4.01 Eukaryotic Cells Part 1

Differences Between Eukaryotes and Prokaryotes

You should remember the following differences between prokaryotes and eukaryotes.

Eukaryotes…

• Have organelles
• Replicate by Mitosis/Meiosis
• Have both linear (in nucleus) and circular (in mitochondria and chloroplast) DNA
• Are roughly between 1-100um (some can get a lot larger however)
• Have histones and chromatin
• Can have the Na+/K+ pump on their plasma membrane (they also have the H+ pump in their mitochondria/plastids)

Prokaryotes

• Have no membrane bound organelles
• Replicate via binary fission
• Have circular DNA
• Are roughly between 0.2-2um
• Have nucleoid proteins
• Have the H+ Pump (proton pump) on their plasma membrane
• Can have capsules

Similarities Between Eukaryotes and Prokaryotes 

Of course, there are many things which eukaryotes and prokaryotes share with each other

Eukaryotes…

• Have ribosomes (80s + 70s)
• Have a cytoplasm
• Have a plasma membrane
• Have DNA/RNA
• Can have Flagella
• Have a cytoskeleton
• Can have a cell wall
  • Plants: made from cellulose
  • Fungi: made from chitin

• Perform Glycolysis, Krebs cycle and Electron Transport Chain

Prokaryotes…

• Have ribosomes (only 70s)
• Have a cytoplasm
• Have a plasma membrane 
• Have DNA/RNA
• Can have flagella
• Have a cytoskeleton
• Can have a cell wall: made from peptidoglycan
• Perform Glycolysis, Krebs cycle and Electron Transport Chain*

*In prokaryotes the Krebs Cycle and Electron Transport Chain work differently to how they work in Eukaryotes, most notably due to the fact that prokaryotes lack any mitochondria. In later lessons we will explore how these two processes work in Eukaryotes only, there is no need to know how they work in prokaryotes for the IMAT.

What Counts as a Eukaryote?

In the IMAT you need to be able to identify a cell as a eukaryote or prokaryote. Eukaryotes come in 4 major kingdoms…

1. Animals: Humans, mammals, reptiles, fish, sponges, crustaceans etc
2. Plants: Trees, ferns, shrubs, mosses etc
3. Fungi: Mushrooms, yeasts, moulds etc
4. Protists: Amoebas, slime moulds, algae

Knowing what counts as a eukaryote will help you if the IMAT gives you a cell by name and asks certain questions about it. 

The Nucleus

We can separate the nucleus into a few components…

The Nucleolus

• Contains: Protein, rRNA, DNA
• Role: 80s ribosome synthesis

The Nuclear Envelope

• Contains: Phospholipids, protein (nuclear pores)
• Role: Separates nucleus from cytoplasm

The Nuclear Pores (on the nuclear envelope)

• Contains: Protein
• Role: Passage of certain molecules
  1. In: Proteins, Ions
  2. Out: Ribosomes (rRNA, Protein), mRNA, tRNA, Ions

Chromatin

• Contains: DNA, Proteins (Histones)
  1. Euchromatin: Transcribable
  2. Heterochromatin: Non-transcribable

• Role:
  1. Packages DNA
  2. Gene Regulation