membranes- transport and potentials

Question 1

ion gradient

Answer 1

the combined gradient of concentration and electrical charge that affects an ion is called electrochemical gradient.

Question 2

permeable cation(K)

Answer 2

accumulates where the impermeable anion (A-) is located has high intercellular (K+)

Question 3

impermeable ion (Na+)

Answer 3

leaks into the cell slowly and is pumped out against a concertation gradient by a Na- pump

Question 4

primary active transport

Answer 4

when the sodium pump requires energy in the form of ATP hydrolysis

Question 5

importance of K+ in generation of membrane potentials

Answer 5

• Intercellular is greater than extracellular
• k+ tends to diffuse out of the cell
• loss of K+ results to a small negative charge on inner side of membrane.
• electrochemical equilibrium is established
• membrane potential has developed.

Question 6

consequences of high intercellular k+ membrane potential

Answer 6

tends to diffuse less, therefore the required membrane potential to balance the movement is less negative.

Question 7

extracellular k+ and membrane potentials
important consequences.

Answer 7

A rise in extracellular k+ will make the membrane potential less negative than resting potential. Membrane will be depolarised.

Question 8

resting membrane potential

Answer 8

• property of all cells
• reflects a difference in charge on either side of the cell membrane.
• cytoplasm side is negative in relation to extracellular fluid.

Question 9

range of resting membrane potential

Answer 9

between -20 NS -95 Mv depends on cell type.

Question 10

ion movement across cell membrane

Answer 10

via ion channels
- they are protein pores that span the phospholipoid bilayer

Question 11

ion channels are classified by the gating stimulus and have:

Answer 11

voltage gated channels

Question 12

how are voltage gated channels activated

Answer 12

by a small change of membrane potential, e.g. due to electrical stimulus.

Question 13

ligand gated channels

Answer 13

extracellular chemical binds to receptor on a membrane- receptor is an ion channel

Question 14

types of ion channels

Answer 14

voltage gated and ligand gated

Question 15

some ligand- gated channels are cation selevtive

Answer 15

this is mainly when Na+ flows into the cell. When activated causes depolarisation and makes the cell more excitable.

Question 16

anion- selective ligand-gated ion channels

Answer 16

where mainly Cl flow into the cell and these channels when activated they cause hyperpolarisation and make cells less exitable.