Osmosis: The Movement of Water Across Membranes

Biology Grades High School 8:03 Video
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Lesson Description

Explore the fascinating process of osmosis, the movement of water across semipermeable membranes from areas of low solute concentration to areas of high solute concentration. This lesson delves into the mechanisms driving osmosis and its significance in biological systems.

Video Resource

Osmosis | Membranes and transport | Biology | Khan Academy

Khan Academy

Duration: 8:03
Watch on YouTube

Key Concepts

  • Semipermeable membranes
  • Solute concentration
  • Solvent (water) movement
  • Concentration gradients
  • Osmotic pressure

Learning Objectives

  • Define osmosis and explain its driving force.
  • Describe the role of semipermeable membranes in osmosis.
  • Explain how solute concentration affects water movement.
  • Relate osmosis to real-world examples, such as the effect of salt on slugs.

Educator Instructions

  • Introduction (5 mins)
    Briefly introduce the concept of diffusion as a review and then introduce osmosis as a special case of diffusion involving water and semipermeable membranes. Show the Khan Academy video 'Osmosis | Membranes and transport | Biology | Khan Academy'.
  • Video Analysis (15 mins)
    Play the video and pause at key points to discuss the concepts being presented. Focus on the explanation of semipermeable membranes, solute concentration, and water movement. Clarify any misconceptions.
  • Mechanism Discussion (15 mins)
    Discuss the mechanisms of osmosis as presented in the video. Emphasize both the physical blockage of water molecules by solute and the role of charged solutes in attracting water molecules. Encourage students to think critically about these mechanisms.
  • Real-World Applications (10 mins)
    Discuss real-world examples of osmosis, such as its role in plant cells, animal cells, and kidney function. Refer to the example of slugs and salt water from the video.
  • Wrap-up and Quiz Introduction (5 mins)
    Summarize the key concepts of osmosis. Inform students that they will be taking a short quiz to assess their understanding.

Interactive Exercises

  • Osmosis Modeling
    Use dialysis tubing filled with different concentrations of sugar solution and place them in beakers of water. Observe the changes in the tubing over time, demonstrating the movement of water due to osmosis.

Discussion Questions

  • How does a semipermeable membrane differ from a permeable membrane?
  • What would happen if a cell was placed in a solution with a very high solute concentration?
  • Can you think of other examples of osmosis in everyday life?

Skills Developed

  • Critical thinking
  • Scientific reasoning
  • Data analysis (observing changes in the dialysis tubing)
  • Model building (understanding the membrane system)

Multiple Choice Questions

Question 1:

Osmosis is the movement of what across a semipermeable membrane?

Correct Answer: Water

Question 2:

Osmosis occurs from an area of _____ solute concentration to an area of _____ solute concentration.

Correct Answer: Low, High

Question 3:

A semipermeable membrane allows which of the following to pass through?

Correct Answer: Some molecules, but not others

Question 4:

According to the video, what is one reason why water molecules might have a harder time moving from an area of high solute concentration to low solute concentration?

Correct Answer: The water molecules are too big

Question 5:

In a solution, the substance that dissolves another is called the:

Correct Answer: Solvent

Question 6:

Which of the following is an example of osmosis in a biological system?

Correct Answer: Water uptake by plant roots

Question 7:

What property of water molecules allows them to be attracted to ions, as mentioned in the video?

Correct Answer: Polarity

Question 8:

If a cell is placed in a hypertonic solution, what will happen to the cell?

Correct Answer: It will shrink

Question 9:

Why do slugs shrivel up when salt is poured on them?

Correct Answer: The salt dehydrates them through osmosis

Question 10:

What is the role of solute concentration in osmosis?

Correct Answer: It determines the direction of water movement

Fill in the Blank Questions

Question 1:

A membrane that allows some substances to pass through but not others is called a __________ membrane.

Correct Answer: semipermeable

Question 2:

The movement of water from an area of low solute concentration to an area of high solute concentration is called __________.

Correct Answer: osmosis

Question 3:

The substance that is dissolved in a solvent is called the __________.

Correct Answer: solute

Question 4:

In the video, the solute particles are shown as being too _____ to move through the membrane.

Correct Answer: big

Question 5:

Water is considered a __________ because it is the substance present in the greater amount.

Correct Answer: solvent

Question 6:

Ions, like sodium and chloride, can attract water molecules because they have a full __________.

Correct Answer: charge

Question 7:

The driving force behind osmosis is the difference in __________ __________ between two solutions.

Correct Answer: solute concentration

Question 8:

A solution with a higher solute concentration compared to another solution is called __________.

Correct Answer: hypertonic

Question 9:

The maintenance of a stable internal environment in living organisms is called __________.

Correct Answer: homeostasis

Question 10:

In the osmosis modeling lab experiment, __________ tubing is used to simulate a cell membrane.

Correct Answer: dialysis

Educational Standards

B.LS1.3:[Standard] Plan and conduct an investigation to provide evidence of the importance of maintaining homeostasis in living organisms. B.LS1.2:[Standard] Develop and use a model to illustrate the hierarchical organization of interacting systems that provide specific functions within multicellular organisms.

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