Glucose transport & glycolysis Flashcards
Where does glucose move to from the lumen and by what process
From lumen -> surrounding epithelial cells
Active transport
What cells does glucose move to from the blood and how
Cells in muscle, adipose, liver
Facilitated diffusion
Using GLUTs
Where are GLUT 1 &;3 found and what is their characteristics
Plasma membrane throughout body
Low Km/high affinity for glucose
So good maintain blood glucose level at 3-6mM
Where is GLUT 2 found and what are it’s characteristics
Liver & pancreatic cells
High Km/low affinity for glucose
Only work at high glucose conc at 15-20mM
Where is GLUT 4 found and what are it’s characteristics
Muscle & adipose tissue
Low Km/ high affinity for glucose
Insulin sensitive
GLUT 4 can be phosphorylase by medormin or anti-diabetic drug to increase insulin sensitivity
How is glucose uptake regulated
When no insulin - GLUT 4 packaged into vesicles &floating in cytosine
When insulin binds to receptors on plasma membrane -> vesicles fuse with membrane
Increase GLUT 4s on membrane increase glucose uptake 8n muscle & adipose tissue
Exercise increase GLUT 4 translocation from vesicles to membrane in muscle
What is insulin resistance
When not enough/few GLUT 4 in muscle
Describe this reaction
Glucose-> glucose 6 phosphate -> pyruvate
Forward reaction is glycolysis
Reversible
Make pyruvate for Krebs to make ATP
Backwards reaction = gluconeogenesis when glucose level is low
Describe this reaction
Glucose-> glucose 6 phosphate-> pentose phosphate
Synthesis if pentose phosphate which is precursor for DNA &RNA
What is glucose phosphorylation catalysed by
Hexosekinase &; glucokinase
How does glucose phosphorylation happen
Hydroxyl group on 6th C of glucose is close to phosphate terminal of ATP promoting catalysis
Water excluded from active site to prevent ATP hydrolysis since transfer of phosphate needed from ATP to glucose
What are the characteristics of hexokinase
Low Km/ high affinity for hexose
High conc of glucose 6 phosphates inhibits enzyme
Stope glucose 6 phosphate movingly out of cell
Increase Intra cellular glucose conc
Prevents uptake of glucose
