igcse2010 -osmosis & diffusion

IGCSE Revision QuestionsHow substances get in and out of cells

Mainly based on the exercises from http://www.biology-resources.com/biology-questions.html

http://biodeluna.wordpress.com

Which one of the following is the best definition of osmosisosmosis?

(i) The movement of water from a concentrated solution to a dilute solution across a

partially permeable membrane. . (ii) The movement of a dissolved substance from a

concentrated solution to a dilute solution across a partially permeable membrane. (iii) The movement of water from a dilute solution to a

concentrated solution across a partially permeable membrane. (iv) The uptake of water by a living cell.

Which one of the following is the best definition of osmosisosmosis?

(i) The movement of water from a concentrated solution to a dilute solution across a

partially permeable membrane. . (ii) The movement of a dissolved substance from a

concentrated solution to a dilute solution across a partially permeable membrane. (iii) The movement of water from a dilute solution to a

concentrated solution across a partially permeable membrane. (iv) The uptake of water by a living cell.

Which of the statements is an acceptable description of diffusion?

(i) The movement of water from a concentrated solution to a dilute solution across a

partially permeable membrane. . (ii) The movement of a dissolved substance from a

concentrated solution to a dilute solution across a partially permeable membrane. (iii) The movement of water from a dilute solution to a

concentrated solution across a partially permeable membrane. (iv) The uptake of water by a living cell.

Which of the statements is an acceptable description of diffusion?

(i) The movement of water from a concentrated solution to a dilute solution across a

partially permeable membrane. . (ii) The movement of a dissolved substance from a

concentrated solution to a dilute solution across a partially permeable membrane. (iii) The movement of water from a dilute solution to a

concentrated solution across a partially permeable membrane. (iv) The uptake of water by a living cell.

Definition of osmosisosmosis

Definition of osmosisosmosis

• ‘The movement of water

from a dilutedilute solution to a concentratedconcentrated solution across a partially permeable membrane'.

Description of diffusiondiffusion

Description of diffusiondiffusion

• ‘The movement of a substance

from a concentratedconcentrated solution to a dilutedilute solution'

Active transport

Active transport

• Movement of materials across the cell membrane requiring the use of energyenergy.

It moves a solute against a concentration gradient

http://media.pearsoncmg.com/bc/bc_campbell_biology_7/media/interactivemedia/activities/load.html?7&F

• http://www.bio.miami.edu/~cmallery/150/memb/membranes.htm

• The diagram shows a vessel which contains a concentrated and a dilute solution separatedby a partially permeable membrane. Draw a similar diagram to show the liquid levels after an hour or two.

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• The diagram shows a vessel which contains a concentrated and a dilute solution separatedby a partially permeable membrane. Draw a similar diagram to show the liquid levels after an hour or two.

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Make two drawings to show how this cell would appear if it were to be immersed for a few minutes in a solution with...

(a) a lower osmotic potential (water potential) than its own cytoplasm

(b) a higher osmotic potential (water potential) than its own cytoplasm.

(a) a lower osmotic potential (water potential) than its own cytoplasm

PlasmolysisPlasmolysis

(b) a higher osmotic potential (water potential) than its own cytoplasm.

                plasmolysis -loss of cytoplasmic structure due to water loss 

                turgidity- swollen cells due to water gain

When meat is salted, bacteria

cannot grow on it. Suggest a reason

for this.

When a cell is respiring aerobically, which two gases are likely to be

diffusing in and out of the cell, and in which

direction will they be diffusing?

The graphs (a) to (d) represent the concentration of certain substances as measured inside and outside a cell. Match the following descriptions to the most appropriate graph.

(i) A substance which the cell is producing and is expelled by active transport.

(ii) A substance which the cell is using and is taken up by active transport.

(iii) A substance which the cell is using and can diffuse freely through the cell membrane.

(iv) A substance which the cell is producing and is free to diffuse across the cell membrane.

The graphs (a) to (d) represent the concentration of certain substances as measured inside and outside a cell. Match the following descriptions to the most appropriate graph.

(i) A substance which the cell is producing and is expelled by active transport.

(ii) A substance which the cell is using and is taken up by active transport.

(iii) A substance which the cell is using and can diffuse freely through the cell membrane.

(iv) A substance which the cell is producing and is free to diffuse across the cell membrane.

(i) (ii) (iii) (iv)

Flashcards to review IGCSE

• http://www.proprofs.com/flashcards/story.php?title=igcse-biology-all-topics

water and iodine

starch and glucose solutions

A piece of dialysis (‘Visking’) tubing is knotted at one end

water and iodine and filled with a 2 % starch solution mixed with a 10% glucose solution. The tube is immersed in.a test-tube of water to which iodine has been added.

(a) Predict what you will see after 30 minutes (i) in the starch and glucose solutions

dialysis tube, (ii) in the test-tube, (iii) when you boil the liquid from the test-tube with Benedict's solution.

(b) Give an explanation of these results.

Keys:• Lugol's iodine solution solution (which is actually

IKI) is a brown solution which turns black in the presence of starches.

• Benedict's solution is used to detect the presence of simple sugars such as glucose. When a simple sugar is mixed in Benedict's solution and heated for a short period of time in a test tube, it goes through a variety of color changes, eventually ending as an orange-red or brick red color.

• Starch is not dissolved in cold water

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