2.3 & 2.4 - Transport across a membrane

Question 1

What is osmosis?

Answer 1

The net movement of free water molecules form an area of higher water concentration to a lower concentration across a partially permeable membrane.

Question 2

What is water potential?

Answer 2

concentration of water (Ψ)

Question 3

What is passive transport?

Answer 3

No metabolic energy (no need for ATP (Adrenosine triphosphate))
Goes through the phospholipids or proteins

Question 4

What are the three types of passive transport?

Answer 4

Diffusion
Osmosis
Facilitated diffusion

Question 5

What are the features of diffusion (through phospholipids)?

Answer 5

Small, non - charged, non - polar molecules.
Higher to low concentration
Passive e.g. O2 and CO2 (is polar but still goes through)

Question 6

What are the features of osmosis?

Answer 6

Small, non - charged, polar molecules
Higher to lower water concentration
Lower to higher solute concentration.
Passive
Small pores: Aqua Porins

Question 7

What are the features facilitated diffusion (through proteins)?

Answer 7

Channel proteins (like a tunnel)
Carrier proteins (change shape)
Both passive
Both high to low concentration

Question 8

What are the features of active transport?

Answer 8

Uses metabolic energy from hydrolysis of ATP
Through carrier proteins
Lower to higher concentration

Question 9

What are the features of endocytosis and exocytosis?

Answer 9

Very large molecules
A cell can surround a substance with a section of it’s cell membrane
The membrane pinches off to form a vesicle inside and outside the cell.
This requires the use of ATP for energy