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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
Q

Glycerol phosphate shuttle is observed in

A
  • Skeletal muscle

- Brain

26
Q

Cytosolic glyceraldehyde-3-phosphate dehydrogenase generates

A
  • NADH in glycolysis
27
Q

The electrons from NADH are donated to

A
  • DHAP
28
Q

DHAP is reduced to

A
  • Glycerol-3-phosphate (alpha-glycerol phosphate)
29
Q

DHAP reduced to glycerol-3-phopshate is

A
  • NAD-linked
30
Q

Glycerol-3-phosphate crosses the

A
  • OMM
31
Q

The glycerol phosphate shuttle donated electrons to

A
  • An FAD-containing glycerol-3-phosphate dehydrogenase, producing FADH2
  • Outer face (cytoplasmic side) of IMM
32
Q

DHAP is reformed and enters

A
  • The cytosol
33
Q

The FAHD2 donates electrons to the ETC at

A
  • Complex II

- Then to ubiquinone

34
Q

Only approximately 1.5 molecules of ATP are generated for every mole of

A
  • NADH produced in the cytoplasm when the glycerol phosphate shuttle is used
35
Q

Glycerol phosphate shuttle is operative at

A
  • Lower cytoplasmic NADH/NAD ratios
36
Q

Eukaryotic cells produce from

A
  • 800 to 2000 mitochondria

- Depends on energy requirements

37
Q

Each mitochondria is composed of

A
  • Two concentric membranes

- Only IMM represents a barrier to small molecules

38
Q

The IMM is usually folded into

A
  • Cristae
39
Q

The OMM is

A
  • Smooth
40
Q

The two shuttle systems allow reducing equivalents to move

A
  • From cytoplasm to the mitochondrial matrix

- NADH itself does not cross the membrane

41
Q

The malate-aspartate shuttle system consists of

A
  • Alternate redox and transamination reactions
  • Operates in the hepatocyte
  • Primary shuttle system
42
Q

Secondary glycerol-phosphate system is operational in

A
  • Muscle

- Includes two glycerol-3-phpsphate dehydrogenases

43
Q

Cytoplasmic glycerol-3-phosphate uses

A
  • NADH as an electron donor
44
Q

Mitochondrial membrane glycerol-3-phosphate uses

A
  • FAD as an electron acceptor

Biochemistry I (34 decks)

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