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BIOL 241 > Topic 5: Organotrophy > Flashcards

Topic 5: Organotrophy Flashcards

1
Q

What is Aerobic Respiration?

A
  • A combustion reaction, where glucose is burned to produce Co2, H2) and energy
  • A series of coupled redox reactions, releasing the free energy of glucose and transfers some of the released energy to other molecules
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2
Q

In Aerobic Respiration what is being oxidized?

A

The Carbon atoms in glucose are oxidized to form CO2

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3
Q

In Aerobic Respiration what is being reduced?

A

The O2 atoms in the reactants are being reduced to form water

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4
Q

Redox potential generated from biological redox reactions is stored in?

A

Electron Carriers

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5
Q

What are Electron Carriers?

A

Energy transport molecules the move electrons from one reaction to another

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6
Q

What is the first step of Cellular Respiration?

A

Glycolysis

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7
Q

What is Glycolysis?

A

Occurs in the cytosol
Inputs: 1 glucose (6C), 2 NAD+
Outputs: 2 Pyruvate (3C), 2 NADH
- Consumed 2 molecules of ATP and produced 4 molecules of ATP (formed by substrate-level phosphorylation)
- NAD+ is reduced
- Pyruvate has a lot of potential energy

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8
Q

What is the main goal of glycolysis?

A

To breakdown one molecule of glucose into 2 pyruvate (producing NADH and ATP in the process)

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9
Q

Electron carriers normally…

A

Reduced, gaining electrons
e.g.
NAD+ in glycolysis

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10
Q

What is Substrate-Level Phosphorylation?

A

When an enzyme catalyzes the transfer of a phosphate from a phosphorylated organic molecule to ADP to make ATP (occurs in glycolysis to produce ATP)

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11
Q

Why is glycolysis only partial glucose oxidation?

A
  • Not much ATP has been made
  • The cell needs to remove pyruvate (the final product should not build up in the cell)
  • The cell needs to restore NAD+ (through oxidizing NADH)
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12
Q

What is the energy investment phase in glycolysis?

A

When 2 ATP molecules are used to add phosphate groups to glucose

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13
Q

What is the pay-off phase in glycolysis?

A

When 4 ATP molecules are made through substrate-level phosphorylation and 2 NADH molecules are made through oxidizing NAD+

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14
Q

What is fermentation?

A

The anaerobic (no or limited oxygen) reduction of Pyruvate

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15
Q

What happens after glycolysis if O2 is available?

A

Pyruvate Oxidation

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16
Q

What happens after glycolysis if O2 is not available?

A

Fermentation

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17
Q

Where does fermentation occur?

A

Cytosol

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18
Q

What is the main goal of fermentation?

A

To oxidize NADH to NAD+, so it can allow glycolysis to continue

19
Q

What are the two kinds of fermentation?

A

Lactate fermentation and Alcoholic fermentation

20
Q

What is Lactate fermentation?

A
  • The reduction of pyruvate to produce a lactate, which is coupled to the oxidation reaction of NADH and H+ to form NAD+
  • This allows glycolysis to continue; indirectly making ATP
21
Q

What is Alcoholic fermentation?

A
  • The decarboxylation of pyruvate (releasing CO2), forms Acetaldehyde which is reduced to an alcohol, which is coupled to the oxidation reaction of NADH and H+ to form NAD+
  • This allows glycolysis to continue; indirectly making ATP
22
Q

What is pyruvate oxidation?

A
  • It occurs in the mitochondrial matrix
  • Connects glycolysis to the Kreb Cycle
    Input: 2 Pyruvate (3C), 2 NAD+, CoA (coenzyme)
    Output: 2 AcetylCoA (2C), 2 NADH, 2CO2
  • Pyruvate undergoes decarboxylation releasing CO2, then undergoes oxidation produce Acetyl Group
  • The oxidation reaction is coupled to the reduction of NAD+ to produce NADH and H+
  • Lose 2 C overall
23
Q

What is the main goal of the Krebs (Citric Acid) Cycle?

A

To finish the oxidation of glucose to CO2

24
Q

What is the Kreb Cycle?

A

Input: Acetyl CoA (2C), 3NAD+, ADP, FAD
Output: 2CO2, 3NADH, ATP, FADH2
- First, oxalacetate (4C) combines with Acetyl CoA, to form citrate (6C)
- Citrate undergoes decarboxylation which releases 2CO2, then NAD+ is oxidized to make NADH, then ATP is restored through substrate-level phosphorylation, and lastly, FAD is reduced to form FADH

25
Q

The Kreb cycle is not just glucose…

A
  • Other fuel sources are broken down and can enter pathways
  • Intermediates can be used in anabolic pathways
26
Q

What is the Electron Transport Chain (ETC)

A
  • A series of proteins in the inner mitochondrial membrane that helps cells make energy
  • Electron flow is coupled to pumping H+ from the matrix to the IMS to generate an electrochemical gradient
27
Q

What are the layers of the mitochondrial membrane?

A
  • Outer mitochondrial membrane
  • Inner membrane compartment
  • Inner mitochondrial membrane
  • Mitochondrial matrix
28
Q

How is electron flow REDOX driven?

A
  • Electrons flow to increasingly more electronegative prosthetic groups until they reach the final electron acceptor, O2
  • With each electron transfer, the electron moves closer to the atomic nucleus
  • Free energy is released
29
Q

What is a prosthetic group in the ETC?

A

Associated with protons but not made of amino acids

30
Q

What is the free energy released in ETC used for?

A

Free energy that is released is used to do work (pump H+ across the membrane; ultimately used to produce ATP)

31
Q

What do Complex I and II do?

A
  1. NADH in the mitochondria matrix donates electrons (reduces) Complex I
  2. H+ is pumped from the matrix to IMS by Complex I
  3. FADH2 in the matrix donates electrons to Complex II only (not enough energy to drop electrons in Complex I)
32
Q

What does Ubiquinone (UQ) do?

A
  • A hydrophobic electron taxi
    1. Taxis electrons from Complex I to Complex III
    2. Taxis electrons Complex II to Complex III
    3. When UQ is reduced it takes up a proton from the matrix, when UQ is oxidized it releases protons in the IMS
33
Q

What do Complex III, Cytochrome C, and Complex IV do?

A
  1. Electrons will flow from Complex III to the taxi Cytochrome C
  2. Cytochrome C is a hydrophilic protein taxi that moves electrons from Complex III to IV
  3. Electrons flow through Complex IV to O2, which is reduced to form water
    - H+ is pumped from the matrix into the IMS by Complex IV
34
Q

How is [H+] lowered in the matrix?

A
  1. Pumped protons across the membrane
  2. Used to reduce oxygen into H2O
35
Q

What is Proton Motive Force?

A

The H+ electrochemical gradient

36
Q

What is the Proton Motive Force used for?

A
  • Chemiosmosis
  • PE of the PMF is used to power ATP Synthase
  • Moves H+ through the enzyme ATP Synthase back into the matrix, which powers the synthesis of ATP from ADP and Pi (using Oxidative Phosphorylation)
37
Q

What is Oxidative Phosphorylation?

A

Energy in the PMF, generated by the ETC is used to make ATP

38
Q

What is ATP Synthase?

A

As protons flow through the channel (Fo), rotate and the energy is used to drive the catalytic part

39
Q

ATP yields in Aerobic Respiration?

A

Total is ~ 32 ATP, but can be as high as 38

40
Q

Why do ATP yields vary in Aerobic Respiration?

A
  • Some PMF is used for other purposes
  • NADH and FADH2 can be used for other reactions
41
Q

If we don’t need ATP what can be stored as?

A
  • Glucose can be stored as a polymer (glycogen in animals or starch in plants)
  • Triglycerides for longer-term storage
    *Can be reversed
42
Q

How does Aerobic Respiration work in Prokaryotes?

A
  • Don’t have membrane-bound organelles, therefore all metabolisms occur in the cytosol and on the cell membrane (other than that, its the same)
43
Q

Intermediates from Glycolysis or Kreb Cycle can be…

A
  • Used to build biomolecules (source of carbons)
  • Carbon is needed for macromolecules (amino acids, proteins, nucleic acid, lipids)
  • Acetyl CoA can be used to generate macromolecules (instead of going through Krebs Cycle), a building block to make fatty acids

BIOL 241 (6 decks)

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