Viruses Chapter 10.17

What you need to know!  The components of a virus.  The differences between lytic and lysogenic cycles.

What’s a Virus?  Not a living cell but an infectious particle  Obligate intracellular parasite Contains: 1.nucleic acids 2.protein coat

Viruses are Tiny

Protein Coats-Capsids  Capsids are made from proteins called capsomeres  Capsids have many different shapes depending on the virus:  Rod shape, Helical, Polyhedral, Icosahedral

Tabacco Mosaic Virus  Helical capsid with RNA

Adenovirus  Respiratory virus in animal  Polyhedral capsid with glycoprotein spikes

Influenza virus  Membrane envelope from host studded with glycoproteins

Bacteriophages  Viruses that infect bacteria  icosahedral shape of a phage resembles a lunar landing probe

Viral Reproduction  Viruses are obligate intracellular parasites  Isolated viruses cannot reproduce  They lack the ribosomes and enzymes for making proteins  Viruses can only infect limited range of host

Lytic Cycle  Virus infects host cell  Cell constructs virus  Cell dies and releases the virus

Lysogenic Cycle  Virus infects host cell  Virus nucleic acid hides inside host DNA  A stimulus triggers the virus into the Lytic Cycle

Protists Chapter 28

Characteristics  Protists are eukaryotes  Can be unicellular, colonial, or multicellular  Predecessor to other eukaryotes: plants, fungi, and animals.  Fossils date back 2.1 billion years  excretion)

Specifics Types: 1.Absorptive, protists (fungus-like) 2.Protozoa - ingestive, animal-like protists 3.Algae - photosynthetic, plant-like protists. Important Structures:  Flagella: Protists have a flagella or cilia during some time in their life cycles.  The eukaryotic flagella are extensions of the cytoplasm with a support of a microtubule system (made from tubullin)  Cilia are shorter and more numerous than flagella.

*Lifestyle  Many protists are symbiots that inhabit the body fluids, tissues, or cells of hosts.  These symbiotic relationships span the continuum from mutualism to parasitism (malaria, giardia)

*Evolution  Endomembrane system of eukaryotes (nuclear envelope, endoplasmic reticulum, Golgi apparatus, and related structures) may have evolved from in-folding of plasma membrane.  Mitochondria and chloroplasts were incorporated through endosymbiosis

Euglena  Freshwater microscopic algae, single celled autotrophic organism (phytoplankton)  Contractile vacuole: bladder-like, pulsing structure that pumps out excess water that enters the cell due to the cell being hyperosmotic in fresh water  Eyespot: detection of light direction  Flagellum: movement toward light source

Amoebas  Pseudopods: extensions of the cytoplasm  Capturing prey, locomotion  Heterotrophic  Movement by pseudopods (false feet): bulging out of plasma membrane followed by cytoplasm

Paramecium  Coordinated movement through ciliates  Complex organelles: contractile vacuole for osmoregulation (pumping out water), oral groove (mouth), anal pore (duh)