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46 Cards in this Set
- Front
- Back
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What type of pathway is glycolysis? Brief steps? |
Catabolic Glucose----> phosphoenolpyruvate ----> 2 pyruvate |
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What does glycolysis generate? |
Both ATP and NADH |
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What does kinase always do? |
Adds a phosphate group- phosphorylation |
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What is gluconeogenesis |
Opposite pathway of glycolysis -Starvation conditions |
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What is the structure of glucose? |
Six carbon compound with 1 aldehyde group and 5 hydroxyl groups nC's n-1 OH groups 1 carbonyl |
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What is the most oxidized carbon? |
The carbon with the least Hs bonded to it - in glucose it is C1 (the aldehyde carbon) Most reduced would have the most Hs bonded (C6 in glucose) - CH2OH |
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Draw glucose in its non-cyclic form |
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Whats another name for a sugar molecule? |
Aldohexose |
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Draw how a glucose molecule cyclizes |
C5 OH attacks C1 (aldehyde carbon) Forms an ether bond at OH group in ring |
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Where does glycolysis occur |
In cytosol/ cytoplasm |
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Glycolysis is the first step in what |
Serves as the first step in the complete oxidation of glucose to CO2 and H2O - Produces a small amount of ATP |
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Glycolysis occurs under what conditions |
Aerobic (90% of time) OR anaerobic (Only metabolize fat) conditions |
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What are the energy investment steps vs energy payout steps of glycolysis? |
Investment: steps 1-3 Payout happens x2 : 5-10 |
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What is stage 1 of glycolysis? |
1. Energy investment: - Glucose needs to be activated; ATP is consumed - involves hexose (6C sugar) |
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What is stage 2 of glycolysis? |
2. Energy payout: - Energy harvested as ATP - NADH generated - Involves triose (3C sugar) |
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Which reactions in glycolysis are irreversible/ regulated? |
Reactions 1, 3, 10 |
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What are all the reactions in glycolysis regulated by? |
Enzymes: 1. Hexokinase, glucokinase (kinase) 2. Isomerase 3. Phosphofructokinase-1 (PKF1) 4. Aldolase 5. Isomerase 6. Dehydrogenase 7. Phosphoglycerate kinase 8. Mutase 9. Enolase 10. Pyruvate kinase |
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How many oxidative steps are in glycolysis and when/where is it/they |
1 oxidative step at reaction 6 -Carried out by Glyceraldyhyde 3-phosphate dehydrogenase |
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Stage 1 in glycolysis summary |
Glucose to glyceraldehyde-3-phosphate (GAP x2) (1-5) -consumes 2 ATP for every glucose -Activation stage |
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Where is the first ATP investment? |
Reaction 1: Glucose----> G-6-P -Irreversible in forward direction - Regulated - Phosphoryl transfer -Coupled to ATP "lysis" (hydrolysis) |
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What does hexokinase do in rxn 1? How much energy is released? |
Hexokinase couples the breaking of a phosphoanahydride bond to the formation of a phosphoester bond Breaking phosphoanahydride releases -32 KJ/mol Forming phosphoester requires +16 JK/mol Sum= -16KJ/mol (-ve means forward direction) |
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When does the transition from glucose to fructose occur and explain it |
- Happens at reaction 2 - Catalyzed by enzyme isomerase - Structural isomers - G-6-P is an aldohexose (6 membered ring_ - F-6-P is a ketohexose (5 membered ring) - Reversible (delta G'~0) Isomerization= aldehyde to ketone |
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When is the second ATP investment? Explain reaction |
- Reaction 3 - Catalyzed by PFK-1 - F-6-P ----> Fructose 1-6 bisp - Rate limiting/ committed step - TIGHTLY regulated - Coupled to ATP hydrolysis - Phosphoryl transfer - 2 C molecules being phosphorylated |
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When can you bypass a reaction step? |
When it is not the committed step - Ex can bypass reaction 1 (1st ATP invest) but not reaction 3 (2nd ATP invest) |
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At which reaction does the 6C compound become 2 3Cs and by which enzyme? Talk about the reaction |
- Reaction 4 - Fructose-1,6-bisphosphate is cleaved by aldolase - Creates a GAP and DHAP which are isomers of each other - Reversible, delta G is 0 (equilibrium) - Reaction 4 is considered a lysis |
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How are 2 molecules of GAP produced? |
1. Lysis (reaction 4) 2. Isomerization (reaction 5) |
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What is stage 2 in glycolysis? |
GAP goes to pyruvate |
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How many molecules of ATP are generated for every glucose? and how? |
4 ATP for every glucose (without the need for oxygen) - Invest 2 ATP - Generate 6 ATP |
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What is a mixed anhydride and what is the net energy? |
Acyl phosphate - Phosphate attached to a carboxyl group - ~48KJ/mol - COP bond |
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What enzyme is the oxidation reaction in glycolysis catalyzed by. Explain reaction |
GAP dehydrogenase (GAPDH) - Reaction 6 - oxidation followed by phosphorylation - generates 2 high energy molecules (NADH and 1,3-BPG) - "Energy capture" |
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What are the high energy intermediates in glycolysis? |
-NADH - 1,3- BPG (acyl phosphate) - PEP |
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Explain substrate-level phosphorylation |
- Coupled reaction - Phosphate transfer reaction that produces a nucleoside triphosphate - ADP ----> ATP - di to tri - Creates a phosphoanhydride bond; requires +32KJ/mol - No O2 is required |
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What phase is considered "paying off the debt" |
Synthesis of ATP from 1,3-BPG - pays back 2 ATP - Reaction 7 - Enzyme kinase - ATP synthesis is coupled to breaking acyl phosphate (mixed anhydride) - SLP reaction "energy capture" |
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Which reactions are coupled in glycolysis? |
Reaction 6 and 7 - consumption of 1,3-BPG in reaction 7 "pulls" reaction 6 forward |
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What is the third isomerase reaction? |
Reaction 8 - mutase |
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What happens in reaction 9 |
-Generation of a PEP a "high energy" intermediate - Catalyzed by enolase - Dehydration reaction - PEP is a high energy (-64KJ/mol) intermediate |
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What is the production of pyruvate catalyzed by? Explain the reaction |
Reaction 10 is catalyzed by pyruvate kinase - 2 steps: 1 is PEP goes to pyruvate enol form (unstable) requiring -16KJ/mol, step 2 is tautomerization stabilizing pyruvate by -46JK/mol - regulated - coupled - SLP - 2 ATP made (energy capture step) |
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What is the balanced equation of glycolysis? |
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Whats the net yield of ATP in glycolysis |
2 ATP - yield-input = 4-2= 2 |
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Why is glycolysis tightly regulated in cells? Why is it important |
- Cells energy needs are met - Fuel is not wasted - Appropriate levels of intermediates required for other purposes |
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What is the rate of flux through metabolic pathways regulated by (processes)? |
1. Substrate availability 2. Alteration of enzyme activity (short term) 3. Alteration of enzyme amount (long term) (gene regulation) 4. Sub-cellular localization/compartmentation (removing enzyme) |
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Explain regulation in glycolysis |
1. Substrate availability - glucose import 2. Enzyme regulation - Hexokinase - PFK-1 many allosteric sites - Pyruvate kinase |
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Hexokinase regulation |
G6P (rxn 2) is an inhibitor to hexokinase - product inhibition |
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PFK-1 regulation |
Allosterically regulated by ADP/AMP and PEP (rxn 9) - Feedback inhibition - Elevated PEP levels signal that the products of glycolysis are not being consumed which stops the utilization of second ATP pathway |
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Pyruvate kinase regulation |
- Allosteric enzyme - Inhibited by ATP but NOT product inhibition - reciprocal regulation (glycolysis and gluconeogenesis) - "feed forward activation" - Activated by fructose-1,6-bisphosphate -ATP is an allosteric inhibitor of pyruvate kinase |
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What are the effects of ATP on PFK-1? |
Acts as both a substrate and inhibitor 2 binding sites on PFK-1: 1. substrate binding site = high affinity 2. Allosteric binding site = low affinity |
