Transport Across Membranes

Question 1

What is meant by semipermeable

Answer 1

Small molecules (such as water, oxygen and carbon dioxide) pass through freely, larger molecules such as glucose need a transport protein to pass through, and very large molecules (starch) cannot move through the membrane at all

Question 2

What is diffusion?

Answer 2

The movement of molecules for, a high concentration to a low concentration (down a concentration gradient).

Question 3

Why is diffusion important to cells?

Answer 3

So they can get rid of waste products (urea, carbon dioxide) and gain useful substances

Question 4

Is diffusion passive or active transport

Answer 4

Passive-it doesn’t require energy

Question 5

What is the definition of osmosis?

Answer 5

The net movement of water from a region of high water concentration to a region of low water concentration through a selectively permeable membrane.

Question 6

Why is osmosis faster than other types of diffusion

Answer 6

Because Water molecules are smaller than salt/sugar so they pass through the membrane more quickly

Question 7

How will animal cells be affected by hypotonic, isotonic, and hypertonic solutions?

Answer 7

Hypotonic- cell swells and bursts
Isotonic- doesn’t change
Hypertonic-cell shrinks

Question 8

How are plant cells affected by hypotonic, isotonic, and hypertonic solutions

Answer 8

Hypotonic- vacuole swells, and presses against cell wall
Isotonic-doesn’t change
Hypertonic- shrinks, cytoplasm peels from wall, becomes plasmolysed

Question 9

What is active transport?

Answer 9

When larger molecules pass through a selectively permeable membrane using a specific transport protein. Goes up/ against a concentration gradient

Question 10

What is the cell membrane?

Answer 10

A semi-permeable bi-layer composed of lipids and proteins