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Hello Mighty Collegiate Stars!!! Is it Alive? Characteristics of Living Organisms 1) All living things are composed of cells. 2) All living things perform certain chemical process such as growth and digestion 3) All living things can reproduce 4) All living things either make their own nutrients or ingest nutrients from the environment. 5) All living things respond to stimuli such as light and touch. Viruses Virus: is a particle that consists of a nucleic acid enclosed within a protein shell that requires a living cell in order to reproduce. Note: Most scientist do not consider viruses to be organisms. Virus are Nonliving Viruses lack nearly every characteristic of life. They are not composed of cells. They don’t respond to stimuli. They don’t use energy for growth and development. They cannot reproduce on their own. Viruses also cannot make food, take in food, or produce wastes. Virus Shapes Viruses vary widely in shape. Some viruses are round, while some are rod-shaped. Other viruses are shaped like bricks, threads, or bullets. There are even viruses that have complex, robot like shapes, such as the bacteriophage A Bacteriophage: (bak TEER ee oh fayj) is a virus that infects bacteria. Virus Shapes Structure of Virus All viruses have two basic parts: a protein coat that protects the virus and an inner core made of genetic material. Capsid: the protein shell that surround a virus In addition to the capsid, some viruses also have protective coating called an envelope. This envelope may be covered with spikes. Note: A virus uses these spikes both to recognize and attach to the cells they infect. Structure of Virus Each virus contains unique surface proteins. The shape of the surface proteins allows the virus to attach to certain cells in the host. Like keys, a virus’s proteins fit only into certain “locks,”. This is known as the lock and key system. Viral Nucleic Acid Viral nucleic acid can either be DNA or RNA. DNA is the nucleic acid responsible for carrying the genetic information of most organism from one generation to the next. RNA is a nucleic acid used by most organisms for protein synthesis Prokaryotes Prokaryotes: is a unicellular organism that lacks a true nucleus and membrane-bound organelles. Remember: Pro-No (Prokaryotes have no true nucleus and membrane bound organelles) Prokaryotes are commonly called bacteria. Living Organism Unlike viruses, bacteria are living organisms. Bacteria possess the characteristics of living organisms. Bacteria is Alive!!! Bacteria Shape & Size Most bacterial cells have one of three basic shapes: spherical (coccus), rodlike (bacillus), or spiral (spirillum). Bacteria Size Bacterial cells is larger that viruses!!! Bacteria Structure Bacterial cells are enclosed by a cell wall. Within the cell wall is a cell membrane that contains the cytoplasm and the hereditary material of the cell. Ribosomes are found in the cytoplasm of the prokaryote cell, but the cell does not contain other organelles. Note: Prokaryotes genetic material is not enclosed in a nucleus. Bacteria Structure Bacterial cells don’t have a nucleus!!! A bacterial cell may also have a flagellum (fluh JEL um) (plural flagella), a long, whiplike structure that helps a cell to move. A flagellum moves the cell by spinning in place like a propeller. A bacterial cell can have many flagella, one, or none. Most bacteria that do not have flagella cannot move on their own. Instead, they are carried from place to place by the air, water currents, objects, or other methods. Bacteria Structure Types of Bacteria Bacteria are classified into two kingdoms based on differences in cell structure: Archaebacteria and Eubacteria. Archaebacteria: most bacteria in this group can survive without oxygen. Eubacteria: this group includes the most prokaryotes. Assignment Students will use the material provided to create a bacteria and virus model. Students must label and describe the function the following parts: Virus: capsid, protein coat, genetic material, spikes Bacteria: cell membrane, ribosomes, cytoplasm, flagellum, cell wall, genetic material, coccus, bacillus, spirillum. Welcome Collegiate Stars !!! Part II Viruses & Bacteria Review Virus Viruses are nonliving The two basic parts: protein coat and inner core that hold the genetic material. Some viruses have a protein envelope that has spikes Viruses are very specific in their invasion of their host Review Bacteria Bacteria is also known as prokaryotes Bacteria is a unicellular organism Bacteria is a living organism Bacteria has three shapes: rodlike (bacillus), spherical (coccus), & spiral (spirillum). Flagellum help the bacteria move How Viruses Multiply After a virus attaches to a host cell, it enters the cell. Once inside a cell, a virus’s genetic material takes over many of the cell’s functions. It instructs the cell to produce the virus’s proteins and genetic material. These proteins and genetic material then assemble into new viruses. Some viruses take over cell functions immediately. Other viruses wait for a while. Active Viruses After entering a cell, an active virus immediately goes into action. The virus’s genetic material takes over cell functions, and the cell quickly begins to produce the virus’s proteins and genetic material. Then these parts assemble into new viruses. When the cell is full of new viruses, the host cell bursts open, releasing hundreds of new viruses as it dies. Active Virus Lytic Cycle Hidden Viruses Other viruses do not immediately become active. Instead, they “hide” for a while. When a hidden virus enters a host cell, its genetic material becomes part of the cell’s genetic material. The virus does not appear to affect the cell’s functions and may stay in this inactive state for years. Each time the host cell divides, the virus’s genetic material is copied along with the host’s genetic material. Then, under certain conditions, the virus’s genetic material suddenly becomes active. It takes over the cell’s functions in much the same way that active viruses do. Soon, the cell is full of new viruses and bursts open. Hidden Virus Lysogenic Cycle Lysogenic Cycle A virus that enters a lysogenic cycle is an example of a mutagen. Mutagen: is anything that changes the DNA of an organism . In this case the virus is a mutagen because it inserts its own genes into the cell’s DNA. Microbes & Diseases Disease: is any change that disrupts the normal function of one or more body systems. Some diseases are caused by exposure to certain chemical in the environment. Other diseases are caused by traits that are inherited. Such diseases are called noninfectious diseases because they are not spread from one organism to another. Microbes & Diseases Many diseases in humans and other organisms are caused by microbes. Pathogen: any microbe that causes a diseases. Infectious disease: any disease that is caused by a pathogen. An illness that is passed from one organism to another is an infectious disease. (ie. Cold) Contagions: infectious diseases that can be transmitted or spread from one organism to another.