Module 3/ Electrochemical gradient

Question 1

Selective permeability

Answer 1

The cell is able to modify (regulate) the entry/exit of molecules through

-Changes in the expression of genes that code for membrane transport proteins

-Temporary opening and closing of the transport proteins

Question 2

The cell can maintain

Answer 2

-A specific cellular concentration of each solute

-A specific electric potential across the membrane

Question 3

Whats the charge inside the cell

Answer 3

Negatively charged relative to the outside

Question 4

Electrochemical gradient

Answer 4

Membrane potential: The difference in charge (voltage) across the plasma membrane=electrical potential

-The attraction of opposite change across the plasma membrane is a source of potential energy.

Question 5

Resting membrane potential

Answer 5

The baseline membrane potential is called the resting membrane potential (E)=-70mV

Question 6

Which is more important? The chemical gradient or electrical gradient?

Answer 6

If a molecule is not charged (or is large), its diffusion only depends on the chemical gradient.

-If a molecule is charges (and small), its diffusion depends on both chemical gradient + electrical gradient= electrochemical gradient.

Question 7

Equilibrium potential

Answer 7

Each ion has its own equilibrium potential=the difference in charges across the membrane due to the difference in its concentration… which results from both the chemical and the electrical gradient.

Question 8

Potassium equilibrium potential

Answer 8

At the potassium equilibrium potential, the membrane potential reaches the equilibrium potential of potassium.->(Ek)=-90mV

Question 9

Equilibrium potential Equation

Answer 9

The equilibrium potential of an ion can be calculated (Nernst equation): 𝐸 = 62𝑚𝑉/charge ×𝑙𝑜𝑔10 (ion(outside)/ion(outside))

-if an ion cross the membrane, the membrane potential converges to its equilibrium

Question 10

The increase and the decrease of membrane potential

Answer 10

The increase of the membrane potential=depolarization (-70mV->-10mV)
The decrease of the membrane potential=hyper-polarization (-70mV->-90mV)

Question 11

Potassium, chlorine, calcium and sodium equilibrium potential

Answer 11

Potassium and chlorine tend to diffuse outside the cell

-Sodium and calcium tend to diffuse inside the cell

-Potassium, sodium, and chlorine are used in the neuron signal transmission. Calcium is used in signaling pathways, neurotransmitter exocytosis, muscle contraction.

The resting potential of most cells is generally determined by the potassium equilibrium potential.