B2.045 Molecular Mechanims for Regulating Metabolism

Question 1

what are the 3 biological “stories” or regulation discussed?

Answer 1

1. isoform/tissue expression
2. allosteric regulation
3. post-translational trafficking and modification

Question 2

how is GLUT4 localization regulated?

Answer 2

insulin stimulation and muscle contraction allow translocation of GLUT4 from vesicles to plasma membrane

Question 3

discuss the relationship between ubiquitous GLUT1 tissue distribution and its value of Km=5ish

Answer 3

Km is similar to normal blood glucose concentrations allowing it to be effective across the range of normal glucose levels

Question 4

relate the low Km=1.4 of GLUT3 to the high energy needs of the brain

Answer 4

this low Km allows glucose transport into the brain even in low glucose conditions because brain requires glucose as fuel even in starved state

Question 5

what would be the effect of increasing GLUT4 concentration on the enzyme activity curve?

Answer 5

vmax would increase

km wouldn’t change

Question 6

how can kcat changes be visualized on an enzyme activity curve?

Answer 6

changes in vmax

Question 7

what does sigmoidal shape tell you about an enzyme?

Answer 7

cooperativity is present, more than one ligand binding site

Question 8

how is the insulin monomer formed?

Answer 8

initial mRNA codes for 110 AAs

AAs are cleaved and disulfide bridges form between two chains

Question 9

what three forms can insulin take?

Answer 9

monomer, dimer, hexamer

Question 10

what is the insulin hexamer?

Answer 10

inactive, storage form of insulin

bound to zinc ions for stability

Question 11

what is the effect of recombinant insulin?

Answer 11

alters equilibrium between monomer-dimer-hexamer forms