Biology Flash Cards

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Biology Definitions

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B CellA type of lymphocyte (white blood cell) which makes antibodies against antigens After a naive B Cell's IgM (Immunoglobulin) receptor encounters its matching antigen, it "digests" the antigen, and then presents it on its MHC Class II receptor. Whereas a Macrophage or Dendritic Cell will "digest" many antigens, and present them on their MHC Class II receptors, a B Cell will only present an antigen on its MHC Class II receptor if it matches its IgM receptor. An activated (one which has previously encountered its matching antigen on the MHC Class II receptor of a Macrophage or Dendritic Cell) T Helper Cell can then bind to the MHC Class II receptor on the B Cell. The T Cell then sends out biochemical "signals" which tell the B Cell to proliferate and undergo "class switching".lymphocyte, antigen, antibody, T Cell, MHC Class II Receptor
BACBacterial artificial chromosome. A scientist, performaing a cloning experiments, can insert DNA into a BAC, and then put the BAC into a bacterial cell.Cloning, BAC
BacteriophageViruses that attack and kill Bacteria. Phage means "to eat". Small particles that attach to a bacteria, insert proteins and nucleic acids into the bacteria which then hijack the cell's machinery to create more and more phage until the cell breaks (lysis). Some bacteria have evolved "restriction enzymes" to fight bacteria phage. Restriction Enzymes have proved very useful in DNA cloning.Virus, Restriction Enzymes, DNA Cloning
Baltimore SchemeA scheme for classifying viruses based on their nucleic acid. This scheme was invented by a virologist, David Baltimore, and takes into account the fact that the purpose of the viral genome is to produce mRNA that can be translated by the host cell's ribosomes (Viruses are "translational parasites"). Baltimore then found that there were seven different ways that viral genomes could accomplish this goal.Virus Structure, Virus Classification, Viral Genomes, Ribosome, DNA, RNA
BaseThere are three different, overlapping definitions of a base; a base is a chemical substance that does one or more of the following: dissociates in water releasing Hydroxyl (OH-) ions, accepts protons (H+) from an acid, or donates a pair of electrons to an acidAcid, Alkali
Base PairingInside a DNA double helix, an Adenine (A) from one strand is always opposite a Thymine (T) on the other strand (forming two Hydrogen bonds), and a Cytosine (C) on one strand is always opposite a Guanine (G) on the other strand (forming three Hydrogen bonds). Note that the Adenine-Thymine (A-T) combination and the Cytosine-Guanine (C-G) combination both span the same distance, so the pairs fit perfectly inside a DNA double helix. Because the two strands are complementary, DNA Replication is made possible.Chargaff's Rules, DNA, Replication
Beta GlobinOne of the two proteins in hemoglobin, a tetromer, that carries Oxygen in the blood. Mutations in the Beta Globin protein can cause diseases such as Sickel cell anemia and Thalassemia.Protein
Beta Pleated SheetTwo or more strands of molecules which lie side by side and are held together by weak Hydrogen bonds, forming a "sheet". The secondary structure of many proteins include domains (regions) which are beta pleated sheets.Secondary Structure, Protein, Alpha Helix, Polypeptide
Beta-galactosidaseProtein used to break down lactose. This protein has been widely studied because of its role in the Lac Operon of some Bacteria.Lac Operon

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