Doesn’t belong to any kingdom -It’s not a plant or an animal. -It’s not a fungi, protist, or bacteria. WHAT IS A VIRUS?

1) A virus is an infectious agent made up of nucleic acid (DNA or RNA) wrapped in a protein coat called a capsid. Some viruses have an envelope, a lipid bilayer (=membrane w/ two layers) that surrounds the capsid. What is a Virus?

2) Viruses have no nucleus, no organelles, no cytoplasm or cell membrane. They are NOT cells. vs. -This is why they do not belong to any kingdom. Are Viruses Cells?

Are Viruses Living? CriteriaYesKind ofNo Reproduce Energy Use Adapt Cells Homeostasis Nucleic Acids (must have both) Growth Organization 3) √ √ √ √ √ √ √ √

Are Viruses Living? 5) Even though viruses do have genetic material (DNA or RNA) and it can change (adapt), they cannot reproduce on their own, they’re not cells, they cannot maintain homeostasis, they do not grow (rather, they’re “assembled”), and they do not have organization. 4) Are they considered living? No, they would have to meet all 8 qualifications to be considered alive.

Classification of Viruses 6) Viruses can be classified based on: a. Nucleic Acid type (DNA/RNA) b. Shape of Nucleic Acid c. Shape of Capsid d. Presence of Envelope 7)

8) Viruses are like parasites—they depend entirely upon another living organism (= a host) for its existence in such a way that it harms that organism. Hosts Viruses infect both prokaryotic and eukaryotic cells.

Capsid (protein coat) – inside contains either RNA or DNA 9) Bacteriophage—viruses that infect bacteria 10) Influenza and HIV, for example, infects human cells. Surface Marker DNA or RNA Capsid (protein coat)

11) Viral Replication is how a virus makes copies of itself. A virus CANNOT reproduce by itself—it must invade a host cell and take over the cell’s “machinery”, make copies of itself, and eventually will cause the cell to burst (lyses), releasing more viruses. This kills the host cell. DNA/RNA is copied. DNA/RNA injected into cell. Virus attaches to cell. Virus copies itself. Cell bursts (lyses) and releases new viruses. Step 1 Step 2 Step 3 Step 4Step 5 Viral Replication

Viral Transmission 12) Outside the host cell, a virus is a lifeless particle with no control over its movements. It is spread by: Air In water In food By body fluids

13) Many viruses cause disease = pathogenic -Pathogen = disease-causing agent (could be a bacterium, protist, fungus) 14) Human diseases caused by viruses: Warts, common cold, Influenza (flu), Smallpox, Ebola, Herpes, AIDS, Chickenpox, Rabies 15) Some viruses can be prevented with vaccines, but NOT treated with antibiotics (antibiotics treat bacteria). Viruses as Pathogens

Benefit of Viruses 16) Genetic Engineering—harmless virus carries good genes into cells.