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Biol190 U2W2

by: Amy Rice

Biol190 U2W2 Biol 190, Intr biology health profession

Amy Rice

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Unit 2 Week 2- Ribosomes and Proteins Protein Structure Lipids and Memebranes
Joanna M. Paterson
Class Notes
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This 6 page Class Notes was uploaded by Amy Rice on Friday February 26, 2016. The Class Notes belongs to Biol 190, Intr biology health profession at Towson University taught by Joanna M. Paterson in Spring 2016. Since its upload, it has received 30 views. For similar materials see Biology in Biology at Towson University.

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Date Created: 02/26/16
BIOL 190 Notes Unit 2 Week 2 Mutation- any change in the nucleotide sequence of DNA; permanent change in the base sequence of DNA Errors in cell cycle are likely to occur during DNA synthesis (‘S’ phase)  Nucleotide substitution- replacement of one nucleotide and its base-pairing partner with another pair of nucleotides; because genetic code is redundant, some substitution mutations have no effect at all  Nucleotide insertion/deletion- when a nucleotide is added or removed to the coding sequence; often has disastrous effects; all nucleotides “downstream” of the insertion/deletion will be regrouped into different codons, possibly resulting in a nonfunctional polypeptide Silent mutation- when a mutation causes an RNA codon to change, but the original and mutated codon code for the same amino acid; one nucleotide is substituted for another, however it does not change the protein Missense mutation- changes amino acid coding; some have little or no effect on shape or function on resulting protein, but others prevent the protein from performing its normal function (sickle-cell disease) EX: mutated hemoglobin in DNA can cause sickle-cell disease (substitutes TA in DNA to AU in RNA) SICKLE CELL ANEMIA  Change in one amino acid (glu to val) [missense mutation]  Sickle hemoglobin has different 3D shape; less efficient in binding oxygen; distorts shape from round to flatter and spikey Nonsense mutations- changes an amino acid codon into a stop codon, resulting in a prematurely terminated protein (truncated protein) that probably won’t be able to function properly Frameshift mutation- one nucleotide is inserted, altering the reading framed Amino acid insertion (3 base insertion)- adds extra codon; one amino acid is inserted in the protein Mutagenesis- production of mutation Mutagens- chemical or physical agent that causes mutations; physical mutagens includes high-energy radiation (x-rays or ultraviolet light); chemical mutagens may be similar to DNAs chemical compositions, but incorrectly pairs (anti-AIDS drug AZT) Evolution by natural selection is made possible by gene mutations, causing such a wide diversity of genes in the living world. Protein Structure Amylase- salivary enzyme that hydrolyzes starch; single polypeptide chain (1), has alpha helices and beta pleated sheets (2), 3D structure (3) Glucagon- regulate blood sugar levels; (1), has helix (2) Hexokinase- catalyzes first reaction in glycolysis; (4) globular Hemoglobin- carries oxygen through the body via red blood cells; composed of four polypeptides; transport protein K+ (potassium ion)- membrane transport protein; quaternary structure Collagen- a fibrous protein; common 3D structure in structural proteins; 3 different polypeptides, therefore has a quaternary structure Quaternary structure is identified via color coding (more than one color) POLYPEPTIDE VS PROTEIN Polypeptide  Linear chain of amino acids or an amino acid chain with helices and pleated sheets, but does not have 3D structure  Cannot perform a function Protein  A polypeptide with a tertiary or quaternary structure in order to make it function  Native conformation- normal/functional structure Dehydration synthesis- Formation of primary structure, structure drives formation of higher levels Denaturation- loss of higher structures (4,3,2) and remains a linear chain of amino acids (1); no enzyme required; in response to change in physical environment; Can be changed with temperature, pH level, and/or salt Hydrolysis- loss of primary structure; water and an enzyme is required LIPIDS Lipids- diverse compounds that are grouped together because they all do not mix well with water (hydrophobic); They are not huge macromolecules, nor polymers built from monomers (Fats, oils, phospholipids, steroids, waxes); Atoms include C, H, O; always a lot more C and H than oxygen  Fats and Oils- 3 fatty acids & 1 glycerol  Phospholipids- 2 fatty acids, phosphate group (PO4), & 1 glycerol Lipid functions  Fats and Oils- long term energy storage; insulation and cushioning  Phospholipids- membrane structure; separation of water-filled cell from watery environment  Steroids- hormones; membrane structure  Waxes- protection; prevent dehydration Fat- a large lipid, made from glycerol and fatty acids; linking 3 fatty acids to glycerol produces a fat Unsaturated fatty acid- Has one fewer hydrogen atom on each carbon of the double bond; liquid at room temp; healthier in diet; kinks at double bonds of fatty acids; loose packing In animal cell membranes, the steroid cholesterol stabilizes the membrane at warm temperatures while also keeping the membrane fluid at lower temperatures. Different types of cells have different membrane proteins. Saturated Fatty Acid- a fatty acid with no double bonds in their hydrocarbon chain; has the maximum number of hydrogen atoms (“hydrogenated vegetable oil” has been converted from unsaturated fat, to saturated fat); closely packed fatty acids; vascular damage, stroke, heart attack; solid at room temp Trans Fats- A form of fat associated with health risks; H are on opposite sides of C-C double bond; form of Saturated Fat Phospholipids- The major component of cell membranes; structurally similar to fats, but contains only 2 fatty acids; Phospholipids made in the smooth ER are inserted in the ER membrane The hydrophilic and hydrophobic ends of multiple molecules assemble in a bilayer of phospholipids to form a membrane Steroids- lipids in which the carbon skeleton contains four fused rings Cholesterol- Starting material for making other steroids, including sex hormones; common component in animal cell membranes 4.8 Endoplasmic Reticulum- one of the major manufacturing sites in a cell Smooth ER- lacks attached ribosomes; enzymes of this are important in the synthesis of lipids, oils, phospholipids, and steroids; stores calcium ions (in muscles cells); Our liver cells has large amounts of smooth ER, these enzymes aide in processing drugs, alcohol, and other potentially harmful substances Rough ER- has ribosomes attached to the outer surface of the membrane with other important functions; makes more membrane As the endoplasmic reticulum membrane grows, portions of it are transferred to other components of the endomembrane system as vesicles. The bound ribosomes attached produce proteins to be inserted into the growing ER membrane, transported to other organelles, or secreted by the cell 5.1 Fluid mosaic- A bilayer of phospholipids with embedded and attached proteins Some proteins help maintain cell shape and coordinate changes inside and outside the cell through their attachment to the cytoskeleton and extra cellular matrix. Other proteins function as receptors for chemical messengers (signaling molecules from other cells) from other cells. Signal Transduction- The binding of a signaling molecule triggers a change in the protein, which relays the message into the cell, activating molecules that perform specific functions. Some membrane proteins are enzymes, which may be grouped in a membrane to carry out sequential steps for a metabolic pathway. Membrane proteins also participate in intercellular junctions that attach adjacent cells. Selective permeability- When membranes allow some substances to cross more easily than others A membrane can enclose a solution that is different in composition from its surroundings. A plasma membrane that allows cells to regulate their chemical exchanges with the environment is a basic requirement for life. 5.3 Diffusion- The movement of molecules from an area of high concentration to an area of low concentration, until the space reaches equilibrium There is a net movement from the side of the membrane where the dye molecules are more concentrated to the side where they are less concentrated Concentration gradient- the region along which the density of a chemical substance increases or decreases Active Transport- a cell has to give off energy in order to move a solute across its concentration gradient; allows a cell to maintain internal concentrations of small molecules and ions that are different from the concentrations in its surroundings; moving anything Passive Transport- When molecules diffuse across a membrane Both oxygen and carbon dioxide are small nonpolar molecules that diffuse easily across the phospholipid bilayer of a membrane. 5.6 Facilitated Diffusion- When polar or changed substances can move across a membrane with the help of specific transport proteins; a type of passive transport because it does not require energy Nonpolar hydrophobic molecules can dissolve in the lipid bilayer of a membrane and cross it with ease. Without the transport protein, the substance cannot cross the membrane, or it diffuses too slowly to be useful. The transport protein is specific for the substance it aids in movement across the membrane. The more transport proteins, the faster the solute diffuses. 5.9 Exocytosis- When a cell exports bulky materials (proteins/polysaccharides) [fibroblast releasing collagen fibers into extra-cellular space for incorporation into the ECM A transport vesicle (containing macromolecules) excretes from the Golgi apparatus, moving to the plasma membrane. Then it fuses with the plasma membrane. Once fused, the macromolecules are released into the new fusion of vesicle and plasma membranes. Endocytosis- opposite of exocytosis; when large molecules are consumed by the cell; A depression in the plasma membrane pinches in and forms a vesicle enclosing material, that was previously outside the cell  Phagocytosis- “cellular eating”; cell wraps pseudopodia around a particle, packaging it in a vacuole. The vacuole then fuses with a lysosome, whose hydrolytic enzymes digest the contents of the vacuole.  Pinocytosis- “cellular drinking”; the cell consumes large amounts of fluid into small vesicles, taking in any and all solutes dissolved in the droplets  Receptor-mediated endocytosis- highly selective; Receptor proteins for specific molecules are embedded in regions of the membrane, lined by a coating of proteins Cells use receptor-mediated endocytosis to take in cholesterol from the blood for synthesis of membranes and as a precursor for other steroids Phospholipid Bilayer Phospholipids have a polar head group with fatty acid tail (nonpolar) Micelle- many phospholipids collect together with the head on the outside, creating a vesicle to protect the hydrophobic tails on the inside Bilayer- two layers of phospholipids, top layer head up, bottom layer head down, creating hydrophobic core. This is the barrier between two layers of water Amphipathic- can survive in and out of water (phospholipids) Water is the most abundant molecule inside and outside the cell. Cytoplasm is 70-90% water. LARGE AND CHARGED CANNOT CROSS THE BILAYER Small and uncharged can cross the P-L tails Materials cross into/out of cells either through the membrane or via membrane vesicles Plasma membrane- membrane that surrounds the cell; phospholipid bilayer & other associated proteins and biomolecule


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