Carbohydrate Digestion Flashcards
lactose intolerance
do not produce lactase to break down lactose for absorption
GLUT1
RBCs
GLUT2
liver, kidney, gut
GLUT3
brain
GLUT4
muscle, adipose
GLUT2 affinity
high Km for glucose (low affinity) so can only bind at high concentrations
GLUT 1, 3, and 5
can take up glucose at both fasting and fed state due to high affinity
GLUT2 can only take up glucose in _ state
fed
only _ is insulin sensitive
GLUT4
GLUT4 when insulin present
fuses with cell membrane for uptake
GLUT4 when insulin absent
located in IC membrane
hexokinases
phosphorylate glucose, which prevents it from transport out of the cell, allowing retention
hexokinase affinity
high affinity so retain glucose even when low concentrations
glucokinase
the hexokinase for liver cells
glucokinase affinity
low affinity to lower glucose retention at low circulating glucose levels (allows release of glucose when needed)
insulin promotes expression of _
glucokinase and hexokinase II (muscles)
glycolysis
glucose –> 2 pyruvate + 2 ATP + 2 NADH
glycolysis pathway
glucose –> glucose 6-P –> fructose 6-P –> fructose-1,6-bisphosphate –> glyceraldehyde-3-phosphate + dihydroxyacetone phosphate –> (2) 1,3-BPG –> (2) 3-phosphoglycerate –> (2) 2-phosphoglycerate –> (2) PEP –> (2) pyruvate
glycolysis step 1 enzyme
hexokinase + ATP–>ADP
glycolysis step 2 enzyme
phosphoglucose isomerase
glycolysis step 3 enzyme
phosphofructokinase + ATP–>ADP
glycolysis step 4 enzyme
aldolase
glycolysis step 5 enzyme
triosephosphateisomerase (DHAP to GAP)
glycolysis step 6 enzyme
glyceraldehyde-3-phosphate dehydrogenase + NAD+–>NADH
glycolysis step 7 enzyme
phosphoglycerokinsae + ADP–>ATP
glycolysis step 8 enzyme
phosphoglyceromutase
glycolysis step 9 enzyme
enolase
glycolysis step 10 enzyme
pyruvate kinase + ADP–ATP
rate limiting enzymes
pyruvate kinase, hexokinase, and phosphofructokinase
