question

In glycolysis, why is MgATP used instead of just ATP for the hexokinase reaction?

answer

-Mg2 shields the negative charges of two of the phosphate oxygen atoms of ATP. -Mg2 makes the ? (terminal) phosphorus atom of ATP more accessible to nucleophilic attack by a glucose -OH group.

question

The galactose derivative that enters the glycolytic pathway

answer

glucose 6 phosphate

question

In the 6th step of glycolysis, how is the high-energy compound 1,3-bisphosphoglycerate produced in the glyceraldehyde 3-phosphate dehydrogenase reaction, which is close to equilibrium?

answer

-The oxidation of the aldehyde is strongly exergonic. -The thioester intermediate is a high-energy compound that "traps" some energy from the oxidation of glyceraldehyde 3-phosphate and enables phosphorylation.

question

In the liver, the fructose derivative that enters the glycolytic pathway:

answer

DHAP and G3P

question

which molecules reduce PFK activity?

answer

-increased phosphoenolpyruvate concentration -decreasing blood glucose concentration in mammals

question

-increased phosphoenolpyruvate concentration -decreasing blood glucose concentration in mammals

answer

-increased levels of frutose 2,6-biphosphate in mammals -activation of PFK-2 (phosphofructokinase-2 in mammals) -increased levels of ADP

question

what is a major control point in glycolysis?

answer

the phosphofrictokinase reaction (PFK). it is the slowest reaction in glycolysis and is regulated by several molecules

question

which step of the glycolysis pathway is the control point? what negative effectors inhibit this enzyme and what positive effectors activate this enzyme?

answer

step 3 phosphofructokinase negative: ATP and Citrate positive: ADP and AMP

question

What would be the limiting factor for ATP production by glycolysis in a strenuously-exercising muscle that lacks lactate dehydrogenase?

answer

the supply of NAD+

question

What is the purpose of the Cori cycle?

answer

Lactate formed by the muscle (by fermentation) is transported through the blood to the liver where it is converted by glucose through gluconeogenesis. Purpose: scavenging lactate; detoxifying muscle cells by removing lactate > converting to glucose; liver takes on part of the metabolic burden from the muscle

question

Location of pyruvate decarboxylation

answer

matrix of mitochondria

question

Location of citric acid cycle

answer

matrix of mitochondria

question

Location of electron transport system

answer

inner membrane of mitochondria

question

Location of High [H+]

answer

intermembrane space of mitochondria

question

fatty acid degradation

answer

matrix of mitochondria

question

An allosteric enzyme usually has two forms, active and inactive. If a competitive inhibitor (NOT an allosteric inhibitor) is added to a solution containing this enzyme, the ratio of active form of this enzyme to inactive form actually increases. Explain how this can happen.

answer

An allosteric enzyme has two forms: an active form is maintained when the active site is occupied, and an inactive form is maintained when the regulatory site is occupied by an allosteric inhibitor. A non-allosteric competitive inhibitor competes against the substrate for the same active site, thus it actually helps maintain the 'active' form.

question

What are the two most important parameters in enzyme kinetics? Which of these two is likely affected by competitive inhibition?

answer

Vmax and Km are the two most important parameters in enzyme kinetics. Km is likely affected by competitive inhibition while Vmax is NOT likely to be affected (Vmax is the V0 when [S] is very high, thus S can out compete the inhibitor)

question

Gluconeogenesis can be considered as the reversal of glycolysis except two important steps. What are these two steps?

answer

1) the conversion between F6P and F1,6BP (F6P to F1,6BP catalyzed by PFK for glycolysis and F1,6BP to F6P catalyzed by FBPase for gluconeogenesis 2) the conversion between PEP (phosphoenolpyruvate) and pyruvate (PEP to pyruvate catalyzed by pyruvate kinase and pyruvate to PEP in two steps

question

If you feed the cell with a 14C labeled glucose labeled with 14C at the fourth carbon. When do you expect this 14C is released as 14CO2? Do you expect any of the Citric Acid Cycle intermediates to be labeled? Explain your answer.

answer

The 4th C on a glucose molecule will become the 1st C on a glyceraldehyde-3- phosphate molecule when the six-C fructose 1,6 BP is split into two C3 molecules (the lower half of the fructose, i.e., #4, #5 and #6 C, becomes glyceraldehyde 3-phosphate). Thus, the 4th C on glucose becomes the 1st C on the pyruvate molecule, the ending point of glycolysis. This 1st C is released as CO2 when pyruvate is oxidized to become acetyl CoA. Thus, acetyl CoA is not labeled, hence no citric acid cycle intermediates will be labeled.

question

What is the function of fructose 2,6 bisphosphate in regulating glycolysis

answer

Epinephrine triggers the synthesis of cAMP, which activates PKA (see signaling pathway of epinephrine). As shown in the diagram above, PKA phosphorylates PFK2-FBPase2 knocking out PFK2 activity, hence reducing the level of F2,6BP, leading to slowdown in glycolysis and enhancement in gluconeogenesis for the synthesis of glucose. F2,6BP is a regulatory molecule activating PFK, thus speeding up glycolysis, and also reducing the inhibitory effect of ATP on PFK. F2,6BP also inhibits the activity of fructose 1,6-bisphosphatase, a key enzyme in gluconeogenesis.

question

What are the unique features of phosphofructokinase 2 (PFK2) and fructose 2,6 bisphosphate phosphatase 2 (FBPase2). [Please note these enzymes are for fructose 2,6-bisphosphate metabolism, while the substrate/product for glycolysis/gluconeogenesis is fructose 6-phosphate and fructose 1,6- bisphosphate]

answer

These are two opposing enzymatic activities located in two different domains in the same polypeptide chain. PFK2 is responsible for the synthesis of F2,6BP, while FBPase2 catalyzes the hydrolysis of F2,6BP to F6P. Phosphorylation and de-phosphorylation regulates the differential activities of these two enzymes (as shown in the diagram above).

question

What reactions are different from glycolysis to gluconeogenesis?

answer

Only the 3 irreversible reactions are different.

question

What are the three irreversible reactions in glycolysis?

answer

Hexokinase, Phosphofructokinase, and Pyruvate Kinase

question

Which step of gluconeogenesis is the main negative control point? (Use the numbering system in the image at right.)

answer

step 8

question

Draw pyruvate to lactate rxn

answer

pyruvate + NADH +H-------> Lactate

question

Chp 16 How is fructose converted into glycolytic intermediates by Fructokinase? In dipose tissue?

answer

Fructose is converted into glycolytic pathways by fructokinase by 1. phosphorylation of fructose into fructose 1 phosphate by fructokinase 2. fructose 1 phosphate is then split into glyceraldehyde and hydroxyl phosphate by fructose 1 phosphate aldolase In adipose tissue fructose can be phosphorylated to the glycolytic intermediate fructose 6-phosphate by hexokinase

question

Chp. 16 How can excessive fructose consumption lead to pathological conditions?

answer

excessive fructose can lead to pathological condition because the actions of fructokinase and triose kinase bypass the phosphofructokinase regulatory step. The glyceraldehyde are processed to pyruvate and eventually to acetylCoA IS converted to fatty acids which can result in obesity causing fat t accumulate in the liver.

question

Chp. 16 List the four steps that need to take place to turn galactose into glucose 6 phosphate

answer

1. Galactose------>galatose 1 phosphate (galactokinase+ATP) 2. Galactose 1-phosphate +UDG-Glucose---->UDP Galactose+ glucose 1-Phosphate (galactose 1-phosphate uridyl transferase) 3. UDP-galactose------>UDP glucose (UDP-galactose 4 epimerase) epimerase inverts the hydroxyl group to carbon 4 to glucose 4. Glucose 1-phosphate------->glucose 6 phosphate (phosphoglucomutase)

question

Chp 16 What is the sum of the reaction forGalactose being converted to Glucose?

answer

Galactose + ATP---------> glucose 1-phosphate + ADP + H

question

In glycolysis name the three enzymes that catalyze the irreversible rxns and as a result are control sites in glycolysis?

answer

hexokinase,phosphofructose kinase, and pyruvate

question

when is glycolysis stimulated?

answer

Glycolysis is stimulated as the energy charge falls a signal that the cell needs more ATP

question

Name the most important control site in glycolysis

answer

Phosphofructokinase

question

Describe how phosphofructokinase works

answer

Phosphofructokinase is an allosteric enzyme where high levels of ATP allosterically hinder it. AMP(NOT ADP) binds competitively to its active site but when bound does not inhibit the enzyme. The activity of te enzyme increases when the ATP/AMP ratio is lowered. Low pH also inhibits the enzyme

question

What enzyme forms ATP?

answer

Adenylate Kinase

question

Why does AMPbut not ADP stimulate the activity of phosphofructokinase?

answer

ADP can be quickly turned into ATP so most atp turns quickly into ATP not staying ADP long enough to be inhibitory

question

Why is glucose 6-phosphate concentration a regulatory step in glycolysis?

answer

Its a regulatory step in glycolysis because high concentrations of glucose signal the cell that it no longer requires glucose for energy and so no glucose is needed to be broken down

question

CHP 15 list electron acceptors in increasing degree of affinity for electrons

answer

NADH, FADH2,O2

question

Chp15 In the oxidation of a substrate what does NAD+ accept

answer

NAD+ accepts an H ion and 2 electrons

question

what is the cori cycle? What does it consist of?

answer

The Cori cycle is a metabolic pathway that involves active muscles and the liver.

Biochemistry Sapling Glycoloysis, Gluconeogenesis – Flashcards

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