MIDTERM: GLYCOLYSIS Flashcards
- is the main pathway of glucose metabolism
GLYCOLYSIS
importance of glycolysis:
- ## Energy Production
- it occurs in the cytosol of all cells, and can function either aerobically or anaerobically , depending on the availability of oxygen and electron transport chain.
GLYCOLYSIS
- results from various causes including impaired activity of pyruvate dehydrogenase , especially in thiamin deficiency
LACTIC ACIDOSIS
end product of glycolysis
PYRUVATE
The enzymes that catalyzes the phosphorylation of glucose to form glucose-6-phosphate in the first step of glycolysis. This is one of the main regulatory steps of this pathway.
HEXOKINASE
- The function of __________ in the liver is to remove glucose from the hepatic portal blood following a meal, so regulating the concentration of glucose available to peripheral tissues.
- It is also found in pancreatic β-islet cells and it is used for glycogen synthesis and lipogenesis
GLUCOKINASE
Glucose-6-phosphate is converted into fructose-6-phosphate by the enzyme ______________
PHOSPHOHEXOSE ISOMERASE
Fructose-6-phosphate is further phosphorylated by the enzyme
__________ using ATP to form fructose-1,6-bisphosphate.
PHOSPHOFRUCTOKINASE (PHOSPHOFRUCTOKINASE -1 (PFK-1))
Fructose-1,6-bisphosphate is split into two three-carbon molecules:
______________ &______________by the enzyme __________
- DIHYDROXYACETONE & GLYCERALDEHYDE - 3 - PHOSPHATE
- ALDOLASE
Dihydroxyacetone phosphate is isomerized into another molecule of glyceraldehyde-3-phosphate by the enzyme __________.
TRIOSE PHOSPHATE ISOMERASE
Each molecule of glyceraldehyde-3-phosphate is oxidized by ___________ producing NADH and converting an inorganic phosphate (Pi) into a high-energy phosphate group on 1,3-bisphosphoglycerate
GLYCERALDEHYDE - 3 - PHOSPHATE DEHYDROGENASE
_________ then transfers the high-energy phosphate group from 1,3-bisphosphoglycerate to ADP, generating ATP and converting it into 3-phosphoglycerate.
PHOSPHOGLYCERATE KINASE
3-Phosphoglycerate is converted into 2-phosphoglycerate through an isomerization reaction catalyzed by ___________
PHOSPHOGLYCERATE MUTASE
At the end of glycolysis, one glucose molecule has been converted into ___ _molecules of pyruvate, and a net gain of_____ATP and____NADH molecules has been produced.
2 PYRUVATE
2 ATP
2 NADH
Give the overall equation for glycolysis from glucose to lactate
Glucose + 2 ADP + 2 Pi→ 2 Lactate + 2 ATP + 2 H2O
These three are markedly exergonic and must therefore be considered to be physiologically irreversible and major sites of regulation of glycolysis.
- HEXOKINASE
- PHOSPHOFRUCTOKINASE
- PYRUVATE KINASE
- is the end product of glycolysis under ANAEROBIC conditions
(eg, in exercising muscle) and in erythrocytes, where there are no
mitochondria to permit further oxidation of pyruvate
LACTATE
Glycolysis is regulated by three enzymes catalyzing non equilibrium reactions
- HEXOKINASE
- PHOSPHOFRUCTOKINASE
- PYRUVATE KINASE
tissues that derived energy from glycolysis and produced lactate
- BRAIN
- GASTROINTESTINAL TRACT
- RENAL MEDULLA
- RETINA
- SKIN
lactase production is also increased in ____________ and many cancers produce lactase
SEPTIC SHOCK
organs that normally take up lactate
- LIVER
- KIDNEY
- HEART
normally take up lactase,
in aerobic glycolysis, how many ATP are produced total (this is including the ATP that NADH could go on to make)?
2
GROSS: 9
NET: 9-2 = 7
glucose to glycogen
GLYCOGENESIS
breakdown of glycogen to glucose
GLYCOGENOLYSIS
formation of pyruvate from non-carbohydrate sources
GLUCONEOGENESIS
the breakdown of glucose into pyruvate
GLYCOLYSIS
is the synthesis of glycogen from glucose
GLYCOGENESIS
is the breakdown of glycogen back into glucose for energy utilization
GLYCOGENOLYSIS
Can glycolysis occur aerobically? Anaerobically? Under what conditions?
Glycolysis can function either aerobically or anaerobically depending on the AVAILABILITY OF OXYGEN and the ELECTRON TRANSPORT CHAIN (and hence of the presence of mitochondria).
What is the enzyme that converts glucose to glucose-6-phosphate? How is this enzyme inhibited?
HEXOKINASE, it is allosterically inhibited by elevated concentrations of its product glucose 6-phosphate.
Enolase is inhibited by what anticoagulant?
FLUORIDE.
Fluoride strongly inhibits the enzyme in the presence of inorganic phosphate. The inhibitory species is the fluorophosphate ion, which when bound to magnesium forms a complex with enolase and inactivates the enzyme.
is the synthesis of glucose from non-carbohydrate precursors (such as lactate, amino acids, and glycerol). It is the reverse process of glycolysis and primarily occurs in the liver and to a lesser extent in the kidneys.
Net outcome: Glucose is produced.
GLUCONEOGENESIS
This pathway involves no net yield of ATP from glycolysis, but provides 2,3-bisphosphoglycerate, which binds to hemoglobin, decreasing its affinity for oxygen, so making oxygen more readily available to tissues
BISPHOSPHOGLYCERATE PATHWAY IN ERYTHROCYTES
How does fructose serve as a factor in the development of obesity?
Fructose enters glycolysis by phosphorylation to fructose-1-phosphate, and bypasses the main regulatory steps, so resulting in formation of more pyruvate and acetyl-CoA than is required for ATP formation. In the liver and adipose tissue, this leads to increased lipogenesis.
What happen to “oxygen debt” after vigorous exercise
When lactate production is high, as in vigorous exercise, septic shock, and cancer cachexia, much is used in the liver for gluconeogenesis (see Chapter 19), leading to an increase in metabolic rate to provide the ATP and GTP needed. The increase in oxygen consumption as a result of increased oxidation of metabolic fuels to provide the ATP and GTP needed for gluconeogenesis is seen as oxygen debt after vigorous exercise.
- when we perform intense exercise, glucose is broken down to provide energy to our muscles , which produces lactic acid as a result . Oxygen is then used to break down the unwanted lactic acid into carbon dioxide and water.
Summarize the glycolysis process
Glucose is initially phosphorylated by the enzyme hexokinase(or glucokinase in the liver) using ATP to form glucose-6-phosphate. This step traps glucose inside the cell and makes it more reactive.
- Glucose-6-phosphate is converted into fructose-6-phosphate by the enzyme phosphoglucoisomerase. This is an isomerization reaction.
- Fructose-6-phosphate is further phosphorylated by the enzyme phosphofructokinase-1 (PFK-1) using ATP to form fructose-1,6-bisphosphate. This step is the commitment step of glycolysis and is irreversible.
- Fructose-1,6-bisphosphate is split into two three-carbon molecules: dihydroxyacetone phosphate and glyceraldehyde-3-phosphate, by the enzyme aldolase.
- Dihydroxyacetone phosphate is isomerized into another molecule of glyceraldehyde-3-phosphate by the enzyme triose phosphate isomerase.
- Each molecule of glyceraldehyde-3-phosphate is oxidized by glyceraldehyde-3-phosphate dehydrogenase, producing NADH and converting an inorganic phosphate (Pi) into a high-energy phosphate group on 1,3-bisphosphoglycerate.
- Phosphoglycerate kinase then transfers the high-energy phosphate group from 1,3-bisphosphoglycerate to ADP, generating ATP and converting it into 3-phosphoglycerate.
- 3-Phosphoglycerate is converted into 2-phosphoglycerate through an isomerization reaction catalyzed by phosphoglycerate mutase.
- Enolase removes a water molecule from 2-phosphoglycerate, forming phosphoenolpyruvate (PEP), which is a high-energy compound.
- Pyruvate kinase catalyzes the transfer of a phosphate group from PEP to ADP, producing ATP and forming pyruvate.
- At the end of glycolysis, one glucose molecule has been converted into two molecules of pyruvate, and a net gain of 2 ATP and 2 NADH molecules has been produced.
What is the enzyme that is dependent on the vitamin-derived cofactor thiamine diphosphate? What is its function?
Pyruvate dehydrogenase- linking glycolysis to citric acid cycle, energy production and regulation of metabolic pathways
When there is impaired pyruvate metabolism, what is produced?
Lactate acid which leads to lactic acidosis
key substrate in the pentose phosphate pathway
Pentose phosphate pathway
