Active Cell Physiology

Question 1

What is osmosis?

Answer 1

The movement of water through a semipermeable membrane to equalise solute concentration

Question 2

Intracellular space vs Extracellular space

Answer 2

Intra is inside the cell
Extra is outside the cell

Question 3

Osmosis works to balance what in the cells?

Answer 3

To tonicity between the intracellular and extracellular spaces

Question 4

What is tonicity?

Answer 4

The capability of a solution to modify the volume of cells by altering their water content

Question 5

Isotonic is what?

Answer 5

When the concentration is balanced on both sides

Question 6

Hypertonic is what?

Answer 6

When the tonicity is high and there is more solute than water.
Water moves from area of high water, low solute concentration to low water, high solute concentration to make to solution isotonic again

Question 7

Hypotonic is what?

Answer 7

When the tonicity is low and there is more water than solute.
Water moves from area of high water, low solute concentration to low water, high solute concentration to make the solution isotonic again.

Question 8

How can imbalanced tonicity affect the integrity of cells? Eg. Bloodstream

Answer 8

Putting water into bloodstream would make the cells hypotonic because the solute conc inside the blood cells is naturally high but to balance the equilibrium the water would try go into the cell, resulting in it absorbing lots of water and sometimes exploding.
Adding extremely sugary/salty substance to blood would do the opposite.

Question 9

Uneven distribution of molecules across a membrane creates what kind of gradient

Answer 9

A chemical gradient

Question 10

Uneven distribution of charges across a membrane creates what kind of gradient?

Answer 10

An electrical gradient

Question 11

The cell membrane resists the flow of ions. What is generally the overall charge of each side of the membrane?

Answer 11

Outside the cell: more positive
Inside the cell: more negative

Question 12

The ions are highly driven to move down their concentration and electrical gradients, but they can’t because the membrane resists ion movement. What will happen when channels open that allow them through?

Answer 12

They rush in/out along their gradient. The bigger the gradient, the faster/stronger the signal

Question 13

Ions can move down the chemical gradient using what channels?

Answer 13

Passive ion channels (no energy required)

Question 14

What are the sodium and potassium gradients maintained by?

Answer 14

Active pumps called sodium-potassium exchange pumps

Question 15

What are the charges of the two cellular spaces at rest?

Answer 15

Intracellular = more -ve charge
Extracellular = more +ve charge
This creates the electrical gradient

Question 16

What is the signal for the ion channels to open? and how does this work?

Answer 16

Depolarisation is the signal for the channels to open.
3 Na+ out 2 K+ in makes it polarised again.
When the stimulus is removed, excess sodium ions are transported out of the cytosol

Question 17

What if tiger?

Answer 17

If you see a tiger, it communicates this via the nerves. The sodium channels open which depolarises it and that message is passed along nerves until it reaches the muscle which then moves. This is the fast reaction