Chapter 19
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Chapter 19. Bacteria and Viruses. Remember homeostasis?. Maintaining proper internal conditions pH, temp., water/salt balance, O2, CO2, etc. Factors for Disease. 1. genetics- inheritance 2. microorganisms pathogen : disease-causing agent 3. pollutants/poisons (ex: asbestos, lead)

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Chapter 19

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Chapter 19

Chapter 19

Bacteria and Viruses


Remember homeostasis

Remember homeostasis?

  • Maintaining proper internal conditions

  • pH, temp., water/salt balance, O2, CO2, etc.


Factors for disease

Factors for Disease

  • 1. genetics- inheritance

  • 2. microorganisms

    • pathogen: disease-causing agent

  • 3. pollutants/poisons (ex: asbestos, lead)

  • 4. organ malfunction

  • 5. harmful lifestyles (tobacco, alcohol, lack of nutritionor exercise)


19 1 bacteria

19-1 Bacteria

  • Prokaryotes

  • Monera

  • Can be beneficial or disease-causing

    • Good: intestinal bacteria

    • Bad: strep throat, pneumonia

  • Everywhere!


Identified by

Identified by:

  • Shape- bacilli (rod), cocci (round), spirilla (spiral)

  • Cell walls- Gram +/- (peptidoglycan)

  • Movement- flagella, slime

  • Metabolic diversity- heterotrophs and autotrophs (chemo- or photo-)


Bacteria e nergy production

Bacteria Energy Production

  • Respiration or fermentation (with or without O2)

  • Obligate aerobes: needs O2 to live

  • Obligate anaerobes: cannot live with O2

  • Facultative anaerobes: can live with or without O2


Bacteria reproduction

Bacteria Reproduction

  • Binary fission: (asexual) DNA is replicated and the organism splits in half

  • Conjugation:(sexual) genetic info is exchanged across a “bridge”

  • Spore formation: haploid cell that can withstand hard conditions and form a new organisms when the time is right


Importance of bacteria

Importance of Bacteria

  • Decomposers- break things down

  • Nitrogen fixation- cycles N thru atmosphere

  • Human uses: food, oil spills, medicine, intestines


Treating bacteria

Treating Bacteria

  • Bacteria have homeostasis too! Change the conditions to stop growth

    • Temp, salt, pH, etc.

  • Sterilization (heat), disinfection (chemicals)

  • Antibiotics- kill bacteria or stop reproduction


19 2 viruses

19-2 Viruses

  • Categorized by what they infect:

    • Plant, animal, bacteriophage

  • Capsid- protein coat- signifies which host to infect (host must have a receptor)

  • NOT alive- has genetic material but can’t repro on own

  • Ex: flu virus, HIV


Virus replication

Virus Replication

  • Lytic: enters host cell, copies itself continuously and bursts (lyses)

  • Lysogenic: combines/replicates viral DNA with host DNA

    • Prophage: viral DNA embedded within host DNA


Treating viruses

Treating Viruses

  • Antibiotics WILL NOT work!

  • Prevention is key!

  • Vaccination: inject a weak form of a virus in order to get the antibodies (immunity)


The body s defense system

The Body’s Defense System

  • homeostasis=includes regulating microbes

  • Lines of defense:

  • 1. physical barriers- block entry (skin)

  • 2. inflammation- increased blood flow

  • 3. immune system


Immune system

Immune System

  • Recognizes the “bad guys”

  • Every bacteria/virus has antigens (proteins)

  • Immune system makes antibodies

  • Antibodies fight the antigens

  • Vaccines- shows antigens ahead of time- allows body to create antibodies (immunity)


White blood cells wbcs

White Blood Cells (WBCs)

  • Immune system MVP

  • 2 types:

  • 1. B cells: make antibodies

    • Memory B cells

  • 2. T cells:

    • Killer T cells: kill infected cells

    • Helper T cells*: help all other WBCs


When the immune system goes wrong

When the immune system goes wrong…

  • Allergic reactions- increase in system- produces histamines

  • Autoimmune diseases- system attacks self

  • Immunodeficiency- decrease in system- helper T cells destroyed (ex: AIDS)

  • inflammation- older people


Other pathogens

Other Pathogens

  • Protozoa- unicellular parasites

  • Algae/Dinoflagellates- produce toxins

    • ex: red tide

  • Fungi- athletes foot, ringworm

  • Parasitic Worms- tapeworm


Viroids and prions

Viroids and Prions

  • Viroids: single stranded RNA molecules enter infected cells

  • Prions: tiny protein particles enter the brain and affect the nervous system- no DNA/RNA

    • Ex: mad cow disease


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