Semester 1, Day 6 Viruses

Agenda  Study  Turn in Homework  Quiz on Enzymes, DNA, RNA, Proteins, & Transcription/Translation  Lecture  Reading/Work Time

Study  Purpose of enzymes  Enzymes are a type of…  Lock & Key Model  Enzyme steps (label diagram)  Characteristics of enzymes  DNA (label diagram)  Why does DNA have a twisted shape? (think hydrophilic/hydrophobic parts)  RNA characteristics  mRNA, rRNA, tRNA  DNA, RNA, and protein functions  Steps of transcription  Steps of translation

Turn in Homework  Questions: 11.1 #1-6, 11.2 #1-6

Quiz  Enzymes  DNA, RNA, Proteins  Transcription & Translation  Question #4

Viruses  What is considered living?  Recall: Cells are the basic unit of life  All cells have:  A plasma membrane  Cytoplasm  Ribosomes  DNA  Bacteria, Archaea, Animals, Plants, Fungi, & Protists are ALL living!  Made of one or more cells  Grows and develops  Reproduces  Responds to environment  Requires energy  Viruses are not considered living:  No organelles (not cells)  Don’t require energy  Can’t grow or replicate on their own Some characteristics of life Much simpler!

Viruses  Virus Parts:  Capsid (coat of proteins)  Genetic Material (DNA or RNA, never both) Must Haves Capsid Genetic Material Fiber Adenovirus Envelope Spike Influenza Virus Capsid Tail Tail Fiber Bacteriophage Genetic Material Tobacco Mosaic Virus Capsid Image Source:

Viruses  Viral Infection: to replicate, virus must enter a host cell  2 Cycles: Lytic & Lysogenic  Lytic: viruses copied using host cell. New viruses then leave by bursting, “lysing”, the host cell  Lysogenic: virus is inactive until stress activates the provirus genes and starts the lytic cycle. Lytic Cycle Lysogenic Cycle Attachment Entry Replication Assembly Release Provirus Formation Bacteria Cell Division Separation

Viruses  Lytic Cycle:  Attachment: Virus attaches to bacterial cell using specific receptors on host cell. The receptors are why viruses aren’t transmitted between species.  Entry: Virus injects its DNA into the bacterial cell  Replication: The virus uses the bacteria’s machinery to replicate the parts of the virus  Assembly: New viruses are assembled from parts  Release: New viruses burst through the host cell, killing it  Lysogenic Cycle:  Provirus Formation: Viral DNA becomes part of the bacterial chromosome  Cell Division: The bacteria cell divides, which replicates the provirus, too.  Separation: Provirus leaves the bacterial chromosome.

Reading/Work Time  Cornell Notes: Section 18.1, 18.2  Questions:  Section Assessment 18.1: #1-6  Section Assessment 18.2: #1-6  Chapter 18 Assessment: #1-17,  Beginning 30 minutes = Silent independent work time

Review  Review Questions