A cell is the smallest structure that can carry out all the functions of life — taking in nutrients, producing energy, and reproducing. Atoms and molecules are smaller but are not alive on their own. Organs are made of many cells working together.
Question 2 True / False
All living things are made of cells.
TTrue
FFalse
Answer: True
This is one of the key ideas in biology, known as cell theory. Every living organism — from bacteria to blue whales — is composed of one or more cells. Non-living things like rocks and water are not made of cells.
Question 3 Short Answer
In your own words, explain why a cell is considered the basic unit of life.
Think about your answer, then reveal below.
Model answer: A cell is the smallest structure that can perform all life functions on its own — it can take in energy, get rid of waste, grow, and reproduce. Nothing smaller than a cell can do all of these things.
The key idea is that life's essential processes happen at the cellular level. Molecules and atoms are important parts of cells, but they cannot independently carry out all life functions the way a complete cell can.