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Lecture 26 Metabolism and Bioenergetics.docx

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University of Toronto St. George
Michael Baker

BCH210H © Lisa| Page 112 L E C T U R E 2 6 : M E T A B O L I S M A N D B I O E N E R G E T I C S  metabolism: the entire network of enzyme rxns in cells  anabolism: rxns that synthesize molecules or make more complex molecules  building up of proteins from the 20 AAs (thousands of diff proteins depending on seq)  makes things that are more complex  divergent—20 AAs to thousands of proteins  NRG input required  ex. pyruvate (3C) to glucose, glucose to branched glycogen, pyruvate to acetyl coA, acetyl coA to fatty acids  catabolism: rxns that degrade larger molecules to smaller molecules  convergent—from thousands of proteins broken down to 20 AAs (smaller # of diff types)  NRG released  ex. glycogen to glucose phosphate  ex. proteins to AA  ex. nucleic acids to nucleotides  ex. fats to FFA  ex. glycolysis—glucose to 2C and 3C parts through  ex. β-oxidation—fatty acids to acetyl coA with release of NRG  ex. glycogenolysis—breakdown of glycogen to glucose-1-phosphate  roles of metabolism:  produce NRG by the breakdown of fuels—glucose, FFA  make molecules—DNA, RNA, lipids, proteins, AAs, glucose  make fuel storage molecules—triglycerides, glycogen  convert one molecule into another—ex. glucose → FFA  generally NRG released during catabolism is used in anabolic pathways or in cellular work ex. muscle contraction  catabolic paths fuel anabolic paths  usually requires many enzymes that work in sequence  complete change is a result of steps of changes with each step with an enzyme  pathways: the synthesis or breakdown of a molecule usu relies on a number of sequential enzyme rxns  product of one enzyme serves as substrate of next enzyme  linear pathway: a number of enzyme steps in seq to achieve a final product ex. glycolysis  potential problems: if there is a block in the pathway, you can’t get past it  pathway can be made more efficient if there is an enzyme with multiple active sites built-in  or diff subunits  mammals have large multifunctional enzymes that have more than one active site  thus, 1 large complex can carry out a seq of rxns  complex enzyme: separate enzymes held together covalently  enzyme cycle: a circle of rxns where the last step generates the first substrate  imp components are the inputs and products put into and going out of the cycle  ex. Kreb’s Cycle BIOENERGETICS  bioenergetics: production of NRG and use of NRG  ATP is the principal carrier of NRG in cells  NRG is stored as ATP BCH210H © Lisa| Page 212  ATP synthesis allows the conservation of NRG released in catabolism to be used in anabolic rxns or do work ex. muscle contraction  ATP is the intermediate shuttling bw catabolism and anabolism  ATP—adenosine triphosphate  ATP is a nucleotide with the base adenine, the sugar ribose and the 3 phosphates  triphosphate—3 phosphate groups (α, β, γ) in a row each on a diff C  2 high NRG anhydride bonds linking γ to the β, and β to the α  phosphoanhydride bonds are very NRGetic  release of a lot of NRG if broken which an support anabolic rxns or active transport or mechanical NRG (muscle contraction)  ester link is the least NRGetic  ATP is often synthesized by the phosphorylation of ADP: ADP + Pi → ATP + H2O  ATP has 4 negative charges at pH 7.4  becomes a more stable molecule as phosphates are released—gets rid of negative
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