What's Inside a Cell? The Tiny Building Blocks of Life

Words to Know

Cell

A tiny living bag — the building block of ALL living things

Your body is made of trillions of cells!

Cell membrane

The skin of the cell — keeps good stuff in and bad stuff out

The cell membrane is like a bouncy castle wall!

Nucleus

The boss of the cell — it tells the cell what to do

The nucleus is like the brain of the cell!

DNA

A recipe book inside the nucleus that says how to build YOU

Your DNA decides what color your eyes are!

Mitochondria

Tiny power plants in the cell that make energy

Mitochondria are like little batteries zooming around!

Microscope

A tool that makes tiny things look big so you can see them

You need a microscope to see a single cell!

Check What You Learned

Fun Facts

• The human body contains approximately 37 trillion cells

  Source: Bianconi et al., 2013, "An estimation of the number of cells in the human body," Annals of Human Biology

• The cell membrane is a thin layer that surrounds every cell, controlling what enters and exits

  Source: National Human Genome Research Institute

• The nucleus contains DNA and directs the cell's activities

  Source: NIH National Library of Medicine, "Cell Nucleus"

• Mitochondria produce energy (ATP) for the cell through cellular respiration

  Source: Nature Education, "Mitochondria"

• Mitochondria have their own DNA, supporting the endosymbiotic theory that they were once free-living bacteria

  Source: Lynn Margulis, 1967; confirmed by molecular biology

• Plant cells have a rigid cell wall made of cellulose; animal cells do not

  Source: Nature Education, "Plant Cells vs. Animal Cells"