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Mitochondrial > Test 1 > Flashcards

Test 1 Flashcards

1
Q

All biochemical reactions involve ___

A

Energy changes

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2
Q

When did bioenergetics rise to prominence

A

1950s

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3
Q

Why did bioenergetics rise to prominence

A

Highly directed search for the solution to the mechanism by which energy made available by the oxidation of substrates, or the absorption of light, could be coupled to uphill reactions such as the synthesis of ATP from ADP and P or the accumulation of ions across a membrane

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4
Q

Central concept of bioenergetics

A

Chemiosmotic theory

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5
Q

Mitochondrial physiology

A

The investigation of the role of mitochondria in the healthy and diseased cell

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6
Q

Result of mitochondrial dysfunction

A

Disorders such as chronic neurodegenerative diseases, stroke, and heart reperfusion injury

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7
Q

What is the majority of ATP synthesis catalyzed by

A

Membrane-bound enzyme systems

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8
Q

What is the minority of ATP synthesis catalyzed by

A

Soluble enzyme systems

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9
Q

Energy transducing membranes

A

Plasma membrane of simple prokaryotic cells (bacteria and blue-green algae), the inner membrane of mitochondria, and the thylakoid membrane of chloroplasts

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10
Q

What do energy transducing membranes have in common

A

Related evolutionary origin

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11
Q

What are chloroplasts and mitochondria thought to have evolved from

A

A symbiotic relationship between a primitive non-respiring eukaryotic cell and an invading prokaryote

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12
Q

Distinguishing features of energy transducing membranes

A
  • Two distinct types of proton pump (primary and secondary)
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13
Q

What does the nature of the primary proton pump of the energy transducing membrane depend on

A

The energy source used by the membrane

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14
Q

How is a gradient of protons generated in mitochondria and respirating bacteria

A

An electron transfer chain catalyses the downhill transfer of electrons from substrates to final acceptors such as O2 and uses this energy to generate a gradient of protons

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15
Q

How is a gradient of protons generated in photosynthetic bacteria

A

They exploit the energy available from the absorption of quanta of visible light

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16
Q

How is a gradient of protons generated in chloroplast thylakoids

A

Same as photosynthetic bacteria, but also drive electrons uphill from water to acceptors such as NADP

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17
Q

Side of the membrane to which protons are pumped

A

P or positive side

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18
Q

Side of the membrane from which protons originated

A

N or negative side

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19
Q

Name of secondary proton pump

A

ATP synthase or the H+ translocating ATPase

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20
Q

How would the secondary proton pump operate in isolation in a membrane

A

It would hyrolyze ATP to ADP and Pi and pump protons in the same direction as the primary pump

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21
Q

Essense of chemiosmotic theory in terms of proton pumps

A

The primary proton pump generates a sufficient gradient of protons to force the secondary pump to reverse and synthesize ATP from ADP and Pi

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22
Q

Metabolism (electron flow or phosphorylation) in the primary and secondary proton pumps is tightly coupled with ___

A

Proton translocation

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23
Q

What does it mean that metabolism (electron flow or phosphorylation) in the primary and secondary proton pumps is tightly coupled with proton translocation

A

One cannot occur without the other

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24
Q

Quantitative thermodynamic measure

A

The proton electrochemical gradient (delta meu H+)

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25
Q

What is an ion electrochemical gradient expressed in

A

KJ mol -1

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26
Q

Ion electrochemical gradient

A

Thermodynamic measure of the extent to which an ion gradient is removed from equilibrium

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27
Q

What happens when an ion gradient is removed from equilibrium

A

Work is done

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28
Q

Proton electrochemical gradient components

A
  • One due to the concentration difference of protons across the membrane (delta pH)
  • One due to the difference in electrical potential between the two aqueous phases separated by the membrane (membrane potential, delta scepter)
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29
Q

Units of electrical potential

A

Millivolts

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30
Q

Bioenergetic convention to convert delta meu H+ into units of electrical potential

A

Protonmotive force (pmf), expressed by delta p

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31
Q

Where does delta p exist mainly as a pH difference across the energy-conserving membrane

A

Chloroplast

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32
Q

pH gradient

A

Delta pH

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33
Q

The proton circuit is closely analogous to ___

A

An electrical circuit

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34
Q

How to avoid short circuits

A

Membrane must be closed and possess a high resistance to protons

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35
Q

Protonophores

A

Synthetic compounds which break the energetic coupling between the primary pump and the ATP synthase

36
Q

Another name for protonophores

A

Uncouplers

37
Q

What do membranes need to provide in addition to proton circuit

A

Mechanisms for the uptake and excretion of ions and metabolites

38
Q

How can negatively charged metabolites be transported into a negative interior

A

Transported together with protons or an equivalent exchange with OH-

39
Q

How does the shape of the cristae of the mitochondria vary

A

Depending on which tissue it was isolated from or what media it is suspended in

40
Q

___ mitochondria tend to have a greater surface area of the cristae than liver mitochondria

A

Heart

41
Q

Why do heart mitochondria have a greater surface area

A

Periods of high respiratory activity are required

42
Q

Space between inner and outer membranes

A

Intermembrane space

43
Q

Contacts of the cristae with intermembrane space

A

Small tubular contacts

44
Q

Mitochondria in some cells (not neurons)

A

Appear to be fused into a continuous reticulum

45
Q

Mitochondria in neurons

A

Discrete filaments which are independently mobile along the axons and dendrites

46
Q

In many cells, mitochondria appear to be in close contact with ___

A

Endoplasmic reticulum (ER)

47
Q

Why are mitochondria in close contact with the ER

A

Aid in the rapid exchange of Ca2+ between the ER and mitochondria

48
Q

Non-specific pores for solutes of molecular weight less than 10 kDa on the outer mitochondrial membrane

A

Proteins

49
Q

Name for proteins on the outer mitochondrial membrane

A

Porins

50
Q

Another name for the mitochondrial porin

A

Voltage dependent anion channel (VDAC)

51
Q

Potential gradient across the highly permeable outer membrane

A

None

52
Q

Which membrane is energy transducing

A

Inner

53
Q

Catalytic components of the ATP synthase

A

Knobs on the N-side of the matrix face

54
Q

What binds to the knobs of the n-side of the matrix face

A

Adenine nucleotides and phosphate

55
Q

Enzymes that bind to the n-face of the inner membrane

A

Enzymes of the citric acid cycle

56
Q

Enzyme of the citric acid cycle that does not bind to the n-face of the inner membrane

A

Succinate dehydrogenase

57
Q

Matrix pools of __ and __ are separate from those in the cytosol

A

NAD+ and NADP+

58
Q

Matrix of ___ and ___ communicate with the cytoplasm

A

ADP and ATP

59
Q

What do ADP and ATP use to communicate with the cytoplasm

A

Adenine nucleotide exchanger

60
Q

___ exist for the transport of many metabolites

A

Specific carrier proteins

61
Q

How are mitochondria usually prepared

A

Gentle homogenization of the issue in isotonic sucrose followed by differential centrifugation

62
Q

Purpose of gentle homogenization of the tissue in isotonic sucrose

A

Osmotic support and to minimize aggregation

63
Q

Purpose of differential centrifugation

A

To separate mitochondria from nuclei, cell debris, and microsomes

64
Q

What types of tissues does the usual preparation of mitochondria useful for

A

Fragile tissues (such as the liver)

65
Q

How to prepare tougher tissues such as the heart

A

Must either first be incubated with a protease, such as nagarse, or be exposed briefly to a blender to break muscle fibers

66
Q

___ are isolated following digestion of the cell wall with snail-gut enzyme

A

Yeast mitochondria

67
Q

Ultrasonic disintegration of mitochondria produces ____

A

Inverted submitochondrial particles (SMPs)

68
Q

Why have SMPs been exploited for investigations into the mechanism of energy transduction

A

Because they have the substrate binding sites for both the respiratory chain and the ATP synthase on the outside

69
Q

Sophisticated technique for investigating mitochondrial function in situ within the cell

A

Fluorescence techniques

70
Q

Energy transduction in bacteria is associated with ___

A

The cytoplasmic membrane

71
Q

Cytoplasmic membrane in gram-negative bacteria

A

Membrane is separated from a peptidoglycan layer and an outer membrane by the periplasm

72
Q

Cytoplasmic membrane in gram-positive bacteria

A

Periplasm is absent and a cell wall is closely juxtaposed to the cytoplasmic membrane

73
Q

Bacteria that are typically of similar size to mitochondria

A

Gram-negative bacteria

74
Q

Cytoplasmic membrane in some organisms with a very high rate of respiration

A

Substantial infoldings

75
Q

Why is it difficult to study energy transduction with intact bacteria

A
  1. Many reagents do not penetrate outer membrane of gram-negative organisms
  2. ADP, ATP, NAD+ and NADH do not cross the cytoplasmic membrane
  3. Cells are frequently difficult to starve of endogenous substrates and thus there can be ambiguity as to the substrate which is donating electrons to a respiratory chain
  4. The study of transport can be complicated by subsequent metabolism of the substrate
76
Q

___ can overcome problems with energy transduction in intact bacteria

A

Cell-free vesicular systems

77
Q

Type of vesicles for most transport studies

A

right-side-out

78
Q

How are right-side-out vesicles obtained

A

Weakening the cell wall with lysozyme and then exposing the resulting spheroplasts or protoplasts to osmotic shock

79
Q

Right-side-out vesicles can only oxidize substrates that have ___

A

An external binding site or can permeate the cell membrane

80
Q

What types of vesicles can hydrolyze or synthesize ATP

A

inside-out vesicles

81
Q

How can inside-out vesicles be prepared

A

Extruding cells at very high pressure through an orifice in a French press

82
Q

What can inside-out vesicles do to NADH

A

Oxidize NADH and phosphorylate ADP

83
Q

Method of vesicle preparation varies between ___

A

Genera

84
Q

___ may give inside-out vesicles or a mixture of two orientation

A

Osmotic shock

85
Q

Disadvantages of vesicle preparations

A
  • Loss of periplasmic electron transport or solute binding proteins
  • Membrane of a vesicle may be somewhat leaky with the result that the stoichiometry of an energy transduction reaction may be adversely affected
86
Q

What do solute binding proteins play a key role in

A

Many aspects of bacterial energy transduction

Mitochondrial (5 decks)

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