To be considered living… An organism must meet ALL 5 criteria: Be made of cell(s); cells are the smallest living units Metabolize nutrients for energy Reproduce Have a genetic blueprint Maintain homeostasis

Cells are the smallest living units They can live as individual entities, or work together to form multi-cellular organisms.  Simple Complex cell tissue organ organ system organism

Cells are the smallest living units Cells convert nutrients to useable energy Cells reproduce Cells have DNA Cells move, grow, respond to their surroundings, and exchange substances with their environment.  Because of these characteristics, cells are classified as LIVING. 

Cells are classified as either… Prokaryotes Eukaryotes Examples Eubacteria, Archaebacteria Plants, Animals, Protists, Fungi Size ~1 µm 1-1000 µm Organelles No membrane bound organelles like a nucleus, but they do have ribosomes YES! Membrane bound organelles Genetic Material DNA is in a circular shape DNA is in chromosomes Reproduction Binary fission or conjugation Mitosis or meiosis

Are Viruses Alive? Viruses are particles containing DNA or RNA surrounded by a protein coat called a capsid.  They do not contain cytoplasm, respire, or grow, and they cannot replicate without a host cell. Because of these characteristics, scientists DO NOT consider viruses as living.

Viruses vs. Cells Viruses Prokaryotes Eukaryotes Examples Influenza, HIV Eubacteria, Archaebacteria Plants, Animals, Protists, Fungi Size 20-300 nm ~1 µm 1-1000 µm Organelles None No membrane bound organelles like a nucleus, but they do have ribosomes YES! Membrane bound organelles Genetic Material DNA or RNA DNA is in a circular shape DNA is in chromosomes Reproduce MUST hijack host cell to reproduce Binary fission or conjugation Mitosis or meiosis

Viral Structure Basic structure: Capsid: a protein coat which contains either RNA or DNA inside. Nucleic acid core: contains either RNA or DNA. Possible additional features: Envelope: surrounds the capsid. Helps virus enter cells. http://www.armageddononline.org/viruses.html doctorgrasshopper.wordpress.com

Viral Shapes Helical viruses (Tobacco Mosaic Virus) Polyhedral viruses – many sides (Adenovirus) Spherical viruses (Influenza) Complex viruses (Bacteriophage) doctorgrasshopper.wordpress.com http://www.bbc.co.uk/schools/gcsebitesize/science/ocr_gateway_pre_2011/ourselves/2_keeping_healthy1.shtml

Virus Reproduction Viruses replicate in either the LYTIC cycle - immediate replication of nucleic acids and lysis of host cell. or LYSOGENIC cycle - delayed replication after latent (dormant) period including integration into host chromosome.

LYSOGENIC CYCLE Virus ATTACHES to host cell Virus INSERTS DNA into host cell, which incorporates it into its own DNA The inserted DNA (prophage) remains dormant until it is activated  Once activated, it separates from the host cell's DNA and enters the lytic cycle

LYTIC CYCLE Virus ATTACHES to host cell Virus INSERTS DNA into host cell Host cell REPLICATES the viral DNA, thousands of new viruses are assembles Host cell bursts to RELEASE the viruses into the body

HIV (human immunodeficiency virus) HIV is a lysogenic virus.  When the virus enters the lytic cycle, it causes AIDS (acquired immune deficiency syndrome).  HIV targets white blood cells of the immune system, and AIDS destroys them.  HIV is a retrovirus that transcribes DNA from RNA.

Influenza (flu) Influenza (flu) virus is a lytic virus. It reproduces and affects the host quickly.  The immune system is capable of destroying it, provided there are no other health complications.  H1N1 is a type of flu virus that is highly contageous.

Viral Treatment Viruses must run their course. saynotomsg.com Viruses must run their course. Only the symptoms of a disease caused by a virus can be treated. Antibiotics do not treat viruses! Vaccines: a substance prepared from killed or weakened pathogens and introduced into a body to produce immunity. It can only protect the body against future infections. connectwithwellness.wordpress.com