4.2 - 4.5 - Diffusion, Osmosis, Active Transport, Co Transport

Question 1

What is the def. of diffusion?

Answer 1

The net movement of particles from an area of higher concentration to an area of lower concentration

Question 2

What is the def. of facilitated diffusion?

Answer 2

The passive, net movement of particles from an area of higher concentration to an area of lower concentration with the help of a protein carrier or protein channel

Question 3

What do channel proteins do?

Answer 3

• form pores in the membrane to allow specific water-soluble ions to pass through (selective)
• specific for different ions

Question 4

What do carrier proteins do?

Answer 4

• move large molecules across membranes
• specific for different molecules
• 1st: large molecule attaches to carrier protein in membrane, 2nd: protein changes shape, 3rd: releases molecule on opposite side of membrane

Question 5

What does the rate of diffusion depend on?

Answer 5

• conc gradient: the higher it is, faster the rate (diffusion slows down over time)
• thickness of exchange surface: the thinner it is, the faster the rate (shorter distance)
• SA: the larger it is, the faster the rate (more successful collisions)
• temp: the higher it is, the faster the rate (more KE)
  Facilitated diffusion: - number of channel/carrier proteins: the higher it is, the faster the rate

Question 6

What is the def. of osmosis?

Answer 6

The movement of water molecules from an area of higher water potential to an area of lower water potential across a partially permeable membrane

Question 7

What is a solute, solvent and solution?

Answer 7

Solute - substance being dissolved
Solvent - what the substance is dissolved in
Solution - the solute and solvent together

Question 8

What is water potential?

Answer 8

• how likely water molecules are to diffuse out of or into a solution.
• measured in kPa (kilopascal)
• pure water has the highest water potential of 0

Question 9

Factors affecting rate of osmosis

Answer 9

• water potential gradient
• thickness of exchange surface
• SA of exchange surface

Question 10

What does hypotonic, hypertonic and isotonic mean?

Answer 10

• hypotonic: solution outside has a lower solute conc (higher water potential) than inside
• hypertonic: solution outside has a higher solute conc (lower water potential) than inside
• isotonic: solution outside has same solute conc (same water potential) than inside

Question 11

How do you make serial dilutions?

Answer 11

For diluting by factor of 2:
- line test tubes in a rack
- add 10cm3 initial solution (most concentrated) to 1st test tube
- add 5cm3 distilled water to all other test tubes
- draw 5cm3 from 1st test tube to the 2nd test tube and mix
- you have 10cm3 of solution w half the conc
- repeat process for all test tubes

Question 12

What is the def. of active transport?

Answer 12

The movement of particles from an area of lower concentration to an area of higher concentration using ATP and carrier proteins

Question 13

Describe direct active transport

Answer 13

• molecule/ion binds to carrier protein
• ATP binds to protein: splits into ADP + phosphate molecule
• protein changes shape + molecule released on other side
• phosphate molecule released from protein: reverts to original shape
• phosphate recombines w ADP forming ATP during respiration