FSE Study Flashcards

Question

T13: *Describe the "link" reaction incl. components of the pyruvate DH complex & cofactors

Answer 1

``` Catalysed by pyru DH complex Composed of 3 distinct enzymes to form a multiple enzyme complex: -E1 (thiamine pyrophosphate attached) -E2 (lipolic acid att.) -E3 (FAD att.) ``` 5 cofactors: - Coenzyme A - NAD+ - FAD - Thiamine pyrophosphate (TPP) - Lipolic acid 3 distinct rxns: 1. Decarboxylation rxn 2. Acylation rxn 3. REDOX rxn

Answer 2

RXN 1: High E, IR condensation. E released by hydrolysis of acetyl-CoA thioester bond RXN 2: R, dehydration a) => hydration b) RXN 3: High E, IR oxidative decarboxylation. NAD reduced to NADH RXN 4: High E, IR oxidative decarboxylation. Similar to link rxn (E1, E2, E3). NAD reduced to NADH RXN 5: Substrate-level phosphorylation. Produces ATP/GTP RXN 6: Dehydrogenation. C=C produced, FAD reduced to FADH RXN 7: Hydration RXN: Dehydrogenation. ∆G' strongly favours malate production -but proceeds to R due to removal of oxaloacetate by highly exergonic rxn 1 to produce citrate.

Answer 3

acetyl-coa = 2C Citrate = 6C Isocitrate = 6C a-ketoglutarate = 5C Succinyl-CoA = 4C Succinate = 4C Fumarate = 4C Malate = 4C Oxaloacetate = 4C

Answer 4

``` Pyruvate DH complex Inhibited by high e levels -ATP -Acetyl-CoA -NADH -FA Stimulated by low e levels -AMP -Coenzyme A -NAD+ ``` ``` Citrate Synthase Inhibited by high e levels -ATP -Succinyl-CoA -NADH -Citrate Stimulated by low e levels -ADP ``` ``` Isocitrate DH Inhibited by high e levels -ATP Stimulated by low e levels -ADP ``` a-ketoglutarate Inhibited by high e levels -Succinyl-CoA -NADH

Answer 5

``` 3 NADH & 1FADH2 1 GTP (ATP) ```

Answer 6

Occurs in IMM e from NADH/FADH2 transferred along chain to O2 Exergonic transfer of e is coupled w/ endergonic pumping of p to intermembrane space (IMS) P move down their gradient back to matrix. This exergonic process is coupled w/ endergonic synthesis of ATP from ADP and Pi

Answer 7

e transport results in H transport -pumping of H ions out of matrix Creates proton gradient -protons pass back through IMM through H+ pore in ATP synthase Flow of H+ down [ ] leads to ATP synthesis -passage of h+ down proton-motive gradient causes a conformational change in 3D structure of ATP synthase, causing synthesus & release of ATP

Answer 8

10 protons are pumped per pair electrons from NADH - 4 at CI -4 at CIII -2 at CIV 6 protons are pumped per pair electrons from FADH2 -4 at CIII -2 at CIV ~ 4 protons are required to drive synthesis of one ATP molecule :: -2.5 ATP are formed from one pair of electrons from NADH -1.5 ATP are formed from one pair of electrons from FADH2

Answer 9

NADH + H+ + 1/2O2 => NAD+ + H2O Highly exergonic -220kJ/mol For each 2 electrons transferred from NADH to O2 through ETC, 10 H+ ions are pumped from matrix to IMS

Answer 10

NADH transferred as NADH | Generates 2.5 ATP

Answer 11

NADH entered as FADH2 | Bypasses CI; generates 1.5 ATP

Answer 12

``` High ATP/Low ADP -glycolysis inhibited -CAC inhibited -Oxidative phosphorylation inhibited Low ATP/High ADP -Glycolysis activated -CAC activated -Oxidative phosphorylation activated ```

Answer 13

TAG's are digested by pancreatic lipase Produce FA, glycerol Products are absorbed by intestinal cells IC convert them back into TAGs and chylomicrons Chylomicrons are released into blood stream/lymph sys to adipose/skeletal muscle TAGs are hydrolysed to FAs & glycerol by lipoprotein lipase Skeletal muscle = FA degraded (b-oxidation), producing ATP Adipose = FA are re-esterified to TAGs for storage

Answer 14

Found in adipose Catalyses breakdown of stored TAGs to FFA & glycerol Regulation: -activated by glucagon & adrenaline -Glycerol is transported via blood to liver, enters glycolysis or gluconeogenesis -FAs transported in blood to liver/skeletal muscle, used as fuel for b-oxidation

Answer 15

1. FAs are activated by attachment of CoA Converted to fatty acyl-CoA by acyl-CoA synthetase in cytoplasm Requires ATP 2. The activated FA (fatty acyl-CoA) is transported to mitochondrial matrix via the carrier carnitine see diagram in book = draw it ``` 3. B-OXIDATION In final cycle, 2 acetyl-CoA released 1 NADH & 1 FADH2 produced 1. Oxidation acyl-CoA-DH ``` 2. Hydration enoyl-CoA-hydratase 3. Oxidation hydroxyacyl-CoA DH 4. Thiolytic cleavage thiolase

Answer 16

(n-2) / 2 C10 - 2 = 8 8 / 2 = 4 (4 rounds b-oxidation) Always 1 round less than number of acetyl groups (or no# rounds + 1 = no# acetyl-CoA) So = 5 acetyl-CoA ............................................................... ``` C14 = 7 rounds b-oxi 1 FADH2 & 1 NADH produced for every round per FADH2 = 1.5 ATP per NADH = 2.5 ATP No# ATP ultimately formed for NADH = 7x2.5 = 17.5 for FADH2 = 7x1.5 = 10.5 ```

Answer 17

A-CoA carboxylase=>uses cofactor biotin Acetyl-CoA (2C) + HCO3 + ATP => Malonyl-CoA (3C) + ADP + Pi ``` FA synthase complex (reverse of b-oxi) 2c + 3c => 4c + 3c => 6C condensation reduction (NADPH consumed) dehydration reduction (NADPH consumed) ```

Answer 18

>FA synthesis | inhibits carnitine acyl-transferase :: inhibits FA degradation

Answer 19

``` FA degradation Glucagon release ∆PKA => GNG ∆hormone sensitive lipase =>mobilises stored FA X acetyl-CoA carboxylase; ```

Answer 20

Glutamine synthetase catalyses addition of NH4+ onto glutamate => glutamine Allows transport of NH4+ in blood Liver; NH4+ re-released by glutaminase => urea

Answer 21

reverse of amination Glutaminase (liver, kidney cortex) -removes NH4+ from glutamine => glutamate ``` Glutamate DH (liver) -removal of amino group from glutamate => a-ketoglutarate ```

Answer 22

aa transfers its amino group to a-ketog & is converted to keto acid glutamate formed no net deamin. need PLP as cofactor

Answer 23

``` Is NOT a major energy source under NORMAL conditions Significant under 3 conditions: -dietary protein ingested in excess -severe starvation -stress situations ``` Catabolism in 4 easy steps! 1. catabolism of protein w/in muscle results in formation of aa's glutamine & alanine 2. Transport of Glu & Ala into blood - Ala => liver - Glu => liver & kidney 3. Kidney - Glu deaminated twice => a-keto g. Ammonium excreted in urine. C skeleton used in glucose formation 4. Liver - Ala & Glu from muscle, & all 20 aa from diet are deaminated => glutamate. C skeleton => glucose or ketone body. Glutamate deamin. in mitochondria & NH4+ converted to urea. Urea => liver => blood => kidney => excretion

Answer 24

1. Pyruvate carboxylase 2. PEP carboxykinase 3. Enolase 4. Phosphoglycerate mutase 5. Phosphoglycerate kinase 6. Glyceraldehyde phosphate dehydrogenase 7. Triose phosphate isomerase 8. Aldolase 9. Fructose 1, 6 Bisphosphatase 10. Phosphohexose isomerase 11. Glucose-6-phosphatase