C Bacteria Archaebacteria Part 1

Viruses Virus: a non-cellular particle made up of genetic material (DNA or RNA) and proteins which invade living cells • Not alive; therefore not in a kingdom o No organelles o No metabolism o Don’t grow like cells o Requires host to reproduce Bacteriophage: a virus that infects bacteria Prophage: an intracellular bacteriophage that is harmless to the host cell Structure 2 main parts: 1. outer capsid o made of proteins o may or may not be surrounded by a membrane envelope 2. inner genetic material • no nucleus Enveloped virus: surrounded by a bilipid fatty membrane like cells (HIV) Glycoprotein: a molecule of protein with attached sugar chains Shapes 1. helical (rabies, measles) 2. icosahedron  polyhedron or a capsid if a virus with 20 triangular faces (chicken pox, herpes) Classification 1. DNA or RNA 2. viral size 3. envelope DNA Viruses Viral Group Papovaviruses

Size (nm) 45-55

Adenoviruses

70-80

Herpesvirses

150-200

Poxviruses

100x200x300

Structure Polyhedral Polyhedral Enveloped polyhedral Helical

Disease Examples Warts Respiratory & intestinal infections, conjunctivitis, sore throat Herpes, chickenpox, shingles, infectious mononucleosis smallpox

RNA Viruses Viral Group

Size (nm)

Structure

Disease Examples Poliomyelitis, infectious hepatitis, common cold

Picornaviruses

20-30

Polyhedral

Myxoviruses

80-120

Enveloped helical

Influenza A,B,C

Rhabdovirus

70x180

rabies

Retroviruses

100

Enveloped helical Glycoprotein enveloped complex

AIDS (depressed immune system)

Types 1. DNA virus • Virus injects DNA into your cells • DNA makes mRNA  viral proteins o This DNA is called a provirus 2. RNA virus • Virus injects RNA into the host & the RNA serves as the mRNA  viral proteins • RNA will translate into DNA using an enzyme called reverse transcriptase • DNA will insert itself into host DNA which makes mRNA • Called a retrovirus [a virus that contains RNA & reverse transcriptase] • Ex. HIV

Viroid • Simpler virus that consists of only a short circular strand of RNA • No capsid • Infect plants & destroy crops Prion • A glycoprotein particle o implicated in diseases with long incubation periods o containing a polypeptide of ≈ 250 amino acids • no nucleic acids • Made of infectious proteins • No DNA or RNA • Convert normal brain proteins into prions • Prions will clump together and kill the cell • Destroy all nerve cells in the brain, leaving holes • Ex. Mad Coe Disease

Host: organism that provides food for parasite viruses are

Obligate Intracellular Parasite: parasite that requires a host cell in order to reproduce Parasite: organism that lives off a host without giving anything positive in return

Viral Cycles Transduction: process in which a virus carries genetic material from one cell to another A) Lytic Cycle • Methods: airborne (inhaling), liquid transfer, blood transfer (fluids) • Viruses that only go through the lytic cycle are called virulent • Steps: 1. Attachment o Virus attaches itself to cell membrane o Virus must recognize a specific protein on the membrane to attach 2. Injection o Viral genetic material is inserted into host cell o Genetic material may or may not insert itself into host DNA o Capsid is discarded 3. Synthesis o Depending on whether it is DNA or RNA, viral proteins will be produced using viral DNA/RNA 4. Assembly o Cell assembles viral proteins into multiple viruses 5. Lysis o The enzyme called lysozyme digests cell membrane, releasing viruses B) Lysogenic Cycle • Occurs after step 2where viral DNA may hide in the host for a varying amount of time • A virus whose replication includes the lysogenic cycle is called a temperate virus • These viruses may insert themselves into host DNA • Factors that activate a “sleeping” (dormant) virus: 1. change in temperature 2. stress 3. lack of nutrients Studying Viruses Tissue Culture: the growing of living cells in a controlled medium Serology: the study of biological fluids/blood serums Electrophoresis: a procedure that separates large molecules by acting on differences in their size and electric charge

Biotechnology 1. Gene Therapy • Uses viruses to carry essential genes into a patient & insert them into host DNA • disadvantages 1. hosts kill viruses so not all cells will have the gene 2. cells eventually die and so will the gene 3. potential for mutation 2. Vaccinations • Solution that contains “harmless” versions of a virus, bacteria, or toxin which causes the body to trigger an immune response • Body creates antibodies which kill the virus • Body remembers this virus so it can easily eliminate the real virus Evolution • No fossil evidence • Most likely did not arise until cells evolved because the rely on cells • Probably either formed spontaneously from existing nonliving organic material or evolved as simplifications of previously existing cells • Existing viruses often evolve rapidly by natural selection • Short generation time of a virus means that natural selection acts quickly to select for viral types that are capable of withstanding destruction in the next host

Pathology of Diseases Pathology: study of diseases caused by pathogens Pathogens: diseases caused by viruses, bacteria, fungi, parasites Epidemic: outbreak of disease in a community Pandemic: outbreak of disease around the world Steps to Pathogenesis 1. 2. 3. 4.

Transmissibility: contagious from host to host Colonizes and multiplies host tissue Evade host immune system Cause physical harm to tissue

Mode of Transmission 1. 2. 3. 4.

food/water blood zoonotic – animals airborne

Health Organizations • CDC: centre for disease control o USA only; not Canada • Public Health Agency o Canadian version of CDC without ability to contain epidemics • WHO – World Health Organization o International o Deal with pandemic o Link resources from different countries

Microscopes 1. compound microscope o use light & lenses to magnify 2. scanning electron microscope (SEM) o use electrons to form image; 1.5-2.0 million times more powerful 3. transmission electron microscope (TEM) o uses electrons; 1 million times more powerful; 3D Eyepiece: magnifies image 10x Low-power: magnifies 4x High-power: magnifies 40x Nosepiece: holds lenses & rotates Body Tube: maintains correct distance b/w eyepiece & lenses Coarse Adjustment: moves stage up & down in large increments Fine Adjustment: moves stage up & down in small increments Stage: supports slide Stage Clips: secure slide in position for viewing Diaphragm: located under stage; controls amount of light allowed to pass through the object Light Source: provides light for viewing the image; light-bulb or mirror Arm: supports the body tube Base: supports the microscope