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52 Cards in this Set

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Glycolysis Step 1
glucose
is phosphorylated via either a)hexokinase or b) glucokinase (in the liver only), converting ATP -> ADP to become
glucose-6-phosphate
Glycolysis Step 2
glucose-6-phosphate
the aldehyde portion is isomerized by
phosphoglucose isomerase into a keto-sugar, becoming
fructose-6-phosphate
Glycolysis Step 3
fructose-6-phosphate
is phosphorylated by
phosphofructokinase-1, converting ATP -> ADP, becoming
fructose 1,6 bisphosphate
Glycolysis Step 4
fructose 1,6 bisphosphate
is cleaved into two 3-carbon molecules by
aldolase, to become:
-glyceraldehyde-3-phosphate and
-dihydroxyacetone phosphate

The second form can be isomerized into the first via triose phosphate isomerase
Glycolysis Step 5
glyceraldehyde-3-phosphate
is phosphorylated by
glyceraldehyde-3-phosphate dehydrogenase, an inorganic phosphate group, and NAD+ -> NADH + H+, to become
1,3 bisphosphoglycerate
Glycolysis Step 6
1,3 bisphosphoglycerate
is de-phosphorylated, giving the Pi to ADP, so ADP + Pi -> ATP via
phosphoglycerate kinase, into
3-phosphoglycerate
Glycolysis Step 7
3-phosphoglycerate is rearranged (the Pi portion moved) via
phosphoglycermutase into
2-phosphoglycerate
Glycolysis Step 8
2-phosphoglycerate loses water via
enclase and vecomes
phosphoenolpyruvate (PEP)
Glycolysis Step 9
phosphoenolpyruvate (PEP) is de-phosphorylated via pyruvat kinase, and making ADP + Pi -> ATP, turning into
pyruvate
Glycolysis Step 10
pyruvate, in ANaerobic conditions, will be reduced by
lactate dehydrogenase and will oxidize NADH -> NAD+, and become
lactate
hexokinase
phosphorylates glucose during step 1 of glycolysis (uses 1 atp)
glucokinase
In the liver, phosphorylates glucose during step 1 of glycolysis (uses 1 atp)
phosphoglucose isomerase
in step 2 of glycolysis, converts G-6-P to F-6-P
phosphofructokinase-1
phosphorylates F-6-P, making fructose 1,6 bisphosphate during step 3 of glycolysis
aldolase
cleaves fructose 1,6 bisphosphate into two 3-carbon molecules, using atp during step 4 of glycolysis
glyceraldehyde-3-phosphate dehydrogenase
phosphorylates glyceraldehyde-3-phosphate during step 5 of glycolysis, with the oxidation of NAD+ to NADH and H+
phosphoglycerate kinase
cleaves an inorganic phosphate group and makes ADP -> ATP during step 6 of glycolysis. makes 3-phosphoglycerate.
phosphoglyceromutase
inorganic phosphate portion movs position to make 2-phosphoglycerate. step 7 of glycolysis.
enclase
removes water from 2-phosphoglycerate, making phosphoenolpyruvate (PEP). Step 8 of glycolysis.
pyruvate kinase
cleaves an inorganic phosphate from PEP and makes ADP -> ATP to make pyruvate. Step 9 of glycolysis.
what is important about phosphorylating glucose in the cell?
By phosphorylating glucose, you trap it inside the cell.
What are the main differences between hexokinase and glucokinase?
Hexokinase: in all cells. inhibited by high levels of G-6-P. Not affected by insulin.

Glucokinase: only present in liver cells. not inhibited by G-6-P. Induced by insulin. Requires higher concentration of glucose to get going than hexokinase does.
What regulates the action of phosphofructokinase-1?
The levels of ATP or ADP:
High levels of ATP are inhibitory, high levels of ADP are stimulatory.
What regulates the activation/inactivation of pyruvate kinase?
Insulin and Glucagon levels, as well as concentrations of ATP and ADP.
Glucagon stimulates the inactivation of pyruvate kinase, while insulin stimulates the activation of the enzyme.
How is NAD+ supplied in anaerobic conditions to keep glycolysis running?
The enzyme lactate dehydrogenase will convert pyruvate to lactate, and oxidize NADH to NAD+
What tissues have absolute (or close to it) dependence on glycolysis for energy? Why?
erythrocytes, cornea, lens, retina, renal medulla, testis, leukocytes, white muscle fibers. This is because these cells have few or no mitochondria, so are unable to further oxidize lactate.
How does pyruvate kinase deficiency cause anemia?
Without this enzyme, the rbc's cannot make pyruvate from PEP. There is a lack of energy in the cell as well as a buildup of PEP. This causes a breakdown of ATP-dependent ion gradient pumps, and the cell collapses and is lysed.
What is the cause of diabetic cataracts (typically)?
The increase glucose in the diabetic patient's lens cells is metabolized via aldose reductase to sorbitol. The sorbitol does not exit the cell, causes an osmotic imbalance, the lens swells, and damages the fibers.
What is the name for DCA?
dichloroacetate.
How is DCA predicted to be effective against cancer?
DCA would increase oxidative metabolism, and therefore would "push" the cells' pyruvate into the TCA cycle instead of anaerobic lactic acid formation.
This would inhibit growth of cancer beyond available blood vessel supplies by impairing the ability to make energy anaerobically.
What is the primary source of substrate for gluconeogenesis?
Proteins! (except leucine and lysine) The proteins are de-aminated and the carbon bits are recycled into glucose. (The discarded amino group is removed via urea formation)
what is a disadvantage to using fats for gluconeogenesis?
even-chain FA's cannot be used.
What are the two reasons why the hexose monophosphate shunt is important?
1) Makes pentoses, which are used for the manufacture of ATP, CoC, NAD, FAD, RNA and DNA
2) Makes NADPH, which is required as a cofactor for many biosynthetic reactions and in maintaining antioxidant defenses.
What are the two stages of the HMPS?
1) The oxidative phase, which is thermodynamically irreversible. This phase produces two NADPH
2) The non-oxidative phase, where 6 molecules of pentose may be undergo a series of rearrangements to yield 5 molecules of hexose.
In what tissues do you find high HMPS activity?
Liver (fatty acid synthesis)
Adipose tissue and mammary glands (fat synthesis)
gonads and adrenal cortex (steroid synthesis)
nervous tissue for nitrous oxide synthesis
rbc's as antioxidants
where in the cell does the HMPS occur?
In the cytosol
Does the HMPS occur in high or low levels in striated muscle tissue?
low levels of G-6-P dehydrogenase, so low levels of the oxidative portion of the HMPS occurs in this tissue type.
What are the 2 main factors in HMPS dysfunction?
1) enzyme deficiency
2) cofactor (vit. B1) deficiency
thiamine (vitamin B1) is a required coenzyme for what enzymes?
transketolase (HMPS)
pyruvate dehydrogenase or PDH
alpha-ketoglutarate dehydrogenase (TCA cycle)
branched-chain ketoacid decarboxylase) catabolism of BCA)
What are the main symptoms shared by all the B-vitamin deficiencies?
Neurological symptoms, lethargy, weakness.
Which vitamins are required cofactors of the PDH enzyme complex?
B1 (thiamine), B2(riboflavin), B3(niacin), B5 (pantothenic acid)
What four cofactors are required for the PDH enzyme complex? (not including the vitamins)
Mg++, Thiamin-PP (comes from vit B1), Lipoic acid, and FAD
pyruvate dehydrogenase
the enzyme that controls production of Acetyl Co-A from pyruvate
pyruvate dehydrogenase kinase
when it phosphorylates PDH, it turns it OFF (inactivates). This means pyrivate cannot be made into Acetyl-CoA
this kinase enzyme is activated by hi-energy state molecules like ATP, AcetylCoA, and NADH.
pyruvate dehydrogenase phosphatase
restores PDH activity, removes the phosphate group. Works constituatively.
what is important about lipoic acid for metabolism?
This molecule acts as a H-holder at the S-S bond portion. The function can be blocked by arsenic and mercury which bind irreversibly. blocks PDH action.
What are the four points on the "Biochemical Traffic Circle?"
oxaloacetate
citrate
alpha-ketoglutarate
succinyl CoA
What is the role of citrate in the "Biochemical Traffic Circle?"
Citrate can be processed through the TCA cycle for energy, can be converted into Acetyl CoA or oxaloacetate.
What is the role of alpha-ketoglutarate in the "Biochemical Traffic Circle?"
this molecule can be used for amino acid synthesis as well as a component of the TCA cycle.
What is the role of succinyl CoA in the "Biochemical Traffic Circle?"
this molecule can be used for the synthesis of amino acids, proprionate (a fatty acid), or porphyrins (ie heme compounds like hgb), as well as being a component of the TCA cycle.
Oxaloacetate's role in the Biochemical Traffic Circle?
This molecule can be recycled in the TCA cycle, or used for the synthesis of carbohydrates and amino acids. This molecule can be made from pyruvate, and is important in both the TCA cycle as well as gluconeogenesis.
How does tremetol pose a threat to grazing animals?
this chemical which is consumed in certain plants, is converted by the liver into a metabolite which inhibits citrate synthase. Since citrate is a key molecule in the TCA cycle, the reduced or halted production of citrate causes serious energy deficiencies which show up as neurological symptoms, ataxia, lethargy and much worse!