Question 1

Malate shuttle provides way to transfer reducing equivalents (NADH) from mitochondrion to cytosol By means of malate shuttle, _________ produced in mitochondria is made available for this later step in cytosol, where it is low A different route is followed when lactate is the precursor –Since NADH is produced in cytosol by LDH, shuttle unnecessary –A mitochondrial PEP CK converts __________to ___________

Accepted Answer

NADH oxaloacetate; PEP

Question 2

Bypass #3: Glucose 6-phosphatase Five protein components Large negative DG; irreversible; enzyme is ________-activated Operative only in certain tissues (___________, __________, and ________); in other tissues, pathway stops at glucose 6-phosphate –Lack enzyme; “want” to keep glucose as Glu-6-P, which cannot exit cell Phosphatase activity located on inner face of _________ Glucose generated is transported out of cell via transporter _______ What disorder is caused as result of a deficiency in Glu-6-phoshatase?

Accepted Answer

Mg2+ liver, kidney, small intestine lining ER GLUT2 Von Gierke’s (a GSD)

Question 3

How does Energy Charge regulate pathways? •Low E.C. –_________[AMP] –Glycolysis ______ •High E.C. –Lots of ___________ present –Biosynthetic reactions _________ –Gluconeogenesis __________

Accepted Answer

High Stimulated ATP promoted stimulated

Question 4

The Three “Bypass” Steps of Gluconeogenesis •Bypass steps catalyzed by: –1)____________________ –2)_______________________ –3________________________ Here, irreversible steps of glycolysis are being replaced Bypass #3 (G6Pase) occurs only in certain tissues: –______________, ____________, and ____________ •First step occurs in ___________, but rest are in ____________

Accepted Answer

Pyruvate carboxylase and phosphoenolpyruvate carboxykinase (replace pyruvate kinase of glycolysis) Fructose 1,6-bisphosphatase (replaces PFK-1) –Glucose 6-phosphatase (replaces hexokinase) Liver, kidney and epithelial cells of small intestine mitochondrion;cytosol.

Question 5

Pyruvate Carboxylase Located in ___________; a _________-dependent enzyme Pyruvate is either transported into mitochondrion or produced from _________ there Reaction occurs in two phases: (i) _________of biotin, and (ii) transfer of_________ group from _________ to ___________ CO2 (HCO3- ) must be “activated” through ____________ first Absolute requirement for acetyl-CoA, a potent allosteric activator A heterotetramer, each subunit contains 4 domains: a _____________ domain (phase 1); a pyruvate carboxylase domain (phase 2); a domain that binds acetyl-CoA; and the domain to which biotin is attached via _________ residue

Accepted Answer

mitochondrion; biotin alanine carboxylation; CO2; carboxybiotin; pyruvate phosphorylation biotin carboxylation; pyruvate carboxylase; acetyl-CoA lysine

Question 6

How does Fructose 2,6-bisphosphate regulate pathways? Acts mainly in __________ Under starvation conditions –What hormone is released? –F2,6BP levels ___________ –Gluconeogenesis ____________ •In fed state –What hormone is released? –F2,6BP levels _______ –Glycolysis_________

Accepted Answer

liver Glucagon Decrease stimulated (glucose is synthesized) Insulin released increase stimulated

Question 7

What shuttle transports oxaloacetate from mitochondrion to cytosol?

Accepted Answer

The Malate-Aspartate Shuttle

Question 8

PEP Carboxykinase Reaction:___________ Located in _________ Carries out _________and_________ oxaloacetate to give PEP Formation of unstable enol compound (__________) is driven by decarboxylation and is trapped by phosphorylation –Is step reversible or irreversible? –carboxylation-decarboxylation sequence is a way of __________pyruvate

Accepted Answer

Oxaloacetate + GTP → PEP + CO2 + GDP cytosol decarboxylation and phosphorylation; PEP Irreversible “activating”

Question 9

The Pentose Phosphate Pathway •Meets the needs of all organisms for __________, which is used for –reductive biosynthesis of a number of important biomolecules Fatty acids Cholesterol and the steroid hormones nucleotides Neurotransmitters –Protection against ______________arising from oxidative stress, which is especially important in __________ and ________ and _________ •Produces________, needed for synthesis of _______and ______, as well as the coenzymes ATP, NADH, FADH2 and coenzyme-A –Especially important in rapidly __________cells such as __________, _________, and __________—also tumors Involves two phases: __________ and ___________ Located in __________

Accepted Answer

NADPH reactive oxygen species (ROSs) erythrocytes; lens;cornea of the eye ribose-5-phosphate; DNA; RNA dividing bone marrow, skin, and intestinal mucosa oxidative and non-oxidative cytosol

Question 10

The Importance of Reduced Glutathione for the Red Blood Cell Glutathione exists in two interconvertible forms: 2 GSH (red.) = GSSG (ox.) GSH protects against __________; it keeps RBCs in ________state (2 GSH = GSSG) GSSG converted to GSH via ___________, which uses ___________as cofactor ROSs cause cellular damage; especially harmful to _________ GSH acts as “___________ buffer”: –Maintains_________ residues of Hb in reduced state –Keeps iron in reduced,__________, state –_____________ peroxides and hydroxyl free radicals •Otherwise: Hb tetramers-Heinz bodies-hemolysis-hemolytic anemia

Accepted Answer

ROSs reduced Glutathione Reductase; NADPH RBCs sulfhydryl Cys Fe2+ Detoxifies

Question 11

How is the lactate that is produced during vigorous exercise dealt with?

Accepted Answer

•It is converted back to glucose via gluconeogenesis in the liver as part of the Cori Cycle.

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Gluconeogenesis and the Pentose Phoshate Pathway Flashcards

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