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Apply the Process of Osmosis to Cells

Worksheet Overview

QUESTION 1 of 10

Ever wondered why your urine is often darker and more concentrated in the summer? Probably not, it's not the nicest thing to be thinking about! But often it's because we tend to sweat more in summer months so we lose a lot more water. Our kidneys then will try and keep a hold of more water for many of our important processes resulting in more concentrated urine! This movement of water into and out of our cells is called osmosis.

Image of particles moving via osmosis

 Osmosis is the diffusion of water molecules from a low concentration solution to high concentration solution, across a partially permeable membrane.

A partially-permeable membrane has holes or pores in it that allow water molecules through but are too small to allow larger molecules through. 

During osmosis, water molecules diffuse from pure water or dilute solution to more concentrated solutions.

  • Dilute solutions have a high concentration of water molecules so have a high water potential 
  • Concentrated solutions have a low concentration of water molecules so have a  low water potential

Osmosis in organisms

Plant and animal cells are surrounded by a partially-permeable plasma membrane. This allows water and other small molecules to diffuse across. Plant cells additionally have a strong cell wall surrounding the membrane which offers support and protection. Animal cells don't have a cell wall. This means they respond differently to plant cells to the gain and loss of water.

Image of osmosis occurring in red blood cells

In dilute solutions, osmosis can cause animals cells, such as red blood cells, to swell up and sometimes even burst. This is because water will move from a high concentration outside the cell to a lower concentration inside the cell.  In concentrated solutions, water loss causes the cells to shrink. In order to remain healthy, animal cells need to maintain a balance. This means that the water concentration both inside and outside the cell are equal.

Image of plant cells in different concentrations of water

Plants require water in order to photosynthesise. The roots of a plant contain root hair cells which are specialised cells that increase the surface area of the cells for maximum absorption of water by osmosis. In pure water, plant cells will take in water via osmosis and become firm or turgid. In a concentrated solution (not much water present) the cell loses water and starts to shrink and becomes flaccid.  

In humans, the concentration of water and salt in the blood are controlled by the kidneys. The kidneys ensure we have the right concentration of water and getting rid of the excess water as urine.

 

Calculations Involving Osmosis

Image of weighing scales

Osmosis can be demonstrated using cubes of potatoes of roughly the same mass. Placing the cubes in different concentrations of sugar solutions the cubes might gain or lose mass, or may even stay the same mass.

Scientists will be able to calculate the percentage change in mass to see how much mass was gained or lost and converting to percentages often makes for easier comparison. Percentage mass is calculated by using the following equation:

((Final mass – initial mass) ÷ initial mass) x 100

For example, a potato cube has an initial mass of 1g. After placing in a sugar solution for 30 minutes its mass was 1.1g. Its percentage change in mass is 10%. 

((1.1g - 1g) ÷ 1g)) x 100 = +10%

The plus sign shows there was an increase in mass. A minus sign shows a loss in mass.

In the following activity, you will apply the process of osmosis to cells. 

Image of particles moving via osmosis

Plant and animal cells use the process of osmosis to transport water into or out of their cells. Describe osmosis. 

Fill in the blanks below to answer this question.

 

Image of particles moving via osmosis

Cell membranes are partially permeable. What is a partially permeable membrane? Choose two answers from below.

A partially-permeable membrane does not have holes in it

A partially-permeable membrane has holes in it

It only allows waste products through

It allows water molecules through but are too small to allow larger molecules through

image of orange juice

Lisa is drinking orange squash. She finds it too sweet so adds more water to her glass of squash. She is diluting it. In terms of water potential what is happening to the squash? Select one answer below.

 

The water potential increases

The water potential decreases

The water potential remains the same

Image of osmosis occurring in red blood cells

What happens to red blood cells when they are placed in a concentrated salt solution? Select one answer below.

 

 

They lose water and shrink

They gain water and swell

They stay the same

Image of plant cells in different concentrations of water

Plants take in water through their root hair cells. What happens if too much water is taken into the cells? Select two answers below.

Cell gains water

Cell loses water

Cell becomes turgid

Cell stays the same

 Image of water molecules Image of water moleculesImage of water molecules

Cell A 

 < Permeable membrane

 Image of water moleculesImage of water molecules

Cell B

The diagram above shows two cells separated by a permeable membrane. Cell A has twelve molecules of water and Cell B has eight molecules of water. Which direction will the water move? Select one answer below.

From Cell A to Cell B

From Cell B to Cell A

No movement

Osmosis can be demonstrated using cubes of potatoes of roughly the same mass. Placing the cubes in different concentrations of sugar solutions the cubes might gain or lose mass, or may even stay the same mass.

Lara did an experiment in school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed it in a beaker of different concentrations of sugar solution. After two hours each potato cube's mass was measured.

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73
% change in mass 10 7.5 -2 (a) -13.5

Calculate the percentage change in mass in beaker 4 (a). Type one answer below.

Lara did an experiment in school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed it in a beaker of different concentrations of sugar solution. After two hours each potato cube was measured.

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73
% change in mass +10 +7.5 -2 -10 -13.5

Explain why the mass decreased in the potatoes in beakers 3, 4 and 5. Select two answers below.

Water entered the potato for respiration

Water left the potato cells by osmosis

The concentration of water outside cells was lower than inside the cells

The concentration of water outside the cells was lower than inside the cells

In which of these scenarios is osmosis occurring? Select two answers.

A red blood cell losing water

Oxygen entering the blood from the lungs

A plant absorbing water from the soil

Glucose moving into bloodstream from small intestine

 Image of water molecules Image of water moleculesImage of water molecules

Cell A 

 < Permeable membrane

 Image of water moleculesImage of water molecules

Image of water molecules

Cell B

The diagram above shows two cells separated by a permeable membrane. Cell A and Cell B have twelve molecules of water. Which direction will the water move? Select one answer below.

From Cell A to Cell B

From Cell B to Cell A

No net movement

  • Question 1

Image of particles moving via osmosis

Plant and animal cells use the process of osmosis to transport water into or out of their cells. Describe osmosis. 

Fill in the blanks below to answer this question.

 

CORRECT ANSWER
EDDIE SAYS
Osmosis is really important for cells, they're able to get the water they need for different processes like photosynthesis. Like gases in diffusion, water molecules move from a less concentrated (more water) solution to a more concentrated (less water) solution.
  • Question 2

Image of particles moving via osmosis

Cell membranes are partially permeable. What is a partially permeable membrane? Choose two answers from below.

CORRECT ANSWER
A partially-permeable membrane has holes in it
It allows water molecules through but are too small to allow larger molecules through
EDDIE SAYS
A partially permeable membrane is selective and only allows water and small particles to pass through it.
  • Question 3

image of orange juice

Lisa is drinking orange squash. She finds it too sweet so adds more water to her glass of squash. She is diluting it. In terms of water potential what is happening to the squash? Select one answer below.

 

CORRECT ANSWER
The water potential increases
EDDIE SAYS
Adding water to orange squash means you are increasing the number of water molecules in the solution. This increases the water potential. This means that the orange squash has more water to mix with making it taste less sweet.
  • Question 4

Image of osmosis occurring in red blood cells

What happens to red blood cells when they are placed in a concentrated salt solution? Select one answer below.

 

 

CORRECT ANSWER
They lose water and shrink
EDDIE SAYS
Water will move out of the red blood cells making them shrink and will look wrinkled.
  • Question 5

Image of plant cells in different concentrations of water

Plants take in water through their root hair cells. What happens if too much water is taken into the cells? Select two answers below.

CORRECT ANSWER
Cell gains water
Cell becomes turgid
EDDIE SAYS
Water moves from a higher concentration to a lower concentration. If the plant's surroundings are wet then water enters the plant cells by osmosis making the cells firm and turgid. So it's important to water your plants but not to overdo it!
  • Question 6

 Image of water molecules Image of water moleculesImage of water molecules

Cell A 

 < Permeable membrane

 Image of water moleculesImage of water molecules

Cell B

The diagram above shows two cells separated by a permeable membrane. Cell A has twelve molecules of water and Cell B has eight molecules of water. Which direction will the water move? Select one answer below.

CORRECT ANSWER
From Cell A to Cell B
EDDIE SAYS
Water will move from a higher concentration to a lower concentration. There are more water molecules in Cell A than Cell B so water will move from Cell A through the partially permeable membrane and into Cell B until there are equal numbers of molecules in each cell.
  • Question 7

Osmosis can be demonstrated using cubes of potatoes of roughly the same mass. Placing the cubes in different concentrations of sugar solutions the cubes might gain or lose mass, or may even stay the same mass.

Lara did an experiment in school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed it in a beaker of different concentrations of sugar solution. After two hours each potato cube's mass was measured.

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73
% change in mass 10 7.5 -2 (a) -13.5

Calculate the percentage change in mass in beaker 4 (a). Type one answer below.

CORRECT ANSWER
-10
EDDIE SAYS
To calculate the percentage change in mass: ((Final mass – initial mass) ÷ starting mass) x 100
  • Question 8

Lara did an experiment in school on the effect of sugar solutions on potato pieces.  The potato pieces were of equal size. She measured the mass of each potato cube and placed it in a beaker of different concentrations of sugar solution. After two hours each potato cube was measured.

Beaker  1 2 3 4 5
Sugar concentration (M)  0.2 0.4 0.6 0.8 1
Initial mass (g) 2 2 2 2 2
Final mass (g) 2.20 2.15 1.96 1.80 1.73
% change in mass +10 +7.5 -2 -10 -13.5

Explain why the mass decreased in the potatoes in beakers 3, 4 and 5. Select two answers below.

CORRECT ANSWER
Water left the potato cells by osmosis
The concentration of water outside the cells was lower than inside the cells
EDDIE SAYS
Water moves from where it is more concentrated to where it is less concentrated. In beakers 3, 4 and 5 the concentration of sugar is high meaning the concentration of water will be high. The water will move out of the potatoes resulting in a decrease in mass.
  • Question 9

In which of these scenarios is osmosis occurring? Select two answers.

CORRECT ANSWER
A red blood cell losing water
A plant absorbing water from the soil
EDDIE SAYS
Remember in questions like these to look for the answers that mention water. An answer that mentions gas is usually referring to diffusion.
  • Question 10

 Image of water molecules Image of water moleculesImage of water molecules

Cell A 

 < Permeable membrane

 Image of water moleculesImage of water molecules

Image of water molecules

Cell B

The diagram above shows two cells separated by a permeable membrane. Cell A and Cell B have twelve molecules of water. Which direction will the water move? Select one answer below.

CORRECT ANSWER
No net movement
EDDIE SAYS
There are equal numbers of water molecules in Cell A and Cell B so water will continue to move at an equal rate between the cells.
---- OR ----

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