Sugar interconversion

Question 0

What transporter is required for movement of all sugars across membrane?

Answer 0

GLUT 2

Question 1

What transporter is required for fructose movement across membrane?

Answer 1

GLUT 5

Question 2

What happens to fructose in order to be part of glycolysis?

Answer 2

Phosphorylated via hexokinase to Fructose 6-phosphate

Question 3

Fructose to Fructose 6-phosphate is common/uncommon? Why?

Answer 3

Uncommon because hexokinase is usually saturated with glucose

Question 4

Fructose is primarily made into?

Answer 4

Fructose 1-phosphate by Fructokinase (requires ATP)

Question 5

Fructose 1-phosphate is…

Answer 5

Catalyzed by aldolase B and made into glyceraldehyde and dihydroxyacetone phosphate which are then metabolized

Question 6

What are the two products of fructose metabolism?

Answer 6

By aldolase B to glyceraldehyde and dihydroxyacetone phosphate

Question 7

Excessive ingestion of fructose leads to?

Answer 7

Sequestering of phosphate by fructokinase and inefficient recycling by metabolism of downstream metabolites

Question 8

Where is fructokinase located?

Answer 8

Liver

Question 9

What is essential fructosuria?

Answer 9

Mutation in fructokinase, usually very benign leading to fructose in urine

Question 10

What is hereditary fructose intolerance?

Answer 10

Aldolase B is mutated and this is severe cqausing liver damage, hypoglycemia, and kidney damage. Happens because intermediates of fructose metabolism F1P sequester phosphorus…too little ATP

Question 11

What is a potential for glucose in elevated circumstances if it does not go through glycolysis/glycogen synthesis?

Answer 11

Aldose reductase takes it to sorbitol

Question 12

How is sorbitol formed?

Answer 12

Excess glucose is taken to sorbitol by aldose reductase and NADPH

Question 13

How is sorbitol potentially broken down?

Answer 13

Via sorbitol dehydrogenase to generate fructose and NADH

Question 14

T or F: Sorbitol is highly osmotic

Answer 14

T

Question 15

Excess sorbitol in tissues leads to?

Answer 15

Cataracts, peripheral neuropathy, and kidney problems (think diabetes)

Question 16

What is galactosemia?

Answer 16

Inability to digest glactose

Question 17

Excess levels of galactose in blood lead to formation of?

Answer 17

Galacticol via an aldose reductase that causes cataracts

Question 18

Describe healthy galactose metabolism

Answer 18

Galactose taken to galactose 1 P via galactokinase and ATP, galactose 1 P taken to glucose 1P via UDP-glucose UDP-galactose 1 P uridylyltransferase

Question 19

What is classical galactosemia?

Answer 19

Break in galactose 1 6 uridylyltransferase leading to severe phosphorus sequestering

Question 20

What is non-classical galactosemia?

Answer 20

Mutation in galactokinase meaning that galactose is not able to be digested

Question 21

What is UDP glucose epimerized to?

Answer 21

UDP galactose via an epimerase enzyme

Question 22

What are glycoaminoglycans?

Answer 22

Repeated dimer of an acidic sugar and a N-acetylated amino sugar

Question 23

What is the precursor for glycoaminoglycans?

Answer 23

UDP glucose

Question 24

What are the general properties of glycoaminoglycans?

Answer 24

Mucopolysaccharides and proteoglycans (think of cartilage in the knee)

Question 25

Chondroitin sulfate is an example of?

Answer 25

Gylcoaminoglycans

Question 26

Heparin is a?

Answer 26

Glycosaminoglycan (anti-clotting)

Question 27

Hunter’s syndrome and Sanfilippo’s syndrome are examples of diseases in?

Answer 27

Glycosaminoglycans

Question 28

What is a glycoprotein?

Answer 28

Protein with a sugar attached either at a N or O of AA

Question 29

What is characteristic of glycoprotein structure?

Answer 29

Core pentasaccarhide of galactose (acetylated) and Mannose (often attached to asparagine or others)

Question 30

What are some functions of glycoproteins?

Answer 30

Cell cell recognition = immune system

Question 31

Cataracts are caused by what two build-ups talked about?

Answer 31

Sorbitol and galactinol