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Biochemistry > Aerobic Respiration and Energy Production > Flashcards

Aerobic Respiration and Energy Production Flashcards

1
Q

The Mitochondria

  1. What is the shape and size of the mitochondria?
  2. The mitochondria has a dual membrane structure consisting of the outer and inner mitochondrial membrane. What are christae and where are they found? What transport system and synthase is found in the inner mitochondrial membrane?
  3. What is the space between membranes called?
  4. What is the interior known as and what does it contain? What 3 things occur here?
A
  1. Football shaped organelle about the size of a bacterial cell.
  2. Inner mitochondrial membrane:
    Highly folded membranes = christae
    Has electron transport system and ATP synthase.
  3. Space between membranes is the intermembrane space.
  4. Interior is the matrix space containing enzymes.
    - Citric acid cycle
    - β-oxidation of fatty acids
    - Degradation of amino acids
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2
Q

Structure and Function

  1. Why does the outer membrane have many pores?
  2. What does the folds of the inner membrane create?
A
  1. For the passage of small molecules.

2. A large surface area with many transport proteins.

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3
Q

Conversion of Pyruvate to Acetyl CoA

  1. Under what conditions is pyruvate from glycolysis completely oxidized to CO2? After this conversion, where does the CO2 enter and what is it converted to? What does this conversion activate?
  2. What 3 things does this activation consist of?
A
  1. Under aerobic conditions. CO2 enters the mitochondria and is converted to acetyl CoA. Activates the acetyl group for entry into the citric acid cycle.
    • Kreb’s cycle
      - Tricarboxylic acid cycle
      - TCA cycle
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4
Q

Structure of Acetyl CoA

  1. What enters the mitochondria? What is it converted to? What must be activated for further reactions?
  2. When does activation occur?
  3. What is Coenzyme A?
A
  1. Pyruvate enters the mitochondria. Converted to a 2-carbon acetyl group.
    Acetyl group must be activated for further reactions.
  2. When the acetyl group is bonded to the thiol group of coenzyme A in a high-energy bond.
  3. Coenzyme A is a large thiol derived from ATP and pantothenic acid, a vitamin.
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5
Q

Overall Decarboxylation and Oxidation of Pyruvate

  1. What are the 3 steps involved in the conversion of pyruvate to acetyl CoA?
  2. What reactions are bundled together as the pyruvate dehydrogenase complex?
  3. What is the full reaction and intermediate in the creation of acetyl coenzyme A?
A
    • Decarboxylation – loss of a carboxyl group as CO2.
      - Oxidation by NAD+ which accepts the hydride anion.
      - Remaining acetyl group linked to coenzyme A via a high-energy thioester bond.
  2. Reactions catalyzed by 3 enzymes and 5 coenzymes.
  3. Pyruvate + Coenzyme A > Acetyl Coenzyme A + CO2.
    - Intermediate is Pyruvate dehydrogenase complex.
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6
Q

Role of Acetyl CoA in Cellular Metabolism

  1. What is central in cellular metabolism? What is it’s major function?
  2. What type of reactions does acetyl CoA also function in and what two things are produced?
  3. What 3 things does acetyl CoA permit the interconversion of?
  4. What 3 things must be degraded to produce Acetyl CoA?
A
  1. Acetyl CoA. To carry the acetyl group to the citric acid cycle.
  2. Biosynthetic reactions to produce cholesterol and fatty acids.
  3. Permits interconversion of energy sources
    Fats, Proteins, and Carbohydrates.
  4. Produced by degrading Glucose, Fatty acids, and Some amino acids.
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7
Q

Overview: Aerobic Respiration

  1. What is aerobic respiration?
  2. What is aerobic respiration also known as? Why?
  3. What is aerobic respiration performed by? Where does this occur?
  4. How many oxidations transfer hydride to NAD+ or FAD?
  5. Where are electrons passed to from NAD+ or FAD?
  6. Where are protons transferred to? What does this lead to?
A
  1. The Oxygen-requiring breakdown of food and production of ATP.
  2. Process also called oxidative phosphorylation as energy from oxidative reactions is used to phosphorylate ADP making ATP.
  3. Performed by enzymes in the mitochondrial matrix.
  4. Three.
  5. to the electron transport chain and then O2.
  6. Protons are transferred to intermembrane space, leads to ATP synthesis as protons return to mitochondrial matrix.
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8
Q

The Citric Acid Cycle (Krebs Cycle)

  1. What is the citric acid cycle?
  2. What two things feed the citric acid cycle?
  3. What is the acetyl group oxidized to? What are then transferred to NAD+ and FAD?
  4. How many steps does the cycle comprise of and how are they controlled?
  5. Under what conditions does the citric acid cycle operate?
  6. What 3 things does the citric acid cycle produce?
A
  1. Citric acid cycle is the final stage in the breakdown of dietary nutrients.
  2. Acetyl CoA and oxaloacetate.
  3. The two-carbon acetyl group is oxidized to two molecules of CO2. High energy electrons are then transferred to NAD+ and FAD.
  4. Cycle comprises 8 enzymatic steps several of which are allosterically controlled.
  5. Aerobic conditions only.
  6. Produces reduced coenzymes NADH and FADH2 and one ATP directly.
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9
Q

Citric Acid Cycle Overview

  1. In the citric acid cycle, what does acetyl (2C) bonds bind to and what is formed?
  2. What two things converts citrate and what is it converted to?
  3. What happens when oxaloacetate bonds with another acetyl?
A
  1. Acetyl (2C) bonds bind to oxaloacetate (4C) to form citrate (6C).
  2. Oxidation and decarboxylation converts citrate to oxaloacetate.
  3. The cycle is repeated.
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10
Q

Reaction 1

  1. What type of reaction occurs in Reaction 1? What two things is this reaction between?
  2. What is this reaction catalyzed by?
  3. What is the product?
A
  1. An aldol condensation reaction between the acetyl group of acetyl CoA and oxaloacetate.
  2. Catalyzed by citrate synthase.
  3. Product is citrate.
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11
Q

Reaction 2

  1. What type of reaction occurs in Reaction 2 and with what? What is this then followed by?
  2. What is released in this type of reaction?
  3. What is hydrated and to what in this reaction?
  4. What is this reaction catalyzed by?
  5. What is the intermediate in this reaction?
  6. What is the final product of this reaction?
A
  1. A dehydration reaction of citrate followed by hydration to isocitrate.
  2. Water.
  3. Hydration of cis-aconitate to isocitrate.
  4. Aconitase.
  5. Intermediate is cis-aconitate.
  6. Final product is isocitrate.
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12
Q

Reaction 3

  1. What is Reaction 3 considered the first step of?
  2. What are the complex 3-steps of this reaction?
  3. What is Reaction 3 catalyzed by?
  4. What is the product of Reaction 3?
A
  1. First oxidative step of the citric acid cycle.
    • Hydroxyl group of isocitrate is oxidized to a ketone.
      - Carbon dioxide is released in a decarboxylation.
      - NAD+ is reduced to NADH.
  3. Catalyzed by isocitrate dehydrogenase.
  4. Product is α-ketoglutarate.
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13
Q

Reaction 4

  1. In Reaction 4, what attaches to α-ketoglutarate in a 3-step reaction?
  2. What enzyme is involved in this reaction?
  3. What are the 3 steps of Reaction 4?
  4. What two things is the bond between in Reaction 4? What is the strength of the bond in this reaction?
A
  1. Coenzyme A, similar to that of the pyruvate dehydrogenase complex.
  2. α-ketoglutarate dehydrogenase complex.
    • First, a-ketoglutarate loses a carboxylate group as CO2.
      - Then, a-ketoglutarate is oxidized with NAD+ reduced to NADH.
      - Coenzyme A combines with succinate to form succinyl CoA.
  4. Bond between succinate and coenzyme A is high-energy.
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14
Q

Reaction 5

  1. Reaction 5 is a very chemically involved step. What is converted to what and by what enzyme?
  2. What happens to the high-energy thioester bond in Reaction 5? What does this add and make as a result?
  3. What does dinucleotide diphosphokinase catalyze the transfer of in Reaction 5?
A
  1. Succinyl CoA is converted to succinate by the enzyme succinyl CoA synthase.
  2. The high-energy thioester bond is hydrolyzed adding an inorganic phosphate group to GDP making GTP.
  3. Catalyzes transfer of the inorganic phosphate group from GTP to ATP.
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15
Q

Reaction 6

  1. What is Succinate oxidized by in Reaction 6? What is formed?
  2. What oxidizing agent is reduced in this step?
A
  1. Succinate is oxidized by succinate dehydrogenase to form fumarate.
  2. FAD, flavin adenine dinucleotide, is reduced in this step to FADH2.
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16
Q

Reaction 7

  1. In Reaction 7, in what two ways can the double bond of fumarate be reduced? What does this produce?
  2. What is this reaction catalyzed by?
A
  1. Reducing the double bond of fumarate by the hydration or addition reaction of H2O produces malate.
  2. Catalyzed by fumarase.
17
Q

Reaction 8

1. What enzyme does the final reaction step use? What 3 things does it do?

A
  1. Final reaction step uses malate dehydrogenase to:
    - Reduce NAD+ to NADH.
    - Oxidize malate to oxaloacetate.
    - Causes cycle to begin as an acetyl group is added to oxaloacetate, bring a full turn of the cycle.
18
Q

Summary of Products in the Citric Acid Cycle

  1. What does Oxaloacetate bond with? What does this form?
  2. What does two decarboxylation remove?
  3. What does 4 oxidations provide?
  4. What does a direct phosphorylation form?
A
  1. Oxaloacetate bonds with an acetyl group to form citrate.
  2. Two decarboxylations remove two carbons as 2CO2.
  3. Four oxidations provide hydrogen for 3NADH and one FADH2.
  4. Forms GTP.
19
Q

Control of the Citric Acid Cycle

  1. What does the citric acid cycle respond to?
  2. When does the pathway speed up?
  3. How are the four enzymes/enzyme complexes in the control of the Citric Acid Cycle regulated?
A
  1. It responds to the energy needs of the cell.
  2. When there is a greater demand for energy.
  3. They are allosterically regulated. (Several regulated steps demonstrate the importance of precise control.)
20
Q

Regulation of Citric Acid Cycle

  1. What stimulates formation of acetyl CoA for the citric acid cycle?
  2. What two things decreases the formation of acetyl CoA and slows down the citric acid cycle?
A
  1. Low levels of ATP.

2. High ATP and NADH levels.

21
Q

Oxidative Phosphorylation

  1. What is the respiratory electron transport system made up of?
  2. What can occur at three sites in the electron transport system?
  3. How many molecules of ATP does NADH and FADH2 provide?
  4. Where does ATP synthesis occur?
  5. What is the final complex for oxidative phosphorylation? Where is this complex located and what does it serve as? What is the role of a portion of this complex?
A
  1. A series of electron carriers embedded in the inner mitochondrial membrane.
  2. Protons, H+, can be pumped from the matrix to the intermembrane space.
    • NADH provides three ATP molecules.
      - FADH2 provides two ATP molecules.
  4. At the ATP synthase.
  5. ATP synthase, a multiprotein complex. Spans the inner membrane serving as a channel for protons. Portion of the complex is an enzyme that catalyzes the phosphorylation of ADP to ATP.
22
Q

Electron Transport Systems

1. What is embedded within the mitochondrial inner membrane? How are they arranged? What is this array called?

A
  1. The electron transport systems/electron carriers coenzymes and cytochromes. Arranged to allow them to pass electrons from one carrier to the next. Called the respiratory electron transport system.
23
Q

The Hydrogen Ion Gradient

  1. What do the protons pumping from the matrix to the intermembrane space at the three sites contribute to?
  2. What does each site pump? What is produced?
  3. What sites does NADH dehyrogenase pass electrons to? What sites does FADH2 oxidation pass electrons to?
A
  1. Contributes to a high-energy H+ reservoir.
  2. Each site pumps sufficient protons to produce one ATP molecule.
  3. NADH dehydrogenase passes electrons along all 3 sites. FADH2 oxidation passes electrons along only 2 sites.
24
Q

ATP Synthase and the Production of ATP

  1. Where does NADH carry electrons?
  2. What happens to NADH?
  3. What two things are then pumped into the intermembrane compartment? Where are they passed through next?
  4. What happens to the electrons with each transfer? Why?
  5. With what molecule do electrons reach the last carrier and what is the electron acceptor? What is the formula displaying this?
  6. What do the protons in the intermembrane space flow back through? What does this activate? What is then catalyzed and what does it cause? What does proton flow provide?
A
  1. NADH carries electrons to the first carrier of the electron transport system, NADH dehydrogenase.
  2. Oxidized to NAD+ which returns to citric acid cycle.
  3. Pair of electrons passed to the next electron carrier and H+ are passed to through the electron transport system.
  4. The electrons lose some energy. This energy is used to transport H+ across the inner membrane.
  5. O2 for both. 1/2 O2 + 2H+ > H2O
  6. Flow back through ATP synthase F0 channel activating F1. F1 catalyzes phosphorylation of ADP to produce ATP. Proton flow provides the energy that drives ATP synthesis by the F1 complex.

Biochemistry (9 decks)

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