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Amino Acids

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NH2- split from leucine combines w/pyruvate to form alanine. Alanine enters circulation & picked up in liver where it is deaminated to form ... – PowerPoint PPT presentation

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Title: Amino Acids


1
Amino Acids
  • Structure
  • ? - amino carboxylic acid
  • Carboxyl carbon 1 (C O O-)
  • ? carbon
  • Amino group NH3
  • Peptide bonds formed between amino acids at ?
    amine of one a.a. and carboxyl group of another

2
Amino Acid Metabolism
  • A.A. undergo constant oxidative degradation
    during
  • Normal synthesis and degradation of proteins
  • When we ingest more a.a. than our bodies can use
    to make proteins or convert to other substances
  • During starvation, fasting, dieting uncontrolled
    diabetes mellitus, when carbohydrates are not
    available

3
Amino Acid Degradation
  • Major site of degradation is in liver
  • Catabolism of individual a.a. Involves two major
    stages
  • Amino acids lose their nitrogen atoms by either
    oxidative deamination or transamination ?convert
    to glutamate
  • Resulting carbon skeletons are fed into specific
    energy-yielding pathways to retrieve their
    chemical energy
  • Muscle removes most amino groups for
    branched-chain amino acids

4
Oxidative Deamination
  • Process occurs in mitochondrial matrix of
    liver NAD--?NADH
  • Amino acid ??Glutamate??NH4 Glutamate
    dehydrogenase
  • ?-ketoglutarate (Krebs cycle intermediate)

5
Amino Acid Metabolism
  • Transamination most common route for A.A.
    nitrogen including muscle tissue
  • Transfer of amine group
  • Glutamate is involved
  • Glutamate pyruvate ?? alanine ? -
    ketoglutarate reaction favors to the right in
    muscle and left in liver

6
Glucose-Alanine Cycle
  • Leucine, isoleucine, valine (available in muscle)
  • NH2- split from leucine combines w/pyruvate to
    form alanine
  • Alanine enters circulation picked up in liver
    where it is deaminated to form urea and pyruvate
  • Pyruvate is converted to liver glycogen or
    glucose
  • Glucose can be re-circulated to working muscle
  • When most amino groups are removed, citric acid
    intermediates such as oxaloacetate, fumarate are
    formed

7
Amino Acid Oxidation
  • Proteins---gtamino acids---gtDeamination---gt Carbon
    skeleton---gt CHO or FA Metabolism
  • During prolonged exercise, when muscle glycogen
    and blood glucose concentrations are low, the
    incorporation of the carbon skeletons from AA
  • Main AA oxidized in skeletal muscle are branched
    chain AA isoleucine, leucine, valine, glutamine
    and glutamate

8
Replenishment of Energy Stores
  • First What is depleted (energetically)?
  • Phosphagens (ATP PC)
  • Glycogen stored in muscle liver
  • What about lipids? Are they depleted?
  • Not replenished during recovery are replenished
    indirectly through replenishment of carbohydrate

9
Oxygen Debt vs. Recovery Oxygen
  • Oxygen Debt (AV Hill) stated most lactic acid
    formed during exercise was converted to glycogen
    (80),
  • Margaria introduced concept of Alactacid and
    lactacid debt components
  • Contemporary termed Recovery Oxygen or Excess
    post-exercise oxygen consumption (EPOC)
  • Fast component and slow component

10
Fast Component
  • Phosphagens (ATP PC)
  • Elevated oxygen consumption during this time
    period fuels the bodys need for
  • restoring myoglobin w/oxygen
  • restoring blood levels of O2
  • O2 cost of breathing
  • Increased heart rate (myocardial O2
  • Replenish phosphagens
  • Magnitude of Fast Component volume is related to
    previous exercise intensity

11
Fast Component Recovery
  • Rapid recovery of phosphagens at start of
    recovery later slows down
  • 70 - 30 seconds
  • 100 - 3-5 minutes
  • PC recovery
  • 84 restored in 2 minutes
  • 89 restored in 4 minutes

12
Replenishment of Energy Stores
  • Restoration of ATP PC
  • Half-time 30 sec 1 min 3/4s 1.5 min 7/8
    3 min 63/64
  • Muscle glycogen
  • .7 g/kg body wt/hr, carbohydrates with high
    glycemic index -
  • On average 5 of muscle glycogen used during
    exercise is re-synthesized each hour after
    exercise minimal 20 hrs to restore muscle
  • Lactic acid removal-oxidation

13
O2 - Myoglobin Stores
  • Found in skeletal muscle
  • Store for oxygen
  • Involved functionally in transfer of oxgyen
  • Inside the cell to inside the mito
  • 11.2 ml/kg of muscle or 500 ml
  • Functional significance related to intermittent
    exercise - rapidly restored following short bout
    of exercise

14
Exercise Related factors that cause extra O2
consumption
  • Temperature effects mitochondrial O2
    consumption, leading to decline in energy
    trapping efficiency (Brooks, 2000)
  • BMR? 13 per degree Celsius increase in body temp
  • Sympathetic stimulation increases metabolic
    rate of numerous tissues
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