Term
| the dual role of the glycolytic pathway |
|
Definition
-degrades glucose to generate ATP
-provides building blocks for biosynthetic rxns |
|
|
Term
| potential sites of control in metabolic pathways |
|
Definition
| enzymes catalyzing irreversible rxns |
|
|
Term
| the control sites (i.e., enzymes tat catalyze irreversible rxns) in glycolysis |
|
Definition
-hexokinase
-phosphofructokinase
-pyruvate kinase |
|
|
Term
| the type of enzymes that regulate glycolysis |
|
Definition
|
|
Term
| what glycolysis in muscle does |
|
Definition
| primarily provides power for muscle contraction |
|
|
Term
| the primary control of muscle glycolysis |
|
Definition
| energy charge of the cell- ratio of ATP to AMP |
|
|
Term
| energy charge of the cell |
|
Definition
|
|
Term
| glycolysis in muscle is regulated by... |
|
Definition
| feedback inhibition to meet the need for ATP |
|
|
Term
| the most important control site in the mammalian glycolytic pathway |
|
Definition
|
|
Term
| how phosphofructokinase is inhibited in muscle |
|
Definition
ATP binds with phosphofructokinase at a distinct site to lower its affinity for fructose 6-phosphate
can also be inhibited by declining pH |
|
|
Term
| how phosphofructokinase is stimulated in muscle |
|
Definition
| AMP binds with phosphofructokinase at the same site to increase its affinity for fructose 6-phosphate |
|
|
Term
| how muscle cells are protected from excess acidity |
|
Definition
| lactic acid lowers the pH, augmenting the inhibitory effect of ATP on phosphofructokinase |
|
|
Term
| why AMP, not ADP, stimulates phosphofructokinase activity |
|
Definition
| because while ATP is being used, aldenylate kinase can convert ADP into ATP |
|
|
Term
|
Definition
|
|
Term
| the rxn aldenylate kinase is involved in |
|
Definition
|
|
Term
| the primary regulatory enzyme in glycolysis |
|
Definition
|
|
Term
| how hexokinase is regulated in muscle |
|
Definition
| it is inhibited by accumulation of glucose 6-phosphate |
|
|
Term
| how inhibition of phosphofructokinase leads to inhibition of hexokinase |
|
Definition
| inhibition of PFK leads to accumulation of fructose 6-phosphate, leading to accumulation of glucose 6-phosphate, leading to inhibition of hexokinase |
|
|
Term
| why hexokinase is not the committed step in glycolysis |
|
Definition
| because glucose 6-phosphate can also be converted into glycogen |
|
|
Term
| why PFK is the committed step in glycolysis |
|
Definition
| because it's the first step unique to glycolysis |
|
|
Term
| why the committed step is the most important controlled element in a biochemical pathway |
|
Definition
| because it regulates flux down the pathway |
|
|
Term
| how pyruvate kinase is inhibited in muscle |
|
Definition
| ATP binds to pyruvate kinase to decrease its affinity for phosphoenolpyruvate |
|
|
Term
| how pyruvate kinase is stimulated in muscle |
|
Definition
| fructose 1,6-bisphosphate activates the kinase to enable it to keep pace with the oncoming flux of intermediates |
|
|
Term
| depiction of glycolysis being inhibited in muscle (at rest) |
|
Definition
|
|
Term
| depiction of glycolysis being stimulated in muscle (during exercise) |
|
Definition
|
|
Term
| the regulation of glycolysis in the liver corresponds to... |
|
Definition
| the biochemical versatility of the liver |
|
|
Term
| how the liver regulates blood glucose |
|
Definition
-stores it as glycogen when high
-releases glucose when low |
|
|
Term
| some things the liver does with glucose |
|
Definition
-stores it as glycogen when high
-releases glucose when low
-uses glucose to generate reducing power for biosynthesis
-synthesize a host of building blocks for other biomolecules |
|
|
Term
| how PFK in the liver is inhibited |
|
Definition
| citrate, since citrate accumulation indicates that there's already enough biosynthetic precursors |
|
|
Term
| the key means by which PFK in the liver responds to changes in blood glucose |
|
Definition
| thru the signal molecule fructose 2,6-bisphosphate (F-2,6-BP) |
|
|
Term
| how PFK in the liver is stimulated |
|
Definition
| fructose 2,6-bisphosphate stimulates PFK by increasing its affinity for fructose 6-phosphate |
|
|
Term
| the enzyme primarily responsible for phosphorylating glucose in the liver |
|
Definition
| glucokinase (hexokinase IV) |
|
|
Term
| glucokinase (hexokinase IV) |
|
Definition
| isozyme of hexokinase; this is what's primarily responsible for phosphorylating glucose in the liver |
|
|
Term
|
Definition
| enzymes encoded by different genes with different amino acid sequences, but catalyze the same rxns |
|
|
Term
| how isozymes/isoenzymes differ |
|
Definition
| usually by kinetic or regulatory properties |
|
|
Term
| some differences between hexokinase and glucokinase |
|
Definition
| glucokinase has a higher KM value and is not inhibited by its product, glucose 6-phosphate |
|
|
Term
|
Definition
| to provide glucose 6-phosphate for the synthesis of glycogen and for the formation of fatty acids |
|
|
Term
|
Definition
| the need to remove glucose from thew blood for storage as glycogen or conversion into fat |
|
|
Term
| some important forms of pyruvate kinase |
|
Definition
|
|
Term
| the form of pyruvate kinase that predominates in the liver |
|
Definition
|
|
Term
| the form of pyruvate kinase that predominates in the muscle and brain |
|
Definition
|
|
Term
| which form of pyruvate kinase is inhibited by alanine? |
|
Definition
| the L form (liver enzyme) |
|
|
Term
| reversible phosphorylation regulates the catalytic properties of which form of pyruvate kinase? |
|
Definition
| the L form (liver enzyme) |
|
|
Term
| the importance of reversible phosphorylation regulating the catalytic properties of the L form of pyruvate kinase (liver enzyme) |
|
Definition
| prevents the liver from consuming glucose when it is more urgently needed by brain and muscle |
|
|
Term
| the function of the GLUT1 to GLUT5 proteins |
|
Definition
| enable glucose to enter and leave animal cells |
|
|
Term
| where the GLUT1 protein is found |
|
Definition
| nearly all mammalian cells |
|
|
Term
| where the GLUT3 protein is found |
|
Definition
| nearly all mammalian cells |
|
|
Term
| the GLUT proteins that essentially continuously transport glucose into cells at a constant rate (function in basal glucose uptake) |
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
|
|
Term
| where the GLUT2 protein is found |
|
Definition
| liver and pancreatic β cells |
|
|
Term
| when glucose enters through the GLUT2 protein at a significant rate |
|
Definition
| when there is much glucose in the blood |
|
|
Term
|
Definition
in pancreas: helps regulate insulin
in liver: removes excess glucose from the blood |
|
|
Term
| where the GLUT4 protein is found |
|
Definition
|
|
Term
| how the number of GLUT4 proteins increases |
|
Definition
-increased insulin, which signals the presence of glucose
-endurance exercise |
|
|
Term
| where the GLUT5 protein is found |
|
Definition
|
|
Term
|
Definition
| primarily as fructose transporter |
|
|
