Basic Parts: What is a Cell?
What is a cell?
- Lemon gelatin dessert mix
- 1-quart (1-liter) resealable plastic bag
- 1-quart (1-liter) bowl timer
- Large red grape
- 5 peanuts (with or without their shells)
- Adult helper
- Have your adult helper prepare the gelatin dessert mix according to the instructions on the box.
- Allow the gelatin to cool to room temperature.
- Pour the gelatin into the resealable bag and seal the bag. Place the bag in the bowl.
- Place the bowl in the refrigerator to chill until the gelatin is firm (about 3 to 4 hours).
- When the gelatin is firm, remove the bowl from the refrigerator and open the bag.
- Use your fingers to insert the grape in the center of the gelatin. Insert the peanuts in the gelatin so that they are distributed evenly throughout the gelatin.
- Reseal the bag and place it on a flat surface, such as the kitchen counter. Observe its shape.
- Hold the bag over the bowl and gently squeeze the bag. Do not squeeze so hard that the bag opens. Observe the shape of the bag as you squeeze.
You have made a model of the four common parts of all cells.
A cell is that part of any organism that is the smallest part that can exist on its own. (Organisms are all living things—people, plants, animals, and tiny living things called bacteria and fungi.) Cells differ in size and shape, but all have four common parts: a cell membrane, cytoplasm, mitochondria, and a nucleus. All four of these parts are represented in the model you made in this activity.
The plastic bag in your model represents the cell membrane. The cell membrane holds the cell together and protects the inner parts. The light-colored gelatin represents the grayish jellylike material, made mostly of water, called cytoplasm that fills the cell. Most of the chemical changes in the cell take place in the cytoplasm. (A chemical change is a change that produces one or more substances that are different from those present before the change.) The grape floating in the gelatin represents the nucleus. The nucleus is the control center that directs all the activities of the cell. The peanuts floating in the gelatin represent the "power stations" of the cell, called the mitochondria. In the mitochondria, food and oxygen (a gas in the air) combine to produce the energy needed for the cell to work and live.
The four common parts of a cell—cell membrane, cytoplasm, mitochondria, and nucleus-all work together and are necessary for the life of the cell. Like the basic model, many cells change shape when pressure is applied.
- How are plant cells different on the inside from other cells? One way is that most plant cells contain chloroplasts. Chloroplasts are green bodies in plant cells that give plants their green color and in which food for the plant is made. Repeat the experiment, using 6 to 10 green grapes in addition to the red grape and peanuts. Insert the green grapes in the gelatin so that they are scattered throughout the gelatin. Do the grapes affect how the bag changes shape when at rest or when you squeeze it? Keep this model of the basic parts inside a plant cell for the next experiment.
- Since plants do not have bones, what gives them support and shape? Set the cell model from the previous experiment in a small box, such as a shoe box. Observe any change in the shape of the box as you place it on a flat surface or squeeze it. The box represents the stiff outer layer of a plant cell, called the cell wall. By placing the bag of gelatin, which represents the basic parts inside a plant cell, inside the box, you now have a basic model of a plant cell. Science Fair Hint: Place the plant cell model on a flat surface and take a photograph. Photograph the basic model of the four common parts of all cells from the original equipment on the same flat surface. Display these photos to demonstrate the support that a cell wall gives to a plant cell.