What Has Cells? A Closer Look at the Building Blocks of Life

The building blocks of life are cells. These small structures are the basic unit of living organisms. Every living thing, from the simplest bacteria to the most complex human being, is made up of cells. But what exactly are cells? What makes them so vital to life? In this article, we will take a closer look at cells, their structures, and their functions.

The Discovery of Cells

“All living things are made up of cells” is one of the fundamental principles of modern biology. But it wasn’t always so. The concept of cells only became widely accepted in the 19th century, and their discovery is credited to two researchers, Robert Hooke and Antonie van Leeuwenhoek.

Robert Hooke

Hooke, an English scientist, is credited with discovering cells in 1665. He did so by examining slices of cork under a microscope he had invented himself. Hooke saw small, empty structures in the cork, which he called “cells” because they reminded him of the small rooms monks lived in.

Antonie van Leeuwenhoek

While Hooke was studying slices of cork, van Leeuwenhoek was using his microscope to examine living things. He discovered bacteria, which he called “animalcules,” and sperm cells. Leeuwenhoek’s discovery was important because it proved that cells were not just found in plants, but also in animals.

The Structure of a Cell

Cells can vary in size and shape, depending on the type of organism they belong to. However, they all have certain features in common.

The Cell Membrane

The cell membrane is a thin layer that surrounds the cell. It is made up of phospholipids, cholesterol, and proteins. The cell membrane is vital because it regulates what goes in and out of the cell.

The Cytoplasm

The cytoplasm is the gel-like substance that fills the cell. It contains all the organelles and structures of the cell.

The Nucleus

The nucleus is the control center of the cell. It contains the cell’s genetic material, or DNA, which determines the cell’s characteristics, such as its shape and function.

Types of Cells

There are two main types of cells: prokaryotic cells and eukaryotic cells.

Prokaryotic Cells

Prokaryotic cells are cells without a nucleus. Bacteria are an example of prokaryotic cells. They are usually smaller and simpler than eukaryotic cells.

Eukaryotic Cells

Eukaryotic cells have a nucleus and are more complex than prokaryotic cells. They make up all complex organisms, including humans, animals, and plants.

The Functions of Cells

Cells have many functions, and these functions vary depending on the type of cell. Here are some of the general functions of cells:

Energy Production

Cells produce energy in the form of ATP (adenosine triphosphate). Mitochondria are the organelles responsible for energy production within a cell.


Cells play a vital role in defending the body against infection. White blood cells, for example, are responsible for locating and destroying harmful pathogens.


Cells also play a role in transporting materials around the body. Red blood cells, for example, transport oxygen from the lungs to the rest of the body.


Cells are the building blocks of life. They come in different shapes and sizes but share a common structure. They have many functions, including energy production, defence, and transportation. Understanding cells is key to understanding life itself.

Common Questions and Answers

  • Q: Can cells survive without a nucleus?
  • A: Some cells, such as red blood cells and some bacteria, do not have a nucleus and don’t need one to survive.
  • Q: What is the difference between prokaryotic and eukaryotic cells?
  • A: Prokaryotic cells do not have a nucleus and are generally smaller and less complex than eukaryotic cells, which have a nucleus and are more complex.
  • Q: Can all bacteria be classified as prokaryotic cells?
  • A: Yes, all bacteria are prokaryotic cells.


Leave a Reply

Your email address will not be published. Required fields are marked *