anyone know cell biology?

Question

Hormones often act on a cell by binding to transmembrane proteins on the plasma membrane which, in turn, cause enzymatic activity in the part of the protein exposed to the cytoplasm.

true or false

Answer 1

TRUE.

(By the way, the question was "Hormones often act ...).
Yes, of course this is correct. Often, hormone receptors may be associated with - and regulate - enzyme activities in the cytoplasm. Hormone receptors may themselves be enzymes such as the insulin receptor (with extracellular insulin-binding domain and cytoplasmic tyrosine kinase enzyme domain) or may be indirectly coupled to enzymes such as is the case for the G-protein coupled receptors as exemplified by the adrenergic "adrenaline"-receptor coupled via G-protein to the enzyme adenylate cyclase (which binds to extracellular epinepherine/nor-epinepherine). Note that hormone binding may stimulate or inhibit enzyme activities associated with the receptor (depending on the particular hormone/receptor).

Answer 2

It depends on the types of horomone you're talking about. In general there are two types on hormones, there is amino acid based and steriods. Amino acid based hormones acot on receptors in the plams membrane coupled with g protein to one or more intracelluar second messengers which mediate the target cells response.
Steroids act on intracelluar receptors- receptors that are inside the cell and directly activate genes (start transcprtion --> translation -> protein synthesis)

Answer 3

Rachel, I posted a great summary of extracellular signaling to you yesterday in response to one of your questions. You should really read all the answers to your old questions before posting new ones. But the answer to this question is true and false. Some hormones do act in this manner, some do not act in this manner, look at my previous answer to understand this.

Answer 4

this is true, but if they are steroid they are lipid soluble and so dont bind to protein on outside, but go inside and cause enzymic activity

Answer 5

True. Check http://en.wikipedia.org/wiki/Hormones on its second paragraph. Also review any university biology textbook.

Answer 6

This is absolutely true for the polypeptide hormones, it is not the same for steroid hormones.

Answer 7

Generally true.

Answer 8

It is true.