Bellwork: 2/4/15 Copy the question and the answer Both euglena and cyanobacteria are photosynthetic unicellular organisms found in pond water. The feature that distinguishes euglena from cyanobacteria is the — A ability to maintain homeostasis B presence of ribosomes C ability to reproduce D presence of a nuclear membrane

Bellwork

Happy Tuesday Bellwork Draw and Label the viruses above using the following terms: Capsid, DNA/RNA, Envelope.

Happy Tuesday Bellwork DNA RNA CAPSID RNA CAPSID CAPSID ENVELOPE Draw and Label the viruses above using the following terms: Capsid, DNA/RNA, Envelope.

Anticipation Guide: Discuss the following statements with a partner Anticipation Guide: Discuss the following statements with a partner. Determine if you think they are true or false. Viruses affect us just like bacteria. Viruses have DNA. Viruses can be cured by antibiotics. Viruses are not alive. Being a zombie is caused by a virus.

Viruses

OVERVIEW

Vocabulary Viruses: are noncellular or acellular infectious agents Virology: study of viruses Virologists: scientists who study viruses Virion: An intact viral particle

Cellular Organisms vs Acellular Particles Eukaryotic Cell Virus Prokaryotic Cell Prokaryotes Eukaryotes Viruses Eukaryotic Nucleus 1 ųm (1000 nm)

Viruses range in size from 20 nanometers (nm) – 250 nanometers (nm) 1 nm = 0.00000004 inches If a cell was the size of your classroom, then an average virus would be the size of a softball. proteins animal cells atom viruses bacteria 0 m 10-6 m 10-5 m 10-7 m 10-8 m 10-9 m Go five more feet! 10-10 m A virus’ size helps it to reproduce. We’ll talk about this tomorrow.

Viral Size 20 nm to 1,000 nm .02 u to 1 u

Viral components Spikes Nucleic acids DNA or RNA Capsid Protein Envelope Lipid Spikes Used to attach to cell ONLY SOME VIRUSES

Generalized Structure of Viruses virions having envelopes = enveloped viruses virions lacking envelopes = naked viruses

Generalized Structure of Viruses

Helical Capsids RNA Helical capsids are rod-like structures with the RNA in the center of the helix. A helix is made by stacking repeating units in a spiral. protein coat

Tobacco Mosaic Virus Tobacco Mosaic Virus (TMV) is an example of a virus with a helical structure. Protein subunits wrap around the spiraling RNA strand. This image taken using an Electron Microscope

Adenoviruses cause diseases like pink-eye or the common cold

Bacteriophage is a virus that infects bacteria.

Enveloped Viruses Enveloped viruses are viruses which have a membrane coat surrounding the protein coat or capsid. These viruses are common in animal viruses, but are uncommon in plant viruses. Herpes Simplex Virus. A membrane (made of proteins) surrounds the capsid (also made of proteins) which surrounds the viral DNA.

Viruses are highly specific to the cells they infect. Examples: Viruses are highly specific to the cells they infect Examples: 1) plant viruses infect plant cells 2) animal viruses infect only certain related species of animals 3) bacterial viruses (bacteriophage) infect only certain types of bacteria. So, what about zombies?

Think-Pair-Share Are viruses alive? (Justify your answer)

Viruses have both living and nonliving characteristics. Living characteristics of viruses: They reproduce at a fantastic rate, but only in living host cells. They can mutate. They contain DNA or RNA

Nonliving characteristics of viruses: They are acellular, they contain no cytoplasm or cellular organelles. They are not made of cells. They carry out no metabolism on their own and must replicate using the host cell's metabolic machinery. They do not grow or develop

Viruses are NOT alive because they DO NOT have ALL of the characteristics of life.

Virus Structure Activity Create a model of a virus as instructed by your teacher Label the model correctly Summarize in 14 words how the structure of your virus is different than a cell.

http://www. dreamstime http://www.dreamstime.com/stock-illustration-structure-virion-ebolavirus-virus-ebola-hemorrhagic-fever-cause-severe-often-fatal-disease-humans-image43685195

http://micro.magnet.fsu.edu/cells/viruses/hivvirus.html

http://www. dreamstime http://www.dreamstime.com/stock-photography-influenza-virus-structure-image23673462

Bellwork: 2/5/15 Virus Structure Cell Structure

Viral Reproduction Cycles Essential Question: How do viruses reproduce?

Could viruses be helpful?

Since viruses can transport DNA and RNA Since viruses can transport DNA and RNA into cells, scientists are exploring Gene Therapy In Gene Therapy, viral genetic material is replaced with new DNA In time, this could be used to cure genetic diseases. Currently we have no cure for these types of illnesses

Why are some viruses harmful? Virus invades cell When your cells make viruses instead of operating normally, YOU get sick Virus forces cell to make copies of virus Eventually so many copies are made, the cell explodes, releasing all of the new viruses

Lysogenic Cycle

Characteristics of the virus Icosahedral (20 sided), enveloped virus Retroviruses transcribe RNA to DNA. Two viral strands of RNA found in core surrounded by protein capsid. Outer lipid envelop contains proteins (these knob-like structures responsible for binding to target cell)

HIV

HIV Replication Reverse transcriptase (enzyme) produces viral DNA from RNA. AZT is the HIV medication that blocks reverse transcriptase Integrates into host DNA. Period of latency occurs.

HIV (arrows) Infecting a T-lymphocyte

Transmission

Viral Replication After a period of latency lasting up to 10 years viral replication is triggered and occurs at high rate. White blood cells may be destroyed in the process, body attempts to replace lost cells, but over the course of many years body is unable to keep the count at a safe level. Destruction of large numbers of white blood cause people to get sick from other diseases

Primary HIV Symptoms Cold or flu-like symptoms may occur 6 to 12 weeks after infection. fever rash headache fatigue diarrhea sore throat neurologic manifestations. no symptoms may be present

LATER HIV Symptoms HIV continues to reproduce, white blood count gradually declines from its normal value of 500-1200. Once white blood count drops below 500, HIV infected person at risk for opportunistic infections. The following diseases are predictive of the progression to AIDS: persistent herpes-zoster infection (shingles) oral candidiasis (thrush) oral hairy leukoplakia Kaposi’s sarcoma (KS)

Oral Candidiasis (thrush)

Oral Hairy Leukoplakia Being that HIV reduces immunologic activity, the intraoral environment is a prime target for chronic secondary infections and inflammatory processes, including OHL, which is due to the Epstein-Barr virus under immunosuppressed conditions

Kaposi’s sarcoma (KS) Kaposi’s sarcoma (shown) is a rare cancer of the blood vessels that is associated with HIV. It manifests as bluish-red oval-shaped patches that may eventually become thickened. Lesions may appear singly or in clusters.

AIDS White blood count drops below 200 person is considered to have advanced HIV disease Most deaths occur with a white blood count less than 50

Lysogenic Cycle Hidden viruses “hide” for a while inside host cells before becoming active Steps to the Lysogenic Cycle: Attach to cell Inject virus DNA/RNA Integrate virus DNA/RNA into cell DNA Wait (cell will grow, divide, etc.) Remove from virus from cell DNA Become active (lytic cycle)

Lysogenic Cycle - Viruses

Lytic Cyle

When a virus invades…

Influenza A virus Properties of the virus Enveloped virus with a segmented RNA genome Infects a wide range of animals other than humans Undergoes extensive antigenic variation (mutations) Major cause of respiratory infections Influenza A virus is the second acute infection to be discussed. Myxovirus Enveloped virus with a segmented RNA genome Infects a wide range of animals other than humans Undergoes extensive antigenic variation Major cause of respiratory infections

Spread of influenza virus Respiratory aerosoles can be generated from the respiratory tract by various means – from speaking to sneezing. During a sneeze, millions of tiny droplets of water and mucus are expelled at about 200 miles per hour (100 metres per second). The droplets initially are about 10-100 micrometres diameter, but they dry rapidly to droplet nuclei of 1-4 micrometres, containing virus particles or bacteria. This is a major means of transmission of several diseases of humans.

Respiratory Tract There are various means by which the host is protected from infection by influenza virus. The droplets containg the virus may be filtered by fines hairs and cilia in the nasal cavity. Muco-cilliary cells lining the trachea can trap virus particles and sweep the virus to the back of the throat from where it is swallowed and excreted via the intestinal tract. Alveolar macrophages can engulf the virus if it enteres as far as the lower reaches of the lung and alveolar sac.

Weekly consultation rates for influenza and influenza-like illness: Weekly Returns Service of the Royal College of General Practitioners, 1988 to 1999 100 200 300 400 500 600 Epidemic activity Higher than expected seasonal activity Baseline activity Rate per 100 000 population Normal seasonal activity Virus epidemiology Infleunza A virus shows regular outbreaks during the winger months. These are either Eopidenics: widespread outbreaks within the coutry Pandemics: Worldwide outbreaks of the virus affecting large numbers of people. 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 Year CDR Weekly Report: 5th November 1999

Lytic Cycle Active viruses enter cells and immediately begin to multiply, leading to the quick death of the invaded cells. Steps to the lytic cycle: Attach to cell Inject DNA/RNA Produce (replicate) virus parts Assemble new virons Release viruses to infect other cells

- Viruses Lytic Cycle

Which part of the lytic cycle is shown below?

Transmission of Viruses Respiratory transmission Influenza A virus Faecal-oral transmission Enterovirus Blood-borne transmission Hepatitis B virus Sexual Transmission HIV Animal or insect vectors Rabies virus ·         As with many infections viruses can be transmitted between susceptible individuals by a variety of means. The details provided related mainly to viruses infecting humans. ·         Many animal viruses do not remain infectious for very long outside the host. Ø     Respiratory: Influenza A virus (and rhinovirus). Transmission in the form of aerosols during coughing and sneezing. The viruses are fairly sensitive to drying and their transmission is highest when individuals are in close contact. Ø     Faecal-oral: Enteroviruses (e.g. poliovirus) A lot of viruses are excreted in faeces following high levels of replication in the gut. Ø     Blood borne: Hepatitis B (and HIV). Transferred through contaminated blood products or via shared needles with drug abuse. Ø     Sexual transmission: (HIV) Animal/insect vector: Rabies. In many instances the virus infection is a specific pathogen of the animal and is not normally transmitted to humans by any other means.

Viral diseases result in cell death

Lytic or Lysogenic? Dengue Fever DISEASE VIRUSES AIDS HIV Wart Herpes Simplex Virus Flu Influenza Measles Morbillivirus . Cancer Hepatitis B Dengue Fever

Lytic Cycle Lysogenic Cycle

LYTIC VERSUS LYSOGENIC INFECTION In a lytic infection, the host cells fills with virions and bursts. The result is cell death. Lysogenic infections are also known as latent infections. The viral genome becomes incorporated into the host cell’s DNA. It can remain this way for an extended period. The host cell lives, until the lytic cycle begins

VIRUS Organisms that live on or near a host and cause harm. Active Viruses Hidden Viruses Host Parasite VIRUS Organisms that live on or near a host and cause harm. A living thing that provides a source of energy for a virus or an organism A tiny, nonliving structure that invades and then multiplies inside of a cell. Some viruses hide for a while and become part of the cell’s genetic material. It may stay inactive and “hidden” for years. Then under certain conditions it becomes active and acts like an active virus. Ex – cold sores A virus that immediately goes into action. It begins to take over cell functions and produce the virus’s proteins and genetic material. These parts then assemble into new viruses. The viruses multiply like a copy machine left on. When it is full the cell bursts open – releases the new viruses and dies.