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Mini biochem chapter 12 > Biochemistry chapter 10 > Flashcards

Biochemistry chapter 10 Flashcards

1
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2
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3
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What is the citric acid cycle ?

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It is the oxidation of acetyl-CoA to CO2 and H20. Its aka Krebs cycle aka tricarboxylic acid (TCA) that occurs in the mitochondria.

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4
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What are the five enzymes that makes up Pyruvate dehydrogenase complex ?

A
  1. * Pyruvate dehydrogenase *
  2. dihydropropyl transacetylase *
  3. dihydropropyl dehydrogenase *
  4. Pyruvate dehydrogenase Kinase *
  5. Pyruvate dehydrogenase phosphatase
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5
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What is fatty acid oxidation (B-oxidation ) ?

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In the intermembrane space, a process known as activation causes a thioester bond ( common intermediates in many biosynthetic reactions, including the formation and degradation of fatty and mevalonate, precursor to steroids) to form between carboxyl groups of fatty acids and CoA

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6
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What is amino acid catabolism ?

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Certain amino acids can be used to form acetyl CoA. These amino acids must lose their amino group via transamination: their carbon skeletons can then form ketone bodies. That’s why they are termed ketogenic .

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7
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What are ketones ?

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Although acetyl CoA is typically used to produce ketones when the Pyruvate dehydrogenase complex is inhibited, the reverse reaction can occur as well.

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8
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What happens when alcohol is consumed ?

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When its consumed in moderate moments, the enzymes alcohol dehydrogenase and acetylaldehyde dehydrogenase convert it to acetyl-CoA. However, this reaction is accompanied by NADH buildup, which inhibits the Krebs cycle.

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9
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What is the overall reaction of the Pyruvate dehydrogenase complex ?

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Pyruvate + CoA-SH + NAD+——acetyl-CoA +CO2 +NADH + H+

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10
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What other molecules can be used to make acetyl-CoA, and how does the body perform this conversion for each ?

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Fatty acids - shuttle acyl group from cystolic CoA-SH to mitochondrial CoA-SH via carnitine; then undergo B-oxidation Ketogenic amino acids - transaminate( transferring amino group one compound to another ) to lose nitrogen: to convert carbon skeleton into ketone body, which can be converted into acetyl-CoA Ketone: Reverse of ketone body formation Alcohol : Alcohol dehydrogenase and acetaldehyde dehydrogenase convert alcohol into acetyl CoA

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11
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What is a Flavoprotein? What enzyme contains it ? What is FAD ?

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  • This enzyme is a integral protein on the inner mitochondrial membrane. Its a protein with a flavin ( naturally occurring pigmentation) nucleotide.
  • Succinct dehydrogenase is covalently bonded to FAD, the electron acceptors in this reaction. *
  • Its a redox cofactor, more specifically a prosthetic group involved in important enzymatic reactions.
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12
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What is total chemical energy harvested per Pyruvate as ATP for PDC, Citric acid cycle, and ATP production ?

A
  • Pyruvate+CoA-SH + NAD+ ——-acetyl-CoA + NADH + CO2 +. H+ Acetyl-CoA +. 3NAD+. + FAD + GDP +. Pi +2H20—–2CO2 + CoA-SH + 3NADH + 3H+ + FADH2 + GTP
  • * For ATP we lookin at 2.5 ATP per NADH, and 1.5 ATP per FADH2, also 1 GTP—-1 ATP
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13
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What exactly is NAD?

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A coenzyme occurring in most living cells and used alternatively with NADH as oxidizing agent or reducing agent in various metabolic processes.

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14
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What is the purpose of all the reactions that collectively make up the citric acid cycle ?

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Complete oxidation of acetyl-CoA to CO2 so that reduction reactions can be coupled with CO2 formation, thus forming energy carriers such as NADH and FADH2 for the electron transport chain

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15
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What enzyme catalyzes the rate limiting step of the citric acid cycle ?

A

Isocitrate Dehydrogenase

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16
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What is proton-motive force ? Cristae?

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  • Electrochemical proton gradient generated by the complexes of the electron transport chain. Its the inner mitochondrial membrane that will be this essential for generating ATP
  • * Pretty much the inner mitochondrial membrane that is into folds
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What is a electrochemical gradient ?

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A gradient that has chemical and electrostatic properties because as H+ increases in the intermembrane space the pH drops in there and the voltage difference between the intermembrane space and matrix increases due to proton pumping.

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What are shuttle mechanisms ?

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  • Transfers the high energy electrons of NADH to a carrier that can cross the inner mitochondrial membrane..
  • How ? Because cystolic NADH formed through glycolysis can’t directly cross into the mitochondrial matrix. Because it can’t contribute its electrons to the transport chain directly, it must find alternative means of transportation.
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Which complexes are associated with pumping a proton into the intermembrane space in the inner mitochondrial membrane ?

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Complexes I, III, IV

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Which complexes are associated with acquiring electrons from NADH in the inner mitochondrial membrane ?

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Complex I

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Which complexes are associated with acquiring electrons from FADH2 in the inner mitochondrial membrane ?

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Complex II

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Which complexes are associated with having the highest reduction potential ?

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Complex IV of having the highest reduction potential cause it increases down the ETC

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What role does the electron transport chain play in the generation of ATP ?

A

Generates the proton-motive force, an electrochemical gradient across the inner mitochondrial membrane, which provides the energy for ATP syntheses to function

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Based on its needs, which of the two shuttle mechanisms is cardiac muscle most likely to utilize ? Why?

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The malate aspartate shuttle because this mechanism is more efficient, it makes sense for a highly aerobic organ as the heart to utilize it in order to maximize its ATP yield.

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What is Chemiosmotic coupling.? F0 ? F1 ?

A
  • A process that couples or links the ETC to ATP synthesis
  • * Its the ion channel, so protons travel through the F0 along their gradient back into the matrix. This is a part of ATP syntheses
  • * Utilizes the energy released from this electrochemical gradient to phosphorylates ADP to ATP.
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What is conformational coupling ? What exactly is proton gradient ?

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  • Relationship between the proton gradient and ATP synthesis is indirect unlike chemiosmotic. Instead ATP is released by the synthases as a result of the conformational change caused by the gradient. *
  • May be used as a intermediate for energy source for heat and flagellar rotation. It results from high concentration of protons outside the inner membrane of the mitochondria than inside the membrane and becomes the driving force behind ATP synthesis/ hydrolysis
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What is the difference between the ETC and oxidative phosphorylation ? What links the two ?

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The ETC is made up of the physical set of intermembrane proteins located in the inner mitochondrial matrix, and they undergo redox reactions as they transfer electrons to the oxygen, the final electron acceptors. As electrons are transferred, a proton motive force is generated in the intermembrane space. Oxidative phosphorylation is the process by which ATP is generated via harnessing the proton gradient, and it utilizes ATP syntheses to do so.

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The G enthalpy of NADH reducing oxygen directly is significantly greater than any individual step along the electron transport chain. If this is the case, why does transferring electrons along the ETC generate more ATP than direct reduction of oxygen by NADH ?

A

By splitting up electron transfer into several complexes, enough energy is released to facilitate the creation of a proton gradient at many locations rather than just one. The greater the proton gradient is, the greater the ATP generation will be. Direct reduction of oxygen by NADH would release a significant amount of energy to the environment, resulting in inefficient electron transport.

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What is citrate synthase, Isocitrate dehydrogenase, a- ketoglutarate dehydrogenase complex ?

A
  • * Its a pace-making enzyme in the first step of the citric acid cycle, also ATP and NADH function as allosteric inhibitors of citrate synthase because they are the products of this enzyme. Citrate also allosterically inhibits citrate synthase directly as succinyl-CoA.
  • * Enzyme that catalyzes the citric acid cycle which is obviously going to be inhibited by products ATP and NADH. ADP and NAD+ act as allosteric activators for the enzyme and enhance its affinity for substrates.
  • * A highly regulated enzyme that can determine the metabolic flux of the Krebs cycle. It converts ketoglutarate to succinyl-CoA and produces NADH which function as inhibitors of this enzyme complex. ATP slows the rate of the cycle unless we have ADp v

Mini biochem chapter 12 (12 decks)

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