Glycolysis and Gluconeogenesis Flashcards
Where does glycolysis take place?
Outside the cell in the cytosol
What is the end product of one cycle of glycolysis?
2 pyruvate molecules, 2 ATP
What occurs in stage 1 of glycolysis?
Glucose is converted to fructose-1,6-bisphosphate and two ATP are used
What occurs in stage 2 of glycolysis?
Two molecules consisting of three carbons each are created: Dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (GAP)
What occurs in stage 3 of glycolysis?
DHAP and GAP are each converted to one molecule of pyruvate, also producing two ATP and one NADH each
How many times does each stage of glycolysis occur?
Stages 1 and 2 occur once, stage 3 occurs twice
What is the net yield of one cycle of glycolysis?
2 ATP (Four are created in stage 3 but two were used in stage 1) + 2 NADH + 2 H+
What enzyme performs first regulated step in glycolysis?
Hexokinase
What enzyme commits the rest of glycolysis to occur?
Phosphofructokinase
Which enzyme is the last regulated step in glycolysis and causes the formation of pyruvate?
Pyruvate kinase
Which enzyme is NOT a part of glycolysis but modifies pyruvate for the TCA cycle?
Pyruvate dehydrogenase
What does pyruvate create in the presence of oxygen?
Acetyl CoA, in mitochondria
What does pyruvate create in the absence of oxygen?
Lactate, in cytoplasm
What two things are needed for gluconeogenesis to occur?
An energy source from the metabolism of fat and a source of carbons
Under what conditions is gluconeogenesis stimulated to occur?
Times of low carbohydrate, fasting or starvation
Where does gluconeogenesis primarily occur and what enzyme allows the process to release glucose into the blood stream?
90% in the liver (10% in kidney), has glucose 6-phosphatase
Where is glucose 6-phosphatase located?
Membrane of rough ER
How does glucose 6-phosphate become glucose at target cells?
In the liver G6-P is transported into the lumen of the rough ER through G6-phosphatase (Which dephosphorylates G6-P into glucose). Then the glucose is enclosed in vesicles, released from the liver into the blood, and travels to energy-poor cells (BRAIN).
Which 5 substrates can be used for gluconeogenesis?
Lactate (From anaerobic glycolysis such as in RBCs or muscle), glucogenic amino acids (From muscle in diet), glycerol (From triglycerides), proprionate (From ruminant VFAs), and TCA intermediates
What type of pH would inhibit gluconeogenesis and the TCA cycle?
Very low pH
What is NOT a substrate for gluconeogenesis?
Acetyl CoA
What does glycerol form after it loses its fatty acid chains and is phosphorylated and undergone dehydrogenase activity?
DHAP (Dihydroxyacetone phosphate)
How are fatty acids converted to Acetyl CoA?
Through beta oxidation
What steps near the beginning of gluconeogenesis are not present in glycolysis?
Conversion of pyruvate to oxaloacetate (OAA) via pyruvate carboxylase and conversaion of OAA to PEP by PEP carboxykinase
