Beta Receptors

[biology_06er]

Hi there,

Quick question...it says in my book that B2-receptors are more sensitive to epinephrine than to norpinephrine....

so does this mean that B2 responds less strongly to epinephrine??

Thanks,
biology_06er

[david23]

sensitive means bind strongly

[blcr11]

I guess another way to put it is to say that it takes less epinephrine (or more norepinephrin) to turn on a beta receptor.

It takes less epi because the beta receptor binds epi more tightly than norepi.

It takes more norepi to saturate the beta receptor than it dose epi.

They're all pretty much saying the same thing. But when it comes to the "strength" of a receptor, I'm not sure how to answer you. To a first appoximation a receptor is either active or inactive.

[biology_06er]

Hey there,

Thanks for the replies...so I came across a similar thing just now...it says that active sites of transcription show increased sensitivity to digestion with DNase (B-globin experiemnt)---so this must mean (putting it simply) that these sites are easily digestable??

right?

Thanks
biology_06er

[david23]

right right right to you 06er

[blcr11]

Well, the concepts both use the word "sensitive," but they're not really the same idea. In the case of the receptor, increased sensitivity means tighter binding of an effector molecule (epinephrine). In the case of active gene transcription it's a statement about chromatin structure and accessibility to nucleases. Actively transcibed genes tend to be located in regions relatively free of nucleosomes and are therefore more exposed and in more open conformations. This makes the genes and their promoters more accessible to the RNA polymerase complex, but it also makes them accessible to attack by restriction endonucleases. Inactive genes, by contrast, tend to be tightly bound up on nucleosomes and are relatively inaccessible to either RNA polymerase or REs. Same word, sensitive, but different concepts.

[biology_06er]

Hey there,

i cccc...I think i've got the concept of sensitivity now...

Thanks for the help,
biology_06er

[biology_06er]

Hi there,

Was doing some multi choice q's and came across this one...

passive water diffusion through a synthetic lipid bilayer:

is sensitive to Hg compounds
is insensitive to changes in temperature
is mediated by aquaporins
all of the above are right
none are correct...

ok so according to my notes passive diffusion is Hg insensitive, and temp. dependent and can't be mediated by the porins cos then it's not passive diffusion so it must be none are correct....right??

so Hg sensitve=Hg compounds are able to pass through??
Hg insensitivity=cannot pass through??

!! this term should be the least of problems considering I have a hard as exam coming up on Thursday but everywhere this term is used!!! arrrrggg

Thanks in advance
biology_06er