metabolic diversity

what does a high permeability coefficient indicate ?

substance is more permeable across the membrane

what units are used to measure permeability ?

m or cm/s

what are the 5 types of protein-dependent transport ?

3 passive: ion channels, porins, facilitated diffusion

2 active: primary (ATP-driven), secondary (ion gradient-driven)

what is the PTS system ?

special transport system where solutes (eg. sugars) are phosphorylated during transport into cell

what enzyme in the PTS system is unique to each sugar ?

enzyme IIc

metabolism

sum of all chemical reactions in cell

catabolism

energy-releasing metabolic reactions

anabolism

energy-requiring biosynthetic reactions

how do microbes conserve energy ?

oxidising inorganic compounds or trapping light energy

what is free energy (ΔG) ?

energy available to do work under constant temperature and pressure

exergonic

releases energy

endergonic

requires energy

what does a negative ΔG indicate ?

reaction is exergonic and proceeds spontaneously forward

do enzymes affect ΔG ?

no - only lower activation energy and speed up the reaction.

ΔE vs E₀′

ΔE is difference in reduction potential between two different half-reactions or the change in reduction potential within a single reaction

E₀′ individual standard reduction potential of specific half-reaction

what is reduction potential (ΔE) ?

measure of a substance’s tendency to gain electrons

what does a larger ΔE value mean in a redox pair ?

more energy is released (more negative ΔG)

how are ΔE and ΔG linked ?

the Nernst equation

how is ΔG calculated ?

ΔG = -nFΔE

n = no. of electrons transferred

F = faradays constant

what is Faraday’s constant ?

the quantity of electric charge carried by one mole of electrons

in redox reactions what happens to the electron donor and acceptor ?

donor - oxidised

acceptor - reduced

in which direction do electrons flow in redox reactions

from lower to higher standard reduction potential E₀′

E₀′

individual standard reduction potential of specific half-reaction

name the key catabolic electron carriers

NAD⁺ NADH

FAD FADH₂

FMN FMNH₂

name the key anabolic electron carriers

NADP⁺ NADPH

where is energy from redox reactions stored ?

in high energy phosphorylated compounds eg. ATP, PEP

what energy-rich compound can drive ATP formation from ADP ?

acetyl CoA and other coenzyme A derivatives

why do microbes store energy as polymers ?

insoluble, polymeric (energy dense), cant diffuse out of cell

examples of long-term energy storage polymers (prokaryotes)

glycogen, poly-β-hydroxybutyrate, sulfur, polyphosphate

what are the 2 major catabolic strategies in microbes ?

fermentation anf respiration

fermentation

anaerobic breakdown of organic compounds with internal electron acceptors eg. NAD

respiration

complete oxidation of substrates with external terminal electron acceptors eg. oxygen

what common pathway do most microbes use to oxidise glucose ?

glycolysis (EMP pathway)

what pathway is used when not using glycolysis ?

Entner-Doudoroff (ED) pathway

both the EMP and ED pathway lead to..

“redox imbalance”

NADPH must be re-oxidised for catabolism to continue

what fully oxidises acetyl-CoA to CO2 ?

TCA cycle

how is acetyl CoA produced ?

oxidation of pyruvate or break down of fatty acids / amino acids

one turn of the TCA cycle produces

• 3 NADH

• 1 FADH₂

• 1 ATP or GTP

• 2 CO₂

how many turns of TCA cycle per glucose ?

2

what cycle do some microbes use to conserve carbon when growing on 2C compounds ?

glyoxylate cycle

how does the glyoxylate cycle differ from TCA ?

bypasses CO₂ producing steps

what two enzymes are unique to the glyoxylate cycle ?

isocitrate lyase and malate synthase

isocitrate is broken down to form

• succinate (4C) - enters gluconeogenesis

• glyoxylate (2C)

where does the glyoxylate cycle occur in eukaryotic microbes ?

glyoxysomes (peroxisomes)

why must NADH and FADH be re-oxidised in respiration ?

allow for continued energy generation and electron flow

what re-oxidises NADH / FADH2 in respiration ?

ETC

what is the terminal electron acceptor in aerobic respiration ?

oxygen

in anoxic conditions what alternative electron acceptors are used ?

nitrate, ferric iron, sulphate, fumarate

why does anaerobic respiration not conserve as much energy as aerobic ?

alternate acceptors have lower E₀′ values than oxygen

what are the 2 mechanisms of ATP production ?

oxidative phosphorylation and substrate level phosphorylation

how does ATP synthase work ?

uses PMF to generate rotational torque driving ATP formation

what are the components of ATP synthase ?

F0 (membrane-embedded motor) and F1 (catalytic ATP-forming motor)

what is substrate level phosphorylation ?

direct transfer of phosphate group from high-energy compound to ADP to form ATP