Page 1 of 2: Q BIOCHEM AGAIN INSULIN

bharatvedin · Credits: 4094 My Scrapbook

GLUCOSE UPTAKE IS NOT AFFECTED BY INSULIN IN-

1- BRAIN

2- SKELETAL MUSCLE

3- LIVER

4- ADIPOSE TISSUE

5- BRAIN AND LIVER

THANX

HEAR SATCH!

sravya · Credits: 28740 My Scrapbook

hi vedin ,

is it brain!

drche · Credits: 11979 My Scrapbook My Reading List 10 Books

brain.,...

dana · Credits: 3703 My Scrapbook My Reading List 9 Books

hi ,
well is the ans brain?I think thats the most specific one.
but wat abt option d liver and brain?
coz both dont need GLUT 4 for glucose uptake thru insulin.
But insulin indirectly increases uptake of glucose in liver.So may be the ans shuld be brain.

drshoaibsmc · Credits: 3066 My Scrapbook

The ans is brain . insulin helps in difussion of glu into the cell by opening the channels thereby diffusion at lower conc than normal difussion (which is approx at 600mg/dl) . glu diffuses normally in brain at lower conc without use of insulin .

ganong phy gives the ans . don't rem the page no

vineetgsvm · Credits: 122753 My Scrapbook

it shud be brain only as in liver insulin facilitates the glucose transport by stimulating hexokinase

dana · Credits: 3703 My Scrapbook My Reading List 9 Books

yes Vineet, ur right.Actually it was this indirect action of Insulin on the liver glucose metabolism that got me confused.
Like I wrote before Brain shuld be teh most specific answer.Waiting for Bharatvedin to confirm it.

bharatvedin · Credits: 4094 My Scrapbook

hi,

1st let me correct vineet. i think ur1st thought was rite. but than u were shaken.

thats ywesay 1st strikeis the best strike.

as far as the q of enzyme induction insulin induces glucokinase not hexokinase.

secondly there is no effect of glucokinase induction on the entry of glucose into the cell.

at last wat vineet said was rite in the beginning. insulin affects entry of glucse in cells wid glut 4 and no other cell else.

so tissues are adipose and muscle.

i agree insulin has a cotribution in glycolysis and glycogenesis and hmp pathway but it does not agffect the entry of glucose in to the liver cell.

simple reason is that liver has a glut 2 receptor which is a very low affinity receptor and it need not be regulated. if glucose uptake increases under the effect of insulin in liver than all peripheral tissues are starving.that is the reason why glut 2 has such a high km.

we allthink that becoz insulin is contributing so much in liver it shud increase gluicose uptakebut its not the case a very confusing aspect.

at last i wud say glucokinase has nothing to do wid increased entry of glucose.
its only function is to trap the sugar in side the cell.

i think i ve explained myself quite satisfactorily. anyway i welcome any doubts if there are any!

so the answer is BOTH LIVER AND BRAIN.

THANX!

SATCH IS THE GREATEST!

vineetgsvm · Credits: 122753 My Scrapbook

well buddy,
see the questions can be perceived in two senses

1) the way glucose enters liver (with or without insulin)
2) how insulin affects entry of glucose in liver

well i'm quoting lines from ganong verbatim

insulin also increases the entry of glucose into liver cells, but it does not exert this effect byincreasing the number of glut 4 transporters .Instead it induces hexokinase and this increases the phosphorylation of glucose , so that the intracellular free glucose concentration stays low faciliitating the entry of glucose into the cell.

regarding gluts is concerned

GLUT 2 and also 7 is found in LIVER

well the b'chem book rana shinde says:
liver which is freely permeable to glucose , insulin exerts a regulatory influence upon the activity of glucokinase

see this also

Postprandial glucose disposal represents the sum of splanchnic and peripheral tissue glucose uptake.[11] Splanchnic glucose uptake includes first-pass extraction from the portal vein as well as uptake via the hepatic artery. As shown in Table 1, the major tissues responsible for postprandial glucose uptake are liver (splanchnic), muscle, brain, and kidney. It may seem surprising that brain plays a substantial role because its uptake of glucose is generally considered to be insulin independent. But because after meal ingestion its use of glucose remains constant while the supply of endogenous glucose decreases, the brain's requirement for glucose must be met by glucose from the meal. Consequently, only about 70% of postprandial glucose uptake occurs in insulin-sensitive tissues.

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hence there is effect of insulin on the glucose entry in the liver....

so it's time for more references ........ and further discussion
bye

bharatvedin · Credits: 4094 My Scrapbook

hi,

vineet ur doubts are justifiable.

but stil i wud say that there is no direct impact of insulin on uptake of glucose by liver.

thanx!

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