Which of the following is (are) true of ligand-gated ion channels? a. they are important

The following of ligand-gated ion channels are true:

a. They are important in the nervous system and they lead to changes in sodium and calcium concentrations in cells.  

b.They are important in the nervous system.

c. They are important in the nervous system, they lead to changes in sodium and calcium concentrations in cells, and they open or close in response to a chemical signal.

Explanation:

Ligand-gated ion channels (LICs, LGIC) also commonly referred to as ionotropic receptors) are a group of trans-membrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl− to pass through the membrane in response to the binding of a chemical messenger, that is, they conduct ion flow through a channel pore in response to the binding of a neurotransmitter. They are different from voltage-gated ion channels, which open in response to voltage (i.e. when the cell gets depolarized) and are sensitive to membrane potentials, and GPCRs, which use second messengers, ligand gated channels open in response to a ligand (some chemical signal) binding to them. Both types of channels are critical for proper activation of the post synaptic neuron.

25m

Explanation:

Let's assume the Jeep attains a velocity of 36km/h ; a constant speed same with that of the car.

While the Jeep is accelerating to that speed, the car with that speed passes it.

Now we can calculate the time taken for the Jeep to attain the velocity of 36km/h on her constant acceleration.

This time is t = v/a; from Newton's Law of Motion:

a = V-U / t ; a-acceleration

V is final velocity = 36km/h

U is initial velocity 0 since the body starts from rest.

Hence t = 36000/3600 ÷ 4 = 2.5s

Note conversting from km/h to m/s we multiply by 1000/3600.

But the distance covered by the car while the Jeep just accelerates is

S = U × t = 10× 2.5 = 25m.

Note From Newton's law of Motion, distance for constant speed is defined as: U × t

Hence the Car would be 25m off the starting point just as the Jeep accelerates. It would overtake the Jeep when it just covers 25m from the Jeep starting point.