Biochem Soto 11/24, 12/1
Biochem Soto 11/24, 12/1 CHEM 351
Popular in Biochemistry
verified elite notetaker
Popular in Chemistry
This 7 page Class Notes was uploaded by Kayli Antos on Saturday December 12, 2015. The Class Notes belongs to CHEM 351 at Towson University taught by Ana Soto in Summer 2015. Since its upload, it has received 16 views. For similar materials see Biochemistry in Chemistry at Towson University.
Reviews for Biochem Soto 11/24, 12/1
Report this Material
What is Karma?
Karma is the currency of StudySoup.
You can buy or earn more Karma at anytime and redeem it for class notes, study guides, flashcards, and more!
Date Created: 12/12/15
Biochem Soto Fall 2015 339 G1 ycol ysis 0 Mechanism NAD is reduced when a hydride ion transfers from the aldehyde of the glyceraldehyde 3 phosphate to the nicotinamide ring of the NAD For subsequent glycolysis NADH needs to be reoxidized to NAD NADH can be aerobically oxidized in the respiratory chain or anaerobically oxidized by the reduction of pyruvate The sulfur of the enzyme bonds to the aldehyde carbon causing the carbonyl bond to become a single bond and the oxygen to have a negative charge Then NAD takes the H and the carbonyl reforms The inorganic phosphate group then attacks the carbonyl carbon and the carbon then detaches from the sulfur of the enzyme thus regenerating it 5 Step 7 Phosphoryl Transfer Prom 13 Bisphophoglycerate To Q The transfer of the phosphoryl group from l3 bisphosphoglycerate to ADP is catalyzed by phosphoglycerate kinase Steps 6 and 7 are a coupled process where the oxidation of glyceraldehyde 3 phosphate is conserved by the formation of ATP When ATP is formed from a phosphoryl group being transferred by a substrate that s substrate level phosphorylation 5 Step 8 Conversion Of 3 Phosphoglycerate To 2 Phosphoglycerate The reversible shift of the phosphoryl group from C2 to C3 is catalyzed by phosphoglycerate mutase This is a two step reaction The enzyme initially is phosphorylated at a His reside and is regenerated by the end of the cycle The enzyme phosphorylates C2 and then dephosphorylated C3 5 Step 9 Dehydration Of 2 Phosphoglycerate To PEP I The reversible removal of one water molecule from 2 phosphoglycerate is catalyzed by enolase Phosphoenolpyruvate PEP is formed I 0 Step 10 The differences between the Gibbs energies of the reactants and products is very large Transfer of A Phosphoryl Group From PEP To ADP I Pyruvate kinase catalyzes the transfer of the phosphoryl group from PEP to ADP The pyruvate product appears here in its enol form and it is then tautomerized to its keto form About half of the energy from the hydrolysis of PEP is conserved in the formation of ATP and the other half drives the reaction towards its synthesis This reaction is irreversible 0 Hexokinase I I I There are four different hexokinases I and II are in the muscle s and are allosterically inhibited by glucose 6 phosphate the product The enzymes KM 01 mM and since the blood glucose level is 5 mM the enzyme is always working as fast as possible The liver enzyme IV has a KM lO mM and its rate will vary with glucose available The liver enzyme is inhibited by a regulatory protein In the presence of fructose 6 phosphate the regulatory protein binds the hexokinase tightly but in the presence of glucose they dissociate Hexokinase is then able to leave the nucleus and enter the cytosol where it works 0 Phosphofructokinase I I I I The reaction that PEK I catalyzes commits glucose to glycolysis High concentrations of ATP inhibit PEK I ADP and AMP allosterically relieve the inhibition of ATP which increase at ATP decreases 0 Gluconeogenesis K K Converts pyruvate to glucose Occurs mainly in the liver but also in the kidneys and intestines Not identical to glycolysis but shares several steps The irreversible glycolysis steps are bypasses be separate enzymes for gluconeogenesis 5 Fructose 16 Bisphosphatase l I The reaction that EBPase l catalyzes is inhibited by AMP I The corresponding glycolytic enzyme PFK l is stimulated by AMP 0 Insulin And Glucagon I When levels of glucose in the blood decrease glucagon signals the liver to produce more Fructose 26 bisphosphate stimulated the activity of PFK l and therefore stimulates glycolysis F26BP is a regulator It is formed when fructose 6 phosphate is phosphorylated by not an intermediate phosphofructokinase II and is broken down by fructose 26 bisphosphatase TT Pancreatic hormones PFK 1 Fructose 6 Pi e9 fructose l6 BiPi FBP 1 PFKF Z Fructose 6 Pi e9 F26BP FBP 2 F26BP activates PFK l and inhibits FBP l 0 Pyruvate Kinase I All pyruvate kinases are allosterically inhibited by high concentrations of ATP acetyl CoA and long chain fatty acids The liver isozyme to regulation by phosphorylation When low blood glucose levels cause glucagon to be but not the muscle one is subject released the L isozyme is phosphorylated In muscle epinephrine activates glycogen breakdown and glycolysis 0 Feeder Pathways For Glycolysis I Many carbohydrates other than glucose can enter glycolysis after being transformed into one of the intermediates 0 Other Hexoses Enter Glycolysis I Ways fructose can enter glycolysis 0 fructokinase catalyzes the phosphorylation of fructose 0 fructose l phosphate can be cleaved to DHAP and glyceraldehyde 0 triose kinase catalyzed the phosphorylation of glyceraldehyde to form glyceraldehyde 3 phosphate 0 Fates Of Pyruvate I Pyruvate is metabolized by one of three ways 0 0 0 Aerobic organismstissues oxidized to acetyl CoA which is then oxidized to C02 in the citric acid cycle NADH is reoxidized to NAD and its electrons are passes to 02 The energy of electron transfer drives the synthesis of ATP 0 Lactic acid fermentation under hypoxic conditions reduced to lactate which accepts electrons from NADH and regenerated NAD under anaerobic conditions pyruvate is converted to ethanol and C02 0 Ethanol fermentation Lactic Acid Fermentation I The reduction of pyruvate is catalyzed by lactate dehydrogenase Ethanol Fermentation I I I Yeast and other microorganisms carry out this process The conversion of pyruvate to C02 requires two steps The first step is catalyzed by pyruvate carboxylase and is a simple decarboxylation In the second step the acetaldehyde is reduced to ethanol by alcohol dehydrogenase Pyruvate To Phosphoenolpyruvate Pyruvate converted to oxaloacetate by pyruvate carboxylase Acetyl CoA activates pyruvate carboxylase 0xaloacetate is converted to PEP by phosphoenolpyruvate carboxykinase GTP is the phosphoryl donor pyruvate ATP GTPI xh 9 PEP ADP GDP Pi C02 Fructose 16 Bisphosphate To Fructose 6 Phosphate I I I Catalyzed by fructose l6 bisphospatase FBPase l The Cl phosphate is irreversibly hydrolyzed fructose l6 bisphoshate HxD fructose 6 phosphate Pi Conversion Of Glucose 6 Phosphate To Glucose I I Catalyzed by glucose 6 phosphatase glucose 6 phosphate H29 glucose Pi Gluconeogenesis Is Expensive I I I 2 pyruvate 4 ATP 2 GTP 2 NADH 2 H 4 HAD9 glucose 4 ADP 2 GDP 6 Pi 2 NAD The six high energy phosphate groups are needed to ensure gluconeogenesis is irreversible intracellular conditions and Under both glycolysis gluconeogenesis are irreversible Pyruvate Carboxylase O 09 0 0 I First control point for gluconeogenesis be converted to acetyl CoA for the citric acid cycle or Pyruvate can oxaloacetate for gluconeogenesis Acetyl CoA inhibits pyruvate dehydrogenase and activates gluconeogenesis The Citric Acid Cycle The Critic Acid Cycle I I Pyruvate from glycolysis is further oxidized to C02 and H20 Cellular respiration is the aerobic phase of catabolism and occurs in three major stages 0 Organic fuel molecules converted to acetyl CoA 0 Citric acid Krebs to C02 and the energy released is conserved as NADH and FADH2 0 0xidative phosphorylation NADH FADH2 transfer their electrons to 02 and the released energy cycle where acetyl CoAis oxidized where and is conserved as ATP To start acetyl CoA donates oxaloacetate and forms citrate 0xaloacetate is regenerated at the end 4 of the 8 steps oxidizing the acetyl group to C02 and FADH2 0H2 For each turn one acetyl is turned into two C02 the acetyl group to The is conserved as NADH are oxidations energy from Production Of Acetyl CoA I I Sugars fatty acids and amino acids can all be degraded to acetyl CoA to enter the citric acid cycle Pyruvate is oxidized to acetyl CoA and C02 via pyruvate dehydrogenase Pyruvate Oxidation The carboxyl group of pyruvate is removed as C02 Three enzymes El E2 and E3 must work in sequence with five coenzymes CoA NAD thiamine pyrophosphate lipoate and FAD for this to occur The NADH formed will later transfer its electrons to 02 in the respiratory train Thiamine Pyrophosphate TPP I The thiazolium ring produces a carbanion which readily adds to a carbonyl group and acts as an electron sink to facilitate decarboxylation Lipoate 0 0 0 0 0 0 I Has two thiol groups that can reversibly be oxidized to a disulfide bond S S Can serve as an electron or acyl carrier Coenzyme A Has a reactive thiol group SH Acyl groups covalently link to the thiol group to form thioesters Thioesters have a large AG of hydrolysis so they donate their acyl group to many acceptor molecules The acyl attached to CoA is activated for group transfer Pyruvate Dehydrogenase Complex Contains multiple copies of three enzymes 0 pyruvate dehydrogenase El which contains TPP 0 dihydrolipol transacetylase E2 which contains lipoate 0 dehydrolipoyl dehydrogenase E3 which contains FAD Substrate Channeling I I The PDH complex carries out 5 functions 1 Cl of pyruvate released as C02 and C2 attaches to TPP as hydroxyethyl 2 The hydroxyethyl is oxidized and the electrons reduce the S S in the lipoyl group esterified to a reduced SH group The acetyl moiety is 3 The acetyl group tranfers from lypoyl to CoA 4 amp EL The lypoyl is oxidized and tjma enzymes get transferred to NAD The enzyme is regenerated Substrate channeling when the enzymes are clustered together to the intermediates will react in sequence Glucogenic And Ketogenic Amino Acids I I Some amino acids can be converted to citric acid cycle intermediates glucogenic Some amino acids can be converted to acetyl CoA ketogenic l NADH eventually yields 25 ATP l QH2 eventually yields l5 ATP glucose 399 2 pyruvate 2 ATP 2 NADH 2 pyruvate 399 2 acetyl CoA 2 NADH 2 acetyl CoA 4 C02 2 ATP 6 NADH 2 QH2 total 4 ATP 10 NADH 2 QH2 4 ATP 25 ATP 3 ATP 0 32 ATP total from 1 glucose
Are you sure you want to buy this material for
You're already Subscribed!
Looks like you've already subscribed to StudySoup, you won't need to purchase another subscription to get this material. To access this material simply click 'View Full Document'