BELL WORK(Buff Binder):

Explain the difference between a PROKARYOTE and a EUKARYOTE.

Also, take out your homework so I can check it!

Set up today’s page in your journal…

• Page: 59• Date: 2-4-15• Title: Viral Structure• Essential Question: How does the

structure of a virus compare to a cell?• YES - Cornell notes, please!

OVERVIEW

VocabularyVirus: a non-cellular (or acellular) pathogen

Pathogen: any disease-causing agent

Virology: the study of viruses

Virion: a viral particle (piece of a virus)

Cellular Organisms vs Acellular Particles

Eukaryotic Nucleus

Prokaryotic Cell

Virus

Eukaryotic Cell

1 ųm (1000 nm)

A virus’s size helps it to reproduce. We’ll talk about this tomorrow.

If a cell was the size of our classroom, then an average virus would be the size of a softball.

Viral Size

Viral components– Capsid (protein coat)

• Made of proteins• Surrounds the core

– Genetic material• DNA or RNA• Inside the capsid

– Envelope• Made of lipids (like cell membranes!)• ONLY ON SOME VIRUSES

– Spikes• Made of proteins• Used to attach to cells• ONLY ON VIRUSES WITH ENVELOPES7

Generalized Structure of Viruses

virions having envelopes = enveloped virusesvirions lacking envelopes = naked viruses

Generalized Structure of Viruses

9

Helical Capsids

Helical capsids are rod-like structures with the RNA in the center of the helix. A helix is made by stacking repeating units in a spiral.

RNA

protein coat

Tobacco Mosaic VirusTobacco Mosaic Virus (TMV) is an example of a virus with a helical structure. Protein

subunits wrap around the spiraling RNA strand.

This image taken using an Electron Microscope

AdenovirusAdenoviruses cause diseases like pink-eye or the common cold

BacteriophageBacteriophage is a virus that infects bacteria.

14

Specificity: viruses are highly specific to the cells they infect

Examples: 1) plant viruses infect plant cells2) animal viruses infect only certain related species of animals3) bacterial viruses (bacteriophage) infect only certain types of bacteria.

So, what about zombies?

For the rest of today…

• Complete your HIV handout from yesterday.• Turn in your packet when you finish.