Metabolism of parasites

Question 1

Why metabolism has to be done?

Answer 1

-Store energy(ATP) for biological functions
ATP: most general energy carrier/storage unit: but energy can be stored in other things, eg. like kreatin for muscles
-Generate building blocks
-Mediate detoxification (like in river)
All needed to proliferate/grow/invade tissues

Question 2

Whats the most important reason of doing metabolism? - for parasites

Answer 2

ATP generation! Parasites are very well adapted to niche, they often take t rest directly from the host
eg. Trypanosoma doesnt do any building blocks, blood is all they need

Question 3

Where can you get the substrates? examples

Answer 3

eg. tsetse fly: trypanosoma carrier
snails
RBC eg. plasmodium
Ascaris: intestine full of worms
Depending on environment, metabolism is adjusted

Question 4

Why study metabolism in parasites?

Answer 4

Fundamental
1) understanding the pathways in general
2) understanding how metabolism is organised: what can you produce from what materials
3) understand eukaryotic evolution
4) understand which organisms have a mitochondrion?
5) study differences btw anaerobes and aerobes
Applied
1) in order to find ways to kill the parasites (drug targets)
2) study bioreactors (H2 production) = hydrogenosomes produce hydrogen, its a organelle of mitochondria origin

Question 5

Heterotrophes ototrophes

Answer 5

heterotrophes cannot fix carbon, eg. photosynthesis is a way to fix carbon
therefore they take glucose from outside

Question 6

how do you generate ATP? ways?

Answer 6

1) Substrate level phosp. (SDF)
= direct phosphorylation of ADP provided by another metabolic event, energuy comes from a coupled reaction
2)Oxphos
= ATP generated from oxidation of NADH-FADH carriers
=subsequent transfer of electrons generate proton gradient, used from ATP synthase to generate ATP
=O2 does not need to be the electron acceptor, eg. you can use nitrogen in bacteria (n2) and make NO = still oxphos

Question 7

OXPHOS? definition

Answer 7

= electron transfer to carriers than final acceptor like O2, redox
=generates ATP by ATP synthase

Question 8

glycolysis steps? classic one

Answer 8

1) glucose is turned to glucose 6 phosp.
= 1 ATP used to activate glucose
2) G6P - F6P
3) from fructose 6 phosphate to 1,6 phosphate
=1 ATP used to activate glucose
4) glucose is separated to 3C x2 - glyceraldehyde 3 phosphate /dihydroxyacetone phosp.
5) dihydroxiacetone phosp. converted back into g3p
6) 2 times 3C (glyceraldehydes) are turned to 1,3 biposphoglycerate
=2 NADH is generated
7) from 1,3 to 3-phosphoglycerate
=2 ATP generated (1 for each C)
8) 3-p to phosphoenolpyruvate
9) phosphoenolpyruvate to pyruvate
mediated by pyruvate kinase
=2 ATP generated (1 for each C)

Net ATP: 2 ATP - all generated from SDP
2 NADH generated

Question 9

describe oxidation reduction

Answer 9

oxidation=lose electron

reduction=gain electron

Question 10

redox examples

Answer 10

eg. Carriers turning NAD to NADH= reduced
oxygen is reduced to water in ETC
glucose is oxidized

Question 11

role of NAD balance- why should we keep NAD and NADH balanced

Answer 11

NAD is the coenzyme in electron transfer
oxidised form: NAD+, reduced form NADH = gets electron, turns natural
With metabolism redox = H is transferred with electrons
NAD + 2H + 2e = NADH+H
balanced: NAD+ = NADH
The total pool of NAD is constant, backbone cant be produced as fast as glycolysis, so you need to recycle it = glycolysis happens in milliseconds

Question 12

net glycolysis reaction?

Answer 12

Glucose + 2NAD + 2ADP + 2P = 2 Pyruvate + 2NADH + 2H + 2ATP + 2H2O
waters come from the phosphoenolpyruvate conversion

Question 13

what would happen if glycolysis ends with pyruvate?

Answer 13

NADH got stuck, also pyruvate can be further oxidized too

Question 14

Further pyruvate processing (respiration vs fermentation definition)

Answer 14

Respiration: usage of terminal electron acceptor FROM OUTSIDE (eukaryotes usually use oxygen/microbes N2) to store electrons
O2 + 4H + 4e = 2H2O

Fermentation: electron is donated into the acceptors that is generated during the metabolism FROM INSIDE

example: 2H + 2E= H2 - yes hydrogen generated from inside

example: fumarate + 2H + 2e= succinate
pyruvate then acetaldehyde + 2H + 2e = ethanol
pyruvate then lactate

So there’s 3 places to put the electrons: O2/N2 respiration, H2 fermentation, acetaldehyde/fumarate = for fermentation

Question 15

general oxphos (krebs etc)

Answer 15

Krebs: generates 3 NADH + 1 FADH each 3C (6 NADH + 2 FADH) + 2ATP
ETC: Electron is loaded from NAD and FAD to ETC: generates 2H + 1/2O2= H2O
and ATP with pump
O2 is the electron acceptor

We had 2 NADH from glycolysis + Pyruvate-AcetylCoA conversion = 2 NADH more + 6 NADH + 2 FADH
= loaded on ETC: get 36 ATP in total
ATP synthase generated with proton influx

Question 16

N2 respiration

Answer 16

N2 = NO then H flux on ATP synthase

Question 17

What do you do after Krebs/glycolysis with NAD problem?

Answer 17

1) Put on ETC
2) On glycolysis: reduce pyruvate to lactate or ethanol
Lactate and ethanol is reduced
3) Excrete pyruvate completely - normally not possible but Trypanosoma can do it

Question 18

hydrogenosomes

Answer 18

malate-pyruvate (ferrodoxin) acetylcoa- acetate
from acetylcoa to acetate, succinate is transferred to succinyl coa = ATP generated w SDF
Hydrogen accepts electrons from ferrodoxin = fermentation!!
Ferredoxin here is free-floating
Once you leave electrons on hydrogen= no ATP= you need to couple it with SDF
Pyruvate oxidised, Ferrodoxin oxidised, Ferrodoxin reduced, Hydrogen reduced

Question 19

normal mitochondria vs hydrogenosome: similar or different?

Answer 19

Similarities
Both are double membrane-bound organelle
Similar chaperone to fold proteins is used
ETC and hydrogenosome Fd is similar, hydrogenosome one is just floating
Some hydrogenosomes have a genome, like mitochondria
Apparently though: everything they use is so similar =
So hydrogenosomes are mitochondria that is anaerobic

Differences: No ETC in hydrogenosome, there’s just ferrodoxin
O2 is terminal e. acceptor, vs H2 is terminal electron acceptor
ATP synthase/gradient/OXPHOS used = SDF/fermentation used

Question 20

organelle classification/how to find what your organelle is

Answer 20

1) Does it generate ATP or not
-Doesn’t: mitosome
-Does: continue
2) Uses ONLY O2 as terminal electron acceptor = aerobic mitochondria
Uses other compounds as well = continue
3) Does not produce H2: anaerobic mitochondria
Does produce H2: continue
4) Has ETC: H2 producing mitochondria
Doesn’t have ETC: hydrogenosome
All of them are organelles of mitochondrial origin - too much similarity

Question 21

Why not everyone is aerobic?

Answer 21

-No O2 around/or need to survive hypoxia for some time due to lifecycle
-There’s enough substrate so no need to be efficient, you can just load the glycose and go SCF/fermentation = faster
-Not much ATP is needed sometimes either, it is enough to get 2 ATP from glycolysis
-Doing all those big pathways also need proteins, and that’s costly
-Also using O2 has the risk of generating ROS: if you put too little O2 you can get superoxides
So oxygen is an opportunity: but often not every opportunity is used

Question 22

Anaerobic metabolism examples / Warburg Crabtree

Answer 22

Crabtree on yeast: Can go either normal oxphos/or fermentation: puts electron on acetaldehyde = ethanol
Yeast does fermentation when there’s too much sugar = it faster rather than efficient= how beers are made!
Warburg on cancer: Cancer cells use glucose very fast, produce lactate even when there’s O2 = muscle cells normally do it too but they get tired/muscle pain when there’s too much lactate, cannot continue

Question 23

Why theres mitosomes if they dont produce ATP?

Answer 23

They have other pathways, but metabolism pathways rather moved to the cytosol.
If it was completely useless it would get lost, so it should have a role

Question 24

True anaerobes definition + how they deal w O2

Answer 24

No need for O2 to survive and multiply
Also cant grow when there’s O2 either: growth inhibited by O2, the enzymes in ATP production, eg. ferrodoxin reductase, does not work = there’s O2: Fd cannot get the electrons instead of O2!!
ex. some bacteria

Since they cnannot live with O2:
they do: 2NADH + 2H + O2 = 2NAD + 2H2O (NADH oxidase-diaphorase enzyme)
So they just load the electrons on O2 directly with no ETC = get their NAD back. They use it as an electron acceptor directly.
No ATP generated
But they are happy that they got rid of O2: still, there’s a ROS risk though
another example. flavodiiron protein

Question 25

Microaerophiles

Answer 25

Can survive in low O2 (%1-10)

grow a bit faster when there’s low O2, its better than none

Question 26

Whats important to study in organelles of mitochondria origin?

Answer 26

• main differences in metabolism
• where does reactions occur
• which class they belong to: the organelle
• what are the terminal electron acceptors

Question 27

How to check the maps of metabolism? / trypanosoma eg.

Answer 27

Check genome.
But careful: often genome will show everything. eg. Trypanosoma genome will show the enzymes generated in every stage, but tsetse fly stage and mammal stage is completely different: tsetse fly stage is huge, mammal stage is much smaller
To differentiate stages: do measurements with labeled glucose: check where it goes, eg. to fermentation or respiration

Question 28

Fasciola hepatica example:

Question 29

anaerobic mitochondria example:

Answer 29

-Generates ATP
-no krebs, no ETC
-no O2 around
-no H2 : NADH puts electron on 1 electron acceptor:then electron goes Rhodoquinine: then it drives fumarate to succinate = fermentation!!! = not SDF see electron carried and put on the carrier generated in the metabolism
terminal electron acceptor: propironate