Download bacteria - Alvin ISD

UNIT 4
BACTERIA ,VIRUSES & THE
IMMUNE SYSTEM
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BACTERIA
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BACTERIA

Bacteria are prokaryotes:
1. Single-celled
2. No nucleus
3. Cell wall and cell membrane
4. Cytoplasm w/DNA
5. Ribosomes
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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

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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

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IDENTIFYING BACTERIA
1.
2.
Shape:
A. Bacilli: rod-shaped
B. Cocci: spherical
C. Spirilla: spiral or corkscrew
Movement
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HOW BACTERIA OBTAIN ENERGY

Autotrophs:
◦ Use energy source to convert CO2 &
H2O to sugar and oxygen
◦ Photosynthetic – use sunlight
◦ Chemosynthetic – use chemicals (like
methane)
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HOW BACTERIA OBTAIN ENERGY

Heterotrophs:
◦ Take in organic molecules for a supply
of energy and carbon
◦ Types:
 Decomposers
 Parasites
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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

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HOW BACTERIA GROW &
REPRODUCE
 Growth
is controlled by:
1. Available food
2. Amount of waste produced
3. Available space
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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

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BACTERIAL SEX?
Binary Fission
Budding
Conjugation
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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

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IMPORTANCE OF BACTERIA
1.
2.
3.
Provide O2 through photosynthesis
Decompose dead matter & recycle
materials back into environment
Human Uses:
A. Wastewater treatment
B. Live in a symbiotic relationship with
organisms in their digestive tracts
C. Used in production of food
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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

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BACTERIA & THE NITROGEN
CYCLE
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BACTERIA & DISEASE

Ways bacteria invade the
body
1. A cut in the skin
2. Inhaled into lungs
3. Swallowed
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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

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VIRUSES
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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

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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
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SOME EXAMPLES OF VIRUSES:
Bacteriophage
Tobacco Mosaic
Avian Flu
Influenza General
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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
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
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
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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
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SPECIAL VIRUS TYPES

Some viruses are
beneficial:
◦ Bacteriophages invade bacterial cells
◦ Can be used for gene
therapy - virus
delivers gene to cell
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THE IMMUNE SYSTEM
& DISEASE
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SECTION 1 INFECTIOUS DISEASE
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Disease - any change, other than injury, that
disrupts homeostasis
 Pathogens: disease-causing agents
1. Bacteria
2. Viruses
3. Fungi
4. Environmental Toxins

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
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
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
Controlling viral diseases:
1. Vaccines
2. Treat with antivirals
3. Best protection is prevention
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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

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SECTION 2 – THE
IMMUNE SYSTEM
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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

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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

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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
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Specific Defenses
Immune response - specific defenses that
attack an antigen (disease-causing agent)
 Antigen - substance that triggers response

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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
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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
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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
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SECTION 3 – IMMUNE
SYSTEM DISORDERS
HIV
Budding from a
Helper T cell
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Allergies
Most common overreaction of immune
system
 Antigens that cause allergic reactions are
called allergens (dust, mold, pollen, stings)

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Steps of Allergic Reactions
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
1.
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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
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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

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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
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