Life Science Reading Lesson · Grades 4–6
What Is a Cell?
A science lesson on cells. Students learn about cell theory, the key organelles of plant and animal cells, the difference between unicellular and multicellular organisms, and how cells work together to keep living things alive.
Subject
Science / Life Science
Grades
4–6
Skill Focus
Cell biology, cell theory, organelles, plant and animal cells
Lesson Length
30–45 minutes
Reading Passage
What Is a Cell?
A cell is the smallest basic unit of a living thing. Every plant, animal, fungus, and bacterium is made of cells. Your own body is made up of trillions of cells working together to help you move, breathe, think, and grow. Without cells, no living thing could exist.
In 1839, scientists Theodor Schwann and Matthias Schleiden developed the cell theory. It states that: (1) all living things are made of one or more cells; (2) the cell is the basic unit of life; and (3) new cells come from existing cells. These ideas remain foundational to biology today.
Some organisms are unicellular — made of just one cell. Bacteria and amoebas are examples. Others are multicellular — made of many cells. Humans, animals, and plants are all multicellular organisms.
Cells have many different parts called organelles, each with a specific job. The nucleus is the control center and contains the cell’s DNA. The cell membrane is a thin layer that surrounds the cell and controls what enters and exits. Mitochondria are the powerhouses of the cell, converting food into energy.
Plant cells and animal cells are similar but not identical. Plant cells have a cell wall outside the cell membrane that provides extra support. They also contain chloroplasts, organelles that capture sunlight and use it to make food through photosynthesis. Animal cells do not have cell walls or chloroplasts.
Understanding cells is fundamental to all of biology. Scientists study cells to learn how diseases develop, how bodies heal, and how life itself works at the most basic level.
Printable Resources
Printable PDF · 5 pages
Cell Lesson and Worksheet
A printable science lesson on cells — cell theory, organelles, and plant vs. animal cells — with comprehension questions and a complete answer key.
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