Transcript chapter 19 - Alvin ISD

UNIT 4
BACTERIA ,VIRUSES & THE
IMMUNE SYSTEM
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BACTERIA
Prokaryotes are the smallest and most
common microorganisms
 Single celled organisms; no nucleus; have
ribosomes
 Divided into 2 kingdoms:
A. Archaebacteria
B. Eubacteria
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Archaebacteria
Smaller, more
“primitive” of 2
kingdoms
 Live in harsh
environments – ice,
volcanoes, hot springs
 DNA very similar to
eukaryotes
 Generally not
pathogenic
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Eubacteria
Larger, less “primitive”
of 2 kingdoms
 Organisms have many
different lifestyles
 This kingdom’s DNA is
most different from all
others
 Many pathogenic
members
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IDENTIFYING PROKARYOTES
Shape:
1. Bacilli: rod-shaped
2. Cocci: spherical
3. Spirilla: spiral and corkscrew
 Movement:
1. No movement
2. Flagella propel them forward
3. Glide along a slime-layer
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HOW THEY GET THEIR ENERGY
Autotrophs:
Use sunlight or chemicals (like methane)
to convert CO2 & H2O to sugar and
oxygen
 Heterotrophs:
Take in organic molecules for a supply of
energy and carbon
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HOW THEY RELEASE ENERGY
Aerobes: must have oxygen to release
energy
 Anaerobes: do not need (and might be
killed by) oxygen
 Some bacteria can live in both
environments which allows them to live
almost anywhere
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HOW THEY GROW AND
REPRODUCE
Growth:
Controlled by availability of food and
amount of waste production
 Reproduction:
1. Binary fission-when the cell reaches a
certain size it divides (mitosis)
2. Conjugation-when bacteria exchange
genes with each other before they divide
3. Budding-new bacteria grows from side of
original
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Binary Fission
Budding
Conjugation
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Eubacteria are able to form an endospore
when they are not in a favorable
condition to reproduce
 This is a thick internal wall around the
DNA and a portion of the cytoplasm
 The endospore can protect the bacteria
indefinitely
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IMPORTANCE OF BACTERIA

Decomposers – break down organic
material and recycle materials back into
environment
Found in soil and water
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IMPORTANCE OF BACTERIA

Nitrogen fixers – certain bacteria take
nitrogen gas from the atmosphere and
convert it into a form plants can use
Critical part of nitrogen cycle
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IMPORTANCE OF BACTERIA

Human Uses:
1. Wastewater treatment
2. Live in a symbiotic relationship with
organisms in their digestive tracts
3. Used in production of food
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VIRUSES
Viruses are a core of DNA or RNA (not
both)
 They are surrounded by a protein coat capsid
 Can reproduce only by infecting living cells
 Are submicroscopic – cannot be seen with a
light microscope
 Viruses have a specific host cell
 Capsid allows virus to bind to the host cell
and “trick” the cell into letting the virus in
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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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Retroviruses – some viruses 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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THE IMMUNE SYSTEM AND
DISEASE
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Section 1 - Infectious Disease
Disease – any change, other than injury, that
disrupts the normal functions of the body
 Germ theory of disease – infectious diseases
are caused by microorganisms of different
types; commonly called germs
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Pathogens – disease causing agents; the
human body provides just the right
environment for growth of these agents
1. Bacteria
2. Viruses
3. Fungi
4. Environmental Toxins
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Disease
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A.
B.
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A.
B.
Bacteria produce disease by:
Directly breaking down cells for food
Releasing toxins that travel through host
Preventing bacterial disease:
Vaccine – injection of weakened/killed
pathogen; helps body produce immunity to
disease
Antibiotics – block growth/reproduction of
bacteria
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C.
Controlling Bacteria:
Heat sterilization
Disinfectants
Proper food storage/preparation
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1.
2.
3.
Viral Diseases:
Disrupt organism’s homeostasis
Treated with antivirals
Best protection is prevention
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A.
B.
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How Diseases are Spread
Physical contact - coughing, sneezing or
direct contact
Some of the most dangerous pathogens are
spread through sexual contact
 Contaminated food and water –
undercooked or improperly prepared meat;
raw sewage in water supply
 Infected animals – called vectors
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Section 2 – The Immune System
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
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Do not discriminate between one threat and
another
First line of defense: skin, mucus, sweat and
tears; skin is the most important of these
Second line of defense:
1. Inflammatory Response - millions of white
blood cells are made and sent to sight of
infection; causes area to become swollen and
painful
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2. 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
If a pathogen is able to get past the
nonspecific defenses, the immune system
reacts with a series of specific defenses that
attack a particular disease-causing agent
 This process is called immune response
 The substance that triggers this response is
called an antigen
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Two types of lymphocytes (B cells and T
cells) recognize specific antigens
1. Humoral immunity – immunity against
antigens and pathogens in the body fluids;
(B cells)
Produced in bone marrow from stem cells
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2. Cell-mediated immunity – immunity against
abnormal cells living inside of living cells;
(T cells)
Body’s main defense against its own cells
when they become cancerous or infected
Recognize cells that are defective/foreign and
destroy them
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Killer T-Cell (upper right) attacking a cancer
cell
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Acquired Immunity
Active immunity – body is injected with a
vaccine to stimulate the production of
antibodies; long term protection from
pathogen (MMR & tetanus shots)
 Passive immunity – antigens produced by
other animals that are directly injected into
the bloodstream; temporary protection from
pathogen (rabies, malaria, flu)
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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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When allergens enter body they attach
themselves to mast cells, specialized immune
cells that initiate an inflammatory response
Mast cells release histamine which increases
blood and fluid flow to affected area
Antihistamines counteract the affects of
histamine
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Autoimmune Diseases
When the immune system makes a mistake
and attacks the body’s own healthy cells
A.
Rheumatoid arthritis – antibodies attack
connective tissue around joints
B.
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);
 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
 HIV is a retrovirus, its genetic material is
RNA that is copied into the T cell’s DNA
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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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Facts About AIDS
There is NO cure for AIDS; new drugs make it
possible to live longer with the disease. This
does not prevent you from dying from AIDS
related diseases, it just slows down when it
will happen!
 The only no-risk sexual behavior with respect
to HIV and AIDS is abstinence!
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In one year, more than 5 million people
worldwide became infected with HIV,
including ~ 800,000 people under 15
 In that same year, 3 million people died from
complications of AIDS
 This brought the total number of deaths
around the world to more that 20 million
people
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