I also believe the answer is A.
The correct statements are:
1. The framework of a membrane is a bilayer of phospholipids with their hydrophilic heads facing the aqueous environment inside and outside of the cell and their hydrophobic tails clustered in the center.
2. The diverse proteins found in and attached to membranes perform many important functions.
5. Because membranes are fluid, membrane proteins and phospholipids can drift about in the membrane.
The correct answer is: Binding of the neurotransmitter causes chemically gated sodium channels to open in the motor end plate (junctional folds of the sarcolemma) and sodium enters the cell.
Action potential travels through the membrane of the presynaptic cell causing the voltage-gated channels permeable to calcium ions to open. Ca2+ flow through the presynaptic membrane and increase the Ca concentration in the cell which will activate proteins attached to vesicles that contain a neurotransmitter (e.g. acetylcholine). Vesicles fuse with the membrane of the presynaptic cell, thereby release their contents into the synaptic cleft-space between the membranes of the pre- and postsynaptic cells. Neurotransmitter ACh binds to its receptors on the postsynaptic membrane and its binding causes depolarization of the target cell (muscle cell). Depolarization occurs because sodium enters the cell as a result of neurotransmitter receptor binding.
Yes, it's important to prevent damage to the nerve cells because if they were to get damaged you could get paralyzed. When your nerve cells are damaged the signals to move different parts of your body don't make it through to the muscles which leads to paralysis.
