Glycolysis, Glycogen, Gluconeogenesis, & Pentose Phosphate Pathway Flashcards
Which low-affinity transporter is located in hepatocytes & pancreatic cells ?
GLUT 2 (captures excess glucose primarily for storage)
Which glucose transporter is located in adipose tissue & muscle, & responds to the glucose conc. in peripheral blood 🩸 ?
GLUT 4
Where does glycolysis take place & what does it convert glucose in to ?
Takes place in the cytoplasm & converts glucose into 2 pyruvate molecules
What are the function. of kinases ?
To attach phosphate group from ATP to their substrates
How do hexokinase & glucokinase differ ?
H is widely distributed in tissues & is inhibited by G6P, while G is only found in liver cells & pancreatic beta islet cells (also induced by insulin)
What is the rate-limiting enzyme & main control point in glycolysis ?
PFK 1 (phosphofructokinase-1)
- Inhibited by ATP & citrate; activated by AMP
- Facilitates rxn of F6P phosphorylated to F1,6BP
What are functions of PFK-2 (phosphofructokinase-2) & how do they impact PFK-1?
- Stimulated by insulin
- Facilitate rxn of F6P to F2,6BP which will then activate PFK-1
- Inhibited by glucagon
Which enzyme catalyzes the oxidation & addition of an inorganic phosphate to glyceraldehyde 3-phosphate to produce 1,3 bisphosphoglycerate ?
Glyceraldehyde 3-Phosphate Dehydrogenase
-Also results in the reduction of NAD+ to NADH
Which enzyme catalyzes the transfer of phosphate from 13BPG to ADP, forming ATP & 3PG ?
3-phosphoglycerate kinase
-A type of substrate level phosphorylation: where ADP IS directly phosphorylated ATP using a high energy intermediate
The last enzyme in aerobic glycolysis that catalyzes a substrate-level phosphorylation of ADP via phosphoenolpyruvate substrate is known as ?
Pyruvate kinase
-Activated by F1,6BP (feed-forward activation)
What is the key fermentation enzyme in mammalian cells & what is its function?
Lactate dehydrogenase
-Oxidizes NADH to NAD+
Dihydroxyacetone phosphate (DHAP) is formed from F1,6BP & can be isomerized to G3P. Where is it used & what is its function ?
Used in hepatic & adipose tissue for triacylglycerol synthesis
What are 1,3-bisphosphoglycerate & phosphoenolpyruvate used for ?
Generate ATP by substrate-level phosphorylation (only ATP gained in anaerobic respiration)
What enzymes make certain steps of glycolysis irreversible ?
Hexokinase & glucokinase
PFK-1
Pyruvate kinase
What do RBCs have that produces 2,3BPG from 1,3BPG in glycolysis ?
Bisphosphoglycerate mutase
The rxn of galactose into galactose-1-phosphate, and galactose-1-phosphate into G1P is catalyzed by which enzymes?
Galactokinase & Galactose-1-phosphate uridyltransferase (respectively)
What is pyruvate converted into for entry into the citric acid cycle when ATP is needed or for fatty acid synthesis ?
Acetyl coA
*Carried out by pyruvate dehydrogenase complex & is irreversibile
Glycogen synthesis & degradation occur primarily in liver & skeletal muscle, but is stored where ?
Cytoplasm (as granules)
What is the difference between stored liver glycogen & skeletal muscle glycogen ?
LG is used to maintain blood glucose levels, while SG is used to as an energy reserve for the muscles during exercise
What is the rate-limiting enzyme of glycogen synthesis ?
Glycogen synthase
- Stimulated by G6P & insulin
- Inhibited by epinephrine & glucagon
What are the functions of a branching enzyme ?
- To hydrolyze a-1,4 bonds to release oligoglucose (few glucose molecules bonded together)
2, Forms a-1,6 bond to create branch
What enzyme breaks a-1,4 glycosidic bonds & releases G1P from the periphery of the granule ?
Glycogen phosphorylase
*cannot break a-1,6 bonds
Slightly different versions of the same protein is known as ?
Isoforms
How are the essential gluconeogenic intermediates converted into glycolytic enzymes ?
Lactate—>pyruvate: lactate dehydrogenase
Alanine—->pyruvate: alanine aminotransferase
Glycerol3P—->DHAP: G3P dehydrogenase
