General Biochemistry notes set 3
General Biochemistry notes set 3 4115
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This 3 page Class Notes was uploaded by Thomas Salazar on Sunday September 25, 2016. The Class Notes belongs to 4115 at Virginia Polytechnic Institute and State University taught by Dr. Richard Helm in Fall 2016. Since its upload, it has received 7 views. For similar materials see General Biochemistry in Biochemistry at Virginia Polytechnic Institute and State University.
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Date Created: 09/25/16
Note set #3 – week 5 General Biochemistry CARBOHYDRATES Carbohydrate sugars are typically “D” form o In Fischer projections, if the –OH group closest to the bottom is on the right, it is a D-sugar, on the left is an L-sugar e.g. sucrose is made up of D-glucose + D-fructose D and L forms of a sugar are enantiomers of each other, and are mirror images, with all –OH groups mirrored Changing just one H/OH pair forms epimers o the general formula for carbohydrates C +n(H O2 n RING STRUCTURES o Closing the ring of an aldose sugar hemiacetal, a ketose sugar hemiketal o If a ring has its C1 –OH group facing down in a Haworth projection, it is α; if the –OH group is facing up, it is β o Chair conformers should be drawn with the C6 facing up in D-sugars, facing down in L-sugars, and the C5 hydroxyl oxygen binding C5 and C1 depending on the stereochemistry of this bond’s formation, the sugar will either be α or β. CYCLIC SACCHARIDES o The Anomeric Position: the carbon that originally carried the carbonyl functional group o Furanoses: 5-membered rings from sugars that bond C5 hydroxyls to C2, where C2 was the anomeric carbon D-form still has C6 up, and C1 position depends on the stereochemistry of the bond formation o Variants: Uronic acid: C6 hydroxyl is oxidized to COOH detoxification Aldonic Acid: C1 hydroxyl oxidized to COOH blood monitoring Sugar alcohols: a carbonyl C=O bond is reduced to hydroxyl –OH Deoxy sugars: C2 has no hydroxyl group, or C6 becomes CH 3 Amino sugars: C2 hydroxyl is removed, then adds amido group Sugar phosphates: conversion of hydroxyls to phosphate groups GLYCOSYDIC BONDING o Accomplished organically by enzymatic processes can either retain or invert the α / β stereochemistry o Adds monosaccharides to the non-reducing end of sugars, and once it is bonded the ring cannot open again In sucrose, both anomeric positions of glucose and fructose are bonded to each other In starches, carbohydrates form branching bonds off C6 positions as well OLIGOSACCHARIDES AND POLYSACCHARIDES Note set #3 – week 5 General Biochemistry o Reducing ends of sugars can form O-linked bonds Serine, and Threonine, or N-linked bonds Asparagine o Glycoproteins: slippery Oligosaccharides are typically found at random coil regions in proteins Can act as cellular markers or identifiers o Proteoglycans: carbohydrates bound to membrane proteins Bound within cell membranes Highly hydrated Usually form part of the structural aspect of a cell o ABO blood scheme The essential “O” antigen is present in everyone, various glycan chains added by certain enzymes will convert this to either an A or B antigen o O-GlcNAc signaling UDP-GlcNAc is synthezied as a “byproduct” of a large number of metabolic pathways that produce energy in cells By analyzing the levels of UDP-GlcNAc and its subsequent forms, one can measure the energy output of a cell LIPIDS o Humans cannot oxidize single bonds to double bonds past C9 on fatty acids o Fatty acids are generally made of chains of equal lengths Nomenclature o Built in units of 2, based on Acetyl-CoA o Unsaturated fatty acids Named as: (Acid Name) C(#of carbons): (# of double bonds) (Δ a,b,c,d,e,f) (cis or trans) e.g. An acid with a 22 carbon chain with 6 double bonds at 4,7,10,13,16, and 19 that are all cis-configuration would have the name: Acid C22: 6 Δ4, 7, 10, 13, 16, 19 cis trans fats are “bad,” but trans-conjugated fatty acids are found to be the most effective anti-carcinogenic found to date Fatty Acids (FA) characteristics o Amphipathic, with non-polar and polar regions (tail and head) o Removing one of the non-polar tails forms a detergent, very hazardous to organic systems o Low solubility in water, blood density of FA’s is very low They must be moved by carrier proteins through the blood stream o Stored typically as triglycerides tri-glycerol base that is modified through esterification reactions to form many different chains and variations R 1OO-CH -CH2CH -OOCR2 3 (COOR ) 2 If all three R groups are the same it is considered simple. If they are different, it is complex Deposited in adipose tissue Note set #3 – week 5 General Biochemistry White adipose tissue has fewer mitochondria Brown adipose tissue has more, burns more energy Adipose tissues can cleave fatty acids as signaling to other cell types (muscles, neurons, etc…) and responds to extracellular signals; we have very little control over how adipose tissue acts Membranes: o Lipid bilayers contain lipophilic substances and proteins o The lipids on the inside of a membrane are different from the ones on the outside layer o The head-group typically has a phosphate ***by convention, the phosphatized group is considered C3 of the triglyceride structure*** o The other two chains, C1 and C2 contain various fatty acids, which lends to a plethora of possible different lipids. C2 chains are typically unsaturated, while C3 chains are typically saturated Phosphatidyl-X C3 phosphate group forms bonds with an R1 group, either choline, ethanolamine, serine, or glycerol Ether glycerophospholipids: present in extremely small quantities, formed during allergic reactions. If concentration >10e-12 M, leads to anaphylactic shock Plasmologens: cis-vinyl ethers Sphingolipids: modified version of the central triglyceride molecule C18 molecule o The central –OH group is converted to a primary amine, reacts o 2° hydroxyl typically not modified, but C3 o 1° hydroxyl reacts 1. Ceramides: acylated at 1° amine 2. Sphingomyelin: acylated at 1° amine + 1° OH converted to phosphorylcholine or phosphorylethanolamine 3. Cerebrosides: acylated at 1° amine + 1° OH converted to β-D-glucopyranosyl or β- D-galactopyranosyl 4. Sulfatides: 1° OH converted to β-D-Galp-3-O
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