Chapter 9 Microbial Genetics – Flashcards
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| What is Genetics? |
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| The study of heredity |
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| What does genetics explore? (4) |
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1. The transmission of biological traits from parent to offspring. 2. The expression and variation of those traits. 3. The structure and function of genetic material. 4. How this materia changes. |
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| What is a genome? |
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| The sum total of genetic material of a cell (chromosomes & mitochondra/chloroplasta and/or plasmids) |
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| What is the genome of cells? |
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| DNA |
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| What is the genome of viruses? |
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| DNA and RNA |
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| What are chromosomes? |
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| Composed of a neatly packaged DNA molecule. |
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| What kind of chromosomes are bacteria? |
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| Single circular loops; |
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| What kind of chromosomes are Eukaryotes? |
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| Multiple (pairs or diploid) or linear (singles or haploid); located in the nucleus |
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| What are Genes? |
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| A part of a chromosome that is the fundamental unit of heredity. It is responsible for a given trait. It provides information for a certain cell function and it contains the vital code for making a protein or RNA molecule. |
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| What are the three basic categories of genes? |
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1. Structural genes: code for proteins 2. Genes that coe for RNA 3. Regulatory genes: control gene expression |
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| What is a genotype? |
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| The genetic make up |
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| What is a phenotype? |
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| The physical/ observable traits that are formed by the genotype |
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| Since genes vary in size, what is the smallest? |
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| Virus that has 4-5 genes |
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| What are the characteristics of E.coli? |
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| It is a single chromosome containing 4,288 genes. It's 1 mm and 1,000x longer than cell. |
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| What are the characteristics of a human cell? |
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| It has 46 chromosomes that contain 31,000 genes. It is 6 feet and is 180,000x longer than cell. |
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| What happened in the end of the 19th century regarding DNA's history? |
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| DNA was known to be chemicals in cells |
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| What happened in the 1930's regarding DNA's history? |
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| The basis of inheritance is a molecule, not a chemical mixture. |
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| What happened in the 1940's regarding DNA's history? |
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| Realized that chromosomes are composed of DNA and protein. |
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| What happened in the 1950s regarding DNA's history? |
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| Discovered that DNA acts as hereditary material. |
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| What happened in the end of the 1950s regarding DNA's history? |
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| DNA's structure was found to be 3-D that gave it unique properties: enabled it to store genetic information and be copied and passed from generation to generation. |
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| What are the characteristics of DNA? |
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| Two strands twisted into a double helix. Consists of a nucleotide. |
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| What is in a nucleotide? |
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| Contains 3 parts: a 5-carbon sugar (deoxyribose), a phosphate group, and a nitrogenous group (Adenine, Guanine, Thyamine, and Cytosine). |
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| How do nucleotides form? |
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| They covalently bond to form a sugar-phosphate linkage called the backbone. Each sugar attaches to two phosphates (5' carbon and 3' carbon). Adenine binds to thymine with 2 hydrogen bonds and Guanine binds to cytosine with 3 hydrogen bonds. |
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| What is the significance in the structure of DNA? |
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1. It maintains the code during reproduction: the constancy of base pairing guarentees that the code will be retained during cell growth and division. 2. It provides variety: The order of bases along the length of the DNA strand provides the information needed to produce RNA and protein molecules, which in turn are responsible for the phenotype of the cell. |
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| What is semiconservative replication? |
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| Each daughter molecule is identical to the parent, but one strand of molecule is new and other (template) is the original parent strand. |
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| What is transcription? |
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| Information stored on the DNA molecule is conveyed to RNA molecules. |
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| What is translation? |
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| The information contained in the RNA molecule is used to produce proteins by the ribosomes. |
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| What is the antiparallel arrangement? |
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| One side of the double helix is rubbing in the opposite direction of the other. One helix runs for 5' to 3' and the other runs from 3' to 5'. |
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| How does transcription and translation work in Eukaryotes? |
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| They are spatially and temporally separated. DNA is transcribed in the nucleus to produce mRNA. mRNA will then exit the nucleus and be translated int he cytoplasm. |
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| How does transcription and translation work in Prokaryotes? What is polyribosomal complex? |
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| Bacterial genes can be transcribed and then translated immediately since they lack a nucleus. Polyribosomal complex is the ability of the mRNA transcript molecule to be fed through multiple ribosomes since it is so long. |
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| How are genes and proteins related? |
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| A gene is an ordered sequence of nucleotides that codes for a protein. |
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| How is DNA related to protein? |
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| DNA is a blueprint that shows which kinds of proteins to make and how to make them (This blueprint exists in the order of triplets along the DNA strands). 2. The order of triplets directs a protein's primary structure--which determines its characteristic shape and function. 3. Proteins contribute significantly to the phenotype by functioning as enzymes and structural molecules. |
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| What are the characteristics of RNA? |
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| Single-stranded molecule, uses DNA as a template in transcription, contains Uracil instead of Thymine, the sugar used in RNA is ribose instead of deoxyribose, and only mRNA is translated into proteins, other types of RNA have different functions. |
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| What is mRNA, tRNA, and rRNA? |
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| Messenger RNA (mRNA): translated from DNA and carries a message in triplets (codons). Transfer RNA (tRNA): transcribed from DNA; molecule bends to create loops that makes it look like a cloverleaf structure; bottom loop of the cloverleaf exposes a triplet (anticodon) that both designates the specificity of the tRNA and complements the mRNA's codons; carries specific amino acids to ribosomes. Ribosomal RNA (rRNA): component of ribosomes where protein synthesis occurs. |
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| What are the 3 stages of transcription? |
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| 1. Initiation 2. Elongation 3. Termination |
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| What happens in the Initiation stage of Transcription? |
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| RNA polymerase binds to the promoter region upstream of the gene. |
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| What happens in the Elongation stage of Transcription? |
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| RNA polymerase adds nucleotides complementary to the template strand of a segment of DNA in the 5' to 3' direction. (NOTE: Uracil is placed as adenine's complement since this is DNA to RNA) Also, the start codon will be AUG. |
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| What happens in the Termination stage of Transcription? |
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| RNA polymerase recognizes another code on DNA near the end of the gene that signals the separation and release of the completed mRNA. The length of the final mRNA molecule depends upon the polypeptide that it encodes (between 100-1200 bases long). |
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| What is the Master Genetic Code? |
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| Represented by the mRNA codons and the amino acids they make. The code is universal (shared by all organisms) and it is redundant (each amino acid is represented by more than one codon). |
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| What happens in Translation in Eukaryotes? |
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| The mRNA leaves the nucleus to go to ribosomes. All the elements needed to make a protein, from the mRNA to the tRNAs with amino acids, are brought together on the ribosomes. |
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| What are the three steps of Translation? |
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| 1. Initiation 2. Elongation 3. Termination 4. Protein folding 5. Protein processing |
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| What happens in the Initiation stage of Translation? |
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| Ribosomes assemble on the 5' end of the mRNA transcript, it scans the mRNA util it reaches the start codon (AUG) or formyl methionine in bacteria. |
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| What happens in the Elongation stage of Translation? |
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| 1. A tRNA molecule with the complementary anticodon (that binds to AUG) and methionine amino acid (AUG) enters the P site of the ribosome and binds to the mRNA. 2. Next tRNA enters A site to begin elongation. A peptide bond forms between the ends of the tRNAs in P and A site. (The bond formed between the amino acids is called (aa)) 3. The "blank" tRNA in P site shifts to E site and exits the ribosome. 4. tRNA previously at A site shifts to P site. 5. New tRNA moves into A site and elongation continues. |
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| What happens in the Termination stage of Translation? |
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| When a stop codon (UAA, UGA, or UAG) is reached. The enzyme releases polypeptide chain from the ribosome. |
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| What happens in the Protein folding stage of Translation? |
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| Polypeptide folding may occur before polypeptide has been released from ribosome. |
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| What happens in the Protein processing stage of Translation? |
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| Aka posttranslational modification: amino acids are removed and cofactors are added. |
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| Transcription and translation in Eukaryotes? |
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| 1. Do not occur simultaneously because transcription occurs in the nucleus and translation occurs in the cytoplasm. 2. Start codon is AUG, but it doesn't use formyl-methionine. 3. mRNA encodes a single protein, unlike bacterial mRNA which encodes many polyribosomal complex. 4. Contains introns (intervening sequences of noncoding DNA) which have to be spliced out of the final mRNA transcript |
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| What are the genetics of animal viruses? |
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| 1. The viral genome is either 1 or more pieces of DNA or RNA and contains only genes needed for producing new viruses. 2. DNA viruses are replicated in the host cell nucleus; RNA viruses are replicated in the host cell cytoplasm. 3. Viral mRNA is translated into viral proteins using host tRNA on host ribosomes. 4. Producing new viruses requires access to host cell's genetics and metabolic machinery to instruct the host cell to synthesize new viral particles. |
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| Why are regulated enzymes important? |
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| It ensures that genes are regulated to be active only when their products are required, therefore, it saves energy |
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| What do operons do and what organism are the present in? |
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| Operons are a set of genes that are regulated as a single unit for a particular metabolic pathway. They regulate genes to be active only when it is required. They are in prokaryotes. |
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| What are the two types of Operons? |
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| 1. Inducible 2. Repressible |
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| What is an indicibule operon? |
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| The operon is normally off and it is turned on by a substrate. They are catabolic (break down) operons that only produce the enzymes needed to metabolize a nutrient when that nutrient is present. ex. lactose operon |
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| What is a repressible operon? |
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| Genes are normally on but are turned off by the product thats being made. They are anabolic (building) enzymes that stop being produced when they are not needed. ex. arginine operon |
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| What are the three parts of the lactose operon? |
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| 1. Regulator: composed of the gene that codes for the protein capable of repressing the operon (repressor). 2. Control locus: composed of the promoter and operator 3. Structural locus: made of 3 genes, each coding for a different enzyme needed to catabolize lactose. B-galactosidase (hydrolyzes the lactose), permease (brings lactose across cell membrane), and b-galactosidase transacetylase (uncertain function). |
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| How does the lactose operon (inducible operon) work? |
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| 1. Normally off. In the absence of lactose (or in the presence of glucose), the repressor binds with the operator locus and blocks transcription of downstream structural genes. 2. When it turns on: Lactose binds to the repressor protein and changes shape which causes it to fall of the operator. RNA polymerase the binds to the promoter and structural genes are transcribed. |
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| How does the Arginine operon (repressible operon) work? |
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| 1. Normally on: as long as arginine is needed by the cell and repressor can't bind to operator at low levels. 2. When there is no need for the product, the operon turns off. When excess arginine is present, it binds to the repressor and changes it (arginine product plays role as a corepressor). Then the repressor binds to the operator and blocks arginine synthesis. |
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| What are the defense mechanisms of the host? |
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| First, Second, and Third line of defense |
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| What is the 1st line of defense? |
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| Nonspecific; any barrier that blocks invasion at the portal of entry i.e., skin, mucous membrane of respiratory, urogenital, eyes, and digestive tract (stomach acid). |
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| Where are 1st line of defenses found? |
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| 1. Skin impregnated with keratin 2. Sweat glands that flush out bacteria 3. Mucous coat impedes attachment and entry of bacteria 4. Blinking and tear production flushes out bacteria 5. Stomach acid 6. Nasal hair traps large particles 7. Damaged cells are quickly replaced. |
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| What are some 1st line of defense chemical defenses? |
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| 1. Sebaceous secretions 2. Lysosome (an enzyme that hydrolyzes the cell wall of bacteria) in tears 3. High lactic acid and electrolyte concentration in sweat 4. Skin's acidic pH 5. Hydrochloric acid in stomach 6. Digestive juices and bile in intestines 7. Antimicrobial chemical in semen 8. Acidic pH in vagina |
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| What are the genetic barriers within the first line of defense? |
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| 1. Some hosts are genetically immune to the disease of other hosts. 2. Some pathogens have great specificity i.e., Humans cant get distemper from cats. 3. Some genetic differences exist in susceptibility i.e., Some humans carry a gene for sickle-cell anemia and are resistant to malaria. |
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| What is the second line of defense? |
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| Nonspecific; Cellular and chemical system that comes immediately into play if infectious agents make it past the surface defenses. ex. Phagocytes that destroy foreign matter and inflammation which holds infections in check. |
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| What are the actions of the second line of defense? |
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| 1. recognition 2. inflammation 3. phagocytosis 4. interferon 5. complement |
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| What is recognition? |
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| Toll-like receptors (protein receptors within the cell membrane of macrophages) detect foreign material and signal the macrophage to produce chemicals which stimulate an inflammatory response (nonspecific) and activity of B and T cells (specific). |
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| What are inflammatory responses? |
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| 1. Redness: increased circulation and vasodilation in injured tissues in response to chemical mediators and cytokines. 2. Warmth: heat given off by the increased blood flow 3. Swelling: increased fluid escaping into the tissue as blood vessels dilate (edema) Pus if formed as WBC's, microbes, debris, and fluid collect in one are. Pus helps to prevent spread of infection. 4. Pain: stimulation of nerve endings. 5. Fever: Pyrogens reset the hypothalamus to increase body temperature; it signals muscles to increase heat production and vasoconstriction (restrict blood flow) |
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| What are the activities of Phagocytes? |
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| 1. Survey tissue compartments and find microbes, matter, and dead or injured cells. 2. Ingest and eliminate unwanted material 3. Extract immunogenic information from foreign matter. |
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| What are the benefits of a fever? |
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| 1. Inhibits multiplication of temperature-sensitive microorganisms 2. Impedes nutrition of bacteria by reducing the available iron 3. Increases metabolism and stimulates immune reactions and protective physiological processes. |
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| What are the types of Phagocytes and what do they do? |
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| 1. Neutrophils: general-purpose; react early to bacteria and other foreign materials, and to damaged tissue; example: Eosinophils (attracted to sites of parasitic infections and antigen-antibody reactions). If you have signs of increased neutrophils, it means you have an infection. 2. Macrophages: derived from monocytes; scavenge and process foreign substances to prepare them for reactions with B and T lymphocytes. |
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| What is Phagocytosis? |
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| The process which is used by cells to engulf and subsequently ingest particles of nutrients or bacteria. |
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| What are the mechanisms of phagocytosis? |
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| 1. Chemotaxis and ingestion: Phagocytes migrate and recognize PAMPs; phagosome is produces. 2. Phagolysosome formation: lysosome fused with phagosome (death of bacteria is within 30 minutes). 3. Destruction and elimination: Oxygen-dependent system (respiratory burst); liberation of lactic acid, lysozyme, and nitric oxide. |
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| What are Interferons (IFN)? |
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| Small proteins produced by certain WBCs and tissue cells. 1. Alpha is produced by lymphocytes and macrophages 2. Beta is produced by fibroblasts and epithelial cells 3. Gamma is produced by T cells. Interferons are produced in response to viruses, RNA, immune products, and various antigens (they provoke an immune response even though they aren't harmful). They bind to cell surfaces and induce expression of antiviral proteins. Inhibit (don't allow) the expression of cancer genes. Part of the innate immune system. |
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| What are Complement Proteins? What does it do? How is it activated? What system is it a part of (innate or adaptive? |
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| Consists of 26 blood proteins that work together to destroy bacteria and viruses. Actions: 1. Contribute to inflammatory response 2. Mark foreign cells for phagocytosis by attaching to the bacteria and signalling the phagocyte to come and destroy the bacteria 3. Attract neutrophils to invade the agent 4. Causes lysis of invader cells. Are activated by cascade reaction. Innate immune system. |
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| What is immunology? |
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| The study of the body's second and third lines of defense. |
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| What are WBCs? |
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| AKA Leukocytes that have an innate capacity to recognized and differentiate any foreign material. |
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| What is Nonself? |
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| foreign material |
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| What is Self? |
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| normal cells of the body |
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| What is a PAMP? |
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| Pathogen-associated molecular pattern: molecules shared by microorganism. They attach to microorganism and act as flags for the WBCs involved in innate immunity. |
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| What are PRRs? |
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| Pathogen recognition receptors: receptors on WBCs for PAMPs. PRRs serve as "feelers" for foreign substances and look for the PAMPs on microorganisms so that the WBCs can attack it. |
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| What is the composition of the blood? |
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| Plasma: 92% water and the rest is proteins, globulins, clotting factors, hormones, and other chemicals and gases to support normal physiological functions. Blood cells: are called formed elements Serum: liquid portion of the blood after a clot has formed minus the clotting factors. |
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| What are stem cells? |
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| Undifferentiated cells, that are made before they are given a "name" they are either made into RBCs or WBCs. |
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| What are the 2 types of WBCs? |
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| 1. Granulocytes 2. Agranulocytes |
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| What are the types of Granulocytes? |
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| 1. Neutrophils: most in number; general phagocytosis 2. Eosinophils: 1-3%; destroy eukaryotic pathogens 3. Basophils: smallest in number; release potent chemical mediators (like Mast Cells that trigger local inflammatory response) to kill large eukaryotic pathogens and recruit other leukocytes. |
