Antibodies, Antigens, Pathogens,
Viruses, and Disease
Lecture for WK: 04/17—04/20
Last Week You Learned:
• 10a: The role of the skin and how it protects
the human body, especially against infection
• Let’s briefly review! YOU SHARE:
• -Integumentary System
• -Roles of Integumentary System
This Week, You Will Learn:
• 10b: Understand the role of antibodies and
how they respond to infections
• **Note: This PowerPoint focuses only on standard 10b
• 10c: Understand how vaccination protects
individuals from infectious diseases
• **Note: On Thursday, we will have a second PowerPoint for
standard 10c
ANTIBODIES
• Antibodies are proteins that recognize and bind to antigens. When
the antibodies bind to antigens on pathogens, the pathogens are
destroyed.
• Vaccines are injections of weakened or mild forms of a pathogen to
produce immunity. Function: Vaccinations stimulate the production
of antigens, preventing bacterial and viral infections.
• VOCABULARY TO KNOW:
-Antibody: A protein that helps destroy pathogens
-Antigens: A substance that triggers an immune response—triggers the
production of antibodies
-Pathogens: disease causing agent
Think of the Antibody and the Antigen as a “lock and key,” you need
the two in order to kill off the pathogen, which is what causes the
infection.
Source: Prentice Hall, Biology (Miller, Levine)
Source: Google Images
Real Life Example
• A farmer’s crop is infected with a disease.
• Result: The leaves of this crop begin to grow
pale spots. Eventually, the disease turns the
leaf yellow and the plant eventually dies.
• What is causing this disease?
•A virus!!!!
Source: Prentice Hall, Biology (Miller, Levine)
What Is A Virus?
• A VIRUS IS ALSO KNOWN AS A PARASITE—
It needs to “freeload” from another living cell in order to carry
out its evil master plan
• Characteristics: Viruses are not alive; they are particles of
nucleic acid, protein, and lipids. They are different in size
and structure
• Function: Viruses all have in common one thing— they
enter living cells and, once inside, use the machinery of
the infected cell to produce more viruses—viruses take
advantage of the living cell’s respiration, nutrition, and all
other important functions
• A typical virus is composed of a core DNA or RNA
surrounded by a protein coat.
Source: Prentice Hall, Biology (Miller, Levine)
This is an example of a VIRUS
The CAPSID is the protein coat, which enables entry into the
host cell
Source: Google Images
How Viruses Work
• A virus must bind to the proteins on the cell
surface.
• Translation: The virus, which is dead,
“freeloads” from the living cell and uses its
organelles to carry out its basic functions, like
“transcribing” and “translating” its genetic
code, thus causing the virus to multiply
• Plant viruses infect plant cells and animal
viruses infect animal cells
Source: Prentice Hall, Biology (Miller, Levine)
Viral Infection
• THERE ARE TWO MAIN TYPES OF INFECTIONS,
WHICH WE WILL LEARN ABOUT NEXT!
• 1. Some may replicate and immediately kill
the “host” cell (Lytic)
• 2. Others may replicate in a way that doesn’t
kill the “host” cell right away (Lysogenic)
Source: Prentice Hall, Biology (Miller, Levine)
A.) LYTIC INFECTION
• In a lytic infection, a virus enters a cell, makes copies of
itself, and causes the cell to burst.
• HOW?
Virus enters the host cell; the host cell cannot tell the
difference between its own DNA and the DNA of the virus,
next, the cells begin to make messenger RNA from the
genes of the virus. The DNA of the virus is like a “thug”
because it corrupts the host cell’s DNA. This results in the
shut down of that host cell—so basically, the virus makes
the host cell its B&*%#!!!
• KEY: Virus=Thug; Host Cell=B*&^%)
• In this manner, the virus begins to replicate its own DNA
molecule inside the host cell—(formation of a new “gang”)
Source: Prentice Hall, Biology (Miller, Levine)
IMAGE
Source: Google Images
B.) LYSOGENIC INFECTION
• In a lysogenic infection, the virus integrates its
DNA into the DNA of the host cell, and the
viral genetic information replicates along with
the host cell’s DNA.
• How does this differ from the Lytic Infection?
Unlike lytic viruses, lysogenic viruses do not kill off—
or take over the host cell right away—these viruses stay
“inactive” for some time before forming their own
“gang”
Source: Prentice Hall, Biology (Miller, Levine)
WHAT’S A PROPHAGE?
• The viruses’ DNA that enters the host cell’s
DNA is called a prophage
• This prophage is the “new” kind of DNA inside
the host cell, and it remains inactive for time.
• Eventually the DNA of that prophage may
“activate,” leave the host cell, and make new
virus particles
Source: Prentice Hall, Biology (Miller, Levine)
IMAGE
Source: Google Images
RETROVIRUSES
• These viruses contain RNA as their genetic
information.
• -A helpful way to remember this: Retrovirus starts
with an “R” and contains “R”NA
• When a retrovirus infects a cell, it produces a
DNA copy of its RNA. Like a prophase, it enters
the host cell and “chills” there inactive until later
on when it becomes active
• Interesting Fact: the virus that causes AIDS is a Retrovirus!!!
Source: Prentice Hall, Biology (Miller, Levine)
DEBATE:
•Is a virus alive?
*Why or why not?
NO, Viruses Are Not Alive…
• It is not made up of living cells; in order to
carry out its evil mission, viruses must
freeload from the host cell.
• They cannot grow or develop alone
• They do not react to the environment
Source: Prentice Hall, Biology (Miller, Levine)
Yes, Viruses Are Alive…
• Because they have many “live” characteristics,
like their ability to reproduce, evolve, and
regulate genes
• They change over time
• They alter DNA and RNA
Source: Prentice Hall, Biology (Miller, Levine)