Carbohydrate Metabolism Pt 1 Flashcards
4 fates of pyruvate
TCA cycle (O2 present)
lactic acid fermentation (O2 absent, animals)
alcohol fermentation (O2 absent, yeast)
conversion to alanine
alcohol fermentation functions to produce…
NAD+
enzyme and cofactor used in alcohol fermentation
alcohol dehydrogenase
TPP
limited O2 in muscle cells
glucose not limited
cori cycle
limited O2 and glucose in muscle cells
cahill cycle
conversion of pyruvate to lactic acid via…
lactate dehydrogenase
what happens to lactic acid in cori cycle?
transported to liver
turned back into pyruvate
pyruvate becomes glucose again (gluconeogenesis)
glucose transported back to muscle
requires 3 bypass rxns
cori cycle
bypass rxn #1
intermediates
enzymes
bypasses pyruvate kinase rxn
pyruvate to oxaloacetate via malate
uses pyruvate carboxylase & PEP carboxylkinase
bypass rxns #2 & 3
enzymes
bypasses hexokinase rxn
glucose 6-phosphatase & fructose 1,6-bisphosphatase
cori ATP loss
4 net
beginning of cahill cycle
muscles begin to degrade into AAs
cahill cycle initial reaction
glutamic acid + pyruvate –> alanine + ketoglutarate
what happens to L-Ala in cahill?
transported to liver
converted to pyruvate
gluconeogenesis
byproduct of amino acid metabolism/cahill cycle
problem?
ammonia; becomes urea
requires 4 more ATP to eliminate
cahill ATP loss
8 net
fructose metabolism, route A
fructose –> F6P via hexokinase
enters rxn 3
fructose metabolism, route B
fructose –> F1P –> glyceraldehyde via fructokinase
enters rxn 5
OR glyceraldehyde –> G3P via triose kinase
enters rxn 6
galactose metabolism
galactose –> galactose 1-phosphate –> G1P via phosphoglucomutase
carrier used in galactose metabolism
UDP
decreases phosphofructokinase activity (3)
high ATP (allosteric)
high citrate (TCA product, helps ATP bind to allosteric site)
high H+ (lactic acid)
F6P regulation
self-regulating
if downstream rxns cannot keep up, converted to F26P for storage, until it is required and changed back
glucagon results in modification of 2 enzymes…
phosphofructokinase 2
fructose bisphosphate 2
decreases hexokinase activity
high G6P
decreases pyruvate kinase activity (3)
high ATP
high glucagon
high alanine
increases pyruvate kinase activity
F16P
glycogenesis
synthesis of glycogen
form of glucose in glycogen
UDP-glucose
core protein of glycogen
glycogenin
glycogenolysis
degradation of glycogen
glycogenesis enzyme
glycogen synthase
glycogenolysis enzyme
glycogen phosphorylase
form of glucose released from glycogenolysis
G1P
epinephrine action
increases glucose available to body
increases glycogenolysis
insulin action
lowers BG
increases glycogenesis
increases glycolysis
decreases gluconeogenesis
glucagon action
increases BG
increases glycogenolysis
decreases glycolysis
increases gluconeogenesis
2 PPP pathways
oxidative
non-oxidative
PPP oxidative pathway generates…
NADPH
5-C sugars (ribose, deoxyribose)
PPP non-oxidative pathway generates…
F6P
G3P
used in glycolysis