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MEDSCI 205 > Energy Supply and Demand > Flashcards

Energy Supply and Demand Flashcards

1
Q

What are the THREE major energy sinks of a muscle cell?

A
  1. Na+/K+ ATPase of sarcolemmal membrane
  2. Ca2+ ATPase of sarcoplasmic reticular membrane (SERCA)
  3. Myosin ATPase of cross-bridges
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2
Q

What is the First Law of Thermodynamics?

A

Energy can be transferred or transformed, but it cannot be created or destroyed.

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3
Q

What is the Second Law of Thermodynamics?

A

Every energy transfer or transformation makes the universe more disordered.

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4
Q

What is Entropy?

A

A quantitative measure of disorder that is proportional to the amount of randomness (symbol, S).

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5
Q

What are the THREE sources of work in a cell?

A
  1. Elastic
  2. Electric
  3. Chemi-osmotic
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6
Q

What THREE processes contribute to energy production?

A
  1. Alactic anaerobic processes
  2. Lactic processes
  3. Oxidative Phosphorylation
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7
Q

What are the TWO alactic energy producing processes/reactions?

A
  1. Creatine phosphokinase reaction

2. Adenylate kinase reaction

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8
Q

What are the TWO lactic energy producing processes?

A
  1. Glycolysis

2. Glycogenolysis

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9
Q

The concentration of ATP stays constant until what percentage of CrP has been converted to Cr and P?

A

90%

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10
Q

How many ATP are produced per splitting of ONE CrP molecule?

A

1 ATP per CrP

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11
Q

If insufficient ATP is present to re-phosphorylate AMP, what two toxic products are formed and what activity do they inhibit?

A 
Inosine monophosphate (IMP) and NH4+
They inhibit muscle contraction (by inhibiting myosin ATPase)
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12
Q

What are alactic anaerobic processes of energy generation useful for?

A

Short intense bursts of exercise

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13
Q

How many ATP are produced through glycolysis of 1 Glucose molecule?

A

nett 2 ATP

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14
Q

How many ATP are produced per event of glycogen-derived glycolysis (glycogenolysis)?

A

nett 3 ATP

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15
Q

How many ATP are produced through oxidative phosphorylation of 1 Glucose molecule?

A

nett 30-32 ATP (depending on which shuttle is used for transport from cytosol to mitochondria).

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16
Q

Cr is re-phosphorylated in the mitochondria to CrP by ATP produced by oxidative phosphorylation so that it can act as a ‘shuttle’ for Pi (TRUE or FALSE)

A

TRUE

17
Q

What is the name of the enzyme used to re-phosphorylate Cr to CrP and is ubiquitous?

A

Creatine phosphokinase

18
Q

What is the definition of fatigue?

A

A failure to maintain the required, or expected, power output, leading to reduced muscle performance

19
Q

Name THREE of the causes of muscular fatigue

A
  1. A failure of the ‘will’
  2. Depression of the action potential in the motor nerve
  3. Synaptic fatigue
  4. Accumulation of K+ in the transverse-tubules
  5. Diminished release of Ca2+ from sarcoplasmic reticulum
  6. Accumulation of inhibitory end-products of metabolic reactions
  7. Diminution of the Free Energy of ATP hydrolysis
20
Q

What are the consequences of central fatigue?

A

Decreased activation from CNS

Decreased number of motor units recruited

21
Q

What are the consequences of peripheral fatigue?

A

Smaller Ca2+ transient
Reduced Ca2+ sensitivity of the myofilaments
Slower cross-bridge cycling

22
Q

What are THREE of the ways in which fatigue can be studied?

A
  1. Trained athlete
  2. Exercising volunteers (sedentary vs. active)
  3. Experimental animals
  4. Isolated whole muscle preparations
  5. Isolated single muscle fibre preparations
  6. Contractile proteins in a test-tube
23
Q

What are the THREE muscle fibre types and what are their basic properties?

A 
Type I (slow twitch, no fatigue)
Type IIa (fast twitch, fatigue resistant) 
Type IIb (fast twitch, fatigable)
24
Q

What are the THREE factors which influence the time taken to reach fatigue?

A
  1. Required force
  2. Maximal force
  3. Intrinsic fatiguability of the muscle
25
Q

Name THREE possible causes of fatigue at the cellular level

A
  1. T-tubule depolarisation (due to accumulation of K+)
  2. Decreased signals to open SR Ca2+ channels
  3. Decreased Ca2+ release from SR
  4. Decreased Ca2+ binding to Troponin-C
  5. Decreased cross-bridge attachment
  6. Decreased force/power generation by cross-bridges
26
Q

What are the TWO proposed causes of peripheral fatigue?

A
  1. Accumulation of metabolites

2. Depletion of muscle energy supplies (e.g. glycogen)

27
Q

What occurs with increased frequency of stimulation of muscle cells?

A
  1. Twitch - generates force and has time to decreased back to resting state (0 force).
  2. Summation - there is not quite enough time for the force to decrease back to resting so there is a slight increase in force generated for each stimulation.
  3. Unfused tetanus - force reaches a steady state with slight fluctuations in force.
  4. Fused tetanus - a constant force is produced with no fluctuation.
28
Q

What is the name given to the response of decreased force production when there is little/no change in Ca2+ concentration?

A

Decreased myofilament calcium sensitivity

29
Q

What type of metabolism dominates in fast-twitch fibres?

A

Anaerobic metabolism (short bursts of fast/powerful contractions).

30
Q

What type of muscle fibres are rich in capillaries and mitochondria?

A

Slow twitch fibres (for aerobic metabolism)

31
Q

What THREE metabolic end-products can cause fatigue?

A
  1. NH4+
  2. Pi
  3. pHi
32
Q

When there is an increase in the concentration of inorganic phosphate (Pi) what effect does this have on the force of contraction of muscles?

A

Decreases the force of contraction

33
Q

What are the THREE main sites of action of Pi to cause fatigue?

A
  1. ‘Direct’ - actomyosin cross-bridges
  2. SR Ca2+ release and Ca2+ force dependence
  3. Reduction in Free Energy from ATP hydrolysis (∆G ATP)
34
Q

Does an increase in pHi increase or decrease the force of contraction?

A

Increases force of contraction

35
Q

What is ∆G ATP?

A

The ‘free energy’ of ATP hydrolysis (-ve value because it is releasing energy)

36
Q

What are the FOUR targets in the body for training to reduce fatigue?

A
  1. Heart - cardiac output
  2. Circulation - plasma volume and skin blood flow
  3. Blood vessels - capillaries
  4. Myocytes - enzyme adaptation and fuel source

MEDSCI 205 (2 decks)

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