Cell Transport, part 1

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Students will be able explain the impact of water on life processes (i.e., osmosis, diffusion).

Big Idea

Whether it’s active or passive transport, molecules move in and out of cells.


5 minutes

Warm-Up: How is floating in a pool different from performing a swim stroke like the back stroke?

This question serves to begin the build a base of understanding about the similarities and differences between active and passive transport.  The intent of this question is for students to identify that movement occurs whether one swims or floats. But, swimming expends more energy than floating and swimming moves you against a current but floating will not. When one floats, they move with the current.

Allow 1-3 students to respond and listen for identification of the points that make floating different from swimming.

Introduce New Material

20 minutes

Before class, place a cup or beaker of water on each table. Begin the lesson by introducing the vocabulary associated with the lesson: equilibrium, osmosis, diffusion, homeostasis, active transport, passive transport, hypertonic, hypotonic, isotonic, exocytosis, endocytosis, cell membrane, selective permeability, turgor pressure, sodium potassium pump, concentration gradient, dynamic equilibrium

Say each word aloud and ask students to repeat the term after you.  Clap out the syllables for the terms with 3 or more syllables.  This helps students hear the word parts of more complex words so that they can pronounce them correctly. 

Instruct students to add the bolded terms to their Vocabulary Map. Remind students that the bolded terms contain prefixes, suffixes, Greek or Latin root words.  Provide explicit instruction of each term when it arises during the course of instruction.

Inform students of the learning target for this lesson:

  • I can explain why homeostasis is important and describe the transport of materials through cell membranes.
  • I can assess the impact of water on cell processes.

Ask students why people soak beans overnight before cooking.  Listen to students’ thoughts and note any misconceptions that arise.  A common misconception is that the cells soak up materials like salt or water.  Refrain from addressing misconceptions at this time.  But, make a mental note to address any identified misconceptions during instruction.

Then, ask students to predict what will happen if a place a drop of food coloring is added to the cup of water on the desk.  Again, allow students to share their predictions.  Listen and note any misconceptions that arise. Make a mental note to address any misconceptions during instruction.

Inform students that they will engage in a lab activity that will allow them to observe hat happens when food coloring is place in water.  Performing this brief lab before introducing the new content allows students to make observations and develop prior knowledge that will help them learn  and retain the new material.

Distribute instructions for the Simple Diffusion Lab. Read the lab procedure aloud to the class.  Instruct students to work in groups of two to conduct the lab.  Walk around and quickly add one drop of food coloring to each beaker on the desks.  Emphasize that students are not to agitate the food coloring in the cup in any way after the drop of color is added.  Walk around to observe students' lab practice to ensure students' adherence to safe lab practice.

While students wait for the food coloring to diffuse into the water, instruct students to begin working on the 6 lab analysis questions.   Collect the student work and quickly assess how well students grasped the concepts from the observation lab. student work 1 shows an basic understanding of the concepts related to diffusion. Comparatively, student work 2  and student work 3 both show a high level of  understanding of the concepts based on their responses to the questions using the content-related vocabulary. 

Use the information gained for this formative assessment to help you determine how to adjust the instruction.  Display visual information as you instruct and ensure students take notes using cell transport guided notes that you provide or use a note-taking strategy that you have taught.  Guided notes provide greater support for the different learning styles of students. 

Explicitly teach the terms equilibrium, hypertonic, hypotonic, isotonic, exocytosis, and endocytosis.  Allow students to identify what the term means using the knowledge they have about the prefixes or suffixes, and Latin or Greek root words.  Ask students to think of other terms that use these prefixes. Point out associations that will help students decode terms, like exo- and exit or endo- and inside.  Provide guidance by helping students first identify the word parts then attach meaning to the word parts.

Integrate checks for understanding into the instruction.  Vary the instructional delivery and show 1-2 animations that illustrate diffusion, osmosis and equilibrium. Play animations at least twice to allow all students ample opportunities to make observations and identify key aspects of the molecules’ movement.

Use of visuals and questions helps to periodically assess if students are grasping the concepts.  For example, use visual 1 and visual 2 as a basis for asking the following questions:

What is the blue double-layered structure?  How do you know? Look for students to be able to correctly identify that the blue structure is the cell membrane.  Listen for the reasoning students used to make this identification.  Look for students to note that the structure has phospholipids aligned tail to tail in a bilayer. If students do not use the correct terminology in their responses, prompt them to do so with reference to the word wall or vocabulary map.

Which way are the molecules moving?  How do you know? Look for students to identify that the molecules are moving left to right.  Listen for the reasoning students used to come to the correct conclusion.  Look for students to note that the molecules are at a higher concentration on the left than the right so the molecules will move down the concentration gradient from higher concentration to lower concentration.  If students do not use the correct terminology in their responses, prompt them to do so with reference to the word wall or vocabulary map.

Guided Practice

10 minutes

Ask, by a show of hands who knows what an acrostic is.  Select 1-3 students to share one thing that they know about acrostics.

Explain that an acrostic is a style of writing in which the first letters of each line spell out a word. Explain to students that the purpose of an acrostic can be to help students’ recall information.  Explain that today’s assignment involves writing an acrostic about diffusion and osmosis in order to help reinforce the key concepts.

Share a brief video clip on how to write an acrostic:

Because students benefit from hearing information multiple times in multiple ways, display a few tips for Writing an Acrostic:

  • Begin by writing the word vertically down the page.
  • Capitalize the first letter of each line.
  • The acrostic does not need to rhyme.
  • Decide what sentence can be written that describes a characteristic of the topic.

Model how an acrostic is written, using your first or last name. Think aloud to help students observe the thought process used to develop the sentence for each line of the acrostic:

S- Sometimes I can be impatient.

H-Humility is a virtue that I value.

A- Art is something that I love.

R- Rarely am I down or unhappy.

O- One person can make a difference.

N- Nothing makes me happier than family.

Independent Practice

20 minutes

Display instructions for Writing an Acrostic. Instruct students to work independently to complete an acrostic for both diffusion or osmosis.  Walk around the room to observe students as they work. 

Be available to offer guidance, but not answers.  Assist students as needed by asking guided questions to help guide them to make the correct associations in order to complete the assignment. Students should be able to use the selected term to develop their own thoughts for each letter of the term used.    

Collect the work as students finish.  Review the students' work to ensure that the statements that they have included in the acrostic are accurate descriptions of osmosis or diffusion.  The student work that is included demonstrates that students were able to convey understanding of the osmotic process. Acrostics one, two and three all show that students possess a working knowledge of osmosis and how to correctly use the content related vocabulary.


5 minutes

Complete the chart using choral response.  Make visual observations to identify students who are not participating.  Draw them into the closing activity by asking secondary questions, like “What does hypo- mean?”

Type of Environment

Description of Conditions

A cell placed in this solution will

How will the water move?