactions are _____________ex?-how can these take place?
oxidation-reduction rxns ("redox rxns")-transfer of electrons: donor => acceptor-2nd key energy source (can be stored)-important for many metabolic processes such as photosynthesis or respiration
redox rxns as energy providers-oxidation-reduction rxns
transfer electrons from donor to acceptor-NAD, FAD
electron carriers
-the tendency of reducing agent to lose electrons aka how good is the donor or acceptor -more negative E0: better electron donor (glucose can give 24 electrons)-more positive E0: better electron acceptor (O2)
standard reduction potential (E0)
flow of electrons "down the tower" releases energy(-) : electron donorsto(+) : electron acceptors -glucose is one of the best compounds to gain energy
redox rxns as energy providers-flow of electron tower
electron transport chain
what harvests energy from redox rxns?
-NAD: nicotinamide adenine dinucleotide(NAD+ is reduced state, NADH is oxidized state)-NADP: nicotinamide adenine dinucleotide phosphate-FAD: flavin adenine dinucleotide-FMN: flavin mononucleotide or riboflavin phosphate -coenzyme Q (CoQ)aka ubiquinone -cytochromes: use iron to transfer electronsiron is part of a heme group-nonheme iron proteins ex: ferredoxin -use iron to transport electrons iron is not part of a heme group
electron carriers in ETC (7)
enzymes are biological catalysts -terminology: substrate and product varied composition - some have more than one polypeptide-some have less than one polypeptide (apoenzyme) + nonprotein component (cofactor) => holoenzyme
enzymes -terminology-varied composition
most exergonic rxns: energy barrier called activation energy^required to form transition state A + B => AB(TS) => C + D-enzyme lowers activation energy and stabilizes TS ^cannot make an unfavorable rxn favorable
enzymes and activation energy-TS
1. lock and key model (outdated)2. induced-fit model : leads to more products due to conformational changes (see diagram)
enzymes: interaction of enzyme and substrate
1. substrate concentration-as it increases, so does rate of rxn (Vmax) until it plateaus Vmax= rate of product formation when the enzyme is saturated with substrate and operating as fast as possible -smaller Km, better enzyme-substrate interactionKm= substrate concentration required by the enzyme to operate at half its max velocity 2. pH and temperature (optimal values)
enzymes: effect of environment on activity
regulation of enzyme activity key 1) competitive inhibition --> inhibitor directly competes with substrate for active site ex: sulfa drugs2) noncompetitive inhibition --> inhibitor binds enzyme at site other than active site -similar to allosteric
enzymes: control of activity -competitive inhibition-noncompetitive inhibition
allosteric regulation-regulatory site has negative/positive effectors on rate -leads to conformational changes at catalytic siteex: E.coli aspartate carbamoyltransferase (ACTase)-pyrimidine synthesis see diagram
enzymes: control of activity -allosteric regulation
covalent modification-reversible addition or removal of a chemical group-activating or inhibitory-ex: phosphorylation -> activation or methylation(see diagram)
enzymes: control of activity-covalent modification
aka end product inhibition ( decreases production)-product acts on earlier enzyme in rxnpacemaker enzyme: catalyzes rate-limiting rxn in the pathway
feedback inhibition
purpose:-conservation of energy and materials-maintenance of metabolic balance despite changes in environment three major mechanisms to regulate metabolic pathway:-control enzyme activity-control number of enzyme molecules present -compartmentation/metabolic channeling
nature and significance of metabolic regulation -purpose-three major mechanisms
differential distribution of enzymes and metabolites -among separate cell structures and organelles ex: cytoplasm vs periplasm metabolic channeling-differential local concentrations of enzymes / metabolites within compartments
compartmentation and metabolic channeling