BIOL-M 350 Lecture Notes - Lecture 16: Non-Competitive Inhibition, Enzyme Kinetics, Competitive Inhibition
Exercise(16!!!!!!
!
1. By!what!process!do!glycolysis!and!the!Entner-Doudoroff!pathway!produce!ATP?!
!
SUBSTRATE!LEVEL!PHOSPHORYLATION!
!!!!!!!!!
2.!Why!might!glycolysis!and!the!Entner-Doudoroff!pathway!make!less!ATP!than!they!could!have!
otherwise!evolved!to?!!
!
The!direction!of!metabolic!flow!is!determined!by!the!Gibbs!Free!energy!(delta!G).!By!producing!
less!ATP!than!might!be!thermodynamically!possible!the!pathway!maintains!a!negative!delta!G!and!
thereby!promotes!flow!in!the!forward,!or!physiologically!useful,!direction.!!
!
3.!How!do!many!fermentative!bacteria!generate!a!proton!motive!force?!!!
!
Using!some!of!the!ATP!they!produced!by!substrate!level!phosphorylation!to!run!ATP!synthase!
(ATPase)!backwards,!thereby!coupling!ATP!hydrolysis!to!the!translocation!of!protons!out!of!the!
cell.!
!
Exercise(19.((
1. Why!do!purple!nonsulfur!bacteria!use!reverse!electron!transfer!whereas!cyanobacteria!do!not?!
Be!sure!to!explain!your!thinking.!Space!is!provided!for!a!diagram!if!it!helps!you!explain.!
!
In!both!cases,!excitation!of!electrons!by!light!gives!the!electrons!more!negative!potential!than!
NADPH.!Cyanobacterial!electron!transfer!chains!(ETC)s!have!ferredoxins!that!have!a!more!
negative!potential!than!NADPH!and!can!thus!directly!donate!electrons!to!NADP+!as!electrons!lose!
energy!moving!through!the!ETC.!However,!the!purples!don’t!have!these!ferrdoxins!and!electrons!
move!to!quinones!which!have!a!more!positive!potential!than!NADPH.!Thus!reverse!electron!
transfer!is!needed!to!energize!the!qunone!electrons!using!energy!from!the!proton!motive!force!to!
donate!electrons!from!quinones!to!NADP+.!
!
2. Many!photoheterotrophic!bacteria!can!use!N2!as!a!nitrogen!source!via!the!enzyme!nitrogenase,!
which!catalyzes!the!following!reaction:!
!
N2!+!16ATP!+!8e-!+!9!H+!!à!2NH4+!+!16!ADP!+!16!Pi!+!H2!
!
Note:!you!could!imagine!the!‘8e-!+!9!H+’!would!be!in!the!form!of!‘4!NADH!+!5H+’!
!
When!photoheterotrophic!bacteria!are!cultured!with!NH4+!as!the!sole!N-source,!the!Calvin!cycle!is!
essential!for!growth.!When!photoheterotrophic!bacteria!are!grown!with!N2!as!the!sole!N-source,!
the!Calvin!cycle!is!NOT!essential!for!growth.!Explain!why?!!!!!!!
!
The!Calvin!cycle!is!normally!important!during!photoheterotrophic!growth!for!the!oxidation!of!
excess!reduced!electron!carriers!(e.g.,!NADH!à!NAD+).!When!the!reductive!CO2-fixing!pathway!is!
not!available,!other!processes!that!oxidize!electron!carriers,!such!as!N2!fixation!above,!can!take!its!
place.!
!
!
!
!
!
!
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
The direction of metabolic flow is determined by the gibbs free energy (delta g). Using some of the atp they produced by substrate level phosphorylation to run atp synthase (atpase) backwards, thereby coupling atp hydrolysis to the translocation of protons out of the cell. Space is provided for a diagram if it helps you explain. In both cases, excitation of electrons by light gives the electrons more negative potential than. Cyanobacterial electron transfer chains (etc)s have ferredoxins that have a more negative potential than nadph and can thus directly donate electrons to nadp+ as electrons lose energy moving through the etc. However, the purples don"t have these ferrdoxins and electrons move to quinones which have a more positive potential than nadph. N2 + 16atp + 8e- + 9 h+ 2nh4. + + 16 adp + 16 pi + h2. + as the sole n-source, the calvin cycle is.
