STRUCTURE and FUNCTION of CELLS

1. Classify cells based on their structure.
2. Identify the major structures and functions of plants and animal cells.

STRUCTURE and FUNCTION of CELLS

Living things are made up of at least one cell. Cells come in many different types. Plant and animal cells are two of the main types of cells. All cells are systems that consist of parts that work together. For example, all cells have a cell membrane, cytoplasm, and genetic material. Each cell part has a particular job or function that it performs.

The cell membrane surrounds the cell and controls what enters and leaves the cell. The cell membrane is semi-permeable, which means that only some substances can pass through it. Substances such as water, oxygen, and nutrients are allowed to enter. Waste products such as carbon dioxide are allowed to exit.

DNA, the genetic material of the cell, is located inside the nucleus. The nucleus is sometimes called the brain or control center of the cell because it is responsible for directing all cell activities.

The inside of a cell is filled with a clear, thick, jelly-like fluid called cytoplasm. Many chemical changes that are important to the survival of the cell go on inside the cytoplasm. The thick fluid constantly flows inside the barrier of the cell membrane.

Mitochondria are often called the powerhouses of the cell because their function is to release the chemical energy that is stored in food. Respiration, a chemical change that occurs between the food and oxygen, occurs in the mitochondrion. Respiration results in energy in a form that can be used by the cell.

Vacuoles are storage compartments inside the cells. They are usually filled with water and other liquids. Plant cells have large central vacuoles that, when full of water, create pressure inside the plant cells to support the plant. If the central vacuoles in plant cells are not filled with water, the plant will wilt or die.

Both plant and animal cells have cell membranes, cytoplasm, DNA protected by a nucleus, mitochondria, and vacuoles. In addition, plant cells contain a cell wall and chloroplasts, which are not found in animal cells. The cell wall is a tough, rigid outer covering that protects each plant cell and gives it shape and support. The chloroplasts are green bodies inside plant cells that make food during a process called photosynthesis. Chloroplasts contain a chemical called chlorophyll that captures solar energy from the Sun. During an energy transformation, the solar energy is changed into chemical energy.

Although cells are the basic unit of structure and function in both plants and animals, their cells are different in several ways. Animal cells do not have chloroplasts to carry on the process of photosynthesis. Animal cells also do not have tough cell walls to give them the rigid, boxy shape of plant cells.

1. Write the letter of the organelle in the box next to its correct definition:

1. What is similar and different between animal and plant cells?

Identify whether these organelles are located within plant or animal cells.