Metabolism of Hexoses Other than Glucose

Question 1

list 4 sources of fuel

Answer 1

Together with glucose, the hexoses fructose, galactose, and mannose are prominent metabolic fuels.

Question 2

How many pathways are there for fructose

Answer 2

Two pathways for the metabolism of fructose; one occurs in muscle and the other occurs in liver

Question 3

what is a Major fuel source in diets that contain large amounts of fruit or sucrose

Answer 3

fructose

Question 4

where do the 2 pathways for fructose metabolism occur?

Answer 4

in the liver and the muscle

Question 5

is fructose metobolism shorter in the muscle or the liver

Answer 5

Fructose metabolism in muscle differs little from that of glucose. Hexokinase phosphorylates fructose, yielding F6P. The entry of fructose into glycolysis therefore involves only one reaction step.

Question 6

does glucokinase have a high or low affinity for hexoses

Answer 6

Liver contains a hexokinase known as glucokinase, which has a low affinity for hexoses, including fructose

Question 7

how many enzymes are involved in the fructose metabolism in the liver

Answer 7

Liver converts fructose to glycolytic intermediates through a pathway that involves seven enzymes

Question 8

can hexokinase or PFK phosphorylate fructose 1 phosphate?

Answer 8

Neither hexokinase nor PFK can phosphorylate fructose-1-phosphate at C6 to form the glycolytic intermediate FBP.

Question 9

what kind of aldolase is in muscle ?

Answer 9

Muscle contains Type A aldolase, which is specific for FBP.

Question 10

which fate of pyruvate process has coupling?

Answer 10

alcohol fermintation. The decarboxylase taking off the co2 makes it go forward so much that the conversion of acetyaldehyde to ethanol is no longer reversible.

Question 11

what does it mean to say that we have a decarboxylation reaction?

Answer 11

we pop off a co2.

Question 12

what is Tpp a co enzyme for?

Answer 12

Pyruvate decarboxylase contains the coenzyme thiamine pyrophosphate (TPP; also called thiamine diphosphate; ThDP)

Question 13

what is the function of Yeast alcohol dehydrogenase (YADH)

Answer 13

Enzyme that converts acetaldehyde to ethanol

Question 14

which enzyme does zinc bind to ?

Answer 14

Zn2+ polarizes the carbonyl group of acetaldehyde to stabilize the developing negative charge in the transition state of the reaction

Question 15

if we have excess mannose will it convert to glucose eventually?

Answer 15

NO. It will be stopped by the single arrow due to hexokinase

Question 16

if we have an excess amount of fructose in the liver , are we able to convert this mannon up the pathway towards glucose?

Answer 16

no. the fructose is unable to go up the pathway due to pfk creating a single arrow.

Question 17

is F1P a substrate of glycolysis?

Answer 17

no

Question 18

where is type B aldolase found?

Answer 18

its found in the liver

Question 19

what does type B aldolase do?

Answer 19

it breaks up F1P

Question 20

name the 2 enzymes that we can use to add a phosphate onto glyceraldehyde when breaking down fructose in the liver

Answer 20

we can use a glyceraldehyde kinase to add a phosphate . or we can use a dehydrogenase

Question 21

Fructose intolerance results from a deficiency in Type ___ aldolase.

Answer 21

Fructose intolerance results from a deficiency in Type B aldolase.

Question 22

how is galactose obtained?

Answer 22

Obtained from the hydrolysis of lactose

Question 23

what sugar does hexokinase not work on

Answer 23

Hexokinase phosphorylates glucose, fructose, and mannose, it does not recognize galactose

Question 24

why does an Epimerization reaction must occur before galactose enters glycolysis.

Answer 24

because hekokinase does not recognize galacose

Question 25

what is the relationship between glucose and galactose

Answer 25

it is an epimer of carbon 4

Question 26

what is vitamin B3

Answer 26

niacin

Question 27

what kind of enzymes move functional groups

Answer 27

mutase

Question 28

what is galactosemia caused by?

Answer 28

Most cases of galactosemia involve a deficiency in the enzyme catalyzing Reaction 2 of the interconversion, galactose and galactose.

Question 29

what is the relationship between mannose and glucose

Answer 29

it is an epimer at carbon 2

Question 30

what 2 enzymes are required to convert mannose into glycolysis?

Answer 30

hexokinase and phosphomannose isomerase