1. UNIT 4 BACTERIA, VIRUSES & THE IMMUNE SYSTEM 1

2. BACTERIA 2

3. BACTERIA Bacteria are prokaryotes: 1.Single-celled 2.No nucleus 3.Cell wall and cell membrane 4.Cytoplasm w/DNA 5.R ibosomes 3

4. BACTERIA Are the smallest and most common microorganisms Are the first organisms to inhabit Earth nearly 3.5 billion yrs ago Are divided into 2 kingdoms: A. Archaebacteria B. Eubacteria 4

5. Kingdom Kingdom Archaebacteria vs Eubacteria More primitive Live in harsh environments DNA very similar to eukaryotes Generally not pathogenic Less primitive Live in many different environments DNA is least like other 5 kingdoms Many pathogenic members 5

6. IDENTIFYING BACTERIA 1. Shape: A.Bacilli: rod-shaped B.Cocci: spherical C.Spirilla: spiral or corkscrew 2. Movement 6

7. HOW BACTERIA OBTAIN ENERGY Autotrophs: ◦ Use energy source to convert CO 2 & H 2 O to sugar and oxygen ◦ Photosynthetic – use sunlight ◦ Chemosynthetic – use chemicals (like methane) 7

8. HOW BACTERIA OBTAIN ENERGY Heterotrophs: ◦ Take in organic molecules for a supply of energy and carbon ◦ Types:  Decomposers  Parasites 8

9. HOW BACTERIA RELEASE ENERGY Anaerobes - oxygen will kill them (use fermentation to get energy) Aerobes - must have oxygen to release energy (use cellular respiration) Some can do both 9

10. HOW BACTERIA GROW & REPRODUCE Growth is controlled by: 1.Available food 2.Amount of waste produced 3.Available space 10

11. HOW BACTERIA GROW & REPRODUCE Reproduction: 1. Binary fission - the cell reaches a certain size & divides (mitosis) 2. Conjugation - 2 bacteria exchange genes with each other before they divide 3. Budding - new bacteria grows from side of original 11

12. BACTERIAL SEX? 12 Binary Fission Budding Conjugation

13. ENDOSPORES A thick wall around the DNA and part of the cytoplasm Forms when conditions are not good for reproducing Can protect the bacteria indefinitely 13

14. IMPORTANCE OF BACTERIA 1. Provide O 2 through photosynthesis 2. Decompose dead matter & recycle materials back into environment 3. Human Uses: A.Wastewater treatment B.Live in a symbiotic relationship with organisms in their digestive tracts C.Used in production of food 14

15. BACTERIA & THE NITROGEN CYCLE Nitrogen fixation – some bacteria take nitrogen gas from the atmosphere and “fix” (convert) it into ammonia so plants can use it Denitrification – some bacteria return “waste” nitrogen to the atmosphere 15

16. BACTERIA & THE NITROGEN CYCLE 16

17. BACTERIA & DISEASE Ways bacteria invade the body 1.A cut in the skin 2.Inhaled into lungs 3.Swallowed 17

18. BACTERIA & DISEASE How bacteria cause disease: 1.Release toxins that disrupt normal body functions 2.Break down cells inside body Antibiotics - chemicals that slow or prevent bacterial cell growth by preventing it from forming a cell wall 18

19. VIRUSES 19

20. VIRUSES Are a core of DNA or RNA (not both) Have 1000’s of different shapes Much smaller than bacteria Have a specific host cell Have a capsid (protein coat) 1.Protects genetic material 2.Allows virus to bind to the host cell and “trick” the cell into letting the virus in 20

21. VIRUSES Why scientists do not consider them living: 1.No cytoplasm 2.No internal metabolism 3.Cannot grow and divide 4.Reproduce only by infecting living cells 21

22. SOME EXAMPLES OF VIRUSES: 22 Bacteriophage Tobacco Mosaic Influenza - General Avian Flu

23. TYPES OF VIRAL INFECTIONS Lytic Infection 1. Virus enters cell 2. Makes multiple copies of itself 3. Cell bursts and send thousands of copies into the organism to infect other cells 23

24. Lysogenic Infection: 1. Virus enters cell 2. It inserts its DNA into the host cell’s DNA 3. Cell and virus reproduce together, sometimes for years 4. Something triggers the virus to become active 5. It becomes lytic 24

25. SPECIAL VIRUS TYPES Retroviruses - contain RNA instead of DNA for genetic info ◦ Infect cell and produce DNA copies until becoming active and destroying cell ◦ Cancer and HIV are examples 25

26. SPECIAL VIRUS TYPES Some viruses are beneficial: ◦ Bacteriophages - invade bacterial cells ◦ Can be used for gene therapy - virus delivers gene to cell 26

27. THE IMMUNE SYSTEM & DISEASE 27

28. SECTION 1 - INFECTIOUS DISEASE 28

29. Disease - any change, other than injury, that disrupts homeostasis Pathogens: disease-causing agents 1. Bacteria 2. Viruses 3. Fungi 4. Environmental Toxins 29

30. Preventing bacterial disease: 1.Vaccine – injection of weakened/killed pathogen; helps body produce immunity to disease 2.Antibiotics – block growth/reproduction of bacteria Controlling Bacteria: 1.Heat sterilization 2.Disinfectants 3.Proper food storage/preparation 30

31. Controlling viral diseases: 1.Vaccines 2.Treat with antivirals 3.Best protection is prevention 31

32. How Diseases are Spread Physical contact - coughing, sneezing or direct contact Sexual contact Contaminated food and water Undercooked or improperly prepared meat Infected animals - called vectors 32

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34. SECTION 2 – THE IMMUNE SYSTEM 34

35. CHARACTERISTICS Recognizes, attacks, destroys and “remembers” each type of pathogen that enters the body Produces specialized cells to inactivate pathogen – called immunity 2 general categories of defenses against disease – specific and non-specific 35

36. Nonspecific Defenses Do not discriminate between one threat and another First line of defense: skin, mucus, sweat and tears; skin is the most important of these 36

37. Second line of defense: Inflammatory Response - white blood cells are sent to sight of infection; causes area to become swollen and painful Fever – elevated body temperature; slows or stops the growth of pathogens; allows the white blood cells to work better 37

38. Specific Defenses Immune response - specific defenses that attack an antigen (disease-causing agent) Antigen - substance that triggers response 38

39. Immunity WBC’s make lymphocytes (antibodies) 1. B lymphocytes ◦ Body’s main defense from outside invaders 2. T lymphocytes ◦ Body’s main defense against its own cells when they become cancerous or infected 39

40. Acquired Immunity Active immunity - body is directly exposed to live pathogen 1.Stimulates the production of antibodies 2.Long term protection from pathogen 3.Examples: MMR & tetanus shots or getting chicken pox 40

41. Acquired Immunity Passive immunity - body is not directly exposed to live pathogen 1.Antigens produced by other animals are directly injected into the bloodstream 2.Examples: rabies, malaria, flu 3.Consumption of breast milk 4.Temporary protection from pathogen 41

42. SECTION 3 – IMMUNE SYSTEM DISORDERS 42 HIV Budding from a Helper T cell

43. Allergies Most common overreaction of immune system Antigens that cause allergic reactions are called allergens (dust, mold, pollen, stings) 43

44. Steps of Allergic Reactions 1. Allergens enter body 2. Mast cells (specialized immune cells) release histamine 3. Histamine increases blood and fluid flow to affected area Antihistamines counteract the affects of histamine 44

45. Autoimmune Diseases When the immune system makes a mistake and attacks the body’s own healthy cells 1.Rheumatoid arthritis – antibodies attack connective tissue around joints 2.Multiple sclerosis – antibodies destroy the myelin sheaths of the neurons in the brain and spinal chord 45

46. AIDS, an Immunodeficiency Disease HIV virus attacks helper T cells (makes individual HIV positive); HIV is a retrovirus, its genetic material is RNA that is copied into the T cell’s DNA Cells die and the immune system response starts to break down As virus progresses to AIDS, the body starts to become vulnerable to any type of pathogen that it encounters 46

47. HIV is transmitted in one or more of four main ways 1. ANY form of sexual contact with an infected person 2. Shared needles or syringes that have come in contact with the blood of an infected person 3. Contact with blood or blood products from an infected person 4. Infected mother to child 47