Chapter 15: Glucose Catabolism Flashcards
converts glucose to
two C3 units (pyruvate)
Glycolysis
do notes on slide 1
is a ubiquitous, relatively nonspecific enzyme that catalyzes the phosphorylation of hexoses such as D-glucose, D-mannose, and D-fructose.
Hexokinase
enzymes that catalyze the same reaction but are encoded in different genes
isozymes
Hexokinases I, II, and III have Km values of about what
0.1 mM
Blood glucose concentration Km values
is 4 to 5 mM
hexokinase IV
Glucokinase
Glucokinase has a Km value of
2-5 mM
does Glucokinase work in high levels of glucose
yes
are allosterically inhibited by their product which happens at high cellular concentration of glucose 6-phosphate
Muscle hexokinases I and II
the three reactions of glycolysis that function with large negative free energy changes in heart muscle under physiological conditions
those catalyzed by hexokinase,
phosphofructokinase
pyruvate kinase
Is the Major Flux-Controlling Enzyme of Glycolysis in Muscle
Phosphofructokinase
plays a central role in control of glycolysis because it catalyzes one of the pathway’s rate-determining reactions.
Phosphofructokinase
acts as an allosteric inhibitor
ATP
is a tetrameric enzyme with two conformational states, R and T .
PFK
In muscle, [ATP] is ~50 times greater than [AMP] and ~10 times greater than [ADP].
[AMP]
[ADP]
a metabolic signal consisting of a decrease in [A TP] too small to relieve PFK inhibition is amplified significantly by what?
adenylate kinase reaction
which increases [AMP] by an amount that produces a much larger increase in PFK activity.
denylate kinase reaction
The most potent allosteric effector of PFK
F2
6P
synthesize and degrade 2,3-BPG
Erythrocytes
how 2,3-BPG is synthesize and degrade
a detour from the glycolytic pathway .
regulates hemoglobin’s oxygen affinity
The level of available 2,3-bisphosphoglycerate (2,3-
BPG)
alter the ability of the blood to carry
oxygen as is indicated by the oxygen-saturation curve of its hemoglobin.
inherited defects of glycolysis in
erythrocytes
Under aerobic conditions what happens to pyruvate
the pyruvate is completely oxidized via the citric acid cycle to CO2 and H2O
Under anaerobic conditions what happens to pyruvate
pyruvate must be converted to a reduced end product in order to reoxidize the NADH produced by the GAPDH reaction
in muscle how pyruvate is reduced to lactate
lactate dehydrogenase (LDH)
to regenerate NAD+ in a process known as
homolactic fermentation
pyruvate is decarboxylated to yield what
CO2 and acetaldehyde
what is CO2 and acetaldehyde reduced by
NADH
what does CO2 and acetaldehyde yield
NAD+ and ethanol
pyruvate is decarboxylated to yield CO2
and acetaldehyde, which is then reduced by NADH to yield NAD+ and ethanol. This process is known as
alcoholic fermentation
can either be exported from the cell or
converted back to pyruvate.
lactate
is carried by the blood to the liver, where
it is used to synthesize glucose
lactate produced in skeletal muscle cells
what is lactate used to synthesize
glucose
The muscle fatigue and soreness it is due to
acidity of lactate
Anaerobic fermentation results in the production of
2 ATP per glucose
oxidative phosphorylation yields up to
32 ATP per glucose
anaerobic glycolysis yields up to
100 times faster than that of oxidative phosphorylation
has a sweeter taste than sucrose and is inexpensive to produce
Fructose
One possible hazard of excessive
fructose intake
PFK-catalyzed step of glycolysis and thereby avoids a major metabolic control point.
galactose is reduced
galactitol
is treated by a galactose-free diet
Galactosemia
is a genetic disease characterized
by the inability to convert galactose to glucose.
Galactosemia
require NADPH in addition to A TP
endergonic reactions
uses the free energy of metabolite oxidation to synthesize ATP
NADH
uses the free energy of metabolite oxidation for reductive biosynthesis.
NADPH
how is NADPH is generated
the oxidation of glucose-6-phosphate via an alternative pathway to glycolysis
what is another name for pentose phosphate pathway
hexose monophosphate shunt
required for several reductive processes in addition to biosynthesis
NADPH
erythrocytes require a plentiful supply of
glutathione (GSH)
are particularly sensitive to oxidative damage, although clinical symptoms may be absent.
individuals who are deficient in glucose-6-phosphate dehydrogenase (G6PD)
resistance to the malarial parasite,
individuals who are deficient in glucose-6-phosphate dehydrogenase (G6PD)
