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31.1 Pathogens and Human Illness
KEY CONCEPTGerms cause many diseases in humans.
40.1 Infectious Diseases
31.1 Pathogens and Human Illness
Germ theory states that microorganisms cause diseases.• proposed by Louis Pasteur
40.1 Infectious Diseases
31.1 Pathogens and Human Illness
Disease-causing agents are called pathogens.
Types of pathogens:• Bacteria • Viruses• Fungi• Protozoa• Parasites
Elephantiasis
40.1 Infectious Diseases
31.1 Pathogens and Human Illness
Pathogens can enter the body in different ways.• Pathogens can be transferred by direct or indirect contact.
1) Indirect contact – does not require touching an
infected individual.– touching an infected surface– breathing in infected air– vectors carry a pathogen and
transmit it into healthy cellsvector = a living organism that carries a pathogen
ex: mosquito, fly, flea2) Direct contact
- requires touching an infected individual.
40.1 Infectious Diseases
31.1 Pathogens and Human Illness
Structures of Bacteria
1) Plasmid = circular DNA2) Cell wall = protection3) Chromosomes = long strands of DNA
19.1 Bacteria
31.1 Pathogens and Human Illness
Structures of Bacteria4) Plasma membrane = control what goes in and out5) Pili = hairlike extensions which help bacteria to
attach to a surface6) Flagellum = whiplike tail7) Capsule = protective gel-like layer surrounding
cell wall
40.1 Infectious Diseases19.1 Bacteria
31.1 Pathogens and Human Illness
Characteristics of Bacteria• all are prokaryotic and unicellular• bacteria consist a single circular piece of DNA
called plasmid• some are autotrophic; some are heterotrophic• some bacteria are pathogenic• many are used in food production
40.1 Infectious Diseases19.1 Bacteria
31.1 Pathogens and Human Illness
Bacterial vs. Viral Diseases
• Bacterial Diseases- pathogenic bacteria kill healthy cells by their toxic membrane coat
- can be cured by antibiotics/antiseptics if treated early
40.1 Infectious Diseases19.1 Bacteria
31.1 Pathogens and Human Illness
Bacterial vs. Viral Diseases
• Treatment for Bacterial Diseases1) antibiotics
- for internal use- interfere with bacteria’s ability to reproduce- target specific pathogens- not effective against viruses- ex: penicillin, amoxicillin
40.1 Infectious Diseases19.1 Bacteria
31.1 Pathogens and Human Illness
• 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 carriesgenes for antibioticresistance on a plasmid.
A copy of the plasmid is transferredthrough conjugation.
Resistance is quicklyspread throughmany bacteria.
40.1 Infectious Diseases19.1 Bacteria
31.1 Pathogens and Human Illness
Bacterial vs. Viral Diseases
• Treatment for Bacterial Diseases2) antiseptics
- for external use- do not target the specific pathogen- ex: soap, vinegar
40.1 Infectious Diseases19.1 Bacteria
31.1 Pathogens and Human Illness
Structure of a Virus • Viruses have a simple structure.
– genetic material (DNA or RNA)– capsid = a protein shell – maybe a lipid envelope, a protective outer coat
capsid nucleic acid
lipidenvelope
surfaceproteins
40.1 Infectious Diseases19.2 Viruses
31.1 Pathogens and Human Illness
Characteristics of Viruses1. not considered living because do not have all the
properties of life2. do not metabolize (no cellular respiration)3. not a cell4. do not grow5. do not maintain homeostasis6. they do reproduce – but ONLY inside a host cell7. cause diseases in many organisms 8. viruses are specific for the type of cell they attack
40.1 Infectious Diseases19.2 Viruses
31.1 Pathogens and Human Illness
Bacterial vs. Viral Diseases
• Viral Diseases- cannot be cured by antibiotics/antiseptics- antiviral drugs can slow down viral reproduction, butcannot eliminate them
- some viruses can never be completely eliminated ex: herpes, AIDS, genital warts
40.1 Infectious Diseases19.1 Bacteria
31.2 Immune System
KEY CONCEPT• The immune system is the body system that fights off
infection and pathogens.• The immune system has many responses to
pathogens and foreign cells.
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31.2 Immune System
Nonspecific Responses - do not target a specific pathogen- “innate” immunity (natural)- first line of defense prevents pathogen from entering the body
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31.2 Immune System
Many body systems work to produce nonspecific responses. Examples of Nonspecific responses: 1) skin
- has oils and sweat; acts as a impenetrable barrier2) mucous membranes
- layers of cells that produce sticky material in areas where pathogens might enter (digestive system, nasal passages, lungs and reproductive tract); help totrap pathogens
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31.2 Immune System
Many body systems work to produce nonspecific responses. 3) Inflammatory Response (inflammation)
histamine is released
Causes capillaries to expand and become leaky (red, swollen, hot, painful)
dead tissues form pus
WBC destroys pathogensby phagocytosis
Injury
WBC and platelets move to wounded area
Platelets seal the wound
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31.2 Immune System
Many body systems work to produce nonspecific responses. • Inflammatory Response (inflammation)
Bacteria
Blood vessel
histamine
Pin or splinter Blood clot
Phagocytes
Swelling
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31.2 Immune System
4) Temperature Response (fever)
help to slow down bacterial growth– Fevers stimulate white blood cells to mature and
Many body systems work to produce nonspecific responses.
– Temperature increases when body is infected
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31.2 Immune System
5) Proteins
Many body systems work to produce nonspecific responses.
- fight off invading pathogens– Complement proteins weaken pathogen membranes.– Interferons prevent viruses from infecting healthy cells.
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31.2 Immune System
6) White Blood Cells
Many body systems work to produce nonspecific responses.
- attack infections inside the body
- phagocytes engulf and destroypathogens
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6) White Blood Cells
Many body systems work to produce nonspecific responses.
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31.2 Immune System
Specific Responses
• If the pathogens get past nonspecific response, then body launches the specific immune responses.
• Specific responses- target a specific pathogen- “acquired” immunity (developed)- second line of defense- use lymphocytes (T and B cells) to fight specific pathogens
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31.2 Immune System
Cells of the immune system produce specific responses.
• Specific immune responses begin with the detection of antigens.– Antigens are surface proteins on pathogens.– Each pathogen has a different antigen (very specific)
virus
antigens
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31.2 Immune System
• Two types of specific immune responses1) Cellular immunity
- uses T cells to destroy infected body cells- T cells are lymphocytes that originated in bone marrow and matured in thymus
- three types of T cells:► killer (cytotoxic) T cells = kill pathogens► helper T cells = activate other lymphocytes► suppressor T cells = regulate the number of
lymphocytes
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31.2 Immune System
pathogen
antigens
T cell
receptors activated T cells
antigens
memory T cells
• Two types of specific immune responses1) Cellular immunity
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31.2 Immune System
• Two types of specific immune responses2) Humoral immunity
- uses B cells to produce antibodies- B cells are lymphocytes originated and matured in bone marrow
- two types of B cells:►B plasma cells = produce antibodies that bind to the
antigen making it immovable;“biological handcuffs”!!
►B memory cells = “remember” the antigen and produce immediate responses the2nd time it enters
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31.2 Immune System
• Two types of specific immune responses
2) Humoral immunity
memory B cellsactivated B cells
antibodies
B cell
T cell
pathogen
B cell
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31.2 Immune System
Antigen vs. Antibody
Antigen:• Invading foreign
substance• Pathogen or Toxic
chemical• Elicits immune
response
Antibody:• “anti” =against• Body’s reaction to an
antigen invasion• Blood protein• Made by plasma cells (a
type of B cells)
Green antibodies battle red antigens!
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31.2 Immune System
The immune system rejects foreign tissues.
• Tissue rejection occurs in organ or tissue transplants.• Tissue rejection is the result of an immune response.
– immune system detects protein markers on the donor tissue
– makes antibodies against the donor’s tissue
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31.2 Immune System
Immunity prevents a person from getting sick from a pathogen.
1)Passive immunity - occurs without an immune
response- ex: mother’s milk, genetics
2) Active immunity - occurs after a specificimmune response
- ex: after an infection, you produce immunity againstthat specific pathogen
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31.2 Immune System
Vaccines artificially produce acquired immunity.
• Vaccines also control pathogens and disease.– given to prevent illness– contain the antigen of a weakened pathogen
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31.2 Immune System
Antigens in a vaccinetrigger an immune response, and memory B cells are made.
1memory B cells
A memory B cell isstimulated 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
• Vaccination provides immunity.– stimulates a specific
immune response
– allows immune system to respond quickly to infection
– causes memory cells and antibodies to be produced
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31.2 Immune System
Innate vs. Acquired Immunity
Innate Immunity:• Natural; born with it• Non-specific• WBC: Phagocytes &
Macrophages• Skin, Tears, Saliva,
Mucus, Sweat
Acquired Immunity:• Developed; build up• Specific• Lymphocytes (T, B cells)• Passive / Active immunity
– Active: exposure to pathogen to obtain immunity or vaccination
– Passive: breast milk or injection of antibodies
40.2 The Immune System
31.6 Diseases that Weaken the Immune System
KEY CONCEPTWhen the immune system is weakened, the body cannot fight off disease.
40.3 Immune System Disorders
31.6 Diseases that Weaken the Immune System
AIDS (Acquired Immunodeficiency Syndrome)
• HIV (human immunodeficiency virus)• HIV infection leads to AIDS.
Attacks and destroys helper T cells
Body unable to recognize and attack pathogens
Body unable to fight off secondary infections (flu, pneumonia, etc.)
40.3 Immune System Disorders
31.6 Diseases that Weaken the Immune System
• HIV can stay dormant for a long time without immediately destroying the cell.
• HIV-positive patients usually do not die from HIV, but from the secondary infections they catch because their immune system is not working properly (compromised immune system).
• AIDS is characterized by very low amount of T cells.
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31.6 Diseases that Weaken the Immune System
• HIV can be transmitted through- infected blood- body fluids- birth
40.3 Immune System Disorders
