Muscle Metabolism IUA 2013

7/30/2019 Muscle Metabolism IUA 2013

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Musclemetabolism

Dr.AtifHassanKhirelsied

DepartmentofBiochemistry

Facult

ofMedicine

InternationalUniversityofAfrica,Khartoum,Sudan


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Learningobjectives

Attheendofthissessionthestudentsshouldbeable

to:

Listthe

energy

sources

of

the

muscles

IdentifythedifferencesinATPsynthesisamongdifferent

types

o

musc e

ce s.

escr e owenergy sut ze ur ngmusc econtraction

Differentiatethetypesofmuscleonthebasisoftheir.


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Introduction

MusclesmustcontinuouslymakeATPtoprovidethe

ener

formuscle

contraction.

12/24/2012 Atif H.Khirelsied3


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Introduction

ATP h drol sis istheimmediatesourceofener for

musclecontraction.

TheenergyreleasedfromtheATPhydrolysiswillbeusedto:

yos n ase

Ca2+ ATPase intheSRmembrane

+ +

12/24/2012 Atif H.Khirelsied4


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MusclecellsregenerateATPbythreeways


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Thefuelsofmuscle

muscleactivity:

.

Glycogenstorage.

ucose

rom

oo . Triacylglycerol(storedwithinthemuscle).

Fattyacids(fromadiposetissue).


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Muscleenergyrequirement

T e ue suse ymusc e i eraccor ingto:

Thetype

of

muscle

fiber

Thetypeofactivity

Theconditionoftheactivit .

, ,

accordingtotheparticularevent,fromthe100m

.


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Factorsdeterminingfuelutilizationbymuscles

selected:

Theamountoffuelstored

e

ranspor

o

ue

o

e

musc e Theavailabilityofoxygenforthemuscle

Theintensityoftheexercise

The

duration

of

the

exercise.


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TypesofSkeletalMuscleFibers

1. Fastfibers(whitemuscle)

2. Slowfibers

(red

muscle)

3. Intermediatefibers


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1. Fasttwitch.

. , .

3. Highglycogencontent.

4. Fewerblood

vessels

and

low

myoglobin.

.

glycolysis.


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1. Slowtwitch.

. , .

3. Dependonaerobicmetabolism.

4. Utilizefats

as

well

as

glucose.

. ave eg ycogens orage.

6. Manyblood

vessels

and

high

myoglobin.


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Comparisonofslowandfasttwitchmusclefibers

Musclefiber TypeI TypeIIa TypeIIb

Use(example) Posture Walking Sprinting

+

ATPase Activity Low High High

Fatigueresistance High Intermediate Low

Capillarydensity High Intermediate Low

Glycolytic enzymes Low Intermediate High

oc on r a con en s g n erm ea e ow


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Themetabolicpathwaysinwhiteandredmusclefibers


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Thetypeoffiberandfuelusagebymuscles

Allfibert escanuse hos hocreatine articularl t e

IIB.

TypeIIBfiberswhichalsoconvertglycogen tolacticacid

IntypeIandIIAfibers,mostoftheglycogeniscompletely

.

T e ateo t eg ycogenwi epen ont eintensityo t e

exerciseandthesupplyofoxygen


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Thetypeoffiberandfuelusagebymuscles

Glucose canbeoxidizedanaerobicall tolacticacidto

generateATP.

Thecapacityofglucoseutilizationislimitedbytheactivity

(tenfold)andsufficienttoprovidealltheATPrequiredto


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Theamountoffuelstoredandfuelusageby

Fuels are stored within the muscle liver and adi ose

tissueandtheiramountsvaryaccordingto:

thepreviousphysicalactivity.

Triacylglycerol,storedwithinthemusclecanbeusedbut

themostfatfuelisderivedfrominadiposetissue.


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Theapproximateamountsofvariousfuelsandenergy

contentinmuscle,liver andadi osetissuein75k male

containing20

kg

muscles

Fuel Tissue

Approx.

Energy(KJ)

con en g

Phosphocreatine Muscle Verylittle 15

Glycogen Muscle

500

8000

Triacylglycerol Muscles Varies 17500

pose

tissues


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Thefueltransportandfuelusagebymuscles

Bloodbornefuelsare:

glucose,whichisderivedfromliverglycogen,

fattyacids

derived

from

adipose

tissue.

Fueluptakedependson:

t e owo oo t roug t emusc e,

theconcentrationofthefuelintheblood

.

muscleandtherateofutilizationofthefuelcanincreaseupto50fold,yettheconcentrationofthefuelsinbloodrema nsremar a ycons an .


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TheOxygensupplyandfuelusagebymuscles

Aerobic l col sis roduces about tenfold reater ATP

thananaerobic glycogenolysis.

Oxygenisthemajorfactorlimitingperformancein

.

Italsolimitsphysicalactivityinmanynonathletesandin

patients(notableinanemicpatients).


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Oxygensupplyandfuelusagebymuscles

Ox ensu l tothemusclesde endsonthefollowin

factors:

Theflow

of

blood

throu h

the

muscle.

sizeof

the

capillary

bed.

Theconcentration(partialpressure)ofoxygenintheblood

.


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factors:

Theuptakeofoxygenfromtheairinthealveoli(canbe

,

diseasee.g.

emphysema).

Theconcentrationof2,3bisphosphoglycerateinthe

.


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by:

.

supplythe

muscle.

Decreasingtheflowthroughabdominalandpelvicviscera

.


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Numberoferythrocytesandfuelusagebymuscles

demonstratedby:

Thebeneficialeffectofblooddopingonathletic

orduringanemia.


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Aerobiccapacityandfuelusagebymuscles

Conditionsdurin whichmostATPis eneratedfrom

phosphocreatine andglycogeninclude:

Veryunfitindividuals,duringanyformofphysical

, ,

runningupstairs).

Inelderlypeople(ageingdecreasesmitochondriaand

x v y .


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Durationofexerciseandfuelusagebymuscles

Astheduration oflowintensityexerciseincreases,the

glucoseandfattyacidsincreases.

Forprolongedactivitiesfattyacidsbecometheonlyfuel

available.


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Estimatesofpercentagecontributionofglucose,glycogenandfatty

acidstoATP enerationoverfourhoursof h sicalactivit


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Thechangeinmusclefuelutilizationwiththedurationof100

e

75nupt

a

Gl co en

Fattyacid

ofoxyg

50

centage

25

l

asper

Bloodglucose

0

Fu

100 200 300

Durationofexerciseinminutes


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afterbeginning

of

physical

activity

h f d f l b


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Theintensityofexerciseandfuelusageby

Asintensity increases,theutilizationofbloodglucose

.

musc eper ormancea ove o max mumpower

output,therateofglycogenincreasesexponentially.


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Thesprints

Onlytwofuelsareusedduringthe100msprint glycogen

.

Theglycogenisconvertedexclusivelytolacticacid.

Asthedistanceextendsto400m,aerobicoxidationof

glycogenoccurs,producingabout25%oftheATP.

presentinthemuscle.


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Fuelutilizationduringsprint


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Themiddledistances

As

the

distance

and

time

taken

for

the

event

extends,

aerobicoxidationbecomesincreasinglyimportantinthe

generationofATP.

Thisis

demonstrated

by

the

decline

in

the

rate

of

, .


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Themarathon

A

full

marathon

(42.2

km),

requires

the

oxidation

of

about700gofglycogen.

owever,s nceon ya ou gcan es ore n ver

plusmuscle,

another

fuel

must

contribute.

Thisisfattyacid,derivedfromtriacylglycerol inadipose


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Indicationsof

the

oxygen

supply

to

muscle,

and

the

pathways

for

ATP

generationindifferentathleticevents

Documents

Muscle Metabolism IUA 2013