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1. What does glycolysis literally translate to?
2. Define glycolysis
3. What is important about this pathway for glucose?
4. What is interesting about its flux of carbons?
1. Breaking of glucose --> glykys = sweet, lysis = loosening
2. Process by which glucose is broken down into 2 3C molecules, yielding energy (ATP) & reducing equivalents (NADH)
3. ALmost universal central pathway for glucose catabolism
4. Pathway with largest flux of C in most cells
1. What are four uses for glucose and examples of each?
2. Where does glycolysis take place in cell?
3. What is better for long-term energy storage? Why? (2)
4. How much energy is released (kJ) after combustion of one glucose?
5. How many reactions comprise glycolysis? Why this many?
1. Synthesis of structural polymers (EC matrix & cell wall polysaccharides), Storage (glycogen, starch); Oxidation via PPP; oxidation via glycolysis
- 2. Cytoplasm
- 3. Fat - b/c when oxidized, it releases much more energy & takes up less space
- 4. -2800 kJ
- 5. 10 - because if we just used one rxn (glucose+O2) we would blow up.
1. What are the two stages of the glycolytic process? Write rxns for each.
2. Why are glycolytic intermediates important? (2)
3. What are the enzymes (in order) in the preparatory phase? Which requires ATP?
4. What is the purpose of phosphorylation of free glucose? (2)
- 1. Energy investment stage: 1 glucose + 2 ATP ---> 2 3C (glyceraldehyde 3 P)
- Energy recovery stage: 2 glyceraldehyde 3P + 2 NAD+ +2ATP ---> 2 pyruvate + 2 NADH + 4 ATP
2. Because they generate energy stored in form of reduced equivalents AND provide C & N skeletons.
3. Hexokinase, phosphohexose isomerase, PFK-1, aldolase, and triose phosphate isomerase
4. To activate glucose (G6P tells cell that glucose is for glycolysis) and keeps it in the cell.
1. What are the dGs of the two irreversible steps in the first phase of glycolysis?
2. What type of enzyme is hexokinase?
3. What cofactor does hexokinase require? Why?
4. Draw a-d-glucose's structure
- 1. Hexokinase (-16.7 kJ/mol) and PFK-1 (-14.2 kJ/mol)
- 2. Transferase
- 3. Mg2+ - shields negative charges of P groups in ATP, making terminal phosphoryl group easier to target for Nu attack by OH of glucose on C6.
1. What do kinases do?
2. What does phosphohexose isomerase responsible for doing? What step is it? What type of enzyme?
3. What is PHI's dG?
4. Is hexokinase the committed step for glycolysis? Why or why not?
5. Why is the phosphohexose isomerase rxn crucial?
- 1. Catalyze transfer of terminal phosphoryl group from ATP to Nu (acceptor
- 2. G6P <---> F6P; step 2; isomerase
- 3. +1.7 kJ/mol
- 4. No, because G6P and F6P can be used in other cellular pathways - it's only the committed step for keeping glucose in that cell!
5. Because it's crucial for carbonyl and hydroxyl rearrangement to set up p'lation & C-C cleaving for steps 3 and 4 .
1. What enzyme is responsible for committed step in glycolysis?
1. What does F1,6 BPase catalyze? What is important about it?
2. What does it require?
3. dG? Is it reversible?
4. What does aldolase do? What type of enzyme is it?
5. What is aldolase's dG? Is it reversible? Why?
6. How is aldolase's dG overcome?
- 1. F6P --> F1,6BP (committed step!!)
- 2. Requires ATP
- 3. -14.2 kJ/mol - no, this rxn is IRREVERSIBLE
- 4. Aldolase (hydrolase): F1,6BP --> dihydroxyacetone phosphate (ketose) + glyceraldehyde-3-P (aldose)
5. dG of aldolase: +23.8, but it is reversible b/c [reactants] in cell are low ,so the actual free energy change is small and aldolase rxn is readily reversible.
6. DHAP + glyceraldehyde 3P are quickly consume, resulting in slightly negative dG that is readily reversible.
1. What is the last step of the preparatory phase of glycolysis: enzyme (type of enzyme) dG? What is the purpose?
2. How does this happen despite its dG?
3. In prep phase of glycolysis, how many ATP are invested? Which Cs are phosphorylated?
4. What is the final substrate product of this phase?
5. What do both irreversible pathways require?
1. Triose phosphate isomerase (isomerase); +7.5 kJ/mol; purpose: DHAP ---> glyceralde 3 P (but it is reversible)
- DHAP must be converted because only G3P can be used in next phase.
- 2. Same mechanism as aldolase - products are quickly pulled away.
- 3. 2 - C1 and C6
- 4. Glyceraldedehyde 3 P
- 5. Phosphorylation by ATP.
1. Draw pathway of substrates of energy investment stage, including enzymes, ATP, etc.
1. Name the 5 enzymes required in the energy recovery stage? Which require ATP (bold)? Which require NAD+?
2. Draw glyceraldedehyde 3 P and DHAP.
3. What type of enzyme is glyceralde 3 P DH? What is its function? What is the substrate and product? What is special about its product?
4. What would happen if there was no oxygen in this step? Why?
5. What is the difference between bisphosphate and diphosphate?
1. Glyceraldehyde 3P DH (NAD+); phosphoglycerate kinase (ATP); phosphoglycerate mutase , enolase (releases H2O), pyruvate kinase (ATP)
- 3. Oxidoreductase; OXIDATION; glyceraldehyde 3 P --> 1,3 bisphosphoglycerate - 1,3 BPG is high energy.
4. It would stop, bc requires NAD+ to be regenerated to transfer electrons.
5. Bis - two phosphates not connected to each other - di is connected to each other.
1. What step in glycolysis is targeted when there is no oxygen?
2. What is 7th enzyme? Type of enzyme? What does it require?
3. 7th enzyme: substrate? product?
4. 7: dG? - reversible?
5. What does phosphoglycerate kinase require? For what purpose?
6. What is this enzyme above named for?
- 1. glyceraldehyde 3 phosphate dehydrogenase
- 2. Phosphoglycerate kinase (transferase) - requires ADP!
- 3. 1,3 bisphosphoglycerate --> 3phosphoglycerate - transfers a acylphosphate group from 1,3BPG to ADP.
- 4. dG = -18.5 --> NOT REVERSIBLE!
- 5. Mg2+, to stabilize phosphate groups on ATP for nucleophilic attack
- 6. The reverse rxn.
1. What do steps 6 & 7 constitute in glycolysis?
2. What is the common intermediate of the energy-coupling?
3. Which is endergonic? Which is exergoinc? What is transferred to ADP?
4. What is the 8th enzyme? What does it do/ What type of enzyme is it? What is its dG? What does it require? what does it release?
- 1. ENERGY COUPLING PROCESSES
- 2. 1,3 BPG
- 3. Endergonic (#6) exergonic (#7) - acyl phosphate group is transferred to ADP in 2nd rxn
- 4. Phosphoglycerate mutase (+4.4 kJ/mol), requires Mg2+ (releases 2 H2O)
1. What is the 9th enzyme? Type of enzyme?
2. Substrate? --> Product?
3. What is special about the product?
4. dG of 9th rxn? What is the puprpose of it?
5. What is required? Why?
- 1. Enolase (lyase/hydrolase)
- 2. 2PG --> PEP
- 3. PEP is high energy
- 4. +7.5 kJ/ol
- 5. Mg2+ stabilizes intermediate.
1. What is the last (10th) enzyme of glycolysis?
2. Substrate? --> Product?)
4. What is the product? (4)
- 1. Pyruvate kinase
- 2. PEP --> Pyruvate
- 3. dG = -31.4
- 4. 2 ATP & 2 pyruvate
1. What happens when pyruvate is first produced?
2. What is energy released from pyruvate formation used for? (2) - what are the dGs for each?
3. What does the last rxn require as cofactors? (2)
4. What are the 3 noteworthy types of chemical transformations during glycolysis?
1. Pyruvate is initially formed in its enol form, but it quickly/spontaneously tautomerizes into its keto form, releasing a TON of energy!
2. The purpose of this is energy: (1) conserved information of phosphoanhydride bond in ATP (dG = -30.5 kJ/mol) and (2) is the driving force pushing rxn toward ATP synthesis (-31.4 kJ/mol)
3. Mg2+ and K+
4. (1) Degradation of glucose's C skeleton yielding pyruvate (2) P'lation of ADP to ATP by glycolytic intermediates w/ high phosphoryl transfer potential (3) Transfer of hydride ion to NAD+ forming NADH
1. What is glucose's detailed equation for glycolysis?
2. What is glycolysis' overall rxn?
3. What is the eventual fate of NADH? where?
4. Draw rxns for glucose --> pyruvate, ADP --> ATP, and overall free energy change
5. Conclusion: Under both standard & nonstandard conditions in cell, glycolysis is essentially IRREVERSIBLE, driven to completion by large net decrease in free energy.
1. How many of the glycolytic intermediates are phosphorylated?
2. Name 3 reasons why these intermediates MIGHT BE PHOSPHORYLATED HAHA- the last one has 3 additional reasons.
3. What do most P groups and glycolytic intermediates form complexes with?
- 1. 9 - all of the intermediates are p'lated
- 2. (1) P'lated sugars can't leave cell - after initial p'lation, no extra energy needed to retain p'lated intermediates in cell despite concentration gradient
(2) Phosphoryl groups are essential components in enzymatic conservation of metabolic energy (energy donated by ATP is conserved in high-energy phosphate compounds (1,3 BPG and PEP) & these compounds eventually donate P groups back to ADP to form ATP.
(3) P groups help enzymes - by binding to active site of enzymes, 1-P groups increase binding energy, 2-lowering activation energy, 3- increases specificity of enzymatic rxns.
1. Why do we need to regulate glycolysis? (2)
2. How is glycolysis regulated? (2 main ones) 1- 3 and 2-2
1. Glycolysis flux is regulated to maintain constant ATP levels & glycolytic intermediates for biosynthetic roles.
2. Short-term: ATP consumption, NADH regeneration, allosteric regulation of glycolytic enzymes (hexokinase, PFK-1, pyruvate kinase)
Long-term: hormones (epinephrine, glucagon, insulin) and transcriptional regulation
1. How do tumor cells differ from normal cells in terms of glucose? (2)
2. Is this true even when O2 is available?
3. Why do cancer cells initially depend on glycolysis?
4. What is glycolysis important for in cancer cells? (2)
5. Do more aggressive tumors have greater or smaller rates of glycolysis?
6. What does transformation from normal cell --> cancer cell entail? (2)
1. Increased glucose uptake and 10x glycolytic rate
3. Because they don't have access to capillaries (must first activate angiogenesis), so must rely on anaerobic glycolysis
4. Produces energy and creates nucleic acids (via PPP)
6. (1) change to dependence on glycolysis for ATP production and (2) development of tolerance to low pH in extracellular fluid (release of lactic acid to regenerate NAD+)
1. Which step is commonly targeted in anticancer therapy?
2. How is glycolytic rate used in diagnostics?
3. Do we include [H+] in Keq calculation? Why or why not? When Q is <1 what happens?
4. Which steps in glycolysis are energetically coupled?
1. Glucose --G6P - prevents going to PPP, etc.
2. High glycolytic rates are seen in PET scans
3. No, because we assume [H+] is constant (10
). When Q<1, dG is negative --> favors forward rxn.
4. Those that require ATP, and glyceraldehyde + NAD+ --> 1,3 BPG).
1. Under aerobic conditions, what happens to pyruvate?
2. Draw possible fates of pyruvate
3. Draw pyruvate --> lactate rxn (dG?)
1. Pyruvate is oxidized to acetate --> acetyl CoA --> TCA cycle --> ETC