Download 5 Lipid and Protein Metabolism

Physiology
Unit1
METABOLISMOFLIPIDSANDPROTEINS
InPhysiologyToday
AlternateFuelSources
• Whenglucoselevelsarelow
• Storedproteinsandlipids
willbemetabolized
• Changesinprimaryfuel
sourcesbetweenresting
andexerciseandfasting
conditions
• Proteinmetabolismwill
happenunderfastingor
starvationconditions
AminoAcids
Essential
Non-Essential
1.
2.
3.
4.
5.
6.
7.
8.
9.
1. Alanine
2. Arginine
3. Asparagine
4. Asparticacid
5. Cysteine
6. Glutamicacid
7. Glutamine
8. Glycine
9. Proline
10. Selenocysteine
11. Serine
12. Tyrosine
Histadine
Isoleucine
Leucine
Lysine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
PeptideBondFormation
DehydrationSynthesis
Transamination
• Makeanothertypeof
aminoacidby
transferringanamine
(NH2) fromanexisting
aminoacidtoaketo
acid
• Anaminegroupis
transferedfromL-alanineto
α-ketoglutaratetomake
pyruvateandL-glutamate
Amine group is BLUE
AminoAcidsasFuel
• Aminoacidscanbeclassifiedinto2groupsas
afuelsource
– GlucogenicAminoAcids
• Aminoacidsfromproteinsconvertedtopyruvicacid
• Thentoglucosebygluconeogenesisintheliver
– KetogenicAminoAcids
• Aminoacidsfromproteinsaredeaminatedtoproduce
acetyl-CoAandacetoaceticacid
• thentomakefattyacidsorketonebodiesorATP
• Cannotbeconvertedtoglucose(WHY?)
OxidativeDeamination
• Theaminegroupfrom
anaminoacidis
removedandgivesrise
toNH3
• Oxygenreplacesthe
nitrogen
• Oxygencomesfrom
splittingH2O
• Givesrisetoaketo acid
orketonebody
• Occursinalltissues
ESPECIALLY theliver
KetoAcids
• Typesofketoacids
– α ketoacid• pyruvicacid
• oxaloaceticacid
• α-ketoglutarate
– βketoacid–
• acetoaceticacid
Pyruvic
acidisan
αketo
acid!
KetoneBodies
• 3watersolublemoleculesmadebytheliverfrom
fattyacidmetabolismduringfastingorcarbohydrate
restrictiontouseasenergyinsteadofglucose
• 2ofthe3areusedbytheheart andbrain and
muscle forATPsynthesis
– Pickedupbycellsandusedtomakeacetyl-CoA
– Inthebrain
•
•
UsedtomakelongchainfattyacidsthatcannotpasstheBBB
Essentialduringfastingandstrenuousexercise
– Intheliver
•
Ketonebodiesusedingluconeogenesisduringstarvation
KetoneBodies
• ProducedifKreb’scannotkeepupwiththeamountofAcetylCoA
thatisbeingproduced
• Formedbyjoiningtogether2acetates
• Thereare2ketonebodiesusedbythebody
1. Acetoaceticacid(4C)
• Convertedtoacetyl-CoA
– Acetone(3C)
• Wasteproduct
• Fasting
• Ketogenicdiet
2. β-hydroxybutyricacid(4C)
• Convertedtoacetyl-CoA
LipidsasFuel
• Triglyceridemetabolism
– Digeststriglyceridesintoglyceroland3fattyacids
• Fateofglycerol
– Gluconeogenesis,Glycogenesis
• Inliver
– Glycolysis
– GlycerolentersglycolysisasPGAL
• Fateoffattyacids
– β-oxidationisthebreakdownoffattyacidchain
– ProducesAcetyl-CoA
– Manyfates
– Dependentontheneedsofthecell
β-Oxidation
• Occursinthematrixof
mitochondria
• Enzymesremove2carbon(acetate)
moleculesfromthe
carboxylendoffatty
acidchain
• FormsAcetylCoA
TriglycerideStructure
TriglycerideStructure
Palmitic Acid (C16H32O2)
Carbonyl Group C=O
Found in chocolate!!
HowMuchATPisFormedfrom
PalmiticAcid?
• 7bonds
– 1NADH+H+ +1FADH2 perbond
CC
CC
CC
CC
CC
CC
CC
• 8acetylCoA
– eachacetylCoA----->Krebscycle
• 1ATP
• 3NADH+H+
• 1FADH2
X8
X8
=
=
X8
8ATP
24NADH+H+
=
8FADH2
CC
ATPFromβOxidationof1FattyAcidChain
• ATP =
• NADH+H+
8ATP
– 7+24=31NADH+H+
– 31X3=
93ATP
• FADH2
– 7+8=15FADH2
– 15X2=
30ATP
Costofinitiatingβ-oxidation
8ATP
93ATP
+30ATP
131ATP
-1ATP
130ATP
HowMuchATPfortheEntireTriglyceride?
• Glycerol
– convertedbacktoPGAL
– Yields20ATP
• Three16-Cfattyacidchains
– 3x130ATP =390ATP
• Grandtotal
– 390+20=
410ATP