Prokaryotes vs. Eukaryotes

Cell Theory

Cell Theory

In the 1800s, hundreds of scientists report seeing cells whenever they looked at living organisms through microscopes.

Based on these observations, researchers developed: Cell theory

– All living things are composed of cells

– The cell is the basic unit of structure and function in living things

– New cells are produced from existing cells

Description Prokaryotes Eukaryotes

When first evolved?

Size:

Types of organisms

# of cells:

Nucleus present?

Ribosomes present?

Mitochondria present?

DNA?

Type of chromosome:

Type of cell division:

Compare/Contrast: Prokaryotes & Eukaryotes

Turn to the back page of your packet

Eukaryotic Cells Have Organelles

• Organelles are internal membranes that partition the cell into different compartments

• Organelles isolate different chemical reactions thereby increasing efficiency

Eukaryotic Cells

Prokaryotic Cell (Bacteria)

2

Eukaryotic Cells Have Membrane-bound Organelles and Compartmentalization

Prokaryotic Cells Have No Organelles and No

Compartmentalization

All activities take place in the cytoplasm

Compare and Contrast Eukaryotic and Prokaryotic Cells

Size: Eukaryotic cells are larger

About 1,000 bacterial cells could fit inside a eukaryotic cell

Both have DNA made of the same 4 monomers: A, T, C, G

Prokaryotes have a single circular chromosome

Eukaryotes have multiple, linear chromosomes

Prokaryotes• No nucleus• Reproduction via binary

fission (a type of cloning)• No membrane-bound

organelles

Eukaryotes• Nucleus• Reproduction via mitosis

or meiosis• Has membrane-bound

organelles

Prokaryotes vs Eukaryotes

Prokaryotic Cells Eukaryotic CellsBacteria & Archaebacteria Plant, Animal, Protista, Fungi

Prokaryotic vs. Eukaryotic Cells

• Bacteria and Archaea-bacteria

• Bound by a plasma membrane

• Chromosomes carrying genes in the form of DNA

• Ribosomes: make proteins

• No nucleus, DNA concentrated in a region called nucleoid, lacks most organelles

• Smaller

• Protists, plants, fungi, animals

• Bound by a plasma membrane

• Chromosomes carrying genes in the form of DNA

• Ribosomes: make proteins

• Nucleus and has many organelles (such as mitochondria and chloroplasts)

• Typically ten times bigger than bacteria

Description Prokaryotes Eukaryotes

When first evolved? Approx. 3.8 billion years ago

Approx. 2.2 billion years ago

Size: 1/10 the size 10 times as big

Types of organisms Bacteria only Fungi, plants, animals, protists

# of cells: Single only Single and multicellular

Nucleus present? No Yes

Ribosomes present? Yes Yes

Mitochondria present? No Yes

DNA? Yes Yes

Type of chromosome: Single, circular Multiple, linear

Type of cell division: Binary fission Mitosis and meiosis

Compare/Contrast: Prokaryotes & Eukaryotes

Endosymbiotic Theory• Mitochondria has a double membrane, just as bacteria do.

• They also have their own unique set of DNA completely separate from the Eurkayotic cell they are in.

• That DNA has a lot more in common with bacterial DNA than that of Eurkaryotes

Endosymbiotic Theory• Chloroplasts also have their own unique DNA independent of

the plant cells they inhabit.

• That DNA is very similar to cyanobacteria

• In fact, the entire structure of a chloroplast is very similar to a bacteria that was engulfed and modified

Endosymbiotic Theory

1. What does the endosymbiotic theory claim about the origin of mitochondria & chloroplasts?

2. The DNA of chloroplasts is most closely related to:

3. The DNA of mitochondria is most closely related to:

4. List three lines of evidence in support of the theory:

Endosymbiosis Theory EvidenceMitochondria and Chloroplasts: • Have their own DNA, which has shape

(circular) and gene-structure like bacteria• Have their own ribosomes• Can copy themselves by binary fission

What is unique about the structure of mitochondria?

Evolution connection: Mitochondria

What is unique about the structure of mitochondria?

Evolution connection: Mitochondria

• their own DNA – a circular chromosome

Photo from Christian Kukat, Christian A. Wurm, Henrik Spåhr, Maria Falkenberg, Nils-Göran Larsson,

and Stefan Jakobs. Super-resolution microscopy reveals that mammalian mitochondrial nucleoids

have a uniform size and frequently contain a single copy of mtDNA. PNAS 2011 108 (33) 13534-

13539

What is unique about the structure of mitochondria?

Evolution connection: Mitochondria

• their own ribosomes

Image from Sukhjit Kaur, Reynald Gillet, Wen Li, Richard Gursky, and Joachim Frank. Cryo-EM

visualization of transfer messenger RNA with two SmpBs in a stalled ribosome PNAS 2006 103 (44)

16484-16489.

What is unique about the structure of mitochondria?

Evolution connection: Mitochondria and Plastids

• multiply by binary fission

Mitochondria image © Rockefeller University Press, 1970; originally published in the Journal of Cell

Biology 47:373-383. Chloroplast image from Shin-ya Miyagishima. Mechanism of Plastid Division:

From a Bacterium to an Organelle. Plant Physiol. 2011 155: 1533-1544.

What is unique about the structure of mitochondria?

Evolution connection: Mitochondria and Plastids

• The size of bacteria

What is unique about the structure of mitochondria

Evolution connection: Mitochondria

• double membrane

Why are mitochondria so weird?

Evolution connection: Mitochondria and Plastids

Because of their evolutionary history! Both evolved via

endosymbiosis.

Endosymbiosis in a series

Evolution connection: Mitochondria and Plastids

Endosymbiosis in a series

Evolution connection: Mitochondria and Plastids

Our house is compartmentalizedEven the rooms in our house are compartmentalizedEach compartment has a different functionEach compartment has a different formIncompatible activities can therefore go on simultaneously

- Food can stay frozen, while other food is cooked- This increases efficiency of important proceses

FreezerKeeps food frozenLong-term storage

FridgeKeeps food coldShort-term storage

Garbage CanStores wasteCan be removed

Cupboards Keeps dry & canned foods organized

Stove/OvenHeats foodCooks food

SinkDelivers fresh waterRemoves waste water

http://www.youtube.com/watch?v=yF7esxWJj1Q

Mitochondrial-DNA

• Inherited only from the egg (maternal-line)• You have the same mitochondrial DNA as mother,

grandmother, etc.• Sons inherit their mitochondrial DNA only from

mom as well

Mutation in mitochondrial DNA 40,000 years ago: Saami of Lapland

Mitochondrial DNA

• https://www.youtube.com/watch?v=ru7Wyt778QQ

Plant cells have:A cell wall, large central vacuole, chloroplasts

Eukaryotic Cells Have Organelles

• Organelles are internal membranes that partition the cell into different compartments

• Compartments can have very different environments

• Compartments allow incompatible processes to go on simultaneously inside the same cell

Cell Part Structure FunctionNucleus

Endoplasmic reticulum

Ribosomes

Golgi apparatus

Vesicles

Mitochondria Bean-shaped, has two membranes, inner membrane with many folds to increase surface area

Supplies energy to the cell: chemical reactions to convert food molecules into energy

Vacuole

Lysosomes

Cell Wall

Chloroplast