Lecture 6

Question 1

definition of metabolism

Answer 1

sum of all reactions in a living organism aimed at maintenance, development and reproduction

Question 2

difference between cost of errors in lab and industry

Answer 2

Way bigger cost in industry because production at a way bigger scale

Question 3

metabolism : what comes in and what comes out

Answer 3

nutrients -> biomass, byproducts, heat

Question 4

2 types of processes in metabolism : which one requires energy ?

Answer 4

Catabolism : spontaneous, yields energy

Anabolism : new biomass, requires energy

Question 5

adding biomass : chemical reaction, how can we estimate oxygen ?

Answer 5

glucose + O2 + NH4+ -> CH1.8O0.5N0.2 + CO2 + h2O + H+

using the perfect gas law

Question 6

gibbs free energy : used for what, what is it

Answer 6

Energy available for cell to use : estimate if a reaction is thermodynamically spontaneous or if energy is required

Question 7

In non-equilibrium systems, what does deltaG depend on ?

Answer 7

On the concentrations !!

Question 8

different ways to measure metabolism rate

Answer 8

Catabolic focus :
- electron acceptor consumption rate (mainly O2)
- byproduct production rate (mainly CO2)
- enzyme activity
- heat

Anabolic focus :
- incorporation assays

Question 9

where and what is the electron transport chain (ETC)

Answer 9

In mitochondria !!

Electrons are transferred from NADH (or FADH2) through protein complexes to the electron acceptor (oxygen).

The electron transport creates a proton gradient (more in intermembrane space) -> drives synthesis of ATP

Question 10

what about microbial ETC ? where ? what else is it used for ?

Answer 10

They don’t have mitochondria -> in membrane.

Proton motive force also used for active transport and rotation of flagella.

Question 11

redox assay : principle

Answer 11

we measure the consumption rate of electron acceptors.

Ex : formation rate of formazan from tetrazolium salt is proportional to catabolism.

Question 12

Name different electron acceptors

Answer 12

oxygen, S, SO4, NO3, organic compounds, metals (Fe, Mn)

Question 13

ATP : what is accounted for, concentration ?, AEC

Answer 13

Account for ATP, ADP and AMP.
Humans : 1-5 mM.
Spores : very low because almost no metabolism needed.

AEC = adenylate energy charge (0.8 in active cell) -> more relevant than absolute concentration of ATP alone.

(ATP + 0.5ADP) / (ATP + ADP + AMP)

Question 14

carbon source : metabolism rate ?, dependance to T, 2 examples

Answer 14

Rate of consumption (and increase of biomass) is proportional to metabolic rate.
When T increases, it becomes faster.

Glucose, Lactose, …

Question 15

examples of byproducts

Answer 15

CO2, NO2, H2S, biomass

Question 16

incorporation assays : 3 examples

Answer 16

1) radioisotope incorporation (radiolabeled compounds in DNA or proteins)

2) stable isotope probing : use of stable isotope labeled substrates to probe the microbial utilization of these substrates to build their macromolecules.

3) substrate analog probing : synthetic compounds analogous (sometimes with fluorescent tags) to natural molecules incorporated into macromolecules

Question 17

link between metabolism and heat (formula)

Answer 17

deltaG = deltaH - t*deltaS

Question 18

is entropy needed in aerobic respiration ?

Answer 18

No it can be neglected

Question 19

calorimetry : what it measures

Answer 19

Real-time monitoring : measures net rate of heat flow over time -> calculate heat produced or consumed

Question 20

how many peaks for e.coli in calorimeter with different substrates

Answer 20

3 :
- glucose respiration
- glucose fermentation
- lactose fermentation

Question 21

2 calorespirometric ratios

Answer 21

1) oxycaloric Q/O2 : fixed at 455+-15 kJ/mole -> deviation means another process is ongoing (except if deltaH = 0)

2) Q/CO2 : variable for sugars, proteins or lipids -> gives indication on carbon source and growth efficiency