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41 Cards in this Set
- Front
- Back
What are the two phases of Glycolysis? |
1) Energy Investment 2) Energy Generating |
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How much ATP is hydrolysed in the energy investment phase of glycolysis? |
2ATP |
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What is produced in the energy generating phase of glycolysis? |
4ATP (net 2) and 2NADH |
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Which glucose transporters are used in glycolysis? What determines direction of transport? |
-GLUT 1, 2 or 4 -Concentration of glucose |
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Why does glucose conversion and ATP hydrolysis need to be coupled? |
-Keeps the reaction delta G negative -Otherwise rise in body temp would be seen |
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Where is hexokinase found? |
In all cells capable of glycolysis |
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Where is glucokinase found? |
Liver and Islets of Langerhans |
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Properties of hexokinase? |
-Low Km and Vmax (allows function even at low bg) -Prevents glucose trapping -Allosterically inhibited by G6P |
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Properties of glucokinase? |
-High Km and Vmax - acts as a glucose sensor -Helps prevent hyper. - active at very high glucose concentrations -Inhibited by F6P Regulation via GKRP - -ve feedback loop |
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Isomerisation of G6P to F6P is a conversion of what? |
An aldehyde to a ketone |
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Which step is the commitment step in glycolysis? |
Conversion of F6P to F16BP via PFK-1. |
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Why is magnesium needed in PEP formation? |
Mg dependent dehydration - needed to stabilise the anion formed when a proton is removed |
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Roles of glycolysis? |
-Energy for cells without mitochondria -Provides G6P for PPP -Intermediate for AA synthesis -Glycerol for TAG synthesis |
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Role of glycolysis in the liver? |
Buffer blood glucose levels |
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Role of glycolysis in the cornea and lens? |
Rely on AG - no bvs, transparent and no mitochondria Obtain glucose from vitreous body and aqueous humour |
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Importance of glycolysis in the kidney medulla? |
High ATP demand for active transport Medulla has poor blood supply |
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Importance of glycolysis in neonates? |
O2 deprived for approx 30 mins during birth AG supplies all glucose during this time |
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Importance of glycolysis in RBCs? |
No mitochondria - rely on AG G6P needed for glutathione prod - dealing with oxidative stress 1,3BPG linked to 23BPG - adapting to high altitude |
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Importance of glycolysis in tumour cells? |
Increasingly hypoxic towards the centre - reliance on AG |
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How does trivalent arsenic inhibit glycolysis? |
-Binds to PDH -Inhibits conversion of pyruvate to Acetyl CoA -Causes decreased Ach production -Leads to CNS pathologies |
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How does pentavalent arsenic inhibit glycolysis? |
-Inhibits GAPDH - a homologue of phosphate so binds to block phosphate -PGK reaction bypassed - 1ATP lost |
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How does iodoacetate inhibit glycolysis? |
Binds to GAPDH, irreversibly inactivates the enzyme |
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How do fluoride ions inhibit glycolysis? |
-Competitively inhibit enolases -Binds to Mg ions -Prevents PEP production, decreases ATP production |
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Partial deficiencies in glycolysis result in? |
Haemolytic anaemia |
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Why are mature RBCs effected in genetic defects in glycolysis? |
-ATP is needed to maintain biconcave shape -ATP needed for Na/K transporters for blood pH |
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What are the regulatory sites of glycolysis? |
-hexokinase reaction -PFK-1 reaction -PK reaction |
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How is PFK-1 regulated? |
-ATP -AMP -Citrate |
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How is PK regulated? |
-Inhibited by ATP -Activated by F16BP |
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Lactose can be broken down into which sugars? |
Galactose and Glucose |
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Sucrose can be broken down into which sugars? |
Fructose and Glucose |
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How can fructose enter pathways in muscle? |
Conversion to F6P to enter glycolysis |
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How can fructose enter pathways in liver? |
-Conversion to F1P, then to Glyceraldehyde or DHAP to be converted to GAP |
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Potential uses of pyruvate? |
-Conversion to lactate -Formation of ethanol -Formation of Acetyl CoA and entry to TCA |
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How is pyruvate converted to ethanol? |
P>acetylaldehyde>ethanol CO2 is released and NAD+ is regenerated |
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How is pyruvate transported to the inner mito membrane? |
Via symport cotransporter with H+ |
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What is the prosthetic group for the E1 PDH subunit? What is the co factor? |
TPP No cofactor |
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What is the prosthetic group for the E2 subunit of PDH complex? What is the co factor? |
Lipoamide CoA |
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What is the prosthetic group for the E3 subunit of PDH complex? What is the cofactor? |
FAD NAD+ |
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What are the subunits of the PDH complex? |
E1 - PDH E2 - DH transacetylase E3 - DHDH |
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How is the PDH complex regulated? |
PDHK - inactivates PDHP - activates Ca2+ - from muscle, switches on PDHP ATP, ACoA +NADH - switch on kinase |
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Severe thiamine deficiency causes... |
inability of E1 to decarboxylate pyruvate Beri Beri syndrome or WK |