Cell Metabolism Study Handouts

What is metabolism? Interconversion of biomolecules using chemical reactions Are catabolic reactions usually oxidative or reductive? Oxidative Are catabolic reactions degradative or biosynthetic? Degradative Are anabolic reactions usually oxidative or reductive? Reductive What is glycolysis? Breaking down of glucose to make pyruvate Two lots of which molecule is required to start glycolysis? ATP How many stages are involved in glycolysis? 3 What is the starting molecule for glycolysis? Glucose What is the end molecule following two lots of phosphorylation in stage one glycolysis? Frutose-1,6-bisphosphate -Ring structure rearranged from a 6-membered (glucose) to a 5-membered What are the key structural changes in (fructose) after one lot of phosphorylastage 1 glycolysis? tion -Ring opens up into a straight chain after the second lot of phosphorylation In glycolysis stage 2, what is input? Nothing, only enzyme action in stage 2 What are the net products of stage 2 glycolysis? 2x glyceraldehyde (3-phosphate) molecules -1x molecule of Dihydroxyacetone (phosWhat is fructose 2,6-bisphosphate initial- phate) ly converted to during stage 2 glycolysis? -1x molecule of Glyceraldehyde (3-phosphate) 1/9 What happens to the one molecule of dihydroxyacetone produced in stage 2 glycolysis? -Converted to the second molecule of glyceraldehyde (phosphate) What enzyme converts dihydroxyacetone into glyceraldehyde? Triose phosphate isomerase What is the first step of the 3rd stage of glycolysis? -Oxidation of glyceraldehyde (3-phosphate) via an NAD molecule -Producing 1,3-Bisphosphoglycerate (two phosphates attached) -And a molecule of NADH What molecule removes one of the phosphates from 1,3-Bisphosphoglycerate to phorm 3-phosphoglycerate? -ADP -Producing a molecule of ATP How does 3-phosphoglycerate become Phosphoenolpyruvate (phosphorylated pyruvate)? Rearrangement of atoms via enzymes What molecule removes the last phos- -ADP phate from Phophoenolpyruvate to form -To produce the second molecule of ATP per each glyceraldehyde pyruvate? How many molecules of ATP are produced during glycolysis PER glucose? FOUR How many molecules of NADH are produced during glycolysis PER glucose? TWO What is the net production of ATP per molecule of glucose in glycolysis? -TWO -As two molecules were used in the first stage of glycolysis When the body is low on oxygen, which oxidising agent is there an absence of? NAD+ -NADH reduced to NAD+ in the electron transport chain (ETC) Why does the Krebs cycle need oxygen? -ETC requires oxygen -Without oxygen there is no NAD+ acting as the reducing agent 2/9 -Conversion of pyruvate (produced in glycolysis) -To R-Lactate (lactic acid) -The conversion process produces a molecule of NAD+ per each R-lactate made In anaerobic conditions, what is the body's response to a lack of NAD+? How does the body produce ATP during anaerobic conditions? Glycolysis Post anaerobic conditions, what does the body do with the excess lactate? -Transported to the liver through the bloodstream -Lactic acid reoxidized back into pyruvate using NAD+ -Pyruvate can then enter the Krebs cycle to produce ATP What is the name of the cycle that recycles R-lactate to glucose (a combination of glycolysis and glucogenesis)? Cori Cycle What is the purpose of glucogenesis? Conversion of R-Lactate to Glucose What enzyme, with NAD+, converts R-Lactate to pyruvate? Lactate dehydrogenase Where does glucogenesis occur? Liver cystol Where does glycolysis occur? The cytoplasm of muscle cells How many molecules of ATP are needed to convert two molecules of pyruvate to one molecule of glucose? SIX To convert glucose to lactate and back to glucose again (one repetition of the Cori cycle), what is the net loss of ATP? FOUR How many molecules of pyruvate are required to make one molecule of glucose? TWO -Enzymes -ATP 3/9 What is required to convert pyruvate to oxaloacetate in gluconeogenesis? -CO2 (where the extra carbon comes from) Where does the conversion of pyruvate to oxaloacetate occur? In mitochondria Following oxaloacetate production in gluconeogenesis, where is it exported to? Liver cystol Once moved to the liver cytosol, what is oxaloacetate converted into? Phosphoenolpyruvate How many molecules of phosphoenolpyruvate (PEP) are needed to make one molecule of fructose-1,6-bisphosphate? TWO -Bisphosphatase How is fructose-1,6-bisphosphate con-'Bi' as it removes the first of TWO phosverted into fructose-6-phosphate? phate groups How does fructose-6-phosphate get converted into glucose-6-phosphate? Enzymes What molecule removes the last phosphate of glucose-6-phosphate to form glucose? Phosphatase How many molecules of NADH are required for gluconeogenesis (conversion of two pyruvates into glucose? TWO What controls the entry of pyruvate into the Krebs/citric acid cycle? Pyruvate dehydrogenase complex How many subunits does pyruvate dehydrogenase complex have? 3 What are the three pyruvate dehydrogenase complexes called? -E1 -E2 -E3 What is the name for the E1 pyruvate dehydrogenase subunit and how many do humans have? -Pyruvate dehydrogenase -Humans have 30 What is the role of the E1 subunit? Decarboxylates pyruvate 4/9 What is the name for the E2 pyruvate dehydrogenase subunit and how many do humans have? -Dihydrolipoyl transferase -Humans have 12 What is the role of the E2 subunit? Makes CoA What is the name for the E3 pyruvate dehydrogenase subunit and how many do humans have? -Dihydrolipoyl dehydrogenase -Humans have 12 What is the role of the E3 subunit? Converts reduced lipoamide to disulfide form (with FAD) What are the 4 steps of formation of acetyl-CoA? -TPP anion added to pyruvate via E1 subunit - CO2 released -Lipoamide disulfide added to the acetyl group via the E2 subunit -Disulfide exchange occurs to form acetyl-CoA and reduced lipoamide (via E2) -Reduced lipoamide is oxidised to its disulfide form using the E3 subunit and FAD What is the tricarboxylic acid cycle? Krebs cycle How many stages are there in the Krebs cycle? 4 What enzyme catalyses the reaction for the addition of oxaloacetate and acetyl-CoA and what does this reaction form? -Citrate synthase -To form a molecule of citrate What happens to the newly formed cit- Rearrangement of atoms to form isocirate in the first stage of the Krebs cycle? trate In stage 2 of the Krebs cycle, how is isocitrate converted to ß-ketoacid? NAD+ and via the loss of CO2 In stage 2 of the Krebs cycle, how is the ß-ketoacid converted to 2-oxoglutarate? NAD+ and via the loss of CO2 In stage 2 of the Krebs cycle, how is 2-oxoglutarate converted to succinyl-CoA? Multi-enzyme complex (CoA) 5/9 How much energy is released when removing the first phosphate of a molecule of ATP? 30.5 KJmol-1 How much energy is released when removing two phosphates from a molecule of ATP to form AMP? 45.6 KJmol-1 What is the main structural difference between NAD and NADP? NADP has an additional phosphate group In stage 3 of the krebs cycle, what replaces the enzyme complex (CoA) to form succinyl? Phosphate group -To remove the enzyme complex In stage 3 of the Krebs cycle what is the -Good leaving group to be removed afpurpose of adding the phosphate group? terwards In stage 3 of the Krebs cycle, how is the phosphate removed and what is it subsequently used to make? -Phosphate group removed by an enzyme -Used to phosphorylate a GDP molecule to form GTP In stage 3 of the Krebs cycle, when the enzyme complex and the phosphate group have been removed from succinyl coA what is formed? Succinate Which biologically significant molecule can GTP be converted into and how? -ATP -Enzyme action In the 4th and final stage of the Krebs cycle, What is the starting and end products? Succinate to oxaloacetate In stage 4 of the Krebs cycle, what molecule is used as the oxidising agent to desaturate the C-C bond in succinate? FAD+ In stage 4 of the Krebs cycle, what happens to the double bond to form S-malate? -Hydration -One side of the double bond gets a hydrgen -The other side gets a hydroxyl group 6/9 In the final step of stage 4 of the Krebs cycle, which molecule oxidises the hydroxyl group to form, a ketone group, and therefore oxlaloacetate? NAD+ Where does the electron transport chain take place? In the mitochondria What are the two key parts of oxidative phosphorylation? -ETC (electron transport chain) -Chemiosmosis What sets up the proton gradient in oxidative phosphorylation? The electron transport chain What provides the electrons in the electron transport chain? Oxidation of NADH What provides the energy for the proton pumps in oxidative phosphorylation? Electrons What membrane-bound protein do H+ ions flow through in order to phosphorylate ADP to form ATP? ATPsynthase Where do the proton pumps move H+ ions from and to? -From the mitochondrial matrix -To the mitochondrial inter membrane space The process of protons flowing down their concentration gradient through ATP synthase to form ATP, from the intermembrane space to the mitochondrial matrix is known as what? Chemiosmosis -Accept extra electrons At the end of the ETC, what is oxygens' -Combine with H+ ions to from water role? -Helps the flow of ETC and maintenance of proton gradient If oxygen is not present, why does the ETC stop? -Nothing to accept the electrons at the end of the ETC -Electron flow stops -No more proton gradient 7/9 -ETC stops -No proton gradient -No proton flow through ATP synthase Why does lack of O2 stop ATP production? Why does NADH in the cytosol yield less It takes ATP to move the NADH into the ATP than NADH in the mitochondria? mitochondria What is UDP-glucose? High energy form of glucose How is glucose-1-phosphate converted into UDP-Glucose? Addition of UTP How is UDP-glucose converted into glycogen? -UDP acts as a leaving group -For addition of glucose molecules to form the glycogen chain On which bonds do glucose molecules attach in glycogen? 1-4 When UDP leaves the UDP-Glucose, what sort of ion is left? Oxycation Which carbons does branching occur on glycogen? 1-6 What is the effect on solubility on increasing glycogen branching? The more branches the more soluble What enzyme degrades the 1-4 glycogen bonds? Glycogen phosphorylase How does glycogen phosphorylase break 1-4 bonds? -Forms oxycation intermediate on the oxygen on carbon 4 -Phosphate adds to the oxycation and the rest of the chain breaks off, leaving glucose-1-phosphate Can glycogen phosphorylase break 1-6 bonds? NO What enzyme removes the 1-6 bonds in glycogen once the 1-4 bonds have been broken? 1,6-glycosidase What are triglycerides composed of? -1 glyceride -3 fatty acids 8/9 What type of tissue are triglycerides(fats) stored in? Adipose What is the reason for storing fats as triglycerides? -Dense in energy What enzyme splits glycerol from the fatty acids? Lipase What is fatty acid ß-oxidation? -The metabolic breakdown of fatty acids to from acetyl CoA -In order to be fed into the Krebs cycle to make ATP What is added to fatty acids to remove the carboxylic acids OH in fatty acid ß-oxidation? -Addition of the CoA enzyme complex What two molecules are used to oxidise the fatty acid chain in fatty acid ß-oxidation? NAD and FAD What sort of reaction splits the fatty acid chain and the glycerol in a triglyceride? Hydrolysis (via Lipase) What two molecules are essential for fatty acid biosynthesis? -Acetyl-CoA -CO2 What is malonyl CoA? -The activated form of acetyl CoA -Precursor for fatty acid synthesis What two molecules are needed to make carboxybiotin? -ATP -CO2 What is the key regulatory enzyme in the reaction that forms malonyl-CoA from acetyl-CoA? Acetyl-CoA carboxylase Where is Acetyl-CoA carboxylase located? Cytosol What is the role of the acyl carrier protein (ACP)? -Carries growing fatty acid chains between lipase enzymes Degradative pathways are ______? Oxidative Biosynthetic pathways are _______? Reductive 9/9