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)