Glycolysis Flashcards
(20 cards)
How do sugars enter the cell?
Sugars enter the cell via sodium-glucose co-transporters (SGLTs) and glucose transporters (GLUTs)
SGLTs actively transport glucose against its concentration gradient using the sodium gradient, while GLUTs facilitate passive diffusion into cells.
What is the sequence of reactions in anaerobic glycolysis?
Glucose → Glucose-6-phosphate → Fructose-6-phosphate → Fructose-1,6-bisphosphate → Glyceraldehyde-3-phosphate + Dihydroxyacetone phosphate → 1,3-Bisphosphoglycerate → 3-Phosphoglycerate → 2-Phosphoglycerate → Phosphoenolpyruvate → Pyruvate
This process results in the production of 2 ATP and 2 NADH.
What are the energetics of anaerobic glycolysis?
Anaerobic glycolysis converts one molecule of glucose into two molecules of pyruvate/lactate and generates two molecules of ATP
This process is crucial for energy production in the absence of oxygen.
What is the primary site of allosteric regulation of glycolysis?
Phosphofructokinase-1 (PFK-1) is the primary site of allosteric regulation in glycolysis
Its activation is crucial for glycolytic flux, especially during high energy demands.
How are fructose and galactose oxidized?
Fructose is phosphorylated by fructokinase in the liver and by hexokinase in muscle. Galactose is converted to UDP-galactose via galactose-1-phosphate uridylyltransferase (GALT)
Different pathways exist for the metabolism of fructose and galactose.
Why do pathologies occur due to a defective enzyme in the pathway?
Defective enzymes can lead to accumulation of substrates and depletion of necessary products, disrupting metabolic balance and causing diseases
For example, hereditary fructose intolerance results from a deficiency of aldolase B, leading to severe metabolic complications.
What is the role of ATP in metabolism?
ATP provides energy for cellular work and is continuously hydrolyzed to ADP and inorganic phosphate
The body metabolizes about 19 lbs of glucose daily to sustain energy needs despite having less than 1 lb of ATP at any moment.
What is the function of SGLTs?
SGLTs actively transport glucose against its concentration gradient using the sodium gradient created by the Na+/K+ ATPase pump
SGLT1 absorbs glucose and galactose in the intestines and kidneys, while SGLT2 reabsorbs glucose in renal proximal tubules.
What are GLUT transporters?
GLUT transporters facilitate the passive diffusion of glucose into cells
Different GLUT isoforms have specific roles in various tissues, such as GLUT1, GLUT2, GLUT3, and GLUT4.
How does glycolysis maintain NAD+ levels?
Cells regenerate NAD+ through oxidative phosphorylation in aerobic conditions or lactate fermentation in anaerobic conditions
NAD+ is essential for glycolysis to continue by acting as an electron acceptor.
What is the first step in glycolysis?
The phosphorylation of glucose to glucose-6-phosphate, catalyzed by hexokinase or glucokinase
Hexokinase is found in most tissues, while glucokinase is specific to the liver and pancreas.
What is feedback inhibition in glycolysis?
Feedback inhibition occurs when glucose-6-phosphate accumulates and inhibits hexokinase, preventing excessive glucose phosphorylation
This mechanism maintains metabolic balance.
What activates PFK-1 during glycolysis?
AMP activates PFK-1, especially during high energy demand situations
The rise in AMP signals low energy status, leading to increased glycolytic flux.
How is glycolytic flux regulated in hepatocytes?
Glycolytic flux is hormonally regulated through phosphofructokinase-2/fructose-2,6-bisphosphatase (PFK-2/F26BPase)
Insulin promotes glycolysis by activating PFK-2, while glucagon inhibits it.
What is hereditary fructose intolerance (HFI)?
HFI is a metabolic disorder caused by a deficiency of aldolase B, leading to the accumulation of fructose-1-phosphate in the liver
This condition disrupts ATP production and can cause severe hypoglycemia and liver dysfunction.
What is classic galactosemia?
Classic galactosemia is caused by a deficiency in galactose-1-phosphate uridylyltransferase (GALT), leading to the accumulation of galactose-1-phosphate
This disorder results in severe complications, including tissue damage and neurological impairments.
What is the role of 2,3-BPG in red blood cells?
2,3-BPG alters the oxygen binding to hemoglobin, stabilizing the low oxygen affinity state
This adaptation is crucial for oxygen delivery in red blood cells.
What is the energy investment phase of glycolysis?
The energy investment phase includes the conversion of glucose to glucose-6-phosphate, fructose-6-phosphate, and fructose-1,6-bisphosphate
This phase requires the input of ATP.
What are the key irreversible enzymes in glycolysis?
Hexokinase, phosphofructokinase-1 (PFK-1), and pyruvate kinase
These enzymes regulate the flux of glucose through glycolysis.
What is the net output of glycolysis per glucose molecule?
2 Pyruvate + 2 ATP (net) + 2 NADH + 2 H2O
This output indicates the efficiency of glycolysis in energy production.
