Student Portal:

Cellular Organization

Investigation 4 – PreLab









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


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.


This Investigation is designed to help you to answer the following Focus Questions:

  • Is the cell membrane of a plant cell permeable to salt? 
  • Are the cell wall and the cell membrane of a plant cell 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? 

Note: These questions are located in your SDR at the beginning and end of the Investigation.



As a class, read the Background(s) in the Investigation. When  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.



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.



  • Complete the Recall section in your SDR. 
    • 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?
  • 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.
  • During Investigation Four, you will investigate two of the cellular structures you observed in the previous activities, the cell wall and the cell membrane.
  • 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. Remember to follow along with your SDR and make any notes that you think might be helpful in the lab.
  • After the video, divide into your lab group to discuss strategy for the lab. For example, you may assign certain group members to perform specific functions during the lab.

Note: The purpose of the video is to allow you to anticipate the laboratory experience you will soon encounter. You 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.


You should review the Investigation in preparation for the Lab.