West Flashcards

Are catabolic reactions exergonic or endergonic? What about anabolic reactions?

What are the three stages of energy generation by catabolic reactions?

Glycolysis is constituted by the conversion of __________ to _________.

Pyruvate is of a higher _______ state than glucose, meaning that it is _______ energy.

The energy lost from Glucose during Glycolysis is recouped in the form of _______ and ________.

During Aerobic Glycolysis, pyruvate is subject to further oxidation all the way to ______ and _______.

In Anaerobic Glycolysis, pyruvate must be converted to _________ to regenerate _______ for continued glycolytic flux. This can later be converted back to pyruvate when _____ is available, or exported to the liver as part of the ______ cycle.

The initial steps of glycolysis require ATP consumption to get going. This is referred to as _________. ATP is generated later in the pathway, ultimately to exceed the investment to yield a payoff of ____ ATP/glucose molecule, and ____ NADH/ glucose molecule. If oxygen is available to accept these electons via oxidative phosphorylation, each NADH is worth ~ _____ ATP.

In the first step of Glycolysis:
Glucose ---> Glucose-6-Phosphate

What enzyme catalyzes this reaction?
Is this exergonic or endogonic?
Is this reversible or irreversible?

Glucokinase, the enzyme involved in the first step in Glycolysis, keeps up with processing when high blood glucose levels pour into hepatocytes via GLUT2, minimizing _________.
When Fructose-6-phosphate is high (as in gluconeogenesis), glucokinase is sequestered and inactivated in the nucleus. High levels of what releases this inhibition?

In the second step of Glycolysis, an aldose-ketose isomerization occurs in which:
Glucose-6-Phosphate --> Fructose-6-Phosphate

What enzyme catalyzes this reaction?
Is this reaction reversible?
Is is rate-limiting?
Is it regulated?

In the third step of Glycolysis:
Fructose-6-Phosphate --> Fructose-1.6-Bisphosphate

What enzyme catalyzes this reaction?
Is this step regulated?
Is this step reversible?

What is the commitment step in Glycolysis?

Phosphofructokinase-1 (PFK-1) catalyzes the rate-limiting step of Glycolysis, which is the conversion of Fructose-6-Phosphate to Fructose- 1,6 - Bisphosphate. What molecules inhibit this enzyme?
What molecules stimulate it?

In the fourth step of Glycolysis:
Fructose-1,6-Bisphosphate --> Dihydroxyacetone Phosphate & Glyceraldehyde-3-Phosphate

What enzyme catalyzes this reaction?
This catalyzes the cleavage of a ____-C sugar diphosphate to two ____-C monophosphates.

In the fifth step of Glycolysis:
Dihydoxyacetone Phosphate --> Glyceraldehyde-3-Phosphate

What enzyme catalyzes this reaction?
Is this step reversible?
Is this step regulated?

The first five steps of Glycolysis require what molecule for the reactions to take place?
The last 5 steps generate what molecule, and electrons are extracted to generate what other molecule?

In the sixth step of Glycolysis:
Glyceraldehyde-3-Phosphate --> 1,3-Bisphosphate

What enzyme catalyzes this reaction?

In the seventh step of Glycolysis:
1,3-Bisphosphate --> 3-Phosphoglycerate

What enzyme catalyzes this reaction?
Is this step reversible?
Since there are two 1,3-Bisphosphoglycerates derived from one Glucose molecule, this step restores the original investment of ____ at the beginning of the pathway.
This enzyme is subject to what type of poisoning?

In the eighth step of Glycolysis:
3-Phosphoglycerate --> 2-Phosphoglycerate

What enzyme catalyzes this reaction?

In the ninth step of Glycolysis:
2-Phosphoglycerate --> Phosphoenolpyruvate

What enzyme catalyzes this reaction?
Is this step reversible?

In the final step of Glycolysis:
Phosphoenolpyruvate --> Pyruvate

What enzyme catalyzes this reaction?
Is this step reversible?
Is this step regulated?
What activates this enzyme? What inhibits it?

Red blood cells lack mitochondria, and are thus highly dependent on ______ for energy generation. These are therefore highly sensitive to mutational deficiencies in this process. Most of the rare genetic defects in this process occur in ____, and 4% occur in ________ _________.
Note that mutations cause partial loss of activity or regulation, as the genes themselves are essential.

What enzyme reversibly catalyzes formation of lactate from pyruvate, and regenerates NAD⁺ for continuing operation of glycolysis in O₂- insufficiency, or in cells that lack mitochondria?

Lactate can enter the bloodstream where it can be recovered by hepatocytes and utilized for gluconeogenesis. What is this referred to as?

Many microorganisms, including yeast, anaerobically convert pyruvate to CO₂ and ethanol by _________ ________, instead of lactate.

This refers to metabolism that results in no net oxidation or reduction of the nutrient

This refers to the original surprising observation that in reduced O₂, cells consume higher levels of glucose. This may be related to the ________ effect, which describes the higher glycolytic rate exhibited by tumor compared to normal cells.

ΔG, or Gibbs free energy, for the entire glycolytic reaction to pyruvate is ____ kJ/mol. Thus, the conversion of glucose to pyruvate would essentially run to completion if the reaction were allowed to achieve thermodynamic equilibrium without regulatory intervention.

Owing the the Warburg effect, cancer cells are often excessively _______, which may reflect limited vascularization, and supplies building blocks for anabolic pathways.
How can this best be detected on imaging?

What are the regulated steps of Glycolysis?

What are the four enzymes that are unique to Gluconeogenesis, and what are the three enzymes they pypass? Why must these enzymes be bypassed?

This is the anabolic process by which glucose is produced from precursors such as pyruvate, lactate, glycerol, and alpha-ketoacids

In the first step of Gluconeogenesis:
Pyruvate --> Oxaloacetate

What enzyme catalyzes this reaction?
This occurs after is has been translocated to the ________ from the mitochondria.
What does this enzyme use to capture carbon dioxide to form a high energy intermediate at the expense of ATP?

In the second step of Gluconeogenesis:
Oxaloacetate --> Phosphoenolpyruvate

What enzyme catalyzes this reaction?
Where in the cell does this occur?
This occurs at the expense of one ______ molecule.
Phosphoenolpyruvate is then translocated by to the _________ via a specific transporter.

Oxaloacetate can also be transported out of the mitochondria and converted to PEP by this enzyme with the utilization of the ________ shuttle.

Glucagon inactivates ____, which diverts PEP from a glycolytic to a gluconeogenic fate.

In the third step of Gluconeogenesis:
Fructose 1,6-Bisphosphate --> Fructose 6-Phosphate

What enzyme catalyzes this reaction?
Is this step energetically favorable?
Is this step regulated?
What stimulates this enzyme?
What inhibits it?

A high insulin/glucagon ratio causes decreased _______ and reduced levels of active protein kinase A, which favors dephosphorylation of PFK-2/FBP-2 complex. Dephosphorylated PFK-2 is ________, whereas FBP-2 is _________; this favors formation of fructose 2,6-bisphosphate. Elevated concentrations of F (2,6) BP activates ________, which leads to increased rates of _________.

A high glucagon/insulin ratio causes elevated ________ and increased levels of active protein kinase A, which favors the phosphorylated form of the PFK-2/FBP-2 complex. Phosphorylated PFK-2 is ________, whereas phosphorylated FBP-2 is _________; this impedes the formation of fructose 2,6-Bisphosphate. Decreased levels of F (2,6) BP decreases the inhibition of ________, which leads to an increased rate of _________.

What enzyme translocates Glucose-6-Phosphate into the lumen of the ER in Gluconeogenesis?

In the final step of Gluconeogenesis:
Glucose-6-Phosphate --> Glucose

What enzyme catalyzes this reaction?
Where does this reaction occur (in what two organs)
A deficiency of this enzyme can cause what two disease states?
What organ lacks this enzyme, ensuring that gluconeogenesis only serves local needs?

The Gluconeogenic formation of one Glucose molecule from ____ pyruvates is coupled to the cleavage of ____ high-energy phosphate bonds, in the form of ____ ATP equivalents, and oxidation of ____ NADH ( = ~ ____ more ATPs).

The ΔG, of Gibbs free energy, of Gluconeogenesis is a favorable value of _____ kJ/mol, which would achieve 99.9% completion in the absense of regulatory intervention.

What are three key regulators of Gluconeogenesis?

Ethanol is oxidized to Acetate via what two enzymes?
The excess _______ can lead to the chemical reduction of pyruvate and oxaloacetate, limiting their availability as substrates for gluconeogenesis.

Lactate accumulation can lead to _______ and _______ (as lactate can compete with urate for excretion by the kidney). Decreased oxaloacetate can lead to _________ _________.

Reduced hepatic gluconeogenesis can result in _________, especially after exercise-induced depletion of glycogen stores, or interaction with effects of insulin therapy.

_________, an inhibitor of aldehyde dehydrogenase, has found utility as a deterrent for alcohol ingestion, because accumulation of reactive acetaldehyde can result in undesirable flushing, tachycardia, hyperventilation,and nausea.

Several hours after ingestion of a bolus of glucose, liver ________ stores become the primary source of blood glucose for up to 18 hours. Gluconeogenesis gradually surpasses this as the primary source at a later time.

This is a rapidly mobilizable source of blood glucose from the liver. This is formed from Glucose 6-Phosphate via intermediaries, and mainly phosphorylated back to Glucose 6-Phosphate via Glucose 1-Phosphate

The primary glycosidic linkage is ________, and branches, spaced every 8-10 sugars, are formed by _______ - linkages.

What allows the glycogen molecule to release or retrieve glucose rapidly?

Uridine Diphosphate-Glucose (UDP-Glc) is a "high-energy" glucose donor whose formation "costs" the equivalent of ____ ATPs. What is the purpose of this molecule?

The initial synthesis of Glycogen requires _________, an enzyme that autoglycosylates itself to form a primer.

What enzyme elongates the primer in Glycogen synthesis by sequential addition of alpha 1,4-linked glucose residues?

This enzyme in Glycogen Synthesis hydrolyzes a ~5-mer from the non-reducing terminus, and transfers it to a new glucose approximately 4 positions in from the breakpoint, to generate a branch point and a new non-reducing terminus. Both new termini can be extended, and are recursively subject to new branching reactions.

The branching enzyme cuts and transfers the J sugar of Glycogen from the ____ position to the ____ position

What is the major regulated enzyme of Glycogen berakdown?

In Glycogen breakdown, what enzyme accomplishes chain shortening? Importantly, this enzyme adds ______, rather than water, across the glycosidic bond, resulting in the formation of Glucose-1-Phosphate.

Branch removal in Glycogen Breakdown requires two enzymatic activities of the same bifunctional protein. The ___________________ activity transfers the outer 3 of 4 residues of one branch to the non-reducing terminus of a neighboring branch. The ________________ activity releases the branch stub as free glucose.

In Glycogenolysis, Glucose 1-Phosphate is reversibly converted to Glucose 6-Phosphate by what enzyme?

In the liver, the Glucose 6-Phosphate generated is transported into the ER by the Glucose 6-Phosphate Translocase and converted to Glucose by ____________. Glucose can then be transported extracellularly.

These diseases are caused by accumulation of glycogen with abnormal structure, or excessive amounts of normal glycogen. They are associated with defects in glycogen assembly or diassembly. Severity ranges from fatal in infancy to mild depending on the nature of the mutation.

Type 1a Glycogen Storage Disease, or Von Gierke Disease, is due to a deficiency in what enzyme?
What deficiency is seen in Type 1b?
What organs do these affect?

Symptoms include severe fasting hypoglycemia; fatty liver, hepato and spleno-megaly; progessive renal disease; growth retardation & delayed puberty; hyperlacticacidemia, hyperlipidemia, & hyperuricemia; normal glycogen structure, increase glycogen stored;

Treatment involves nocturnal gastric infusions of glucose or regular administration of uncooked cornstarch.

A Type II Glycogen Storage Disease, or Pompe Disease, is due to a deficiency in what enzyme?

Symptoms include: inborn lysosomal enzyme defect; generalized (primarily liver, heart, & muscle); excessive glycogen concentrations found in abnormal vacuoles in the lysosomes; normal blood sugar levels; massive cardiomegaly;
Infantile Form: early death typically from heart failure; normal glycogen structure

Enzyme replacement therapy is available

In Type V Glycogen Storage Disease, or McArdle Syndrome, what enzyme is deficient? What organs are primarily affected?

Symptoms include: temporary weakness and crampign of skeletal muscle after exercise; no rise in blood lactate during strenuous exercise; normal mental development; myoglobinemia & myoglobinuria; relatively benign, chronic condition; high level of glycogen with normal structure in muscle

________ promotes glycogenolysis; _________ promotes glycogenesis.

In Glycogenolysis, Glucagon binds to its receptor, which activates _______ _______ resulting in accumulation of cAMP which activates cAMP-dependent _________ _________ _____, which in turn phosphorylates _________ _________ ________, converting it from its less active b-form to its active a-form, which in turn phosphorylates __________ ____________ converting it form its inactive b-form to its active a-form.

In Glycogenesis, Insulin activates __________ ________ _____, which dephosphorylates and returns _______ _________ _________ and ________ __________ to their less active b-forms

During muscle contraction, calcium is released from the sarcoplasmic reticulum. Calcium binds to the calmodulin subunit of _________ __________, activating it without phosphorylation. This can then activate _________ __________, causing glycogen _________.

In muscle, under extreme conditions of anoxia and depletion of ATP, ______ activates glycogen phosphorylase b without it being phosphorylated.

Glucagon-activated cAMP-dependent protein kinase A phosphorylates __________ __________ converting it from its active a-form to its inactive b-form.

Insulin activates ________ _________ via dephosphorylation by activating protein phosphatase-1.

Glycogenesis is promoted by ________ energy levels

Regulation of Glycogen Levels:
Glucose-6-Phosphate allosterically activates ___________ and inhibits _____________ in liver and muscle.

Regulation of Glycogen Levels:
ATP inhibits ___________ in liver and muscle

Regulation of Glycogen Levels:
Glucose allosterically inhibits ___________ in liver

Glycogenolysis is promoted by _______ energy, ___________, or _________.

Regulation of Glycogen Levels:
In response to exercise in muscle, calcium binds to calmodulin and the complex activates ___________ (in absense of activation of PKA)

Regulation of Glycogen Levels:
In response to epinephrine, the liver releases calcium from ER stores that activates hepatic __________, and activates protein kinase C that can phosphorylate (and inactivate) ___________.

Regulation of Glycogen Levels:
AMP (signals low energy) allosterically activates __________ in the absense of its phosphorylation.