Foundations in Microbiology
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Transcript Foundations in Microbiology
An Introduction to Microbial
Metabolism
Chapter 8
energy
The capacity to do work or cause change
Kinetic energy is actively performing work,
Potential energy is stored (ability to perform
work based on location/arrangement)
1st law of thermodynamics – energy
conservation
Endergonic reactions – consume energy
Exergonic reactions – release energy
Endergonic:
X + Y + energy Z
Exergonic:
X + Y Z + energy
Energy conversions
Cell takes PE of chemicals (in
electrons/bonds) and eventually converts
them to cellular work (KE)
Endergonic/exergonic reactions are usually
coupled so that the energy can either be
used immediately or stored (ATP) for later
use
Metabolism
The sum total of all chemical
reactions & physical workings
occurring in a cell
2 types of metabolism
_________________ - biosynthesis
building complex molecules from simple ones
requires energy (ATP) - endergonic
_________________ - degradation
breaking down complex molecules into simple ones
generates energy (stored as ATP) - exergonic
Example - glycolysis
Enzymes
Needed to keep pace (speed up reactions)
Reaction involves either breaking a molecule
apart or brining one together
Catalyze reactions without becoming
products or being consumed in the reaction
Act upon ______________ to form
_________________
Lower _________________ so reaction rate
increases
Enzyme-substrate interactions – lock and key fit
Active site
“Induced fit”
Enzyme - structure
Simple enzymes – consist of protein alone
Conjugated enzymes or holoenzymes –
contain protein and nonprotein molecules
apoenzyme –protein portion
cofactors – nonprotein portion
metallic cofactors – iron, copper, magnesium
coenzymes - organic molecules - vitamins
How enzymes work: example - sucrase
Role of
coenzyme:
Transfer
functional group
from one
substrate to
another
Control of enzyme activity
1.
2.
_________________ inhibition –
substance that resembles normal substrate
competes with substrate for active site
_________________ inhibition – enzymes
are regulated by the binding of molecules
other than the substrate on the active site
•
•
Enzyme _____________– inhibits at the genetic
level by controlling synthesis of key enzymes
Enzyme _____________– enzymes are made
only when suitable substrates are present
Enzyme repression
Enzyme induction
Things that affect enzymes
Temperature, pH, pressure
Enzymes have optimal T and pH for
activity
Can be denatured by extreme
temperatures or pH (changes protein
structure)
Roles of enzymes: Pathogenesis
Produced by pathogenic microbes--make
microbe a better pathogen (evade host
response, destroy host tissues)
Examples:
Hemolytic enzymes (hemolysins)
Elastase, collagenase (destroy connective tissue)
Lecithinase C (destroys cells)
Penicillinase (inactivates penicillin – antibiotic
resistance)
Note: names end in -________
Types of enzymes (location, quantity)
_______enzymes – transported extracellularly, where
they break down large food molecules or harmful
chemicals; cellulase, amylase, penicillinase
________enzymes – retained intracellularly & function
there
_________________– always present regardless of
substrate concentration (glycolysis enzymes)
_________________– produced in presence of
substrate, prevents cell from wasting resources
Figure 8.6 Types of enzymes
27
Figure 8.7 Constitutive and regulated enzymes
28
Types of reactions catalyzed by
enzymes
Synthesis or _________________ reactions –
_________________ reactions to form covalent
bonds between smaller substrate molecules,
require ATP, release one molecule of water for
each bond
_________________ reactions–
_________________ reactions that break down
substrates into small molecules, requires the
input of water
Figure 8.8 Enzyme-catalyzed synthesis and
hydrolysis reactions
Transfer reactions by enzymes
1.
2.
3.
4.
5.
Aminotransferases – convert one type of amino acid
to another by transferring an amino group
Phosphotransferases – transfer phosphate groups,
involved in energy transfer
Methyltransferases – move methyl groups from one
molecule to another
Decarboxylases – remove carbon dioxide from
organic acids
Oxidation-reduction (redox)reactions – transfer
of electrons (may involve _________________ )
REDOX reactions
The process by which electrons are transferred
between atoms is called an oxidation/reduction
reaction (redox) – we can track movement of e- by
following H transfers
_________________ = loses e- (donor becomes
oxidized; reducing agent)
_________________ = gains e- (acceptor
becomes reduced; oxidizing agent)
Occurs as a paired reaction
“LEO says GER” or “OIL RIG”
Cellular respiration is one big
redox reaction!
Redox reactions involve electron transfers
OILRIG
(Oxidation is Losing; Reduction is Gaining)
Redox reactions
Involve electron transfers (energy transfers)
always occur in pairs
electron donor + electron acceptor = redox pair
process salvages electrons & their energy.
released energy can be captured to
_________________ ADP or another compound
Redox reactions
Electron donor + Electron acceptor
NOTE: electron transfers involve a hydrogen atom (proton + electron)
= ____________________ and involves an electron carrier
REMEMBER: Cellular respiration
is one big _________________ !
Metabolic Pathways
37
Electron carriers
Redox reactions
resemble __________ that are loaded and
unloaded with electrons and hydrogen
most carriers are __________, NAD, FAD, NADP,
coenzyme A & compounds of the respiratory chain
donor
shuttle
acceptor
NAD reduction (carries 2 e- )
Redox reactions
Electron carriers – coupled reaction
Overview of cell respiration – electrons are removed from glucose and
eventually used to make ATP
_____________________________
NADH
1/
The path
that
electrons
take on their
way down
from glucose
to oxygen
involves
many stops
(from food via NADH)
2 H
2 e
2
Energy for
synthesis
of
2 e
1/
2
H
2
Figure 6.6
ATP – the energy shuttle
3 part molecule consisting of
adenine – a nitrogenous base
ribose – a 5-carbon sugar
3 phosphate groups
_________________
_________________
_________________
How does ATP “give” energy?
ATP transfers energy to compounds that are going to be
catabolized (or going to do work) by donating the high
energy phosphate
_____________
of glucose by ATP
How is ATP regenerated?
ATP used for Energy must be
regenerated (ADP + Pi)
1.
2.
3.
substrate-level phosphorylation
oxidative phosphorylation
photophosphorylation
1. substrate-level phosphorylation
Other ways of making ATP
2. Oxidative phosphorylation: Used by
aerobes. series of redox reactions (electron
transport system). Involves chemiosmosis.
3. Photophosphorylation – used in
photosynthetic organsims. Driven by sunlight
(series of reactions).