Carbohydrate metabolism Flashcards
how many carbs does body need?
55%
what happens when you have fructose?
hexokinase can turn fructose into F6P in the muscle cells; in the liver, fructo-kinase adds phosphate on 1st carbon of fructose and makes F1P which then has to go through other modifications
galactose?
galactose can enter glycolysis via conversion of galactose to G1P through UDP- galactose4-epimerase
sugar being added to glycogen always adds to
non-reducing end
debranching enzymes
debranches glycogen for use in glycolysis
phosphoglucomutase
transfers phosphate on G1P to G6P for use in glycolysis
steps in glycolysis
G–> G6P (hexokinase)- phosphorylation (energy investment)
G6P–> F6P (phosphoglucose isomerase)
F6P–> F1,6BisP (phosphofructokinase)-phosphorylation (energy investment)
Fructose is cleaved (aldolase)
2 molecules of glyceraldehyde-3-P (triose phosphate isomerase)
Makes 1,3BPG (glyceraldehyde-3-phosphate dehydrogenase) and results in NADH (oxidation and phosphorylation)
1,3BPG–> 3PG (phosphoglycerate kinase)
results in 1 ATP
3PG–> 2PG (phosphoglycerate mutase- isomerization)
2-PG–> Phosphoenolpyruvate (enolase- dehydration)
–> Pyruvate (pyruvate kinase) and get ATP
basic glycolysis steps
energy investment to make Fru1,6BP from glucose
cleavage to get 2 same molecules- 1,3BPG and make 2 NADH
Produce 2 ATP, isomerize some more, produce 2 more ATP, then create pyruvate
Use of Mg+ in glycolysis
Mg-ATP- ATP has a lot of negative charge and the positive charge in Mg+ neutralizes and helps in active site
how is pyruvate from glycolysis used
enters into mitochondria and used in TCA cycle
how is NADH used from glycolysis?
can enter mitochondria and be used in TCA cycle via Malata aspartate shuttle or glycerophosphate shuttle
NADH in malate-aspartate shuttle
protons transfer to oxaloacetate and turns into malate and can enter matrix of mitochondria
NADH is glycerophosphate shuttle
transfer protons to FADH2 for use in ETC
why is NAD+ necessary
used in ETC; if no NAD+ or no O2, entire mechanism can shut down
alternative methods of NAD+ regeneration
via lactate dehydrogenase; pyruvate–> lactic acid and oxidizes NADH to NAD
NAD+ regeneration in yeast
via alcohol dehydrogenase producing ethanol; ONLY IN YEAST
how is glycolysis regulated?
different enzymes catalyze forward (glycolysis) and reverse (gluconeogenesis) reactions
essentially irreversible steps in glycolysis
- hexokinase (G–> G6P)
- PFK (F6P–> F16BP)
- PK (phosphoenolpyruvate–> pyruvate)
role of ATP in metabolism
inputting ATP energy can insure that both opposing pathways are favorable; allosteric effectors and phosphorylation can control direction of flux effectively
F26BP
only used for regulation purposes; allosteric activator for PFK
phosphofructokinase
main regulatory site for glycolysis
where do substrates for gluconeogenesis come from?
citric acid cycle- amino acids
how does glucose get into blood from liver
glucose-6-phosphatase dephosphorylates G6P for release of glucose into blood; liver uses alanine to make glucose via glucose-alanine cycle;
branching of glycolysis
via UDP-glucose pyrophosphorylase; requires energy input; the UDP-glucose can then bind with glycogen (branching enzyme)
pentose phosphate pathway
generates NADPH (used to build stuff) and ribose production- both used to build macromolecules
pyruvate kinase deficiency
leads to build up in 2,3 BPG because it is a part of the glycolysis pathway–> increase of O2 affinity and so oxygen releases
fructose intolerance
aldolase deficiency- F6P cannot be cleaved into two molecules and builds up; reduces ATP because it blocks ATP making steps in the further pathway
