SC.6.6.2.b: Develop and use a model to describe the function of a cell as a whole…

Cells: The Smallest Living Things Grades 7–8 · partly supports this outcome

How small is a cell, how does water get in, what's inside, and why are cells so tiny? Four lessons with potatoes, strawberries and gelatin that work with a microscope or without one.

• How do things get in and out of a cell? Two sessions: 45 min, then 30 min the next day

  Students weigh potato strips, soak them in plain and salty water, and measure how their mass and stiffness change. They use the results to explain diffusion and osmosis, and why a wilted salad goes limp.

• Can you pull DNA out of a strawberry? 50–60 min

  Students mash strawberries with dish soap and salt, filter the juice, and watch a cloudy white tangle of DNA appear when the teacher layers cold rubbing alcohol on top. They explain what each ingredient did to the cell, and test what happens without soap.

Printable practice for SC.6.6.2.b

• Cells: The Smallest Living Things workbook included with the unit

  3 practice pages, 3 readings, 2 English-support pages, 1 word wall, 1 unit review, 1 unit test, with answer keys.

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