VIRUSES Herpes

are particles that are NOT ALIVE. Viruses – are particles that are NOT ALIVE.

Viruses reproduce ONLY inside a living CELL.

The Structure Of a Virus Inner core of nucleic acid (This is the Viruses genetic material) Some contain DNA or RNA but never both. Surrounded by one or two protein coats called a capsid.

EXAMPLES OF THE MANY DIFFERENT SHAPES OF VIRUSES Tobacco Mosaic Virus Polio Virus Human Immunodeficiency Virus (HIV) Bacteriophage T4

E. Coli and the Bacteriophage What it looks like in real life

T4 Bacteriophage

Every virus has a specially shaped device called an attachment protein that can only attach to a few kinds of cells.

Example of what bacteriophage (a type of virus) does to a cell: Step 1: ATTACHMENT Step 2: ENTRY: Bacteriophage injects nucelic acid into the bacterial cell Step 3: REPLICATION: Host’s metabolic machinery makes viral nucleic acid and proteins

Step 4: ASSEMBLY: New Virus particles are assembled Step 5: LYSIS AND RELEASE: Host cell breaks open and releases new virus particles

Receptor proteins are proteins embedded in the cell membrane that bind to a signal molecule enabling it to respond to the signal molecule. Viruses are segments of nucleic acids contained in a protein coat. They are pathogens and reproduce by infecting cells and using the cell to make more viruses. Are viruses living? NO

Viruses have a protein coat and nucleic acid which are characteristics of living cells. Viruses also have characteristics of nonliving cells which are: viruses do not respire, do not grow and CANNOT reproduce outside a living cell.

BECAUSE THEY DO NOT HAVE ALL THE PROPERTIES OF LIVING THINGS BIOLOGISTS DO NOT CONSIDER THEM LIVING.

Viruses reproduce using 2 different cycles: Lytic cycle : Virus injects the cell with its genetic information, the information is integrated with the host’s DNA , the host is now replicating viral genes assembles the new viruses, and host cell is broken to release the new viruses. EX: cold & flu Lysogenic cycle_: Virus infects the cell, integrates its genetic information with the host’s DNA, the host divides normally, and then provirus may enter the lytic cycle. EX: herpes & HIV

attaches Bacterial Lytic cycle DNA normally viruses Viruses DNA

HIV is a virus that causes AIDS. It has spikes on its surface that matches a receptor protein on macrophages, which is an immune system cell that engulfs pathogens, and infections fighting cells called lymphocytes.

AIDS is: a disease in which an individual is unable to defend the body against infections that do not normally occur in healthy individuals. HIV infected people feel healthy for years and can spread it to others without knowing they are infected. HIV is NOT spread through casual contact but is transmitted in body fluids. This includes: sexual contact, blood, and breast milk

Structure of HIV: envelope composed of lipid bilayer from host cell, capsid and genetic material in the form of RNA. HIV attached to the cell at the receptors called CD4 which activates a co-receptor that in turn starts endocytosis.

This process occurs for years after infection an eventually mutates to a point it now recognizes a new cell surface receptor on T-Cells. HIV reproduces in the T cells and destroys them. This increases the amount of viral particles in the blood. The destruction of T cells blocks the body’s immune response and signals the onset of AIDS.

Ebola

Hepatitis

Polio

Rabies

Smallpox 30% Fatal

Vaccines Are used to PREVENT viral infections- What vaccines have you received in your lifetime? Viruses grown on chicken embryos are attenuated vaccines Another type of vaccine is made by heat killing the virus

BACTERIA (MONERANS) Are the simplest of all living things and are prokaryotes (unicellular, Do NOT have a nucleus, and NO membrane bound organelles) Most are heterotrophs (Feed on other organisms).

Characteristics of Bacteria: Small Unicellular Circular DNA called a plasmid Can form endospores under harsh conditions

2 types of reproduction: Binary fission (Asexual) – Chromosomes replicate and the cell divides Conjugation (Sexual) – Exchange of genetic material through cell to cell contact

2 Groups of Bacteria: Archaebacteria (Ancient) Methanogens – produce methane Thermophiles – live in hot water Halophiles – live in salty conditions (in the Dead Sea) Eubacteria

Archaebacteria Methanogens- Produce methane **Found in peat in marshes or hot springs **Responsible for flatulence

Archaebacteria Thermophiles- live in HOT water                                             Thermophiles produce some of the bright colors of Grand Prismatic Spring, Yellowstone National Park Pompei worms survive with symbiotic relationship with thermophilic archaebacteria

Archaebacteria Halophiles- Live in salty conditions (Dead Sea)

STRUCTURE OF BACTERIA Capsule: prevents bacteria from being easily engulfed by white blood cells Flagella: Long thread-like (whip-like) tail that enables the bacteria to move Cell wall: gives the cell shape and prevents osmosis from bursting the cell (Scientist use Gram-Staining to reveal the cell wall structure)

STRUCTURE OF BACTERIA Chromosomes (nuclear material): not enclosed in a nucleus; a single DNA molecule; arranged as a CIRCULAR chromosome Plasma Membrane: regulates what enters and leaves the cell

SHAPES OF BACTERIA Bacilli,or rod-shaped Spirilli, or spiral Cocci, or round

ANTIBIOTICS Pathogens Are used to kill bacterial infections DO NOT WORK AGAINST VIRUSES Pathogens Any living organisms or particle that can cause an infectious disease is called infectious agent, or pathogen

Mutualism Symbiosis in which two of the species live together in such a way that both benefit from the relationship Ex. E. coli Escherichia coli