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Prokaryotic Cell Structure and Function

We’re going to start with eukaryotic cells even though they tend to be more complex than prokaryotes. There’s a method to our madness, though. You are a eukaryote and have eukaryotic cells, so we thought you might relate better. “Eukaryotic” also comes before “prokaryotic” in the dictionary. 

Honestly, we could come up with reasons all day, but the simple fact is that eukaryotic cells are up first. C’est la vie.

Eukaryotic Cell Structure and Function

A cell is defined as eukaryotic if it has a membrane-bound nucleus. Any organism composed of eukaryotic cells is also considered a eukaryotic organism. Case in point: you. Oh, and all other people, too.

Biologists do not know of any organism that is composed of both eukaryotic and prokaryotic cells. However, many different types of prokaryotic cells, usually bacteria, can live inside larger eukaryotic organisms. Creepy, but true.

We humans, for example, have trillions of bacteria living in our colons, not to mention in our mouths and stomachs and small intestines and…you get the picture. Despite the fact that we have gobs of prokaryotic cells living inside and on us, humans are still categorically eukaryotic organisms. This means that all human cells—including those found in the brain, the heart, the muscles, and so on—are also eukaryotic. 

Here is what one of these little guys looks like:

Okay, we are impressed. That is a lot of stuff jam-packed into something so small.

All of the organisms we can see with the naked eye are composed of one or more eukaryotic cells, with most having many more than one. This means that most of the organisms we are familiar with are eukaryotic. However, most of the organisms on earth, by number, are actually prokaryotic. 

Here are some examples of eukaryotes:

  • Animals
  • Plants
  • Fungi (mushrooms, etc.)
  • Protists (algae, plankton, etc.)

Most plants, animals, and fungi are composed of many cells and are aptly classified as multicellular. Most protists consist of a single cell and are classified as unicellular. Funny how that works. 

All eukaryotic cells have the following:

  • nucleus
  • Genetic material
  • plasma membrane
  • Ribosomes
  • Cytoplasm, including the cytoskeleton

Most eukaryotic cells also have other membrane-bound internal structures called organelles. Organelles include:

  • Mitochondria
  • Golgi bodies
  • Lysosomes
  • Endoplasmic reticulum
  • Vesicles

There are a few major differences between animal, plant, fungal, and protistan cells. And guess what? We’ve got some handy-dandy lists to help you learn those differences. 

All plant cells have the following:

  • cell wall made of cellulose
  • A large central vacuole
  • Chloroplasts

Some animal and protistan cells have:

  • Flagella
  • Cilia

But all animal cells have: