Intro to Microbial Cell Metabolism

all cells require …

1. water

2. carbon source

3. free energy

4. reducing power

free energy

energy available to do work (metabolism)

reducing power

source of electrons to generate free energy & perform biosynthesis

catabolic metabolism

used to obtain energy

• breakdown

anabolic metabolism

requires energy

• synthesis of macromolecules

free energy is expressed as _______

G (Gibbs)

delta G

change in free energy at standard conditions

what does - delta G indicate?

exergonic/exothermic → energy is released

+ delta G

energonic (energy is required)

phototrophy

light-based energy sources

end goal of metabolism

produce ATP and related energy storage molecules

vast majority of metabolism is carred out thru _______ rxns

redox

chemoorganotroph

organic (C-based) energy source

chemolithotroph

inorganic energy source

redox rxn

transfer electrons in 2 half rxns

2 half rxns of redox rxn

1. e- are transferred from a donor

2. e- are passed to acceptor

reduced

gains electrons

oxidized

loses electrons

__________ from donor to acceptor is absolutely critical for life to function

the flow of electrons

rxns are written with _________ on the left and _________ on the right

oxidized / reduced

what determines the flow of electrons? (if it accepts or donates)

reduction potential (E’ → measured in volts)

what does a negative E’ mean?

pair will lose electrons

what does a positive E’ mean?

pair will gain electrons

redox potential

• E’

• affinity of a molecule to gain electrons

________ and _________ metabolism will often yield the most energy (electron transfer) via aerobic respiration

glucose / sugar

glucose and sugar metabolism will often yield the most energy (electron transfer) via _________

aerobic respiration

anaerobic organisms do not use O2 as an acceptor, so they have to rely on ______

nitrate (NO3-)

electron carriers & transport chains are required to hand off e- in a ___________

stepwise cascade

the process of cycling rxns is one way in which the ________ is generated

PMF

example of electron carrier

NAD+/NADH

where do electron carrier/transport chain rxns occur?

cytosol

what does -G mean?

forms spontaneously

Gf

free energy of formation

formula to calculate delta G

delta G = Gf[C+D] - Gf[A+B]

• C and D are products

• A and B are reactants

what is the sign of delta G that leads to an exergonic rxn and thus yields energy to form ATP?

negative

3 major ways to generate ATP

1. Substrate-level phosphorylation (direct hydrolysis or bond breaking drives ATP production)

2. Oxidative phosphorylation (movement of electrons generates the proton motive force)

3. Photophosphorylation

substrate-level phosphorylation

direct hydrolysis or bond breaking drives ATP production

oxidative phosphorylation

movement of electrons generates the proton motive force

does delta G tell us anything about the rate of rxn?

no

• only exergonic or not

enzyme effect on activation energy of rxn

lower

effect of enzyme on rxn rate

speed up

example of prosthetic group

heme bound to cytochrome c (ETC)

what 2 things affect enzyme affinity, function, & rates?

1. coenzymes

2. prosthetic groups

coenzymes that associate with many different enzymes are usually ______

vitamins

prosthetic group

• type of cofactor that is tightly bound to enzyme/protein

• can be metal ions or small organic molecule

cofactor

• non-protein chemical compound that is loosely bound to an enzyme or other protein molc.

• small organic molc.