Glycolysis Flashcards
(39 cards)
the fed state under the influence of
Insulin
Phase of energy evolution
-In the second phase, five subsequent reactions
convert these two molecules of glyceraldehyde-3-phosphate into two molecules of pyruvate
Products of Glycolysis
ATP
NADH
Pyruvate/Lactate
Fate of Glucose-6-P
❑ Glycolysis
❑ Pentose phosphate pathway,
❑Uronic acid pathway
❑ Glycogenesis.
Hexokinase
Low Km
Hexokinase inhibited by
G6P
Hexokinase deficiency causes
Hemolytic anemia
Hexokinase maintains
Intracellular glucose concentration
Gluokinase distribution
Liver and Beta cells of pancreas
Gluokinase
High Km
Is Glucokinase inducible?
Yes, amount present in liver is controlled by insulin
Patients with DM show less activity of
Glucokinase
Significance of glucokinase
Involved in maintaining blood glucose concentration
Rate limiting step in glycolysis
PFK-1
Pyruvate kinase deficinecy leads to
Hemolytic aneima
Anaerobic glycolysis conditions
Glycolysis proceeds in the absence of oxygen (anaerobically)
* When cells have a limited supply of oxygen (renal medulla),
* Under conditions of hypoxia
* In cells lacking mitochondria (RBCs)
* In conditions of greater demands for ATP such as skeletal muscle during
high-intensity exercise
The Metabolic Fates of Pyruvate under aerobic conditions
Pyruvate can be sent (through formation
of Acetyl Co A) into the citric acid cycle,
where it is oxidized to CO2 with the
production of additional NADH and
FADH2
The Metabolic Fates of Pyruvate under anerobic
condition
Pyruvate is reduced by the NADH to
lactate, catalyzed by lactate
dehydrogenase
Coupling reactions
Reoxidation of NADH via lactate formation allows glycolysis to proceed in the absence of O2 by regenerating sufficient NAD+ used for glyceraldehyde 3 phosphate dehydrogenase
Tissues that function under hypoxic conditions
produce Lactate
tissues that normally derive much of
their energy from glycolysis and produce
lactate include
brain, gastrointestinal tract,
renal medulla, retina, and skin
Significance of RL Shunt
- It does serve to provide 2,3
-bisphosphoglycerate,
which binds to hemoglobin, decreasing its affinity
for oxygen, and so making oxygen more readily
available to tissues. - 2,3-BPG can help to prevent tissue hypoxia in
conditions where it is most likely to occur. - Fetal hemoglobin (HbF) exhibits a low affinity for
2,3-BPG, resulting in a higher binding affinity for
oxygen. - That’s the way O2 flows from the mother to the
fetus.
Characteristics of pyruvate kinase deficiency
Inheritance autosomal recessive
* Chronic anemia
* Absence of Heinz bodies (Heinz bodies are more characteristic of glucose-6-P
dehydrogenase deficiency)
* Increase 2, 3 BPG concentration, thus lesser than normal oxygen affinity.
* Normal exercise tolerance
Causes of lactic acidosis
Circulatory insufficiency (shock, cardiac failure),
* Severe anemia, mitochondrial enzyme defects, and
* Inhibitors (carbon monoxide, cyanide)
* Alcohol intoxication
* Pyruvate dehydrogenase complex deficiency,
* Severe muscular exercise,
* Von Gierke’s disease
