The Electron Transport Chain. Flashcards
What is a prosthetic group?
These are organic in nature and not made of protein.
They are very tightly bound (usually covalently) to the enzyme.
What are prosthetic groups also known as?
A coenzyme.
Which step of aerobic respiration will generate the most ATP?
The ETC.
What is the final electron acceptor in the ETC?
Oxygen.
What is the goal of the ETC?
To produce energy in the form of ATP via the oxidation of NADH and FADH2.
Where in the cell does the ETC occur?
In the mitochondrial matrix and in the inner mitochondrial membrane.
Give a quick summary of the ETC?
Hydrogen atoms are stripped from NADH and FADH2 and transported into the inter membranous space.
This creates a proton gradient and the ions want to re-enter the mitochondrial matrix.
The ions can re-enter by passing through ATP synthase.
As each H+ ion passes through, one molecule of ATP is generated.
How many complexes are in the ETC?
4.
Where are the 4 complexes in the ETC found?
Embedded into the inner mitochondrial membrane.
What are the 4 complexes in the ETC?
Complex 1. The NADH dehydrogenase complex.
Complex 2 = Succinate dehydrogenase.
Complex 3 = Cytochrome reductase.
Complex 4 = Cytochrome oxidase.
What are the 2 mobile electron carriers in the ETC?
Co-enzyme Q.
Cytochrome C.
What 2 prosthetic groups are used at complex 1?
FAD.
FMN.
What gets oxidised at complex 1?
NADH.
What happens at complex 1 in the ETC?
NADH is oxidised and the electrons passed on to co-enzyme Q.
2 H+ ions are pumped into the inter-membranous space.
What prosthetic groups are used at complex 2?
None.
What happens at complex 2 in the ETC?
FADH2 is oxidised by co-enzyme Q.
The electrons 2 are also passed to complex 3 by co-enzyme Q to complex 3.
What gets oxidised at complex 2 in the ETC?
FADH2.
What oxidises FADH2 at complex 2?
Co enzyme Q.
Is succinate dehydrogenase involved in any other steps of aerobic respiration?
In the TCA cycle in step 6 where the 2 FADH2 molecules are made.
What happens at complex 3 in the ETC?
Co-enzyme Q delivers electrons from complex 1 and 2 to reduce complex 3.
2 more H+ ions are pumped into the inter-membranous space.
The electrons will then be handed to cytochrome C to be transferred to complex 4.
What prosthetic groups are used at complex 3?
Heme.
What happens at complex 4 in the ETC?
Cytochrome C delivers electrons to complex 4 and they are passed onto O2.
2 more H+ ions are pumped into the inter-membranous space.
What prosthetic groups does complex 4 have?
Heme.
Calcium ions.
What complexes will pump H+ into the inter membranous space?
Complexes 1, 3 and 4.
Which complexes contain iron sulphur proteins which are involved in the electron transfer process?
Complexes 1,2 and 3.
What is complex 1 called?
NADH dehydrogenase complex.
What is complex 2 called?
Succinate dehydrogenase.
What is complex 3 called?
Cytochrome reductase.
What is complex 4 called?
Cytochrome oxidase.
Why cant the H+ ions cross back through the inner mitochondrial membrane?
It is highly impermeable.
How can H+ ions re-enter the cell?
Through ATP synthase.
ATP synthase is also known as what complex?
Complex 5.
What happens when the H+ ions pass through ATP synthase?
It causes the enzyme to rotate which generates enough kinetic energy to phosphorylate an ADP.
Is ATP a bi-functional enzyme?
Yes.
It allows the protons to pass through while generating ATP at the same time.
At what steps of the TCA cycle is NADH formed?
Malate dehydrogenase step.
Alpha keto gluterate dehydrogenase step.
Isocitrate dehydrogenase step.
Is any NADH formed at the PDH complex?
1.
What are other sources of NADH?
Beta oxidation of fatty acids.
Sources from outside the mitochondria (glycolysis).
What step in the TCA cycle is FADH2 generated?
Succinate dehydrogenase step.
What are other sources of FADH2?
Glycerol phosphate shuttle.
Beta oxidation of fatty acids.
How does the ATP formed in the ETC get to the cytoplasm?
Adenine nucleotide translocase will transport ATP to the cytoplasm.
How does ADP get from the cytoplasm to the mitochondria?
Adenine nucleotide translocase will transport ADP from to the mitochondria to be phosphorylated.
What 2 toxins can inhibit the transport of ATP from the mitochondrial matrix to the cytoplasm
Atractyloside.
Bongkrekic acid.
What is adenine nucleotide translocase inhibited by?
Atractyloside.
Bongkrekic acid.
What 3 inhibitors will affect complex 1?
Rotenone.
Piericidin A (antibiotic).
The barbiturate amytal.
What inhibitor will affect complex 3?
Antimycin A (antibiotic).
What 3 inhibitors will affect complex 4?
Carbon monoxide (CO).
Hydrogen sulphide (H2S).
Cyanide.
What inhibitor will affect complex ATP synthase?
Oligomycin (antibiotic).
Inhibitors of the ETC will result in what?
A decrease in ATP synthesis.
A decrease the rate of the ETC.
A decrease in oxygen consumption.
What are uncouplers?
A class of inhibitors and they will create holes in the inner mitochondrial membrane.
What effect will uncouplers have on the ETC?
The holes allow hydrogen ions to re-enter the mitochondrial matrix.
No proton gradient is formed.
Hydrogen ions do not pass through ATP synthase, so no ATP is generated.
What are the 4 classes of uncouplers?
DNP (Dinitrophenol).
ASA (aspirin).
Thermogenin.
Ionophores.
How will uncouplers affect ATP synthesis and oxygen consumption?
They will decrease ATP synthesis.
Increase the rate of the ETC.
Increase oxygen consumption
The NADH and FADH2 produced in the ETC and PDH complex will be located in what organelle?
The mitochondrial matrix.
Where are the 2 NADH molecules that are produced in glycolysis located?
In the cytoplasm
What must happen to the 2 NADH molecules from glycolysis for them to enter the ETC?
They must travel from the cytoplasm to the mitochondrial matrix.
What are the 2 shuttles that transport the NADH from glycolysis to the mitochondrial matrix?
The glycerol phosphate shuttle.
The malate-aspartate shuttle.
How does the malate aspartate shuttle work?
NADH goes to the inter membranous space in the mitochondria.
An enzyme will transfer the electrons from NADH to reduce oxaloacetate and form malate and NAD+.
Malate crosses into the matrix where it is oxidised back to oxaloacetate.
This reduction allows NAD+ to be oxidised to NADH.
What enzyme converts NADH and oxaloacetate to malate in the malate aspartate shuttle?
Cytosolic malate dehydrogenase.
Can NADH cross the inner mitochondrial membrane?
No.
What is NADH converted to to cross the mitochondrial membrane in the malate aspartate shuttle?
Oxaloacetate is reduced to malate.
What enzyme converts malate to oxaloacetate and NADH in the malate aspartate shuttle?
Mitochondrial malate dehydrogenase.
What happens in the glycerol phosphate shuttle?
NADH goes to the inter membranous space.
DHAP is oxidised to glycerol 3-phosphate.
NADH is reduced to NAD+.
G 3-P can enter the matrix and is re-oxidised to DHAP andFAD is reduced to FADH2.
Will more energy be produced by use of the glycerol phosphate shuttle or by the malate aspartate shuttle?
The malate aspartate shuttle.
What enzyme converts NADH and DHAP to glycerol 3-phosphate in the glycerol phosphate shuttle?
Cytosolic glycerophosphate dehydrogenase.
What enzyme converts G 3-P to DHAP and FADH2 in the glycerol phosphate shuttle?
Mitochondrial glycerophosphate dehydrogenase.
Every NADH that enters the glycerol phosphate shuttle will form what?
FADH2.
How much ATP from NADH is generated from glycolysis if the malate aspartate shuttle is used?
6 ATP generated.
How much ATP from NADH is generated from glycolysis if the glycerol phosphate shuttle is used?
4 ATP generated.
How much total ATP is generated from glycolysis if the malate aspartate shuttle is used?
6 ATP from 2 NADH + 2 ATP from glycolysis = 8 ATP.
How much total ATP is generated from glycolysis if the malate aspartate shuttle is used?
4 ATP from 2 FADH2 + 2 ATP from glycolysis = 6 ATP.
The ETC is driven by the ratios of what molecules?
NADH/NAD+ and ATP/ADP.
What molecules will activate the ETC?
A lot of NADH.
A lot of ADP.
What are the substrates in the ETC?
NADH.
ADP.
What are the products of the ETC?
NAD+.
ATP.
What will inhibit the ETC?
High levels of NAD+.
High levels of ATP.
What is hypoxia?
A deficiency in oxygen.
What happens in the ETC if someone is hypoxic?
The energy from FADH2 and NADH will not be converted to ATP.
