Prokaryote vs. Eukaryote

Prokaryote vs. Eukaryote

• 1st division

Prokaryotes

• Prokaryotes (bacteria and archea)– Lack a true nucleus

• Keep DNA in nucleoids

– No membrane bound organelles

– Many are anaerobic• Do not require O2

– Unicellular

Eukaryotes

• Eukaryotes (protists, plants, fungi, animals)

– Presence of a nucleus– Presence of

membrane bound organelles

• For example Mitochondria to give energy

– Most are aerobic• Require O2 for cellular

respiration

– Most are pluricellular

Summary chart

• Prokaryotes– Lack a true nucleus– No membrane bound

organelles– Many are anerobic– Unicellular

• Eukaryotes– Presence of a nucleus– Has membrane bound

organelles– Most are aerobic– Mostly pluricellular

But where do viruses fit in?

• Debate over whether viruses are “alive”

– A) Non-living arguments1. Cannot live independently (require a host or

remain dormant)

2. Not Cellular

– B) Living arguments1. Contain genetic material (RNA and DNA)

2. Reproduce

Classifying viruses

• Classification based on1. Capsids

• Protein coat that surrounds the genetic material of a virus

– Spherical– Cylindrical– Crystalline

Classifying viruses

– 2. Diseases they cause• Viruses that affect humans are divided into 21

groups based on the differences in their genome and replication methods

Going viral(how viruses replicate)

• Virus replication (No cellular division)– 1. The Lytic cycle

• Kills host cell• Process

– Virus binds to host (attachment)– Injects the genetic material into the host cell (entry)– The host replicates the viral genetic material (replication)– New viral particles are assembled (assembly)– The host cell breaks (lysis) and releases new viral

particles (release)

The lytic cycle

• 1. Attachment• 2. Entry• 3. Replication• 4. Assembly• 5.a) Lysis• 5. b) Release

Virus replication

– 2. the Lysogenic cycle• As the viral RNA becomes part of the cells

chromosomes, the onset of disease can be postponed until the virus goes into its lytic cycle

• Process– Attachment– Entry– Viral DNA becomes part of the host cell’s chromosomes

(provirus formation)

The lysogenic cycle

1. Attachment

2. Entry

3. Provirus Formation

Viral disease

• Cyclical symptoms can be explained via the replication method of a virus– E.g cold sores

• Appear during the lytic cycle• Disappear during the lysogenic replication cycle

Virus working for us

• Virus use in biotechnology– ability to direct the activity of the hosts cell

DNA• Addition of a specific gene into the virus• Virus can deliver and force organism to replicate

that gene

Prions

• Prions– Protein

• Do not contain RNA or DNA (not a virus)

– Becomes harmful when it changes its molecular shape

– Cause several deadly brain diseases• Creutzfeld-Jakob disease• Mad-cow disease in bovine