4. all of the above is the answer
The complete question is :
Which of the following best describes how ACh changes the ion permeability of the sarcolemma?
A) ACh activates acetylcholinesterase.
B) ACh entry into the axon terminal causes neurotransmitter release.
C) ACh binds to receptors in the junctional folds.
D) ACh entry into the muscle fiber causes Ca2+ to be released by the sarcoplasmic reticulum.
Answer:
C) ACh binds to receptors in the junctional folds.
Explanation:
Sarcolemma is the term used for the cell membrane of the skeleton muscle fiber cell.
At the motor end plate, there are several folds present in the sarcolemma that are known as junctional folds.
These junctional folds have several acetylcholine (Ach) receptors present on them and these are ion channels that are chemically gated.
These ion channels open upon binding of Ach and thus, the ions can diffuse into the sarcolemma.
Thus, the binding of Ach on the receptors located in the junctional folds increases the ion permeabiltity of the sarcolemma.
Answer:
Polar molecules occur when there is an electronegativity (a charge) difference between the bonded atoms. Nonpolar molecules offur when electrons are shapred between atoms of a diatomic molecule or when polar bonds in a larger molecule cancel each other out.
Explanation:
Or basically, polar molecules occur with a charge, as nonpolar molecules do not. And yes, lipids are molecules.
A six-carbon sugar is an example of a monomer that can join with other molecules to form a polymer such as starch of cellulose.
