Bacteria, viruses and the immune system Biology

2 Bacteria Kingdoms Archaebacteria Eubacteria Harsh environment High temperatures High salinity Acidic Eubacteria Found in normal environments. These are the type of bacteria that we come into contact with on a daily basis!!!

General Structure of Bacteria  Prokaryotic No nucleus or membrane bound organelles Lots of ribosomes Thick cell wall Circular chromosomes (DNA) Some have a sticky capsid located outside the cell wall; this allows them to stick to surfaces…. like your teeth!! 

General Structure of a Bacterial Cell

Bacterial Reproduction Reproduce by binary fission Asexual reproduction Makes an exact copy Happens quickly

Binary Fission in Bacterial Cells Bacteria Grows DNA replication occurs Cytokinesis occurs Two identical cells result

Bacteria…Good, Bad or Both? Bacteria is good! food (yogurt) medicines (insulin) recycles nutrients decompose nitrogen fixation (in plants) Bacteria is bad! Decay/rot food Rot teeth Cause disease/ infections (strep throat)

Antibiotics Antibiotics are used to clear up bacterial infections. Antibiotics put holes into bacterial cell walls causing them to burst and die.

Viruses Considered to be nonliving because it cannot reproduce on its own General Structure Protein coat on the outside Nucleic acid on the inside (DNA or RNA)

Virus Structure

Examples of Viruses Influenza- the flu HIV- AIDS Varicella- chicken pox & shingles Polio virus- polio Rubella or measles- measles Rhinovirus- cold

Reproductive Cycles Lytic Cycle Virus DNA enters the host cell Hijacks host to make DNA and protein Host cell puts viruses together Cell bursts and releases virus

Lysogenic Cycle Lysogenic Cycle Very similar to lytic cycle Virus DNA is integrated into host cell Cell eventually ruptures with new virus after several generations

Examples of Viruses with a Lysogenic Cycle HIV Herpes Simplex I = Cold sores Herpes Simplex II = Genital herpes Varicella = Chicken pox/ Shingles

Our Immune System Responsible for protecting the body from diseases caused by bacteria and viruses

Lines of Defense 1st line: skin and mucus Skin acts as a barrier Mucus traps microorganisms 2nd line: cells release chemicals blood flow to invaded region increases (swelling) Raises body temperature (fever)

3rd line: Special white blood cells attack invaders foreign antigens are detected and Helper T white blood cells are alerted Helper T cells “activate” white blood cells called B cells B cells multiply and either become plasma cells or Memory B cells Plasma cells produce antibodies that attach to the foreign antigens and “mark” them for destruction Memory B cells stay in the body in case another infection arises

Uh OH!!! What if a cell is already infected?!?!?! Helper T cells alert Killer T cells Killer T cells poke holes in the infected cell to kill it

Types of Immunity Active Immunity Exposed to disease Develop disease and become immune Longer lasting Passive Immunity Injected with antibody that another organism made Not permanent Some vaccines have to be received every year because the pathogen that causes the illness is always mutating!!!