Chapter 19 Viruses And Prokaryotes 19.1 Studying Viruses And Prokaryotes I. Infection Causing Agents (Pathogen) A.Virus 1. = Infectious Particle Made Of Dna/Rna Surrounded By Protein Coat 2. Not Considered Living Organisms A) Don’T Reproduce On Own & Not Made Of Cells B.Bacteria 1. = 1 Celled Microorganism That Can Cause Infection 2. Prokaryote C.Viroid 1. = Infectious Particle That Causes Disease In Plants 2. Made Of Single Strand Of Rna 3. Passed Thru Seeds & Pollen 4. Can Stunt Plant Growth D.Prion 1. = Infectious Particle Made Of Proteins 2. Cause Other Proteins To Unfold/Fold Incorrectly A) Protein Shape Very Important 3. No Genetic Material 4. Can Cause Several Brain Diseases A) Mad-Cow Disease B) Creutzfeld-Jakob Disease C) Can Go For Long Period Of Time W/O Effect - Once Symptoms Start They Continue Fast & Always Fatal Viral Structure And Reproduction - 19.2 I. Structure Of Viruses (Virion) A.Capsid = Protein Shell 1. Surrounds Genetic Material 2. Various Shapes 3. May Be Surrounded By Lipid Envelope = Protective Outer Coat A) May Have Sugar & Protein Spikes B) Helps Attach To Host C) Can Be Used For Identification 4. Capsid, Genetic Material (Dna/Rna) & Few Enzymes Only Things That Makeup Virus B.Structure & Shape Important To How They Work 1. Very Specific To What They Can Infect 2. Has To Fit Into Protein Receptor On Cell Membrane 3. Shapes A) Enveloped (Flu) B) Helical (Rabies) C) Polyhedral (Foot And Mouth) D) Protein Spikes Are What Immune System Targets 4. Genetic Material A) Can Have Dna Or Rna - Not Both B) Can Be Single-Stranded, Double-Stranded, Linear, Circular, Or Segmented C.Bacteriophage (Phage) 1. = Virus That Infects Bacteria 2. Uses Tail & Spikes To Attach To Bacteria A) Uses Enzymes To Break Thru Membrane B) Inserts Genetic Material W/ Tail Sheath Punching Thru Bacterial Membrane D.Viruses That Infect Eukaryotes 1. Can Enter Cell By Endocytosis 2. If Have Envelope Some Will Fuse W/ Cell Membrane A) Then Release Capsid Into Cytoplasm Of Cell (Hiv Virus) 3. No Matter How Virus Gets In, Once In Cell It Attacks The Nucleus Ii. Virus Replication A.2 General Pathways 1. Lytic Infection (Pathway) A) The Virus Takes Control Of Host’S Dna - Turning On Genes To Copy Viral Genes B) Host Cell Makes Viral Capsid & Enzymes - Which Makes Viral Dna C) Host Cell Makes New Viruses D) Host Cell Bursts Open Releasing New Viruses E) Destroys Host Cell 2. Lysogenic Infection (Pathway) A) Combines Viral Dna Into Host Dna = Prophage (Bacteriophage) Or Provirus (All Other Organisms) B) Prophage/Provirus Copied W/ Host Cell’S Dna Into All Daughter Cells C) Prophage/Provirus Can Remain Dormant In Host Cell Or Eventually Become Triggered (Stress) D) When Triggered Cell Then Enters Lytic Phase E) Ex. Herpes Simplex Virus And Aids

Virus

Infectious particle of DNA/RNA in a protein coat; not living.

Bacteria

Single-celled prokaryotes that can cause infections.

Viroid

Infectious RNA particle affecting plants; stunts growth.

Prion

Protein-based infectious agent causing brain diseases (e.g., mad-cow disease).

Capsid

Protein shell surrounding genetic material of a virus.

Envelope

Protective outer coat of a virus with spikes for attachment.

Bacteriophage

Type of virus that infects bacteria.

Eukaryotic viruses

Viruses that enter host cells via endocytosis or fusion.

Lytic Infection

Type of viral infection where the virus takes over the host, replicates, and destroys the cell.

Lysogenic Infection

Type of viral infection where viral DNA integrates into host DNA, can remain dormant, and may trigger lytic phase later.