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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
What is an ion electrochemical gradient expressed in
KJ mol -1
26
Ion electrochemical gradient
Thermodynamic measure of the extent to which an ion gradient is removed from equilibrium
27
What happens when an ion gradient is removed from equilibrium
Work is done
28
Proton electrochemical gradient components
- 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)
29
Units of electrical potential
Millivolts
30
Bioenergetic convention to convert delta meu H+ into units of electrical potential
Protonmotive force (pmf), expressed by delta p
31
Where does delta p exist mainly as a pH difference across the energy-conserving membrane
Chloroplast
32
pH gradient
Delta pH
33
The proton circuit is closely analogous to ___
An electrical circuit
34
How to avoid short circuits
Membrane must be closed and possess a high resistance to protons
35
Protonophores
Synthetic compounds which break the energetic coupling between the primary pump and the ATP synthase
36
Another name for protonophores
Uncouplers
37
What do membranes need to provide in addition to proton circuit
Mechanisms for the uptake and excretion of ions and metabolites
38
How can negatively charged metabolites be transported into a negative interior
Transported together with protons or an equivalent exchange with OH-
39
How does the shape of the cristae of the mitochondria vary
Depending on which tissue it was isolated from or what media it is suspended in
40
___ mitochondria tend to have a greater surface area of the cristae than liver mitochondria
Heart
41
Why do heart mitochondria have a greater surface area
Periods of high respiratory activity are required
42
Space between inner and outer membranes
Intermembrane space
43
Contacts of the cristae with intermembrane space
Small tubular contacts
44
Mitochondria in some cells (not neurons)
Appear to be fused into a continuous reticulum
45
Mitochondria in neurons
Discrete filaments which are independently mobile along the axons and dendrites
46
In many cells, mitochondria appear to be in close contact with ___
Endoplasmic reticulum (ER)
47
Why are mitochondria in close contact with the ER
Aid in the rapid exchange of Ca2+ between the ER and mitochondria
48
Non-specific pores for solutes of molecular weight less than 10 kDa on the outer mitochondrial membrane
Proteins
49
Name for proteins on the outer mitochondrial membrane
Porins
50
Another name for the mitochondrial porin
Voltage dependent anion channel (VDAC)
51
Potential gradient across the highly permeable outer membrane
None
52
Which membrane is energy transducing
Inner
53
Catalytic components of the ATP synthase
Knobs on the N-side of the matrix face
54
What binds to the knobs of the n-side of the matrix face
Adenine nucleotides and phosphate
55
Enzymes that bind to the n-face of the inner membrane
Enzymes of the citric acid cycle
56
Enzyme of the citric acid cycle that does not bind to the n-face of the inner membrane
Succinate dehydrogenase
57
Matrix pools of __ and __ are separate from those in the cytosol
NAD+ and NADP+
58
Matrix of ___ and ___ communicate with the cytoplasm
ADP and ATP
59
What do ADP and ATP use to communicate with the cytoplasm
Adenine nucleotide exchanger
60
___ exist for the transport of many metabolites
Specific carrier proteins
61
How are mitochondria usually prepared
Gentle homogenization of the issue in isotonic sucrose followed by differential centrifugation
62
Purpose of gentle homogenization of the tissue in isotonic sucrose
Osmotic support and to minimize aggregation
63
Purpose of differential centrifugation
To separate mitochondria from nuclei, cell debris, and microsomes
64
What types of tissues does the usual preparation of mitochondria useful for
Fragile tissues (such as the liver)
65
How to prepare tougher tissues such as the heart
Must either first be incubated with a protease, such as nagarse, or be exposed briefly to a blender to break muscle fibers
66
___ are isolated following digestion of the cell wall with snail-gut enzyme
Yeast mitochondria
67
Ultrasonic disintegration of mitochondria produces ____
Inverted submitochondrial particles (SMPs)
68
Why have SMPs been exploited for investigations into the mechanism of energy transduction
Because they have the substrate binding sites for both the respiratory chain and the ATP synthase on the outside
69
Sophisticated technique for investigating mitochondrial function in situ within the cell
Fluorescence techniques
70
Energy transduction in bacteria is associated with ___
The cytoplasmic membrane
71
Cytoplasmic membrane in gram-negative bacteria
Membrane is separated from a peptidoglycan layer and an outer membrane by the periplasm
72
Cytoplasmic membrane in gram-positive bacteria
Periplasm is absent and a cell wall is closely juxtaposed to the cytoplasmic membrane
73
Bacteria that are typically of similar size to mitochondria
Gram-negative bacteria
74
Cytoplasmic membrane in some organisms with a very high rate of respiration
Substantial infoldings
75
Why is it difficult to study energy transduction with intact bacteria
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
___ can overcome problems with energy transduction in intact bacteria
Cell-free vesicular systems
77
Type of vesicles for most transport studies
right-side-out
78
How are right-side-out vesicles obtained
Weakening the cell wall with lysozyme and then exposing the resulting spheroplasts or protoplasts to osmotic shock
79
Right-side-out vesicles can only oxidize substrates that have ___
An external binding site or can permeate the cell membrane
80
What types of vesicles can hydrolyze or synthesize ATP
inside-out vesicles
81
How can inside-out vesicles be prepared
Extruding cells at very high pressure through an orifice in a French press
82
What can inside-out vesicles do to NADH
Oxidize NADH and phosphorylate ADP
83
Method of vesicle preparation varies between ___
Genera
84
___ may give inside-out vesicles or a mixture of two orientation
Osmotic shock
85
Disadvantages of vesicle preparations
- 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
What do solute binding proteins play a key role in
Many aspects of bacterial energy transduction

Mitochondrial (5 decks)

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