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8. (a) (i) Which substance moves through cell membranes by osmosis? ....................................................................... - Leaving Cert Biology - Question 8 - 2013
Question 8
8. (a) (i) Which substance moves through cell membranes by osmosis? ........................................................................ (ii) Name one other te... show full transcript
Worked Solution & Example Answer:8. (a) (i) Which substance moves through cell membranes by osmosis? ....................................................................... - Leaving Cert Biology - Question 8 - 2013
Step 1
Which substance moves through cell membranes by osmosis?
Answer
The substance that moves through cell membranes by osmosis is water. Osmosis is a specific type of diffusion that pertains to water molecules moving from an area of high water concentration to an area of low water concentration through a semi-permeable membrane.
Step 2
Name one other term used in biology to describe the movement of substances through cell membranes.
Answer
Another term used in biology to describe the movement of substances through cell membranes is diffusion. Additionally, active transport is also a term, but it refers to the movement of substances against a concentration gradient with the expenditure of energy.
Step 3
In the space below, draw a labelled diagram of the apparatus you used in your demonstration.
Answer
While I can't draw a diagram in this format, the typical apparatus for demonstrating osmosis includes Visking tubing or dialysis tubing, a beaker filled with water, and possibly a solute like sugar or salt. Ensure to label the tubing as the semi-permeable membrane, the beaker labeled as the solution, and indicate the direction of water movement.
Step 4
Suggest a control that you might use in this activity.
Answer
A control that could be used in this activity is to set up another bag of Visking tubing containing only water and place it in a beaker filled with water at the same concentration as the experimental setup. This allows for comparison of osmotic movement without the influence of solutes.
Step 5
State the result(s) of your investigation.
Answer
The results of the investigation typically indicate whether there was an increase or decrease in the mass or volume of the Visking tubing. For example, if water moved into the tubing, it would show an increase in mass, while if it moved out, there would be a decrease.
Step 6
Briefly explain the result(s) referred to in part (iii).
Answer
If the mass of the Visking tubing increased, it suggests that water moved into the tubing from the surrounding environment due to osmosis, caused by a higher solute concentration inside the tubing. Conversely, a decrease in mass indicates water left the tubing due to a lower concentration of solutes inside compared to the external solution.
Step 7
What is the purpose of a control in scientific experiments?
Answer
The purpose of a control in scientific experiments is to provide a standard for comparison. It helps ensure that the results are due to the experimental variable alone and not other factors, thus allowing for a more accurate and reliable conclusion.