Bio Question

[melonbobo]

Advertisement - Members don't see this ad

Which of the following substances probably would not cross a membrane by simple diffusion?
A. Hemoglobin

B. Glucose

C. Water

D. Ethanol

E. Chloride ion



--------------------------------------------------------------------------------
The answer if B. but I picked A, can hemoglobin diffuse across the membrane??? 😕

btw,, anyone using ace the dat, I found many mistakes in their practise test. do any one feel the same? or jsut I am wrong

 

[DrTacoElf]

hey i remember this question and i was as equally perplexed. To my knowledge hemoglobin, a rather large protein tetramer doesn't readily cross cell membranes otherwise it wouldn't stay in erythrocytes. However neither does glucose by simple diffusion anyway. Thats what i would take away from this question. The body uses energy to move glucose around against concentration gradients because it is such a valuable molecule.

 

[HBomb]

Where the heck did you get that question? It's a horrible question and very unlikely to be asked in that way because they're all unlikely to diffuse effectively (except maybe water but even that's because of aquaporins). Cl- is charged, ethanol is polar, Hb is BIG, and glucose is big. Usually, the DAT questions are easier to deduce. Not in this case however. But I'm with all of you guys...I think it should be answer choice A.