Reading 14.2/Lecture 13 Funneling into Glycolysis Flashcards
Which type of enzyme is responsible for breaking glycosidic bonds using water in glycolysis?
Hydrolases
Which type of enzyme is responsible for phosphorylating monosaccharides in glycolysis?
Kinases
Which type of enzyme is responsible for changing monosaccharides into glucose or fructose in glycolysis?
Isomerases
Which type of enzyme is responsible for making sugars of sugar-alcohols in glycolysis?
Dehydrogenases
How is fructose metabolized in the body?
Most cells weakly absorb fructose. There are not many cellular transporters of fructose. Fructose is metabolized in the liver.
Fructose Transporter
Present in the liver; process; phosphorylate fructose into fructose 1- P (fructokinase) ; Fructose -1-P aldolase produces DHP and G3P; TPI works on DHP x2 G3P; This is not regulated, because of the absence of phosphofructokinase-1, which would have been the committed step in glycolysis.
How does glycerol shuttle into glycolysis?
glycerol is phosphorylated by glycerol kinase (Glycerol 3-P) and then is converted to dihydroxyacetone-P by Glycerol 3-P dehydrogenase
How does mannose shuttle into glycolysis?
Mannose is converted to mannose-6-phosphate by hexokinase, and is then converted to fructose-6-phosphate by mannose-6-phosphate isomerase
What is the purpose of phosphorylating a saccharide while funneling it into glycolysis?
to keep the sugar inside the cell and maintain the blood/cell absorption gradient.
amylase
works by hydrolyzing internal glycosidic linkages of starch;
Limit Dextrins
oligosaccharides; fragments of amylopectin containing (a1 to 6) branch points;
What enzyme catalyzes the conversion of sucrose to glucose?
sucrase
What enzyme catalyzes the conversion of trehalose to glucose?
trehalase
How does dietary starch/glycogen get converted into glucose?
alpha-amylase
How does endogenous glycogen feed into glycolysis?
endogenous glycogen in converted to Glucose-1-phosphate by phosphorylase, which is then converted into glucose-6-phosphate by phosphogluco-mutase
Q # 34 Does the degradation of glycogen (starch) to a form of glucose that can enter glycolytic pathway require an input of energy?
glycogen phosphorylase mediated breakdown of glycogen conserves energy. It breaks down glycogen and produces glucose-1-phosphate, which is then converted to g-6-p by phosphoglucomutase without the expenditure of cellular ATP; does not include dietary glycogen
Glycogen phosphorylase
catalyzes the breakdown of glycogen; pi attack (a1 to 4) bond
Q # 36 Why is the Cell’s ability to regenerate NAD+ critical to glycolysis? Which glycolytic enzyme requires NAD+?
NAD+ is critical to glycolysis to continue the breakdown of glyceraldehyde-3-phosphate and the substrate phosphorylation that follows with it. The glycolytic enzyme that requires NAD+ is glyceraldehyde-3-p dehydrogenase.
Q # 37 What is the most important consequence to the cell of the reduction of pyruvate to lactate by lactate dehydrogenase?
The regeneration of NAD+ and the generation of ATP. It enables organisms to regenerate NAD+ in the absence of O2 or in cell types, like erythrocytes who lack mitochondria, who are unable to use O2.
Step of Lactic Acid Fermentation
1) Pyruvate formed from glycolysis 2) pyruvate is reduced to lactate by lactate dehydrogenase and NADH + H+;
Steps of alcohol fermentation
1) Pyruvate decarboxylized by pyruvate decarboxylase in the presence of Mg2+ and TPP, forms acetylaldehyde 2) Acetylaldehyde converted to ethanol by alcohol dehydrogenase in the presence of NADH and H+
Thiamine Pyrophosphate
TPP; a coenzyme derived from vitamin B1; facilitates decarboxylation reactions.
What is the Cori cycle and why is it important?
The Cori cycle allows lactate dehydrogenase to run in reverse by changing cellular concentrations; the liver maintains a high NAD+/NADH ratio; and converts lactate to pyruvate to be used as an energy source.
What are the prosthetic groups in pyruvate dehydrogenase?
TPP, lipoyllysine, and FAD
What is the function of CoA?
Accept and carry acetyl group
