Reading 14.2/Lecture 13 Funneling into Glycolysis

Question 1

Which type of enzyme is responsible for breaking glycosidic bonds using water in glycolysis?

Answer 1

Hydrolases

Question 2

Which type of enzyme is responsible for phosphorylating monosaccharides in glycolysis?

Answer 2

Kinases

Question 3

Which type of enzyme is responsible for changing monosaccharides into glucose or fructose in glycolysis?

Answer 3

Isomerases

Question 4

Which type of enzyme is responsible for making sugars of sugar-alcohols in glycolysis?

Answer 4

Dehydrogenases

Question 5

How is fructose metabolized in the body?

Answer 5

Most cells weakly absorb fructose. There are not many cellular transporters of fructose. Fructose is metabolized in the liver.

Question 6

Fructose Transporter

Answer 6

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.

Question 7

How does glycerol shuttle into glycolysis?

Answer 7

glycerol is phosphorylated by glycerol kinase (Glycerol 3-P) and then is converted to dihydroxyacetone-P by Glycerol 3-P dehydrogenase

Question 8

How does mannose shuttle into glycolysis?

Answer 8

Mannose is converted to mannose-6-phosphate by hexokinase, and is then converted to fructose-6-phosphate by mannose-6-phosphate isomerase

Question 9

What is the purpose of phosphorylating a saccharide while funneling it into glycolysis?

Answer 9

to keep the sugar inside the cell and maintain the blood/cell absorption gradient.

Question 10

amylase

Answer 10

works by hydrolyzing internal glycosidic linkages of starch;

Question 11

Limit Dextrins

Answer 11

oligosaccharides; fragments of amylopectin containing (a1 to 6) branch points;

Question 12

What enzyme catalyzes the conversion of sucrose to glucose?

Answer 12

sucrase

Question 13

What enzyme catalyzes the conversion of trehalose to glucose?

Answer 13

trehalase

Question 14

How does dietary starch/glycogen get converted into glucose?

Answer 14

alpha-amylase

Question 15

How does endogenous glycogen feed into glycolysis?

Answer 15

endogenous glycogen in converted to Glucose-1-phosphate by phosphorylase, which is then converted into glucose-6-phosphate by phosphogluco-mutase

Question 16

Q # 34 Does the degradation of glycogen (starch) to a form of glucose that can enter glycolytic pathway require an input of energy?

Answer 16

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

Question 17

Glycogen phosphorylase

Answer 17

catalyzes the breakdown of glycogen; pi attack (a1 to 4) bond

Question 18

Q # 36 Why is the Cell’s ability to regenerate NAD+ critical to glycolysis? Which glycolytic enzyme requires NAD+?

Answer 18

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.

Question 19

Q # 37 What is the most important consequence to the cell of the reduction of pyruvate to lactate by lactate dehydrogenase?

Answer 19

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.

Question 20

Step of Lactic Acid Fermentation

Answer 20

1) Pyruvate formed from glycolysis 2) pyruvate is reduced to lactate by lactate dehydrogenase and NADH + H+;

Question 21

Steps of alcohol fermentation

Answer 21

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+

Question 22

Thiamine Pyrophosphate

Answer 22

TPP; a coenzyme derived from vitamin B1; facilitates decarboxylation reactions.

Question 23

What is the Cori cycle and why is it important?

Answer 23

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.

Question 24

What are the prosthetic groups in pyruvate dehydrogenase?

Answer 24

TPP, lipoyllysine, and FAD

Question 25

What is the function of CoA?

Answer 25

Accept and carry acetyl group