L9 Respiration and chemiosmosis hypothesis

Question 1

What is it called when bacteria like E.coli use nitrate to respire

Answer 1

dissimilatory nitrate reduction

Question 2

what happens when we drink nitrate in water

Answer 2

bacteria in gut convert nitrate into nitrate which can oxidise our blood

Question 3

under anaerobic conditions what does pyruvate get transformed into

Answer 3

formate

Question 4

where do the electrons that are required to reduce nitrate come from

Answer 4

formate dehydrogenase (membrane-bound protein) reduces formate which produces CO2 and H+ and electrons

Question 5

what is the oxidative complex within the nitrate reductase complex loop

Answer 5

formate dehydrogenase

Question 6

where do the electrons from the reduction reaction of formate go

Answer 6

move down formate dehydrogenase to menaquinone

Question 7

what does menaquinone do

Answer 7

takes the two electrons from formate reduction and 2 protons from cytoplasm to become menaquinol

Question 8

what happens to the menaquinol

Answer 8

gets oxidised back to menaquinone passing the electrons to nitrate reductase and the protons go into the periplasm

Question 9

what are the electrons that are passed to nitrate reductase used for

Answer 9

reduce nitrate into nitrite

Question 10

how do bacteria generate a proton motor force during anaerobic respiration

Answer 10

using a redox loop

formate dehydrogenase and nitrate reductase are an example

Question 11

what is the proton motor force

Answer 11

electrochemical gradient

Question 12

what is a proton motor force used for

Answer 12

drive endothermic reactions in the cell

ATP synthase/lac permease

Question 13

why is succinate dehydrogenase a unique enzyme

Answer 13

part of Kreb cycle and electron transport chain

Question 14

who is sir peter Mitchell

Answer 14

pioneer of the chemiosmotic hypothesis

Question 15

how did sir peter Mitchell prove his hypothesis? 2 experiments

Answer 15

fed succinate to intact cells then

• measured how much ATP is produced
• measured oxygen consumption

fed succinate to cells that had been broken with a sonicator

• measured ATP
• measure oxygen consumption

Question 16

what happened to the succinate when Peter fed it to an intact cell

Answer 16

gets translocated by the major facilitator superfamily and then gets oxidised to fumarate in the Krebs cycle.
-because it is oxidised in the membrane it can create a proton motor force

Question 17

why was it so important that peter Mitchell used succinate (a non-fermentable carbon source) as a substrate instead of glucose or alpha-ketoglutarate

Answer 17

succinate cannot be used to produce ATP whereas glucose can undergo glycolysis which produces ATP
-alpha-ketoglutarate can produce GTP which can be converted to ATP

Question 18

what happened when Mitchell fed succinate to broken cells

Answer 18

• oxygen was still consumed because succinate diffused into the cell and was oxidised to fumarate
• ATP was not produced because no proton motor force could be formed with a broken membrane

Question 19

what is the pH difference between the inside and outside of cells

Answer 19

6. 5 outside

7. 5 inside

Question 20

when the protons are translocated across the membrane what two gradients occur

Answer 20

pH gradient (Z delta pH)/ chemical gradient 
electrical gradient/membrane potential (delta sigh)

Question 21

what is meant by an electrical gradient

Answer 21

the H+ on the outside of the cell makes the outside positive and the inside negative