Citric Acid Cycle and Respiratory Chian Flashcards
What is the citric acid cycle?
Common path by which all fuel molecules are broken down to carbon dioxide and water
Provide a broad overview of the citric acid cycle
- A 2-carbon molecule is condensed with a 4-carbon molecule to form a 6-carbon molecule
- The 6-carbon molecule is broken down in stages, finally resulting in formation of a new molecule of the original 4-carbon compound
- During this process, two molecules of CO2 and one molecule of GTP are formed.
- At the same time 3 molecules of NADH and one molecule of
FADH2* are formed. –The hydrogen is eventually combined with molecular O2 (forming water) in a process coupled to ATP synthesis
What is FAD and what is it formed from?
Flavin adenine dinucleotide
Formed from vitamin riboflavin (vitamin B2)
What does deficiency in riboflavin (vitamin. B2) cause?
lesions of the mucous membranes
cracked, sore lips and corners of mouth; similar lesions in genital regions; tongue swollen, tender, magenta
What parts of the citric acid cycle occur within the mitochondria?
All of them
Where in the mitochondria does the citric acid cycle occur?
All reactions from the breakdown of pyruvate, including all steps of the citric acid cycle take place in the MATRIX of the mitochondria
When pyruvate enters the mitochondrion, what happens?
After pyruvate has been translocated into the mitochondrion it undergoes decarboxylation to become acetate.
What does coenzyme A (CoA) do in translocation of pyruvate and decarboxylation to acetate?
Coenzyme A (CoA) forms a high energy bond with carboxylic acids such as acetate
What is CoA?
Coenzyme A is a nucleotide that contains
the vitamin pantothenic acid (= vitamin B5)
What is the first step of the citric acid cycle?
condensation of the acetyl group of Acetyl-CoA with the keto acid oxaloacetate to form citrate synthase
What is the bodies response to handling reactive ketogenic acids?
They can be decarbonated into a more stable form, eg:
Isocitrate -> Oxalosiccinate -> α-Ketoglutarate + CO2
What is the respiratory chain also known as in the citric acid cycle?
electron transfer chain/oxidative phosphorylation
Where does the respiratory chain take place?
on macromolecular assemblies in the inner mitochondrial membrane
What is the respiratory chain?
Hydrogen and electrons taken from fuel molecules by NAD+ are
passed down a chain of electron-carrying molecules until they are passed to molecular oxygen
The respiratory chain consists of 4 complexes, what are they?
Complex I - NADH-q reductase
Complex II - FADH2 in flavoproteins
Complex III - Cytochrome reductase
Complex IV - Cytochrome oxidase
What are the three large protein complexes that are linked together by molecules that act as electron shuttles in the respiratory chain?
Complex I - NADH-q reductase
Complex III - Cytochrome reductase
Complex IV - Cytochrome oxidase
What molecules feed electrons into the system at different places?
NADH and FADH2
What do NADH and FADH2 do in the respiratory chain?
feed electrons into the system at different places
What chemical agents target the respiratory chain?
Rotenone –Insecticide, piscicide (Complex I inhibitor)
Antimycin A –Antibiotic (Complex III inhibitor)
What effects do cyanide and carbon monoxide have on the respiratory chain?
block the final step by which hydrogen combines with
oxygen (Complex IV inhibitors)
How is energy released in the respiratory chain?
Electrons are passed from one member of the chain to another
In this way the energy released by passing electrons from NADH or FADH2 so oxygen is used more efficiently
What does the movement of electrons down the chain generate?
a H+ ion (pH) gradient across the inner mitochondrial membrane
Where are the H+ ions (protons) pumped to to create the ion gradient in the respiratory chain?
proteins are pumped into the intermembrane space
What is the ion gradient used for in the respiratory chain?
The electrochemical gradient is used to drive ATP synthesis by way of ATP synthase (= H+-ATPase)
Describe the action of ATP synthase
Think of it as a system that works in the opposite direction from the sodium pump (Na-K ATPase) in the surface membrane
The sodium pump uses ATP to generate an ion gradient, while the ATP synthase uses an ion gradient to generate ATP
Oxidation of each molecule of NADH produces about 2.5 molecules of ATP, while each molecule of FADH2 generates 1.5 ATP molecules
What is the ATP yield from the breakdown of a carbohydrate going through glycolysis and the citric acid cycle?
30-32???*
What does the oxidation of NADH and FADH2 in ATP synthase yield in terms of ATP synthesis?
Oxidation of each molecule of NADH produces about 2.5 molecules of ATP, while each molecule of FADH2 generates 1.5 ATP molecules
