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Biology
Metabolic Pathways
| Question | Answer |
|---|---|
| Which step in glycolysis goes from glucose to glucose-6-phosphate? What is the enzyme used for this conversion? | - This step 1 of glycolysis - The enzyme used is called hexokinase ( it involves the transfer of a terminal phosphate group of an ATP unit to some other compound) - ATP is converted into ADP |
| Which step in glycolysis goes from glucose-6-phosphate to fructose-6-phosphate? What is the enzyme used for this conversion? | - This is step 2 of glycolysis - The enzyme used is called phosphoglucoisomerase |
| Which step in glycolysis goes from fructose-6-phosphate to fructose-1,6-diphosphate? What is the enzyme used for this conversion? | - This is step 3 of glycolysis - The enzyme used is called phosphofructokinase - ATP is converted into ADP |
| Which step in glycolysis goes from fructose-1,6-diphosphate to DHAP and glyceraldehyde-3-phosphate? What is the enzyme used for this conversion? | - This is step 4 of glycolysis - The enzyme is called aldolase |
| Which step in glycolysis goes from DHAP to glyceraldehyde-3-phosphate? What is the enzyme used for this conversion? | - This is step 5 of glycolysis - The enzyme used is called triose phosphate isomerase |
| How many molecules of glyceraldehyde -3-phosphate can be made from 1 fructise-1,6-diphosphate? | Two |
| Which steps in glycolysis are apart of phase 1 of glycolysis? | Steps 1 - 5 |
| Which step in glycolysis goes from glyceraldehyde-3-phosphate to 1,3-diphosphoglycerate? What is the enzyme used for this conversion? | - This is step 6 in glycolysis - The enzyme used is called glyceraldehyde-3-phosphate dehydrogenase - 2 NAD+ and Pi are converted into 2 NADH and 2 H+ |
| Which step in glycolysis goes from 1,3-diphosphoglycerate to 3-phosphoglycerate? What is the enzyme used for this conversion? | - This is step 7 in glycolysis - The enzyme is called phosphoglycerate kinase - ADP is converted into ATP |
| Which step in glycolysis goes from 3-phosphoglycerate to 2-phosphoglycerate. What is the enzyme used for this conversion? | - This is step 8 in glycolysis - The enzyme is called phosphoglyceromutase |
| Which step in glycolysis goes from 2-phosphoglycerate to phosphoenolpyruvate? What is the enzyme used for this conversion? | - This is step 9 of glycolysis - The enzyme used is called enolase |
| Which step in glycolysis goes from phosphoenolpyruvate (PEP) to pyruvate? What is the enzyme used for this conversion? | - This is step 10 in glycolysis - The enzyme used is called pyruvate kinase - ADP is converted to ATP |
| What causes lactate to be produced? | It occurs in the cells of organisms when oxygen becomes a limiting factor |
| What are the two different pathways that pyruvate can take to regenerate NAD+ ? | 1) The production of lactate 2) The production of Ethanol (yeasts) |
| The convention from pyruvate to lactate uses what enzyme? | Lactate dehydrogenase |
| What enzymes are used to convert pyruvate to ethanol? | 1) pyruvate decarboxylase (pyruvate to acetaldehyde)(H+ converted to CO2) 2) alcohol dehydrogenase (acetaldehyde to ethanol) (NADH + H+ converted to NAD+) |
| What does high ATP levels inhibit? | Phosphofructokinase from step 3 of glycolysis |
| What does low levels of AMP stimulate? | Phosphofructokinase |
| What kinds of disaccharides can enter glycolysis and which must be converted first then enter into glycolysis? | - Can enter = glucopyranose - Converted first then enter = fructofuranose |
| What are the different names for the Krebs cycle? | The citric acid cycle and the tricarboxylic acid cycle |
| Where does the citric acid cycle take place? | The mitochondria |
| Where does glycolysis take place? | The cytosol |
| In anaerobic conditions, pyruvate can be converted into what? | - Bacteria pyruvate = lactic acid - Yeast pyruvate = carbon dioxide and ethanol |
| In aerobic conditions, pyruvate is converted into what? | Carbon dioxide |
| Define cristae | It is what the inner membrane is folded into and it increases the surface area of the inner membrane |
| What is the purpose of the Penrose phosphate pathway? | It is to generate reducing power in the form of NADPH and 5 carbon sugars such as ribose-5-phospahte |
| Where dose the pentose phosphate pathway occur? | In the cytosol |
| What are the mobile electron carriers found in the electron transport chain? What are their charges? | - NADH (2e-) - UQH2 (1-2e-) - Cyt c (1e-) |
| What are the non mobile electron carriers found in the electron transport chain? What are their charges? | - FADH2 (1-2e-) - Fe-S (1e-) |
| Where does the electron transport and oxidative phosphorylation occur? | They occur on the inner membrane of the mitochondria |
| What is another name for complex 1 of the respiratory chain? | NADH-Q Reductase |
| What is another name for complex 2 of the respiratory chain? | Succincte-Q Reductase |
| What is another name for complex 3 of the respiratory chain? | Cytochrome Reductase |
| What is another name for complex 4 of the respiratory chain? | Cytochrome Oxidase |
| Define cytochromes | They are electron transporting proteins that contain a heme prosthetic group with an iron atom that alternates between the Fe2+ and Fe3+ condition |
| Does the ETC have a positive or negative delta G not? | Negative |
| Why does FADH2 only generate 2 molecules of ATP in oxidative phosphorylation? | The electrons from FADH2 enter into the ETC at a lower energy level than the electrons from NADH |
| All of the ATP produced in the ETC is dependent of what? | The presence of oxygen |
| What is the enzyme used in oxidative phosphorylation? | F0F1 ATPase |
| Is the ATPase complex apart of the ETC? | No |
| Oxidative phosphorylation takes place in the inner membrane of the mitochondria, but where exactly in the inner membrane does it take place? | - Oxidation actually takes place in the respiratory chain - phosphorylation takes place in the ATPase complex |
| What are the different ways that NADH is transported into the mitochondrial matrix? | Via the glycerol phosphate shuttle or the malate-aspartate shuttle |
| How many ATP molecules can transported in each shuttle? | - Glycerol phosphate shuttle = 2 ATP molecules - Malate-aspartame shuttle = 3 ATP molecules |
| Which steps in the pentose phosphate pathway is part of the oxidative phase? | Steps 1 - 3 |
| Which steps in the pentose phosphate pathway is part of the non oxidative phase? | Steps 4 - 8 |
| Since mature erythrocytes do not have a mitochondria, where do they obtain their NADH from? | The pentose phosphate pathway |
| Where does the conversion of lactate to glucose take place? | In the liver |
| Define gluconeogenesis | It is the synthesis of glucose from non-carbohydrate precursors such as lactate, amino acids like alanine, and glycerol (which are all 3 carbon molecules) |
| During glycolysis and gluconeogenesis, how much ATP is gained or lost? | - Glycolysis = + 2 - Gluconeogenesis = - 6 |
| What enzyme is used to convert fructose- 1,6-diphosphate into fructose-6-phosphate? | Fructose- 1,6 - diphosphate phosphate |
| What enzyme is used to convert glucose - 6 - phosphate into glucose? | Glucose - 6 - phosphate phosphate |
| Are fats metabolized aerobically or anaerobically? | Aerobically |
| What happens to fats when they are broken down? | Fats are broken down into glycerols and fatty acids. Both will be converted into acetyl CoA (happens with two different pathways). The acetyl CoA will then enter into the kreb cycle and be converted into ATP |
| How does a fat become acetyl CoA through glycerol? | Fats -> glycerol -> DHAP -> pyruvate -> acetyl CoA |
| How does a fat become acetyl CoA through fatty acids? | Fats -> fatty acids -> acetyl CoA |
| What is step 1 in fatty acids oxidation via glycerol and what enzymes and coenzymes if any are used? | - Fat converts into 1 molecule of glycerol and 3 fatty acids residues - The enzyme used is lipase along with 3 H2O molecules |
| What is step 2 in fatty acids oxidation via glycerol and what enzymes and coenzymes if any are used? | - Glycerol to glycerol - 3 - phosphate - The enzyme used is glycerol kinase w/ coenzyme ATP |
| What is step 3 in fatty acids oxidation via glycerol and what enzymes and coenzymes if any are used? | - Glycerol - 3 - phosphate into DHAP - The enzyme used is called glycerol phosphate dehydrogenase with coenzymes NAD+ |
| What is step 4- 9 in fatty acids oxidation via glycerol and what enzymes and coenzymes if any are used? | It is steps 5 - 10 of glycolysis |
| What is step 10 in fatty acids oxidation via glycerol and what enzymes and coenzymes if any are used? | - Pyruvate into acetyl CoA - Enzyme used is pyruvate dehydrogenase complex with coenzyme NAD+ |
| What is step 1 in fatty acids oxidation via fatty acids and what enzymes and coenzymes if any are used? | - Fat converts into 1 molecule of glycerol and 3 fatty acids residues - The enzyme used is lipase along with 3 H2O molecules |
| What is step 2 in fatty acids oxidation via fatty acids and what enzymes and coenzymes if any are used? | - Fatty acid + ATP into acyl adenylate + PPi - Enzyme used is called acyl- CoA synthetase |
| What is step 3 in fatty acids oxidation via fatty acids and what enzymes and coenzymes if any are used? | - Acyl adenylate + HS-CoA into acyl-CoA + AMP - Enzyme used is acyl-CoA synthetase |
| What is the beta- oxidation pathway? | It is when the fatty acyl-CoA is in the mitochondrial matrix ready to be oxidized to fully become acetyl- CoA |
| How does activated fatty acyl-CoA enter into the mitochondrial matrix? | It is shuttles across the inner mitochondrial membrane by carnitine |
| What is step 4 in fatty acids oxidation via fatty acids (step 1 of the beta-oxidation pathway) and what enzymes and coenzymes if any are used? | - Fatty acyl-CoA into enoyl-CoA - The enzyme used is acyl-CoA dehydrogenase with coenzyme FAD - This is an oxidation reaction |
| What is step 5 in fatty acids oxidation via fatty acids (step 2 of the beta-oxidation pathway) and what enzymes and coenzymes if any are used? | - Enoyl-CoA into L-hydroxyacyl-CoA - The enzyme used is called enoyl-CoA hydratase with the addition of water - This is an hydration reaction |
| What is step 6 in fatty acids oxidation via fatty acids (step 3 of the beta-oxidation pathway) and what enzymes and coenzymes if any are used? | - L-hydroxylacyl-CoA into ketoacyl-CoA - The enzyme used is called L-3-hydroxyacyl-CoA dehydrogenase with coenzyme NAD+ - This is an oxidation reaction |
| What is step 7 in fatty acids oxidation via fatty acids (step 4 of the beta-oxidation pathway) and what enzymes and coenzymes if any are used? | - Ketoacyl-CoA into fatty acyl-CoA (two carbons shorter) + acetyl- CoA - The enzyme used is called beta-ketothiolase with a second molecule CoA-SH - This is a thiolysis reaction |
| How would an unsaturated fatty acid go through beta-oxidation? | - If the double bond is in the alpha-beta position (trans) then it can go ahead through the bet-oxidation pathway - If the double bond is in the beta-gamma position (cis) then it must be converted to the alpha-beta position with the enzyme isomerase |
| What happens when a fatty acid has an even number of carbons? | It must go keep going through beta-oxidation until the fatty acid has only two carbons left. They will all be considered a two carbon acetyl CoA residue |
| What happens when a fatty acid has an odd number of carbons? | It must go keep going through beta-oxidation until the fatty acid has only two carbons left, but there will be one 3 carbon molecule and the rest will be a two carbon acetyl CoA residue |
| Where is the major site in mammals amino acid degradation take place? | In the liver |
| In the urea cycle, what is it called when a protein converts into an amino acid? What molecule is used in this conversion? | - It is called transamination - H2O is used |
| The conversion of amino acids into alpha-keto acids is phase 1 of the urea cycle, what is the other name for this phase, what is the enzymes and coenzymes if any are used, and what are the reactants and products? | - Oxidative deamination - The enzyme is amino-transferase w/ coenzyme PLP - Alpha-amino acid + alpha-ketoglutarate -> alpha-keto acid + glutamate |
| What happens to the glutamate after oxidative deamination? | - It reacts with NAD+ or NADP+ + H2O to form alpha-ketoglutarate + NADH or NADHP + NH4+ - H+ leaves the reaction - The enzyme used is glutamate dehydrogenase |
| Why is the kreb cycle an intermediate to the urea cycle? | Since amino acids are degraded they will form metabolic intermediates which can be funneled into the kreb cycle |
| Steps 1 & 2 of the urea cycle occur where? | In the mitochondria |
| Steps 3 - 5 of the urea cycle occur where? | In the cytoplasm |
| Are there any ATP dependent steps in the urea cycle? | Yes, step 3 |
| What are the activators for step 1 of glycolysis? | ADP, AMP, NAD+, NADP+, & FAD |
| What are the deactivators for step 1 of glycolysis? | ATP, NADH, NADPH, & FADH2 |
| What are the allosteric activators for step 3 of glycolysis? | ADP, AMP, & [F-2,6-BP] |
| What are the allosteric inactivators for step 3 of glycolysis? | ATP & Citrate |
| What are the allosteric activators for step 10 of glycolysis? | AMP & F-1,6-BP |
| What are the allosteric inactivators for step 3 of glycolysis? | ATP & Acetyl-CoA |
| What enzyme is used to convert pyruvate into acetyl-CoA, and coenzymes if any? | The enzyme used is pyruvate dehydrogenase complex and the coenzymes used is NAD+ into NADH |
| What enzymes consists of the pyruvate dehydrogenase complex? | E1: pyruvate dehydrogenase E2: dihydrolipoyl transacetylase E3: dihydrolipoyl dehydrogenase |
| What are the cofactors involved in the conversion of pyruvate to acetyl-CoA? | TPP, CoA-SH, Lipoyllysine (LL), FAD, & NAD+ |
| What is step 1 of the Krebs cycle? What enzyme and coenzyme is used if any? | Acetyl-CoA to Citrate Enzyme is called citrate synthetase |
| What is happening during step 1 of the tricarboxylic acid cycle? | A Perkin condensation is taking place. It means a formation of a C-C bond is from an ester and ketone |
| What are the positive regulators of step 1 of the citric acid cycle? | ADP |
| What are the negative regulators of step 1 of the Krebs cycle? | ATP, NADH, & Citrate |
| What is step 2 of the tricarboxylic acid cycle? What enzyme and coenzymes is used if any? | Citrate to isocitrate Enzyme is called aconitase |
| What is happening during step 2 of the citric acid cycle? | Dehydration and rehydration is taking place |
| What is step 3 of the Krebs cycle? What enzyme and coenzyme is used if any? | Isocitrate to alpha-ketoglutarate Enzyme is called isocitrate dehydrogenase Coenzymes are NAD+ to NADH (2x) |
| What are the negative regulators of step 3 of the tricarboxylic acid cycle? | ATP & NADH |
| What are the positive regulators of step 3 of the citric acid cycle? | ADP & divalent metal cations (ex: Mg2+, Zn2+, & Cu2+) |
| What is happening during step 3 of the Krebs cycle? | Oxidative decarboxylation |
| What is step 4 of the tricarboxylic acid cycle? What enzyme and coenzyme is used if any? | Alpha-ketoglutarate to succinyl-CoA Enzyme is called alpha-ketoglutarate dehydrogenase complex Coenzymes are NAD+ to NADH (2x) |
| What are the enzymes used in the alpha-ketoglutarate dehydrogenase complex and their coenzymes? | Alpha-ketoglutarate dehydrogenase (thiamine pyrophosphate) Dihydrolipoyl transsuccinylase (Lipoic acid and Co-SH) DIhydrolipoyl dehydrogenase (FAD & NAD+) |
| What is step 5 of the Krebs cycle? What enzyme and coenzyme is used if any? | Succinyl-CoA to succinate Enzyme is called succinyl-CoA synthetase Coenzymes are GDP+Pi to GTP (2x) (will be converted into ATP later) |
| What is happening during step 4 of the tricarboxylic acid cycle? | Oxidative decarboxylation |
| What is happening during step 5 of the Krebs cycle? | Substrate level phosphorylation |
| What is step 6 of the citric acid cycle? What enzyme and coenzyme is used if any? | Succinate to fumarate Enzyme is called succinate dehydrogenase Coenzymes are FAD to FADH2 (2x) |
| What is happening during step 6 of the tricarboxylic acid cycle? | Dehydration. As well as succinate being inside the mitochondrial membrane and FAD being enzyme bound |
| What is step 7 of the Krebs cycle? What enzyme and coenzyme is used if any? | Fumarate to malate Enzyme is called fumarase |
| What is happening during step 7 of the citric acid cycle? | Hydration |
| What is step 8 of the citric acid cycle? What enzyme and coenzyme is used if any? | Malate to oxaloacetate (OAA) Enzyme is called malate dehydrogenase Coenzymes are NAD+ to NADH (2x) |
| What is happening during step 8 of the tricarboxylic acid cycle? | Dehydration |
| What the major regulatory steps of the tricarboxylic acid cycle? | Step 1,3,& 4 |
| What are the positive regulators of step 4 of the citric acid cycle? | Divalent cations |
| What are the negative regulators of step 4 of the tricarboxylic acid cycle? | NADH |
| What is the net gain of the Krebs cycle? | 2 ATP, 6 NADH, & 2 FADH2 |
| What is the net gain of the conversion of pyruvate into acetyl-CoA? | 2 NADH |
| What is step 1 of the urea cycle? What enzyme and coenzyme is used if any? | NH4+ + CO2 to Carbamoyl phosphate Enzyme is called carbamoyl phosphate synthetase Coenzymes are 2 ATP to 2 ADP + Pi |
| What is step 2 of the urea cycle? What enzyme and coenzyme is used if any? | Ornithine to citrulline Enzyme is called ornithine transcarbamoylase Coenzymes are carbamoyl phosphate to Pi |
| What is step 3 of the urea cycle? What enzyme and coenzyme is used if any? | Citrulline to arginosuccinate Enzyme is called arginosuccinate synthetase Coenzymes are aspartate |
| What is step 4 of the urea cycle? What enzyme and coenzyme is used if any? | Arginosuccinate to arginine Enzyme is called arginosuccinase Fumarate leaves |
| What is step 5 of the urea cycle? What enzyme and coenzyme is used if any? | Arginine + H2O to ornithine Enzymes is called arginase Urea leaves as byproduct |
| Where do the components of water go in step 5 of the urea cycle? | H2 attaches to arginine to make up ornithine O makes up the final part of urea |
| Where are steps 1 & 2 of the urea cycle located? | In the mitochondria |
| Where are steps 3-5 of the urea cycle located? | In the cytoplasm |
| What are the glycerol phosphate shuttle and the malate-aspartate shuttle? | They are two different ways that extra-mitochondrial NADHs are transported in the mitochondrial matrix |
| What happens if the glycerol phosphate shuttle is used? | Each cytoplasmic NADH yields 2 ATPs In total it yields 36 ATPs |
| What happens if the malate-aspartate shuttle is used? | Each cytoplasmic NADH yields 3 ATPs In total it yields 38 ATPs |
| What is the purpose of the pentose phosphate pathway (PPP) ? | Is to generate reducing power in the form of NADPH and five carbon sugar such as ribose-5-phosphate |
| How is the PPP and glycolysis connected? | G-6-P gets pulled into the PPP. As well as G-3-P and F-6-P which can enter into glycolysis from the PPP |
| Which steps in the PPP are considered the oxidative steps and which are the non oxidative steps? | 1-3 = oxidative 4-8= non oxidative |
| What is step 1 of the pentose phosphate pathway? What enzymes and coenzymes is used if any? | Glucose-6-phosphate to 6-phosphate-D-gluconolactone Enzyme is called G-6-P dehydrogenase Coenzymes are NADP+ to NADPH + H+ |
| What is step 2 of the pentose phosphate pathway? What enzymes and coenzymes is used if any? | 6-phosphate-D-gluconolactone to 6-phosphogluconate Enzyme is called lactonase Coenzymes are H2O |
| What is step 3 of the pentose phosphate pathway? What enzymes and coenzymes is used if any? | 6-phosphogluconate to ribulose-5-phosphate Enzyme is called 6-phosphogluconate dehydrogenase Coenzymes are NADP+ to NADPH + H+ CO2 leaves |
| What is step 4 of the pentose phosphate pathway? What enzymes and coenzymes is used if any? | Ribulose-5-P to ribose-5-P Enzyme is called phosphopentose isomerase |
| What is step 5 of the pentose phosphate pathway? What enzymes and coenzymes is used if any? | Ribulose-5-P to xylulose-5-phosphate Enzyme is called phosphopentose epimerase Coenzymes are NAD-linked |
| What is step 6 of the pentose phosphate pathway? What enzymes and coenzymes is used if any? | Ribose-5-phosphate + xylulose-5-P to G-3-P + sedoheptulose-7-phosphate Enzyme is called transketolase |
| What is step 7 of the pentose phosphate pathway? What enzymes and coenzymes is used if any? | G-3-P + sedoheptulose-7-P to F-6-P + erythrose-4-phosphate Enzyme is called transaldolase |
| What is step 8 of the pentose phosphate pathway? What enzymes and coenzymes is used if any? | Erythrose-4-P to F-6-P + G-3-P Enzyme is called transketolase Coenzymes are xylulose-5-P |
| During the Krebs cycle and glycolysis, what kind of phosphorylation was happening? | Substrate level |
| When does oxidative phosphorylation occur? | During the ETC |
| What is the net gain of glycolysis? | 2 ATP & 2 NADH |
| What is the net gain of the electron transport chain? | 10 NADH (3 x 10) & 2 FADH2 (2 x 2) Which converts to total of 34 ATPs |
| What is the net gain of ATPs from the aerobic carbohydrate metabolism? | 36 ATPs (via the glycerol phosphate shuttle) |
| Where is the ETC and oxidative phosphorylation located? | In the inner membrane f the mitochondria |
| What is 2,3-dinitrophenol (2,4-DNP)? | It is one of the first compounds discovered that causes a problem with the integrity of mitochondrial membranes. It is also a sufficiently strong acid |
| What will be the effect of 2,4-DNP on a system, where the hydrogen ion gradient was the coupling aspect of electron transport and ATP formation? | It will uncouple. This causes the hydrogen ion gradient to be getting -52 kcals and no work. Which means that all the chemical energy will be dispersed as heat |
| What is a disadvantage of fats? | They cannot be metabolized anaerobically. They must be metabolized aerobically |
| What is acylcarnitine translocase? | It is an important enzyme for fatty acid metabolism. It transports the fatty acyl-CoA + carnitine into the mitochondria |
| Where is the acylcarnitine translocase located? | On the mitochondrial inner membrane |
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