carbohydrate metabolism Flashcards
What is produced during glycolysis?
NADH is produced
which statements below about glucose is NOT true
it is catabolized in gluconeogenesis
TRUE of hexokinase
it requires ATP in the reaction it catalyzes
TRUE regarding phospho-gluco-isomerase catalysis
the reaction is readily REVERSIBLE
TRUE of PFK
it is activated by high concentrations of ATP
Which of the following occurs during the aldolase reaction
one six carbon molecule is split into 2 molecules of 3 carbons each
during the breakdown of fructose-1,6-biphosphate to dihydroxyacetone phosphate and glyceraldehyde-3-phosphate by aldolase enzyme, how does a cell overcome the energy barrier?
by pushing and pulling process
TRUE about Triosephosphate isomerase(TPI)
the TPI enzyme catalyze interconversions of 1,3- biphosphoglycerate and 3-phosphoglycerate in the glycolysis pathway
deficiency of this, results in the accumulation of dihydroxyacetone phosphate (DAP)
TRUE of glyceraldehyde-3-phosphate
it is the only molecule in glycolysis that gets oxidized
TRUE of the conversion of 1,3 biphosphoglycerate to 3-phosphoglycerate
it results in substrate level phosphorylation
TRUE of 2,3 biphosphoglycerate
it can be produced from 1,3 BPG and 3 phosphoglycerate
TRUE of phosphoenolpyruvate(PEP)
it is very high energy compound
which of the following statements about pyruvate kinase is NOT true
the reaction it catalyzes is readily reversible
molecule that participates in the release of O2 from hemoglobin at the tissue or metabolically active cell sites
2,3-biphosphoglycerate
TRUE of pyruvate kinase
it must be REGULATED for gluconeogenesis to function
TRUE of pyruvate
it is made into lactate during fermentation
which of the ff statements about fermentation is incorrect
it requires acetaldehyde dehydrogenase
TRUE of fermentation: Anaerobically, SIMPLY as extraction of energy from carbohydrates in the absence of oxygen.
under AEROBIC conditions, what does the pyruvate get converted into
acetyl-CoA
TRUE of the futile cycle
they use energy and produce no net amount of molecules
the higher concentrations of AMP molecules activate which enzyme?
PFK
higher concentrations of citrate activate which enzyme
FBPase (fructose 1,6-bisphosphate)
TRUE of gluconeogenesis
gluconeogenesis and glycolysis -> highly exergonic under cellular conditions
it bypasses three enzyme reactions of glycolysis
pyruvate carboxylase catalyzes which type of reaction
a reaction that requires biotin (B7)
TRUE about the enzyme phosphoenolpyruvate carboxykinase(PEPCK)
gluconeogenic enzyme
allows hepatic parenchymal cells to produce glucose from pyruvate derived from amino acid metabolism
true to fructose 1,6-biphosphatase (F1,6BP)
it releases phosphate in reaction it catalyzes
TRUE of glucose-6-phosphatase
release free glucose into the bloodstream: liver, kidney, and small intestinal epithelium.
true of glycogen
it is a storage form of glucose in animals
glycogen phosphorylase does which of the following
it uses phosphate to create glucose-1-phosphate from glycogen
Phosphoglucomutase (PGM) does which of the
following:
catalyzes the interconversion of glucose 1-phosphate and glucose 6-phosphate via glucose 1,6-diphosphate (G1,6DP) intermediate
IT IS A KEY ENZYME in: glycolysis, gluconeogenesis.
true regarding the breakdown of galactose
It occurs ultimately in glycolysis
Debranching enzyme does
Transfers part of a glucose branch of
glycogen and releases free glucose
Which of the following is true of UDP (Uridine diphosphate) glucose?
It is an activated intermediate with a high
energy bond
glycosyltransferase reactions
Which of the following statements about
regulation of glycogen metabolism is
incorrect?
Glycogen phosphorylase A is the
dephosphorylated form of the enzyme
Which of the following enzyme is not
matched correctly to the reaction carried by
it?
Phosphoglucomutase - galactose-1-
phosphate to glucose-6-phosphate
Branching enzyme in glycogen synthesis
helps in the formation of what linkage
Alpha 1,6 linkage
Which of the following hormones
participates in the glycogen breakdown
Glucagon
Which of the following signaling molecules
inside the cell promote the glycogen
breakdown
cAMP
Which of the following enzyme plays a key
role in the reversal of the effect of
phosphorylation cascade during glycogen
metabolism
Protein phosphatase 1
The epinephrine - triggered cAMP cascade
leads to the deactivation of which of the
following
Glycogen synthase
Which statement below about the
metabolism of fructose is not true?
It is inhibited by excess glucose
Which of the following is true of
phosphodiesterase?
It does not cut cAMP in the presence of
caffeine
Which of the following statements about
insulin is not true?
It stimulates release of glucose from cells
Which statement regarding the pentose
phosphate pathway is true?
It generates intermediates for other
pathways
Which statement regarding the 10
molecules in the pentose phosphate pathway
is true?
They all are sugars or sugar derivatives
Deficiency of glucose-6-phosphate
dehydrogenase can result in which of the
following?
Anemia
Which statement regarding the reaction
catalyzed by glucose-6-phosphate
dehydrogenase is true?
It is the rate-limiting step of the pentose
pathway (PPP)
Which statement regarding the reaction
catalyzed by 6 - phosphogluconate
dehydrogenase is true?
It is the only decarboxylation of the
pentose phosphate pathway (PPP)
Which statement regarding ribose-5-
phosphate isomerase is true?
It catalyzes the formation of ribose-5-
phosphate
Which of the following enzymes participate
in fructose metabolism before glycolysis?
(Chose all that apply)
D. Fructokinase
E. Fructoaldolase
Which statement regarding transketolase
is true?
It requires thiamine pyrophosphate to
function
Which statement regarding transaldolase
is true?
It mostly catalyzes the transfer of 1-carbon
units
Which condition results when
transaldolase enzyme is deficient
Liver cirrhosis
Which compounds are the connectivity
points for glycolysis or gluconeogenesis?
Glyceraldehyde-3-phosphate (G3P)
Fructose-6-phosphate (F6P)
Which of the following amino acids is not
synthesized from alpha-ketoglutarate of the
citric acid cycle?
Tyrosine
Which of the following statements is not
true regarding the citric acid cycle?
The citric acid cycle enables the yeast or a
bacterial cell to get metabolic energy from
acetyl CoA in the absence of oxygen
Which of the following statement is not
true regarding the pyruvate dehydrogenase ?
The pyruvate dehydrogenase enzyme
converts the acetaldehyde to ethanol in
the yeast cell in the absence of oxygen
Which of the following is not correctly
matched?
Malate : gluconeogenesis
How many oxidation reactions take place
in the citric acid cycle?
Four
Which of the following enzymes are unique
to the glyoxylate cycle?
D. Malate synthase
E. Isocitrate lyase
Which of the following statements is not
correct regarding the glyoxylate cycle
The glycoxylate cycle is exclusive to the
muscle cells as it helps in the synthesis of
glucose from the acetyl CoA during
contraction process
Which of the following molecule acts as a
branch point between the synthesis of ketone
bodies and cholesterol in animal bodies
Beta-hydroxy-beta-methylglutaryl-CoA
Which of the following enzyme is not a part
of ketone body metabolism?
FBPase
Which of the following is correct regarding
the energy output per cycle of the citric acid
cycle?
3 NADH2, 1 FADH2, and 1 GTP
Which of the following enzyme of citric
acid is embedded in the inner mitochondrial
membrane?
Succinate dehydrogenase
Which of the following enzyme participates
in both the TCA cycle and ETC?
Succinate dehydrogenase
Which of the following molecules is central
to most of the biological reactions in the cell
during metabolism?
Acetyl CoA
The reaction that helps maintain normal acid-base balance is:
glutaminase
GABA is an inhibitory NT because it causes:
influx of chloride ions
Which AA test dose administration is used to diagnose folate deficiency (B9)?
histidine
Which AA test dose administration is used to diagnose pyridoxal phosphate deficiency (B6)?
tryptophan
TRUE about thyroglobulin
it contains 115 tyrosine residues
TRUE of the concentration of IODIDE
it is an energy dependent process and is linked to the ATPase dependent Na-K pump
Intracellular calcium is mobilized in the cytoplasm by this PIP2-derived 2nd msgr
inositol triphosphate
TRUE about mineralocorticoids
synthesis of mineralocorticoids depends on the presence of enzyme 18-hydroxylase (18-hydroxycorticosterone)
TRUE of glycemic index
foods with a low glycemic index cause less fluctuations in insulin secretion
This water-soluble vitamin requires a specific transport protein:
cobalamin (B12)
gastric intrinsic factor (IF)
cubilin receptor
transcobalamin II (transporter)
TC II-R (receptor)
form of vitamin A that involves regulation of gene expression
retinoic acid
main storage of vitamin D is
25-hydroxycholecalciferol
This vitamin participates in the transfer of 1-carbon methyl units:
folic acid (B9)
These peptides arise from the PRO-OPIO-MELANO-CORTIN gene
melanocyte-stimulating hormone
corticotropin-like intermediate lope peptide
adrenocorticotrophic hormone
List of glycoproteins to remember
TSH
FSH
HCG
Prolactin is not a glycoprotein, its a polypeptide. Single-chain and secreted by lactotrophs in the anterior pituitary.
MOST utilized pathway for testosterone synthesis in human testes
DHEA pathway (de-hydro-epi-androsterone)
Conversion of cholesterol to pregnenolone in the mitochondria of the testes is promoted by:
Luteinizing hormone
The glycemic index is a measure of:
digestibility
The phosphorylation of glucose during glycolysis involves:
an enzyme inhibited allosterically by the product
Coenzyme of the pyruvate dehydrogenase complex
biotin, coenzyme A, lipoic acid
NOT pyridoxine
This enzyme of the krebs cycle catalyzes a substrate level phosphorylation reaction:
succinate thiokinase
Reactions that synthesizes purine nucleotides
synthesis forms amphibolic intermediates
phosphoribosylation of nucleobases
phosphorylation of purine nucleosides
