Prokaryotic & Eukaryotic Cells

As you have already learned, everything is made up of living cells. And the cells themselves are made up of many different parts . There are many different cells that do many different things, but all of these cells fall into one of the two main categories: Prokaryotic cells & Eukaryotic cells

What the words mean Prokaryotes Eukaryotes Pro = before Karyose = kernel, which represents the nucleus So prokaryotes occurred before cells with a nucleus Ex. Bacteria Eu = true Karyose = kernel, the nucleus So eukaryotes are the cells with a true nucleus Ex. Found in animals, plants, and fungi (yeast)

What they have in common DNA Cell (plasma) membrane Ribosomes Simple in Prokaryotic, complex in Eukaryotic Cytoplasm Allow the flow of nutrients and wastes to enter and leave the cell Have similar metabolic ( life processes) like photosynthesis and respiration Require a supply of energy Made from the same basic chemicals Carbohydrates, proteins, nucleic acid, fats, minerals, and vitamins

Differences That’s what they have in common, but there are significant differences too. The two main ones are age and structure.

Age Differences Scientists believe that prokaryotic cells (in the form of bacteria) were the first life forms on earth. They are considered “primative” and originated 3.5 billion years ago. That is 2 billion years before eukaryotic cells and billions of years before our earliest ancestor, the hominids. 4.6 billion years ago – Earth was formed 3.5 billion years ago – the first life arose: prokaryotic bacteria 1.5 billion years ago – eukaryotic cells arose 500 million years ago – multi-celled eukaryotes arose 3 million years ago – our earliest ancestor, the hominids, appeared Read the passage and tell students to write down the age of prokaryotes and eukaryotes.

Structural Differences Eukaryotic cells contain two important things that prokaryotic cells do not: A nucleus Membrane bound organelles Tell them to write this in their notes.

DNA Although both contain DNA: The DNA in eukaryotic cells in in the membrane bound nucleus The DNA in prokaryotic cells floats around in the cell in what we call a Nucleoid – not a real structure, just a word to describe the inside of the cell where the nuclear material sits Read and tell them to write down the differences between the two types of DNA in cells.

Organelles The organelles in eukaryotic cells allow them to perform more complex functions than prokaryotic cells. Prokaryotic cells do not have organelles like eukaryotic cells. Both have ribosomes, but they are much more complex in Eukaryotic cells. They do not need to write any of this, just read it to them and point out the nucleoid in the prokaryotic cell. Also point out the ribosomes in both and how the eukaryotic cell has many more organelles.

Chloroplasts and mitochondria Evidence suggests that chloroplasts and mitochondria were once bacteria that developed a symbiotic relationship with cells that have a nucleus Chloroplasts and mitochondria have their own DNA that is not a part of the cells. Yes, plants have both chloroplasts and mitochondria. Just for fun info. Tell them to read it.

Size Eukaryotic cells are about 10 times larger than prokaryotic cells. Have them write this in their venn diagram.

Cell Wall Both have a cell wall, but they may be made up of different substances. Have them write this in their venn diagram.

Flagella & Cilia Flagella and cilia are the structures that help cells move. Eukaryotic flagella are more complex than prokaryotic flagella. Point out the structures on the overhead. Also, tell them that not all eukaryotic cells will have these structures, but some do. AND that prokaryotic cells may have one or the other or both.

Check for Understanding Eukaryotic and Prokaryotic Cell Structure Cell Structure Prokaryotic Cell Typical Animal Eukaryotic Cell Cell Membrane Yes Cell Wall No Cilia or Flagella Yes, simple Yes, complex Endoplasmic Reticulum Golgi Complex Lysosomes Mitochondria Nucleus Ribosomes Have them participate in a thumbs up, thumbs down activity. Tell students that you will say the organelle and if the prokaryotic cell has it they should give you a thumbs up. If the cell does not have it they should give you a thumbs down. Tell students they can reference their notes if they are not sure.

New Discoveries Until recently, it was thought that only eukaryotic cells existed in multi-celled groups like in organs and tissue. Recent discoveries suggest that some prokaryotic cells do too. This is just one more example of how new discoveries are always changing what we know – or think we know. But that is what makes science so exciting! http://www.ted.com/talks/lang/eng/bonnie_bas sler_on_how_bacteria_communicate.html