Osmosis, Tonicity, and the RMP

Question 1

What is the most abundant substance to diffuse through the cell membrane

Answer 1

Water, can move freely between the intracellular and extracellular fluid

Question 2

What is the ratio between water that diffuses in vs. out of the cell

Answer 2

Exactly the same amount is diffused out and in to maintain cell volume

Question 3

What is the definition of osmosis

Answer 3

Is the net movement of water down its [ ] gradient. Water moves to dilute the more concentrated solution

Question 4

What is the definition of tonicity

Answer 4

The ability of a solution to cause osmosis across biological membranes

Question 5

What are the 3 thing osmosis across a cell membrane is affected by?

Answer 5

1. Permeability of the membrane
2. [ ] gradients of the solutes
3. Pressure gradient across the membrane

Question 6

What is osmotic pressure

Answer 6

The pressure applied to exactly oppose the osmotic movement of water

Question 7

What is osmotic pressure proportional to

Answer 7

To the [ ] of a solute in number of molecules

Question 8

What is an intact molecule

Answer 8

When a molecules is put into solution and does not dissociate

Question 9

What is the definition of Osmolarity

Answer 9

The number of particles/L of solution (osmol/L)

-concerned only with the number of particles in solution

Question 10

What are the 2 things we need to know in order to calculate osmolarity

Answer 10

1. Number of moles of the substance in the solution

2. Whether the substance dissociates or not

Question 11

What is the osmolarity of body fluids

Answer 11

300mosmoles/kg

Question 12

What is the definition of isotonic

Answer 12

Has the same osmolarity of body fluids

Question 13

What is the definition of hypertonic

Answer 13

Has a higher osmolarity than body fluids

Question 14

What is the definition of hypotonic

Answer 14

Has a lower osmolarity than body fluids

Question 15

What happens when the chemical and electrical gradients are in opposite directions?

Answer 15

Movement of the ion will depend on the balance of the 2 gradients

• ion will move down electrochemical gradient, until an electrochemical equilibrium is established
• when the electrical gradient force of and ion becomes equal in magnitude to its chemical gradient force
• at this point the movement of this ion across the membrane stops

Question 16

What is the RMP

Answer 16

Resting membrane potential is the electrical potential of a cell membrane resulting from the unequal distribution of a key ions across biological membranes

Question 17

What are the 2 factors that affect the cells MP

Answer 17

1. [ ] gradients of different ions across the membrane

2. the permeability of the membrane to those ions