Calling all biochemists

[percival]

I have the sinking feeling that the following definition of active transport from my Tucker 2000 Anatomy and Physiology textbook - you know, the crappy one - is just RONG:

"active transport - when substances are too large to pass directly through the membrane, or are not soluble in fat, a carrier substance takes them from the outside to the inside. Glucose and amino acids are both transferred by active transport. It is active because energy is used."

Now, according to my other textbook, energy is ONLY used if these substances do NOT move along the concentration gradient. So, the sodium/potassium pump is active, because the cell actively maintans low Na and high K concentrations in the cytoplasm, but the facilitated transport of glucose using a glucose transporter is PASSIVE, because the glucose concentration inside the cell is kept low by chemical processes.

Grumble. The Tucker book is the ITEC standard text book. They want me to learn RONG things for my EXAM???

Please help. any help (e-mails, too) would be mucho appreciated.

Comments

it is

[helenllama.livejournal.com]

when it is against the conc. Gradient - I will check tommorow - but those to big to go through the pores go through by carrier proteins. well, i WILL copy my notes for you and either e-mail or post them to you

Helen

[sannalim.livejournal.com]

I wrote you an answer, but it got too long to be posted as a comment. Since I was already logged into LJ, I made an entry of it in my LJ.

yes, but

[saucebook.livejournal.com]

"active because energy is used" is just a sort of "helpful" throwaway line. Bear in mind that all you're going to have to do for the ITEC exam, at the very most, is recognise the broad difference betwee, say, active transport and osmosis.

Re: yes, but

[perceval.livejournal.com]

That should be no problem. Still ... it makes me afraid of the standard I'm going to be exposed to in the rest of the book

[spin1978.livejournal.com]

I echo Sannalim. I was taught there were three basic categories of membrane transport:

active transport, where transport across a membrane goes against a concentration or electrochemical gradient and therefore requires an expenditure of energy;

facilitated transport, where transport across a membrane follows the gradient but requires a membrane pore or specific transport protein due to solubility problems/size/other complicating factor; and

passive transport, where transport across a membrane follows the gradient, diffusing directly through the membrane.

[perceval.livejournal.com]

thank you!

[perceval.livejournal.com]

thank you!

that's really helpful.

[sff-corgi.livejournal.com]

This has nothing to do w/ biology, but it does with linguistics in a fluffy way.

Linguist Geek Code

Also, I was wondering -- in all the tumult, did you get to mail that box yet? [hopeful look]

[siri-eerin.livejournal.com]

Hey!

Sorry to bother you again but:

OK, I have managed to translate my translation except for a part of a sentence. Here is that sentence and the proceeding one the italised part is the part I'm having problems with, even after asking seraphinhunter for help:

Seine rosige Haut fand ich damals ganz besonders attraktiv. Sie fiel jedem auf, der ihn sah, und ich war der Meinung, dass sie sehr gut zu seinen blonden Haaren passte.

I've looked up auffallen and it means, as far as I can tell, "To stand out" which seems to fit into the context of the sentence, and Yulio agreed. Still having problems though. Can anyone help??

So confused. Don't suppose you could help me with this? I put out a general SOS in my journal, but the chances are I won't get any replies.