Destroyer #97 bio

[peRsEVERENCE]

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alright it's a w/c statement is false. One of the choices is "Artelioles offer the greatest resistance to blood flow in the circulation" <-- is true according to answer. What confuses me is that I thought capillaries should give the greatest resistance to blood flow, since they are the smallest, thereby forcing the blood to squeeze through.

was also wondering if anybody could explain #28 ochem. In the first step, how come the Br radical does not grab proton off the methyl group? In the second step (elimination), why does the base extract proton off the methyl and not a nieghboring proton off the ring?

THanks in advance

 

[fancymylotus]

Capillary cross sectional area is alot larger than that of arteries or veins. Blood vol flowing rate is pretty constant, and blood velocity is inversely proportional to the cross-sectional area. Blood moves the slowest through the capillaries, Bernouilli's equation says that pressure is inversely related to cross-sectional area but since blood flowing isnt an ideal flow, it doesnt apply here. BP is highest near the heart and pretty much at its lowest when its in the capillaries. The velocity of blood is largest when the cross-sectional area is the smallest, and vice versa.

 

[nemetrazol]

in regards to ochem 28: radicals will attack (in order) benzyllic H, Allylic H, Tertiary H, then secondary H. in this case the tertiary is the highest ranking one present. In the elimination step, look at the species of base. it is very very big and bulky, so it will eliminate the least substituted H that neighbors Br. in this case it is a methyl proton.

 

[peRsEVERENCE]

Capillary cross sectional area is alot larger than that of arteries or veins. Blood vol flowing rate is pretty constant, and blood velocity is inversely proportional to the cross-sectional area. Blood moves the slowest through the capillaries, Bernouilli's equation says that pressure is inversely related to cross-sectional area but since blood flowing isnt an ideal flow, it doesnt apply here. BP is highest near the heart and pretty much at its lowest when its in the capillaries. The velocity of blood is largest when the cross-sectional area is the smallest, and vice versa.

So your saying that capillaries don't offer the greatest amount of resistance, and that arterioles do? Velocity of blood is largest when cross- sectional area is smallest, than arterioles have the smallest amount of cross- sectional area? capillaries have a large cross sectional area collectively as one unit, is that correct?

thanks again guys