BCHM 3050 Exam #4- Clemson University, Dr. Anderson

where does glycolysis take place?

cytosol

what are oxidative reactions?

catabolic

what are reductive reactions?

anabolic

what is glycogenolysis?

breaking glycogen down into glucose residues

what is glycogenesis?

making glycogen to store excess glucose

what is gluconeogenesis?

non-carbohydrate precursors (pyruvate) used to make glucose

when does glycolysis take place?

when the cell needs energy and glucose is available

what is the equation for glycolysis?

glucose + 2 NAD+ + 2 ADP + 2 Pi -> 2 pyruvate + 2 NADH + 2 ATP

what is the first step of glycolysis?

glucose + ATP -> glucose-6-phosphate + ADP; enzyme= hexokinase; regulated step

what is the second step of glycolysis?

glucose-6-phosphate -> fructose-6-phosphate; enzyme= phosphoglucose isomerase

what is the third step of glycolysis?

fructose-6-phosphate -> fructose-1,6-bisphosphate; enzyme= phosphofructokinase; most important step! commitment step of glycolysis; regulated step

what is the fourth step of glycolysis?

fructose-1,6-bisphosphate -> glyceraldehyde-3-phosphate + dihydroxyacetone phosphate; enzyme= aldolase

what is the fifth step of glycolysis?

glyceraldehyre-3-phosphate + dihydroxyacetone phosphate -> ; enzyme= triose phosphate isomerase perfect enzyme

what are the first 5 steps of glycolysis considered?

the energy investment phase

what is the sixth step of glycolysis?

glyceraldehyde-3-phosphate + NAD+ + Pi -> 1,3-bisphosphoglycerate + NADH + H+; enzyme= glyceraldehyde-3-phosphate dehydrogenase; gives 2 NADH

what is the most potent activator of phosphofructokinase in mammals?

fructose-2,6-bisphosphate; acts as an allosteric regulator

what is phosphofructokinase-2 activated by?

activated by high levels of glucose in the bloodstream

what acts as an inhibitor of phosphofructokinase-1 in glycolysis in mammals?

ATP

what activates phosphofructokinase in bacteria?

ADP

what inactivates phosphofructose kinase in bacteria?

phosphoenolpyruvate

what is the seventh step of glycolysis?

1,3-bisphosphoglycerate + ADP -> 3-phosphoglycerate; enzyme= phosphoglycerate kinase; coupled with previous step

what is the eighth step of glycolysis?

3-phosphoglycerate -> 2-phosphoglycerate; enzyme= phosphoglycerate mutase

what is the ninth step of glycolysis?

2-phosphoglycerate -> phosphoenolpyruvate; enzyme= enolase

what is the tenth and final step of glycolysis?

phosphoenolpyruvate + ADP -> pyruvate + ATP; enzyme= pyruvate kinase; 2 ATP synthesized at this point; regulated step

what are the three regulated steps of glycolysis?

hexokinase (1), phosphofructokinase (3), & pyruvate kinase (10)

is glycolysis anaerobic or aerobic?

anaerobic

what can happen to pyruvate?

in the presence of O2: converted to acetyl-coA (releases CO2) or converted to oxaloacetate (requires CO2)

in the absence of O2: converted to lactate in mammals or converted to ethanol + CO2 in yeast

what happens to pyruvate during exercise?

temporarily converted to lactate using lactate dehydrogenase

how is NAD+ regenerated in yeast?

pyruvate -> acetaldehyde (using pyruvate decarboxylase) then acetaldehyde -> ethanol* (using alcohol dehydrogenase; NADH oxidized to NAD+ in second step

what can pyruvate be further oxidized to?

acetyl-coA using pyruvate dehydrogenase

what does pyruvate carboxylase use as a cofactor?

biotin

what two amino acids are not broken down in gluconeogenesis?

leucine and lysine

when does gluconeogenesis occur?

when no sugar is available, the body will breakdown proteins in a strategic manner; when all of the glycogen has been used/ starvation

where does gluconeogenesis occur?

the liver & a bit in the kidneys

how does gluconeogenesis work?

reverse of glycolysis

what is the cost of gluconeogenesis?

6 ATP and 2 NADH

how is pyruvate converted to phosphoenolpyruvate?

pyruvate -> oxaloacetate using pyruvate carboxylase (REQUIRES 1 ATP); oxaloacetate -> phosphoenolpyruvate using phosphoenolpyruvate carboxykinase (REQUIRES 2 ATP)

at which step is gluconeogenesis regulated?

fructose bisphosphatase

what happens with gluconeogenesis when there is a lot of glucose?

there is an increase in F2,6P to activate phosphofructokinase and glycolysis

what happens with gluconeogenesis when there is no glucose?

there is a decrease in F2,6P to inactive FBPase and turn off gluconeogenesis; one step to turn on glycolysis and turn off gluconeogenesis

what is glycogen a polymer of?

glucose-6-phosphate converted to glucose-1-phosphate using phosphoglucomutase and glycogen made up of glucose-1-phosphate monomers

how is glycogen synthesized?

glucose-1-phosphate is converted to UDP-glucose and then glycogen synthase adds glucose to extend the polymer

what is glycogenin?

the starting molecule for glycogen

what does branching enzyme do?

adds branch points in glycogen; cleaves an alpha 1,4 linkage and moves it to create an alpha 1,6 linkage

what is the process of glycogenolysis?

glycogen to glucose-1-phosphate using glycogen phosphorylase, then glucose-1-phosphate to glucose-6-phosphate using phosphoglucomutase, then glucose-6-phosphate to glucose using glucose-6-phosphatase

what does debranching enzyme do?

cleaves an alpha 1,6 linkage and forms an alpha 1,4 linkage

when does the pentose phosphate pathway occur?

when cells are dividing rapidly and storing energy as fat

where does the pentose phosphate pathway occur?

all cells in the cytosol

what are the products of the pentose phosphate pathway?

5C sugars and NADPH to be used in lipid and nucleic acid synthesis

what is pyruvate a precursor to?

oxaloacetate

what are the 5 steps of the pyruvate dehydrogenase complex?

1. E1 decarboxylates pyruvate; CO2 is released

2. a leftover hydroxyethyl group is transferred to E2

3. an acetyl group is transferred to CoA

4. E2 is restored

5. E3 is restored and NADH is produced

what is the cofactor of E1?

TPP (thiamin pyrophosphate)

what is the cofactor of E2?

lipoamide

what is the process of E2?

disulfide bond

what is the cofactor for step 3?

coenzyme A

what is the cofactor for step 4?

FAD

what is the cofactor for step 5?

NAD+

what is reaction 1 in the TCA cycle?

oxaloacetate + acetyl-coA converted to citrate using citrate synthase; regulated step

how does citrate synthase bind oxaloacetate?

undergoes a conformational change upon binding oxaloacetate allowing for binding of acetyl-coA

what is the second rxn. of the TCA cycle?

citrate converted to isocitrate using aconitase

what is the third rxn. of the TCA cycle?

isocitrate converted to alpha ketoglutarate using isocitrate dehydrogenase; regulated step

what is the fourth rxn. of the TCA cycle?

alpha ketoglutarate converted to succinyl-coA using alpha ketoglutarate dehydrogenase; regulated step

what is the fifth rxn. of the TCA cycle?

succinyl-coA converted to succinate using succinyl-coA synthetase; substrate level phosphorylation

what is the sixth rxn. of the TCA cycle?

succinate converted to fumarate using succinate dehydrogenase

what is the seventh rxn. of the TCA cycle?

fumarate converted to malate using fumarase

what is the eighth rxn. of the TCA cycle?

malate converted to oxaloacetate using malate dehydrogenase

what are the products of the TCA cycle?

2 acetyl co-A, 2 CO2, 8 e-, 1 ATP

what is alpha ketoglutarate a precursor for?

amino acids, nucleotides/nitrogenous bases

what is succinyl-coA a precursor for?

heme

what is fumarate a precursor for?

amino acid backbones

what is malate a precursor for?

pyruvate

what is oxaloacetate a precursor for?

glucose

what is citrate a precursor for?

fatty acids, cholesterol

what two intermediates of the TCA cycle cannot be used elsewhere?

isocitrate and succinate

how can citrate and pyruvate cross the mitochondrial membrane?

via specific membrane transport proteins

what does anaplerotic mean?

replenish intermediates when we have been using them in various ways

what can pyruvate be converted to during exercise to boost the TCA cycle?

alpha ketoglutarate

are reoxidation rxns. exergonic or endergonic?

exergonic

what does a higher reduction potential mean?

more likely to accept e-; oxygen is final e- acceptor and has the highest reduction potential

is substrate level phosphorylation direct or indirect?

direct

is oxidative phosphorylation direct or indirect?

indirect

what is the outer membrane of a mitochondrion like?

porous; molecules can almost flow freely through

what is the inner membrane of a mitochondrion like?

contains the ETC and is very restrictive

what transports ADP/ATP across the mitochondrial membrane?

ATP translocase; imports ATP into cytosol and exports ADP into matix

what moves protons and inorganic phosphates across the mitochondrial membrane?

a symport protein pumps them from the cytosol into the mitochondrial matrix

what does the first complex of the ETC do?

moves 4 H+ into the inner membrane space, oxidizes NADH to NAD+ and reduces Q to QH2

what does the second complex of the ETC do?

a ubiquinol pool; QH2 can come from the TCA, fatty acid breakdown, or cytosolic NADH conversion to QH2

what is complex 3 of the ETC?

the heme group of a b cytochrome; soluble in the inner membrane

what does the Q cycle do?

reduces two cytochrome c and uses 2 QH2; collects e-

what happens in the first round of the Q cycle?

QH2 donates 1 e- to the ISP then to cytochrome c and its other to cytochrome b then to Q (semiquinone)

what happens in the second round of the Q cycle?

a second QH2 gives its two e- to complex III and its 2 H+ to the intermembrane space; 1 e- goes to cytochrome b and the other regenerates QH2

what does the third complex of the ETC do?

pumps 4 H+ into the inner membrane space, reoxidizes Q and reduces 2 cytochrome c

what does the fourth complex of the ETC do?

cytochrome c oxidase; is embedded in the membrane; has heme groups; pumps 2 H+ into the inner membrane space; reduces O2 to H2O

how many cytochrome c does it take to fully reduce O2?

4 (4 e-)

how do we generate a proton gradient/proton motive force?

pump 10 e- from inner membrane space across matrix to get 2.5 ATP molecules

what does ATP synthase do?

the F0 portion is located in the membrane and pumps protons; the F1 portion is located in the matrix and synthesizes ATP

where is ATP made in ATP synthase?

the B subunit

what happens when ATP synthase is open?

ATP is released

what happens when ATP synthase is loose?

binds ADP and + Pi

what happens when ATP synthase is tight?

ATP forms