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SC BIOL 541 - Metabolism
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BIOL 541 1st Edition Lecture 12 Outline of Last Lecture I. Enzymes. Outline of Current Lecture II.MetabolismIII. GlycolysisIV. Citric acid cycleCurrent LectureBiochem Lecture 12- Principles of Metabolism:Definitions:Metabolism – is sum of all processes that handle or alter materials within living organisms. It is basically divided into:1. Mineral and water metabolism: Here Na can not be altered by absorption, hence not considered in this course.2. Energy metabolism:a. Catabolism- breakdown of substance to release energy.b. Anabolism- synthetic pathway.All processes are enzymatically catalysed. It allows for regulation of processes: Hb has protein that regulates oxygen. Non enzymatic reaction occurs where vitamin D is converted to active form. Vitamin D is not a coenzyme but pro- hormone which can not be absorbed in the gut.1. Vitamin D goes to the skin where one ring is ruptured by uv light.2. Addition of OH group occurs in the liver and kidneys- enzymatic reaction.Children working in factories can not absorb Ca as not exposed to sunlight. The bones are not well ossified, less rigid, leg bows as rickets develops.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Within every pathway at least one irreversible step called committed step is a high control step. It may ormay not be same as rate limiting step or bottle neck or slowest step but is also highly regulated. Committed step allows forward and backward step to be separated and have separate control of regulations.Carbohydrates are polyhydroxy aldehydes or polyhydroxy ketones or derivatives. C chain has C=O at end is termed aldehyde. C cahin with C=O at the inside is ketone: many groups of OH is termed as polyhydroxy. Sugars are generally represented as flat projections. However, they are tetrahedral in form- horizontal bond wedge shaped to indicate lines out of board and vertical bond in dotted shape indicatinginto the board. OH on right, or OH on left, not superimposable.Asymmetrical C has OH flipped to another side, example D-ribose -- D. Arabinose and each needs a different enzyme. All natural sugars are in D form and lab created ones are in L form. There are 5 sugars and eight isomers. In solution, hemiacetyl forms as aldehyde reacts with OH. This intramolecular hemiacetyl is due to aldehyde and OH in the same compound.Haworth formula shows structure as flat ring- lower portion is thickened and out of board.OH group on down is termed as alpha.OH group on up is termed as beta.Fructose:C=O at 2C, 5C of OH forms bonds. 1C forms furan ring.Ketones are symmetrical.Hemiacetyl are asymmetrical.Glucose has different conformations:Boat- nose and tail up.Chair- OH groups in equatorial position and less interference in solution. This form has lower energy when in solution.Furanose rings: 2 conformations: Envelope- one atom out of plane.Twisted- several atoms out of plane.In solution, DNA structure occurs as twisted form for the type of helix.Glucose can be polymerized to form polysaccharides. They serve structurally and functionally as cellulose as depots of energy as starch or glycogen. Two major types of polysaccharide conformation:1. Glucose homo polysaccharide- Alpha 1,4 linkage coupling between 1C and 4C. Some polysaccharide alternate bonds as staircase appearance is favored just like spiral. Spiral form occurs when polysaccharide acquires helix form alpha 1, 4 linkage.2. Cellulose homo polysaccharide also has 1, 4 linkage but as beta in equatorial and strand is flat and parallel to one another with lots of H bonding. Cellulose forms sheets Beta 1, 4 Linkage. Fibrous sheets are in the core of the cell wall.Differences between Polysaccharides and Proteins: Polysaccharides Proteins1. Synthesis Enzymes- Glycogen synthesis Ribososmes- Variability2.Sequence Enzyme specificity Template- m.RNA3. Monomers Monosaccharides Amino Acids4. Size No counter –estimate only Start site and stop Site, size fixed5. Bond Glycosidic (ether) peptide (amide)6. Variability Location of bond Amino acid in cis or1,6 1,4 or 1,3 trans7. Branching Common RarePathways that breakdown glucose:1. Glycolysis- 6C glucose is cut into 2 pyruvate of 3C. 2 ATP formed as substrate level phosphorylation. 2 NADH formed and held in advance.2. TCA (Tricarboxylic acid or citric acid cycle: 2 Acetate (2C) ---- 4 CO2 + H+ (H+ O2 --- H2O). 2 CO2 per acetate.2 Substrate level phosphorylation: Pyruvate dehydrogenase bridges TCA cycle to glycolysis.Oxidative decarboxylation of pyruvate: Pyruvate-- CO2 leaves (decarboxylation). Ketone -- acetate (oxidative process).3. Electron Transport Chain (ETC):H+ plugged into ETC to form water and regenerate oxidized form of co- enzyme NAD. This is where bulk of energy is generated.During oxygen deficiency as in exercise, more reduced form of co- enzymes form and TCA cycle shuts down. Energy from glycolysis is 2 ATP only: since reduced NAD is not formed, glycolysis can not go further.Pyruvate becomes H+ acceptor and H+ across C=O to form lactate or lactic acid.Glycolysis – is also termed as anaerobic respiration as it can function in absence of oxygen.Gluconeogenesis- is the reverse of glycolysis. Gluconeogenesis refers to creation of new glucose, as glucose can be formed from non carbohydrate sources. In the body only few hours of energy are released from glycogen. Brain can not use fat and needs glucose.Amino acids --- GlucoseAmino acids ---- pyruvate except 3 irreversible


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