Italicized font represents information to be shared orally or physically completed with the students at this time.

The non-italicized font represents additional information included to support the teacher’s understanding of the content being introduced within the CELL.

ASK WHY

Remind students that all known living things are made of cells. Studying cells helps us understand how living things function.

BRANCH OUT

Remind students that epidemiologists study diseases to find ways to cure or prevent them, researching diseases that affect the whole human body, like HIV, or focusing their research on illnesses that target one region of the body, such as the lungs or heart. Clinical epidemiologists usually work in hospitals or outpatient centers, where they collaborate with doctors to stop or prevent the outbreak of diseases.

GET FOCUSED

Inform students that the Investigation is designed to help them to answer the following Focus Questions:

• Is the cell membrane of a plant cell permeable to salt? The cell membrane of a plant cell is not permeable to salt.

• Are the cell wall and the cell membrane of a plant cell permeable to water? The cell wall and cell membrane are permeable to water.

• How does the structure of the cell wall and cell membrane affect the movement of substances in and out of a cell? The structure of the cell wall and cell membrane determines whether or not each structure is permeable to salt and water.

Note: These questions are located in students’ SDRs at the beginning and end of the Investigation.

Note: These are succinct responses to the Focus Questions and are placed here for your reference at this time. Fully developed responses to the Focus Questions can be found on the PostLab page.

GO DEEPER

As a class, read the Background(s) in the Investigation. Have students read the information aloud or silently to themselves. When students have finished, discuss the following concepts as a class:

• Plant and animal cells are completely surrounded by a cell membrane.
• The cell membrane separates the cytoplasm of the cell from the external environment that surrounds the cell.
• In addition to the cell membrane, plant cells are also surrounded by a cell wall that adds strength and structure to the plant cells.
• Cell membranes are selectively permeable. This means that only certain, selected substances can cross the membrane.
• Certain, selected substances move from the area of higher concentration to the area of lower concentration until the concentration of the substance is equal on both sides of the membrane.
• The process of substances moving from areas of high to low concentration is called diffusion.
• The diffusion of water across a selectively permeable membrane is given a special name- osmosis.
• In the process of osmosis, water always moves from the area of its highest concentration to the area of its lowest concentration.

Note: These concepts are integrated into the Background(s) and are used to deepen students’ comprehension of the big ideas.

LEARN THE LabLearner LINGO

The following list includes Key Terms that are introduced in the Investigation Background(s). They should be used, as appropriate, by teachers and students during everyday classroom discourse.

• diffusion
• osmosis

Note: Definitions to these terms can be found on the Introduction page to the CELL.

Note: Additional words may be bolded within the Background(s). These words are not Key Terms and are strictly emphasized for exposure at this time.

SET FOR SUCCESS

• Direct students to complete the Recall section in their SDRs. Student answers will vary.

• What is the function of the cell wall?
• What is the function of the cell membrane?
• Do all cells have a cell wall and cell membrane?

• Assess students’ prior knowledge of concentration. Explain to students that a solution is more concentrated if it contains more solute per solvent and is less concentrated if it contains less solute per solvent. For example, a sugar solution containing 20 grams of sugar per 100 ml of water is less concentrated than a solution containing 40 grams of sugar per 100 ml of water.
• Tell students that during Investigation Four they will investigate two of the cellular structures they observed in the previous activities, the cell wall and the cell membrane.
• Explain that a property of the cell wall is to provide structure and support for plant cells. The cell membrane allows water and certain solutes to move in and out of the cell. The cell membrane also prohibits the movement of some solutes, keeping them from passing in and out of the cell.
• Play the video below. Stop to ask students questions or answer students’ questions when necessary. Remind students to follow along with their SDRs and make any notes that they think might be helpful.
• After the video, direct students to divide into their lab groups to discuss their strategy for the lab. For example, they may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow students to anticipate the laboratory experience they will soon encounter. Students should leave this PreLab session with a firm idea of what to expect and how to perform in the lab.

Note: Homework is posted below the video.

HOMEWORK

Tell students that they should review the Investigation in preparation for the Lab.