Metabolism of Other Carbohydrates

Question 1

sucrose components

Answer 1

fructose + glucose

Question 2

lactose components

Answer 2

glucose + galactose

Question 3

maltose components

Answer 3

glucose + glucose

Question 4

beta-fructosidase

Answer 4

breaks sucrose into fructose + glucose

Question 5

SLGT1

Answer 5

symporter for glucose and galactose into cell

Question 6

GLUT5

Answer 6

channel for fructose

Question 7

How does fructose enter glycolysis to be metabolized to glucose?

Answer 7

fructose –> fructose-1-P (fructokinase) –> DHAP by aldolase-B –> DHAP can not enter the glycolysis pathway

Question 8

essential fructosuria

Answer 8

fructokinase deficiency which results in high fructose levels in urine; no treatment needed

Question 9

hereditary fructose intolerance

Answer 9

aldolase B deficiency (liver) which results in poor feeding, irritability, neonatal jaundice, vomiting, sleepiness, intolerance to fruit

Question 10

What happens when you have an aldolase B deficiency?

Answer 10

inhibits glycolysis and gluconeogenesis and depletes the ATP pool; will lead to accumulation of fructose-1-P

Question 11

inhibition of gluconeogenesis

Answer 11

leads to lactic acidosis

Question 12

accumulation of fructose-1-P

Answer 12

depletes the ATP pool and leads to hyperuricemia (AMP converted to uric acid)

Question 13

polyol (sorbitol) pathway

Answer 13

glucose –> sorbitol –> fructose

Question 14

aldol reductase

Answer 14

glucose –> sorbitol

Question 15

sorbitol dehydrogenase

Answer 15

sorbitol –> fructose

Question 16

When is polyol pathway active?

Answer 16

at high glucose levels

Question 17

What tissues express high levels of sorbitol dehydrogenase?

Answer 17

liver, ovaries, and seminal vesicles

Question 18

increased polyol pathway causes _

Answer 18

osmotic and oxidative stress

Question 19

Why does polyol pathway increase oxidative stress?

Answer 19

aldose reductase requires the conversion of NADPH into NADP+, depleting NADPH in the cell –> NADPH can not form glutathione which results in increased oxidative stress

Question 20

increased sorbitol causes _

Answer 20

osmotic stress (cell edema) and decreased ATPase activity (NT delay)

Question 21

symptoms of increased polyol pathway

Answer 21

chronic complications including neuropathy, retinopathy, and renal failure

Question 22

tissues with low levels of sorbitol dehydrogenase are susceptible to _

Answer 22

high glucose levels leading to diabetic neuropathy and diabetic retinopathy (no sorbitol dehydrogenase)

Question 23

primary lactose intolerance

Answer 23

lactase production decreases in adulthood

Question 24

secondary lactose intolerance

Answer 24

lactase production decreases after an illness, injury, or small intestine surgery

Question 25

tertiary lactose intolerance

Answer 25

congenital lactase deficiency

Question 26

galactose is metabolized by the _

Answer 26

Leloir pathway

Question 27

Leloir pathway

Answer 27

galactose --> galactose-1-P --> glucose-1-P

Question 28

galactokinase (GALK)

Answer 28

galactose --> galactose-1-P

Question 29

galactose 1-P uridylyltransferase (GALT)

Answer 29

galactose-1-P --> glucose-1-P; also converts UDP-glucose into UDP-galactose

Question 30

galactosemia

Answer 30

results from defect in Leloir pathway

Question 31

GALT deficiency

Answer 31

leads to type I galactosemia; most common form

Question 32

GALK deficiency

Answer 32

leads to type II galactosemia

Question 33

type II galactosemia treatment

Answer 33

galactose and lactose restricted diet, calcium supplements to maintain bone density

Question 34

type II galactosemia symptoms

Answer 34

elevated galactose, cataracts due to increased galactitol

Question 35

type I galactosemia symtpoms

Answer 35

failure to thrive, liver and renal dysfunction, cataracts, abnormal liver development, and sepsis

Question 36

type I galactosemia treatment

Answer 36

low galactose and lactose diet

Question 37

UDP-glucose-4-epimerase (GALE)

Answer 37

converts UDP-galactose to UDP-glucose to be made into glycogen

Question 38

GALE deficiency

Answer 38

type III galactosemia

Question 39

type III galactosemia symptoms

Answer 39

similar to GALT deficiency if severe form

Question 40

type III galactosemia treatment

Answer 40

low galactose and lactose treatment

Question 41

mild form of type III galactosemia

Answer 41

restricted to blood cells, asymptomatic

Question 42

congenital disorders of glycosylation symptoms

Answer 42

low muscle tone, misaligned eyes, poor growth, developmental delay, liver disease, stroke-like episodes, seizures, abnormal bleeding/blood clotting

Question 43

alpha-galactose syndrome

Answer 43

caused by an allergic response to glycoproteins (galactose-alpha-1,3-galactose in meat) causing rashes, hives, nausea, vomiting, breathing difficulty, low BP, dizziness, and stomach pain

Question 44

xenobiotics are solubilized by _

Answer 44

conjugation to glucuronate for removal by liver