Infectious Diseases
What causes them, and
How do we stay healthy?
Standard Organisms have a variety of
mechanisms to combat disease.
10:
• 10A -- Students know the role of the
skin in providing nonspecific defenses
against infection
• 10B -- Students know the role of
antibodies in the body’s response to
infection
• 10C -- Students know how vaccination
protects an individual from infectious
diseases
• 10D -- Know the important differences
between bacteria and viruses (i.e.: their
requirement for growth and replication,
the body’s primary defenses against
bacterial and viral infections, and
effective treatments of these infections)
• 10E -- Know why an individual with a
compromised immune system (ex: a
person with AIDS) may be unable to
fight off and survive infections by
microorganisms that are usually benign
• 10F -- Students know the roles of
phagocytes, B-lymphocytes, and
T-lymphocytes in the immune
system
What is a Virus?
• Nonliving particles that have a nucleic
acid core and a protein-containing capsid.
• Cause disease by disrupting the body’s
homeostasis (balance).
• Don’t exhibit all life criteria:
Don’t carry out respiration
No growth or development
(all they can do is replicate)
• Host Cell – where a virus replicates
• Cannot be killed by antibiotics (medicines)
Viral Structure:
T4 Virus – E. Coli
HERPES
HIV
Influenza – The common Cold
Viral Replication – Lytic Cycle
1. Attachment – attaches to host cell
2. Entry – injects nucleic acid into host
cell
3. Replication – host uses it energy to
replicate viral nucleic acid
4. Assembly – New viruses made (in 30
minutes, 200 new viruses)
5. Lysis and Release – Host cell breaks
open, and virus particles are released
What is Bacteria?
• Small cell with all the structures
necessary to carry out its life functions.
• 2 types of Bacteria:
1. Archaebacteria – inhabit extreme
environments
2. Eubacteria – live almost everywhere
else. (heterotrophs, photosynthetic
autotrophs, and Chemosynthetic
autotrophs)
Structure of Bacteria
• Prokaryotic Cells (typically)
• Contain:
Chromosomes – Single DNA molecule
(no nucleus)
Cell Wall – shape and support
Plasma Membrane – regulates entry and
exit
Pilus – help stick to a surface and bridge
for DNA exchange
Flagellum – Whip-like tail for locomotion
Ribosomes – helps in protein formation
Bacterial Reproduction
• Asexual
Binary Fission –
1. Chromosome replicates, attaches to
plasma membrane
2. Cell grows and splits
• Sexual Reproduction
Conjugation –
Transfers all or part of chromosomes to
another bacteria through its pilus
How do bacteria make you sick?
• Produce disease in one of 2 ways:
1. Damage cells and tissues of the
infected organism directly, by
breaking down the cells for food.
2. Release toxins (poisons) that travel
throughout the body interfering with
homeostasis of the host.
Defense Against
Infectious Diseases
How do we stay healthy?
What is an Infectious Disease?
• Disease = a change that disrupts the
homeostasis in the body
• Pathogens = disease causing agents
(what makes you sick)
Our Bodies Defense Mechanisms:
• Skin – the first line of defense
• Phagocytes, B-lymphocytes, and Tlymphocytes – the 2nd line of defense
• Antibiotics and Vaccines – outside
sources of help
What is the role of Phagocytes?
• Phagocytes – White blood cells that
surround and destroy pathogens.
• Macrophages –
Located in body’s tissues
Giant Scavengers – engulf pathogens and
damaged cells
What if phagocytes don’t help?
• Acquired Immunity – defense against
a specific pathogen by building up
resistance
• Lymphatic System – the body’s system
that is in charge of keeping it healthy
• Uses T-lymphocytes (T-cells) and Blymphocytes (B-cells)
What are T and B cells all about?
Produced in bone marrow
• Helper T-cell – activates B-cells
• Cytotoxic T-cell – “killer T-cells”
produce clones to enter infection site,
release enzymes into pathogens which
causes them to lyse (explode) and die.
• B-cells – turn into antibodies once
activated by T-cells
• Memory B-cells – remain in blood
stream armed and ready for a 2nd attack
What are antibodies?
• Antibodies – proteins produced to react
with and disable antigens
• Antigens – Foreign substances that
stimulate an immune response in the
body
Antigens are displayed on pathogen like
an address (mark pathogens),
Antibodies attach to antigens to help
the body fight the intruder.
What about Antibiotics?
• Substance produced by a
microorganism that kills or inhibits the
growth of other microorganisms
• Use to fight and kill bacteria
• Does NOT work with viruses
Why do you think that is?
How can Vaccinations help?
• Vaccine = substance with weakened,
dead, or incomplete portions of
pathogen (typically a viral pathogen)
• Produces an immune response
• Creates antibodies in the body (T and B
cells)
What are Retroviruses
• Contain RNA instead of DNA
• When cell is infected, it produces
DNA copy of RNA to insert into the
Host Cell’s DNA
• Lays dormant for long time (hidden
from bodies defenses)
• HIV is a retrovirus
• Harder to stop because can undergo
more mutations.
What is HIV and AIDS all about?
• Caused by HIV (Human
Immunodeficiency Virus)
• Compromises your immune system
• Kills white blood cells (Helpers T-Cells)
and can lead to AIDS (Acquired
Immune Deficiency Syndrome)
• HIV contains 2 copies of RNA that
penetrate a cell and hide for months. In
the infected cell, RNA is used to
synthesize viral DNA.