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Biochemistry I > Chapter 19: Mitochondrial Shuttles > Flashcards

Chapter 19: Mitochondrial Shuttles Flashcards

1
Q

Two mitochondrial shuttle systems

A
  • Malate-aspartate shuttle

- Glycerol-phosphate shuttle

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2
Q

Numerous mitochondria found in this type of eukaryotic cell

A
  • Parietal cell

- Has two membranes

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3
Q

Outer membrane of mitochondria is

A
  • Freely permeable
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4
Q

The IMM is relatively

A
  • Impermeable
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5
Q

The IMM is impermeable to

A
  • NADH
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6
Q

Specific transport systems needed to bypass IMM

A
  • Pyruvate
  • ATP
  • Citrate
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7
Q

NADH is formed in glycolysis by

A
  • Glyceraldehyde-3-phosphate dehydrogenase step

- Must be reoxidized for glycolysis to continue

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8
Q

In the absence of oxygen, NADH reoxidation occurs via

A
  • Lactate dehydrogenase
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9
Q

In the presence of oxygen and mitochondria, electrons from NADH can be

A
  • Shuttled into the mitochondria with the synthesis of ATP
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10
Q

Malate-aspartate shuttle occurs in

A
  • The liver

- More complex and more efficient

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11
Q

Glycerol-phosphate shuttle occurs in

A
  • Muscle
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12
Q

NADH produced by glycolysis in the cytosol must

A
  • Enter the mitochondria for aerobic oxidation
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13
Q

The malate shuttle system consists of

A
  • Alternate redox and transamination reactions
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14
Q

Malate shuttle is the primary mechanism for

A
  • Oxidation of cytoplasmic NADH
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15
Q

Malate shuttle is observed in the following places

A
  • Kidney
  • Liver
  • Heart tissue
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16
Q

Glyceraldehyde-3-phosphate dehydrogenase increases

A
  • Cytoplasmic NADH
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17
Q

NADH from G3P reduces

A
  • Cytoplasmic OAA to malate

- Reaction is catalyzed by MDH

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18
Q

Malate crosses the IMM in exchange for

A
  • Alpha ketoglutarate
19
Q

Inside the mitochondria, malate is reoxidized to

A
  • Oxaloacetic acid

- Catalyzed by mitochondrial MDH

20
Q

Mitochondrial MDH is an enzyme that is also involved in

A
  • The Citric Acid Cycle
21
Q

The NADH enters the ETC at

A
  • Complex I

- Generates 2.5 ATPs

22
Q

Cytoplasmic NADH reduces

A
  • Oxaloacetate to malate
23
Q

Malate-Aspartate shuttle is also observed in the pathway of

A
  • Gluconeogensis
24
Q

The glycerol phosphate shuttle requires

A
  • Two glycerol-3-phosphate dehydrogenases (alpha G3Ps)

- 3 steps

25
Glycerol phosphate shuttle is observed in
- Skeletal muscle | - Brain
26
Cytosolic glyceraldehyde-3-phosphate dehydrogenase generates
- NADH in glycolysis
27
The electrons from NADH are donated to
- DHAP
28
DHAP is reduced to
- Glycerol-3-phosphate (alpha-glycerol phosphate)
29
DHAP reduced to glycerol-3-phopshate is
- NAD-linked
30
Glycerol-3-phosphate crosses the
- OMM
31
The glycerol phosphate shuttle donated electrons to
- An FAD-containing glycerol-3-phosphate dehydrogenase, producing FADH2 - Outer face (cytoplasmic side) of IMM
32
DHAP is reformed and enters
- The cytosol
33
The FAHD2 donates electrons to the ETC at
- Complex II | - Then to ubiquinone
34
Only approximately 1.5 molecules of ATP are generated for every mole of
- NADH produced in the cytoplasm when the glycerol phosphate shuttle is used
35
Glycerol phosphate shuttle is operative at
- Lower cytoplasmic NADH/NAD ratios
36
Eukaryotic cells produce from
- 800 to 2000 mitochondria | - Depends on energy requirements
37
Each mitochondria is composed of
- Two concentric membranes | - Only IMM represents a barrier to small molecules
38
The IMM is usually folded into
- Cristae
39
The OMM is
- Smooth
40
The two shuttle systems allow reducing equivalents to move
- From cytoplasm to the mitochondrial matrix | - NADH itself does not cross the membrane
41
The malate-aspartate shuttle system consists of
- Alternate redox and transamination reactions - Operates in the hepatocyte - Primary shuttle system
42
Secondary glycerol-phosphate system is operational in
- Muscle | - Includes two glycerol-3-phpsphate dehydrogenases
43
Cytoplasmic glycerol-3-phosphate uses
- NADH as an electron donor
44
Mitochondrial membrane glycerol-3-phosphate uses
- FAD as an electron acceptor

Biochemistry I (34 decks)

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