BIOL 4576 Exam # 1 Study Guide Lectures: 1 - 3Lecture 1 (January 15th)Virus - an intracellular parasite that must use the host cell’s machinery to make new progeny infectious viral particles. A virus cannot grow, metabolize, or synthesize proteins on its own. They must be viewed through an electron microscope (except pox viruses that can be seen by light microscopes). Definitions:virion: infectious viral particle (there can be non-infectious particles)capsid: protein coatcapsomere: morphological subunit of a capsidnucleocapsid: capsid containing genetic materialenvelope: lipoprotein membrane that surrounding the nucleocapsidtegument: area between envelope and nucleocapsid, usually containing proteins and enzymesCapsids can be icosahedral, helical, or complex. Icosahedral capsids have a 5:3:2 symmetry. Helical capsids are shaped like a spiral and have RNA as their genome. Complex viruses are shaped like bricks. They also have lateral bodies and a core. They can replicate in viral factories in the cytoplasm of a cell. These complex viruses are pox viruses.Any of these types of viruses can have an envelope. The virus acquires its envelope from any membrane of the cell including the golgi, ER, nuclear membrane, or the plasma membrane. Thisis called budding. These enveloped can either be tight or loose fitting. Loose envelopes are pleomorphic because their shape can change. Viral proteins are inserted into the envelope. They assist in attachment and immune response. These structures are known as peplomers or spikes. If a virus is enveloped, it cannot be infectious without one. They are also less stable that a naked virus because the envelope is more sensitive to environmental pressures like heat and ion concentration.The tegument can function as an antigen with regards to an immune response. They are also the first proteins to take action when the virus enters the cell. Genomes: viruses can have DNA or RNA, be linear or circular, be single stranded or double stranded, all in one piece or segmented. DNA viruses usually have a double stranded genome but a few are single stranded like parvoviruses. They can be either circular or linear. They are either icosahedral or complex. Also, most DNA viruses are assembled in the nucleus except for poxviruses. RNA viruses are usually small and have single stranded genomes (except reoviruses).They could be in a single piece or segmented. They are helical in shape as usually assemble inthe cytoplasm (except orthomyxoviruses). RNA genomes can either be plus stranded or minus stranded. +RNA can act directly as mRNA; -RNA needs to be made into +RNA by either an RNA or DNA intermediate. These need special enzymes like RNA dependent RNA polymerase and RNA dependent DNA polymerase (reverse transcriptase). Classification: the name of the classification system for viruses is called the Baltimore Classification scheme. 1-dsDNA, 2-ssDNA, 3-dsRNA, 4-ssRNA(+), 5-ssRNA(-), 6-ssRNAto dsDNA with reverse transcriptase, 7-dsDNA(+/-hybrid) with reverse transcriptase.Steps of replication1) Attachment: virus attached to cell surface 2) penetration/adsorption: virus enters cell 3)uncoating: virus loses the capsid 4) transcription: early genes to early mRNA 5) translation: earlymRNA to early proteins (enzymes) 6) genome replication 7) transcription 2: late genes to late mRNA 8) translation: late mRNA to late proteins (structural) 9) Assembly: capsid assembles including genome, can include envelope 10) release: viruses exit cellTypes of infectionsproductive: produces a lot of new infectious progeny. Host cell is usually killed quicklychronic persistent: produces few new infectious progeny. Host cell survives for a long time. Cell function is either not impaired or partially impaired. abortive: replication is blocked after entry. Host cell cant provide something for the virus so cell infection is terminated. latent: virus goes dormant. Little transcription and translation. Future events may trigger reactivation of productive viral replication. transformation: yields a heritable change in the cells genome. It doesn’t kill the cell but causes itto multiply more vigorously. Lecture 2 (January 20th)GLIAL CELLS (10X more of these than neurons)hold neurons in place, provide nutrients and oxygen, help maintain homeostasis, provide electrical insulation for neurons (wrap themselves to make myelin sheath), destroy pathogens, regulate neuronal repair (CNS glia suppress repair, PNS glia promote repair), remove dead neurons, participate in signal transmission (clear NTs from the synapses)Types of glial cells: astrocytes, oligodendrocytes, microglia, ependymal cells-CNSschwann cells and satellite cells-PNSAstrocytes (most abundant)anchor neurons to their blood supply: build the blood brain barrier and regulate vessel sizeregulate external chemical environment: removes excess ions like potassium, recycle NTsthey can signal each other using calcium: there are gap junctions that allow IP3 to pass betweenthem thus activating Ca channel. This calcium causes more IP3 production. This makes a propagating Ca wave.only glia that express GFAP, glial fibrillary acidic protein, used to visualize them2 types:protoplasmic: short, thick, highly branched, found in gray matterfibrous: long, thin, few branches, found in white matterOligodendrocytesthese cells make the myelin sheath to raise the efficiency of the signal propagation. Microgliathese are small “glia” that are not derived from neural tissue. These are the “macrophages” of the brain. They constantly sample the environment of the CNS and multiply when there is damage.Ependymal cellsthey line the walls of ventricles and spinal canal and secrete and circulate CSF.Schwann cellsthese myelinate the axons of the PNS. They also have phagocytic activity that helps clear away debris and promote regrowth of damaged peripheral neurons.Satellite cellsthese are small cells located on the exterior of PNS neurons that help regulate the external chemical environment.NEURONSThe neuron doctrine: by Santiago Ramon and Cajalcellularity: the neuron is the fundamental structural and functional element of the brainsynaptic communication: the terminals of neurons axon communicate with the dendrites of another neuron only at specific sites called synapses.connection specificity: neurons for synapses and communicate with certain neurons and not with others.dynamic polarization: signals in a neural circuit only travel in one direction (dendrites