Chapter 10.3

Question 1

Does the proton gradient or flow of electrons produce ATP

Answer 1

-it is the flow of protons

Question 2

Is formation of ATP endergonic and is the electron transport chain exergonic or endergonic

Answer 2

-formation of ATP is endergonic, while the electron transport chain is exergonic

Question 3

Why is oxygen a great final acceptor in the electron transport chain

Answer 3

-because it has high reduction potential

Question 4

Describe what happens in complex one of the electron transport chain

Answer 4

-the transfer of electrons from NADH to coenzyme Q is catalyzed in the first complex

• NADH first donates electrons to FMN
• > FMN becomes reduced to FMNH2
• FMNH2 then becomes reoxidized as iron sulfur clusters are reduced
• > then iron-sulfur clusters are oxidized as they transfer electrons to coenzyme Q
• > coenzyme Q becomes CoQH2

-here four protons move across to the intermembrane space

Question 5

Describe what happens in complex two of the electron transport chain

Answer 5

-here there is transfer of electrons from FADH2 to coeqnzyme Q

• first succinate is converted to fumurate
• > donates electrons to FAD to form FADH2
• > FADH2 then donates electrons to iron-sulfur clusters
• > iron-sulfur clusters then donate these electrons to coenzyme Q
• > coenzyme Q becomes CoQH2

-here no protons move across to the intermmebrane space

Question 6

Describe what happens in complex 3 of the electron transport chain

Answer 6

• this complex transfer electrons from coenzyme Q to cytochrome c in a few steps
• > two cytochrome c molecules are needed for this transfer to occur
• in the Q cycle. two electrons are shuttled from ubiquonol(CoQH2) to a molecule of ubiquinone(CoQ)
• > another two molecules are given to cytochrome c, reducing them

-note altogether, complex 3 pumps 4 hydrogen ions to the intermembrane space

Question 7

Describe what happens in complex 4 of the electron transport chain

Answer 7

• the transfer of electrons from cytochrome c to oxygen

- >through the use of cytochrome oxidase

Question 8

What happens in the intermembrane space as more hydrogen ions are pumped there

Answer 8

• the pH drops
• > and the voltage difference between the intermembrane space and the matrix increases due to proton pumping
• > these two changes are referred to as the ELECTROCHEMICAL GRADIENT

Question 9

Describe the glycerol 3-phosphate shuttle

Answer 9

• cytosol contains glycerol 3-phosphate dehydrogenase, which oxidizes cytosilic NADH to NAD+
• > this forms glycerol 3 phosphate from DHAP
• on the mitochondrial outer membrane, there is another isoform of glycerol-3-phosphate dehydrogenase that is FAD dependant
• > this mitochondrial FAD is the oxidizing agent and ends up being reduced to FADH2
• > FADH2 donates 1.5ATP for every cytosolic NADH that participates in this pathway

Question 10

Describe the malate-aspartate shuttle

Answer 10

• cytosolic oxaloacetate which cannot pass through the inner mitochondrial membrane is reduced to malate
• > this is done through malate dehydrogenase
• > NADH is converted to NAD+ in the process
• once malate is the matrix, it is oxidized again to form oxaloacetate
• > NAD+ is converted to NADH again and generates 2.5 ATP of molecules
• when malate enters the innter mitochondrial membrane, aspartate leaves
• > oxaloacetate can also be converted into aspartate and aspartate can be converted to oxaloacetate