Transport Across the Membrane Osmosis Teaching

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Transport Across The Membrane

Osmosis



Objectives of unit:

Explain passive transport mechanisms of diffusion and facilitated diffusion,including the role of channel and carrier proteins

Define the process of osmosis

Explain the process of active transport and the role of proteins and ATP

Explain the processes of endocytosis and exocytosis

Describe the properties of gas exchange surfaces in living organisms

Explain how the structure of the mammalian lung is adapted for rapidgaseous exchange



What can you remember about osmosis fro

IGCSE/GCSE? (convert pointer to pen tool by right clicking)

Osmosis



The diffusion of solvent molecules, such as water,

is known as osmosis

water

glucose Solvent

moleculese.g. water

Solute

molecules

e.g.glucose

Water is the solvent used in nature





Question 1: Complete the definition

Osmosis is the net movement of solvent

molecules from a region of their high

concentration to one of their low concentration

across a partially permeable membrane

answer



Osmotic concentration relates to the amount of

dissolved solutes in a solution

high osmotic concentration low osmotic concentration

Insoluble molecules do not affect the osmotic concentration

(concentrated) (dilute)



Water molecules will move down their

concentration gradient



Partially permeable membranes only let water

and very small molecules through

A partially permeable membrane results in an uneven distribution

across the membrane

Low osmotic

concentration:

A dilute solution

with a high water potential

High osmotic

concentration:

A concentrated

solution with alow water

potential



Which way will osmosis occur ?

water

glucoseNET osmosis

low osmotic concentrationhigh osmotic concentration

partially permeable membrane



Osmosis can be modelled using an osmometer

Pure water

Sucrose

solution

30 minutes later

Water molecules enter

the tubing by osmosis

Pure water

Sucrosesolution

30 minutes later

Water molecules leaves

the tubing by osmosis



Question 2: An osmometer was used to

investigate the affect of temperature on osmosis:

TemperatureoC

Rate of osmosis

mm/minute

Average rate

mm/minute

10 9 12 12

20 14 14 11

30 15 15 15

40 17 16 18

50 18 19 20

1. Calculate the averages and plot a graph to illustrate the

affect of temperature on the rate of osmosis.

2.Ex

plain the results. answer



Isotonic solutions have the same osmotic

concentration as the cytoplasm of the cell

external solution

blood cell

No NET osmosis

Cell just not change



Hypertonic solutions have a higher osmotic

concentration than the cytoplasm of the cell

external solution

blood cell

NET osmosis out of the cell

Causes animal cells to shrink



Hypotonic solutions have a lower osmotic

concentration than the cytoplasm of the cell

external solution

NET osmosis into the cell

blood cell

Can cause animal cells to burst



Question 3: Match the terms with the definitions

isotonic

hypotonic

hypertonic Same concentration as cell cytoplasm

higher concentration than cell cytoplasm

lower concentration than cell cytoplasm

answer



Question 4:

A scientist placed some red blood cells in a solution and

viewed the cells with a light microscope. After a few minutes

she noticed that many of the cells burst.

Explain why this may have occurred.

answer



Osmosis in red onion cells

Isotonic solution

Incipient plasmolysis

osmosisHypertonic solution

Full plasmolysis

osmosis

Causes a plant to wilt

Hypotonic solution

Turgor

Cell wall exerts an inward pressure

osmosis



Question 5: Match the label to the solution

A B C

1. Isotonic solution 2. hypertonic solution 3. hypotonic solution

answer



Question 6: Predict, with reasons, what will

happen to the flowers in the diagram below:

answer

very salty water



Summary:

Keywords you need to know the meaning of:

Osmosis

Partially permeable membrane

Isotonic

Hypertonic

HypotonicTurgor

Plasmolysis



Activity

Read pages 106 ± 107

Make brief notes

Answer questions 1 and 2 on page 107



End

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Answers to questions



Question 1 answer

Osmosis is the net movement of solvent

molecules from a region of their high

concentration to one of their low concentration

across a partially permeable membrane



Question 2 answer

Temperature/oC

10 20 30 40 50

20

1816

14

12

10

8

6

4

2

Rate of

osmosis

mm/minxx

x

xx

xTemp Average

rate

10 11

20 13

30 15

40 1750 19

With increasing

temperature the

water molecules

gain kinetic

energy;

Increasing therate of osmosis



Question 3 answer

isotonic

hypotonic

hypertonic same concentration as cell cytoplasm

higher concentration than cell cytoplasm

lower concentration than cell cytoplasm



Question 4 answer

The solution was hypertonic;

So water entered the cells;

By osmosis;

Causing them to swell and burst



Question 5 answer

A B C

1. Isotonic solution 2. hypertonic solution 3. hypotonic solution

3 2 1



Question 6 answer

The salty water is hypertonic;

As it has a higher osmotic

concentration than the cell cytoplasm;

So water leaves the cells of the stems;

By osmosis;

Causing the cells to plasmolyse;

And the flowers to wilt;



END

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Transport Across the Membrane Osmosis Teaching

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