1. 31.1 Pathogens and Human Illness KEY CONCEPT Germs cause many diseases in humans.

2. 31.1 Pathogens and Human Illness Germ theory proposes that microscopic particles or microorganisms cause certain diseases. –proposed by Louis Pasteur –led to rapid advances in understanding disease

3. 31.1 Pathogens and Human Illness Particles are disease-causing agents called pathogens. Supported by Koch’s postulates. Four conditions that prove a pathogen causes a disease

4. 31.1 Pathogens and Human Illness There are different types of pathogens. Bacteria are single-celled organisms. –cause illness by destroying cells –release toxic chemicals

5. 31.1 Pathogens and Human Illness Viruses are genetic material surrounded by a protein coat. –force host cells to make more viruses –very small

6. 31.1 Pathogens and Human Illness Fungi can be multicellular or single-celled. –take nutrients from host cells –occur in warm and damp places

7. 31.1 Pathogens and Human Illness Protozoa are single-celled organisms. –use host cells to complete their life cycles –take nutrients from host cell

8. 31.1 Pathogens and Human Illness Parasites are multicellular organisms. –grow and feed on a host –possibly kill the host

9. 31.1 Pathogens and Human Illness Different pathogen cause common infectious diseases.

10. 31.1 Pathogens and Human Illness Pathogens can enter the body in different ways. Pathogens are spread by Direct contact: requires touching an infected individual Kissingsexual intercourseHand shaking Indirect contact: does not require touching an infected individual touching an infected surface breathing in infected air

11. 18.2 Viral Structure and Reproduction KEY CONCEPT Viruses exist in a variety of shapes and sizes.

12. 18.2 Viral Structure and Reproduction Viruses differ in shape and in ways of entering host cells. Viruses have a simple structure. –genetic material –capsid, a protein shell –maybe a lipid envelope, a protective outer coat capsid nucleic acid lipid envelope surface proteins capsid nucleic acid lipid envelope Surface proteins capsid surface proteins nucleic acid helical (rabies) polyhedral (foot-and-mouth disease) enveloped (influenza)

13. 18.2 Viral Structure and Reproduction Bacteriophages infect bacteria. capsid DNA tail sheath tail fiber

14. 18.1 Studying Viruses and Prokaryotes What are viruses? Are viruses living? Why not?

15. 18.1 Studying Viruses and Prokaryotes Viruses differ from living cells. Living things –Reproduce on their own –Use nutrients and energy –Grow and develop –Respond to the environment viruses 50-200 nm prokaryotics cells 200-10,000 nm prion 2-10 nm viroids 5-150 nm 100 nm 1 nanometer (nm) = one billionth of a meter Viruses are not living because: –Don’t carry out respiration, grow, or develop –Can’t reproduce on their own

16. 18.1 Studying Viruses and Prokaryotes Viruses, bacteria, viroids, and prions can all cause infection. Any disease-causing agent is called a pathogen. viruses 50-200 nm prokaryotics cells 200-10,000 nm prion 2-10 nm viroids 5-150 nm eukaryotics cells 10,000-100,000 nm 100 nm 1 nanometer (nm) = one billionth of a meter

17. 18.1 Studying Viruses and Prokaryotes Differences between the types of small particles Particle or Organism Description Prion Made of proteins only; cause other proteins to fold incorrectly which makes them NOT work No cure; body can not defend against proteins; MAD COW disease Viroid Single stranded DNA or RNA & NO protein coat Disease of plants that passes through seeds or pollen Virus Made of DNA or RNA with a protein coat Must have a host cell to reproduce FLU, HIV, SARS Bacteria Living cell contains DNA & RNA Reproduce easily on their own Salmonella, E coli

18. 18.1 Studying Viruses and Prokaryotes Differences between the types of small particles

19. 18.1 Studying Viruses and Prokaryotes Viruses enter cells in various ways. colored SEM; magnifications: large photo 25,000; inset 38,000x –bacteriophages pierce host cells and inject their DNA into the cell

20. 18.1 Studying Viruses and Prokaryotes –viruses of eukaryotes enter by endocytosis Viruses enter cells in various ways.

21. 18.1 Studying Viruses and Prokaryotes –viruses of eukaryotes also fuse with membrane Viruses enter cells in various ways.

22. 18.2 Viral Structure and Reproduction host bacterium The bacterophage attaches and injects it DNA into a host bacterium. The host bacterium breaks apart, or lyses. Bacteriophages are able to infect new host cells. The viral DNA directs the host cell to produce new viral parts. The parts assemble into new bacteriophages. The viral DNA forms a circle. Viruses cause two types of infections. A lytic infection causes the host cell to burst. The virus may enter the lysogenic cycle, in which the host cell is not destroyed.

23. 18.2 Viral Structure and Reproduction A lysogenic infection does no immediate harm. The viral DNA is called a prophage when it combines with the host cell’s DNA. Although the prophage is not active, it replicates along with the host cell’s DNA. Many cell divisions produce a colony of bacteria infected with prophage. The prophage may leave the host’s DNA and enter the lytic cycle.

24. 31.2 Immune System KEY CONCEPT The immune systems consists of organs, cells, and molecules that fight infections. The immune system is the body system that fights off infection and pathogens

25. 31.2 Immune System Many body systems protect you from pathogens. Many other tissues and systems help the immune system. –Skin is a physical barrier to infection. –Mucous membranes trap pathogens entering the body. –The circulatory system transports immune cells.

26. 31.2 Immune System Cells and proteins fight the body’s infections. White blood cells attack infections inside the body. –Phagocytes engulf and destroy pathogens. –T cells destroy infected cells. –B cells produce antibodies.

27. 31.2 Immune System Three types of proteins fight off invading pathogens. –Complement proteins weaken pathogen membranes. –Antibodies make pathogens ineffective. –Interferons prevent viruses from infecting healthy cells. antibody pathogens

28. 31.2 Immune System Immunity prevents a person from getting sick from a pathogen. Passed through genetics Or through mother’s milk Acquired after the body undergoes a specific immune response Prevent future illness if the body becomes infected

29. 18.3 Viral Diseases KEY CONCEPT Some viral diseases can be prevented with vaccines.

30. 18.3 Viral Diseases Viruses cause many infectious diseases There are many examples of viral infections. –common cold

31. 18.3 Viral Diseases –influenza Viruses cause many infectious diseases There are many examples of viral infections. –common cold

32. 18.3 Viral Diseases –influenza Viruses cause many infectious diseases There are many examples of viral infections. –common cold –SARS

33. 18.3 Viral Diseases –HIV HIV-infected white blood cell Viruses cause many infectious diseases There are many examples of viral infections. The body has natural defenses against viruses.

34. 18.3 Viral Diseases Vaccines are made from weakened pathogens. A vaccine stimulates the body’s own immune response. Vaccines prepare the immune system for a future attack. Vaccines are the only way to control the spread of viral disease.

35. 18.6 Bacterial Diseases and Antibiotics KEY CONCEPT Understanding bacteria is necessary to prevent and treat disease.

36. 18.6 Bacterial Diseases and Antibiotics Some bacteria cause disease. Bacteria cause disease by invading tissues or making toxins. A toxin is a poison released by an organism.

37. 18.6 Bacterial Diseases and Antibiotics Normally harmless bacteria can become destructive. –may colonize new tissues

38. 18.6 Bacterial Diseases and Antibiotics –immune system may be lowered Normally harmless bacteria can become destructive.

39. 31.4 Immunity and Technology KEY CONCEPT Living in a clean environment and building immunity help keep a person healthy.

40. 31.4 Immunity and Technology Many methods are used to control pathogens. Antibiotics and antiseptics cause pathogens to burst.

41. 31.4 Immunity and Technology Antiseptics kill pathogens outside of the body. –do not target specific pathogens –examples include vinegar and soap Antibiotics kill pathogens inside the body. –target one specific bacterium or fungus –not effective against viruses –Vaccines help to identify and make viruses ineffective –Given to a person to prevent illness –Can be made of dead or weakened virues

42. 31.4 Immunity and Technology Antibiotic resistance can cause medicines to become ineffective. –Some bacteria in a population have genes that make them immune to antibiotics. –These bacteria spread the gene, making the antibiotics useless. A bacterium carries genes for antibiotic resistance on a plasmid. A copy of the plasmid is transferred through conjugation. Resistance is quickly spread through many bacteria.

43. 31.4 Immunity and Technology Vaccines artificially produce acquired immunity. Vaccines also control pathogens and disease. –given to prevent illness –contain the antigen of a weakened pathogen

44. 31.4 Immunity and Technology Vaccination provides immunity. –stimulates a specific immune response –allows immune system to respond quickly to infection –causes memory cells to be produced –has such a fast response, a person will not get sick A memory B cell is stimulated when the real pathogen binds to it. 2 The B cell quickly activates and makes antibodies that fight the pathogens before you get sick. 3 Antigens in a vaccine trigger an immune response, and memory B cells are made. 1 memory B cells