Metabolism of fructose, galactose, and pentose phosphate pathway

Question 1

Is fructose and galactose entry into a cell insulin dependent?

Answer 1

no

Question 2

which sugars do not promote secretion of insulin

Answer 2

fructose and galactose

Question 3

which is faster: fructose metabolism or glucose metabolism

Answer 3

fructose

Question 4

fructose is phosphorylated by fructokinase to form ____

Answer 4

fructose-1-p

Question 5

dietary fructose is metabolized mainly in the ____ by _____

Answer 5

liver by glycolysis

Question 6

what cleaves fructose-1-p to DHAP and glyceraldehyde?

Answer 6

aldolase B

Question 7

enzyme that turns glyceraldehyde into glyceraldehyde 3P

Answer 7

triose kinase

Question 8

DHAP to glyceraldehyde 3-P performed by what enzyme

Answer 8

triose-P isomerase

Question 9

this can be cleaved by aldolase A, B, and C

Answer 9

F1,6BP

Question 10

Fructose 1-P can only be cleaved by ____

Answer 10

aldolase B

Question 11

hereditary fructose intolerance is a deficiency in what enzyme and what gene

Answer 11

aldolase B, ALDOB gene

Question 12

what is the consequence of having high levels of fructose 1-P accumulate due to hereditary fructose intolerance?

Answer 12

inorganic P is not available for glycolysis

Question 13

without Pi what happens to glycolysis and ATP production?

Answer 13

inhibited

Question 14

Decreased hepatic ATP from hereditary fructose intolerance causes _____ to become inhibited

Answer 14

gluconeogenesis

Question 15

Symptoms of hereditary fructose intolerance include

Answer 15

hypoglycemia
lactic acidosis
hyperuricemia
liver failure

Question 16

To prevents liver failure and possible death due to hereditary fructose intolerance ____ is removed from the diet

Answer 16

fructose

Question 17

Diagnosis of hereditary fructose intolerance include:

Answer 17

gene (DNA) sequencing

fructose test in urine

Question 18

Essential fructosuria is deficiency of what gene

Answer 18

KHK gene

Question 19

Essential fructosuria is caused by what

Answer 19

inability of fructokinase to convery to fructose 1-P

Question 20

In essential fructosuria, hexokinase converts fructose to _____ which is metabolized in glycolysis. The hexoinase has (low or high) affinity for fructose.

Answer 20

fructose 6-P. low affinity

Question 21

when there is no threshold for fructose and it accumulates in the urine, what disease process

Answer 21

essential fructosuria

Question 22

essential fructosuria: does it have toxic metabolites and is it malignant or benign?

Answer 22

no toxic metabolites. benign

Question 23

hepatocytes, ovaries, and seminal vessicles use what pathway to generate fructose from glucose?

Answer 23

polyol pathway

Question 24

describe steps of polyol pathway

Answer 24

1. glucose to sorbitol through aldolase reducase

2. sorbitol to fructose through sorbitol dehydrogenase

Question 25

kidneys, lens, retina, and schwann cells lack what enzyme that causes sorbitol to accumulate

Answer 25

sorbitol dehydrogenase

Question 26

cells that lack sorbitol dehydrogenase are

Answer 26

kidney, lens, retina, and schwann cells

Question 27

accumulated sorbitol triggers what to these cells?

Answer 27

influx of water causing them to swell

Question 28

damage by sorbitol accumulation can manifest as

Answer 28

retinopathy, cataracts, and peripheral neuropathy

Question 29

uncontrolled diabetes/hyperglycemia cause lots of glucose to accumulate in cell and when sorbitol accumulates what disease processes occur

Answer 29

peripheral neuropathy, cataracts, nephropathy, and retinopathy

Question 30

mechanisms that contribute to retinopathy include

Answer 30

polyol pathway, non-enzymatic glycation, and oxidative stress

Question 31

after hydrolyzation of lactose by lactase, beta galactose must be converted to alpha galactose by

Answer 31

galactose mutarotase

Question 32

alpha galactose is converted to ____ by galactokinase

Answer 32

galactose 1-P

Question 33

UDP glucose reacts with galactose 1-P through GALT to form

Answer 33

UDP galactose and glucose 1-P

Question 34

what is rate limiting step in ultimate conversion of galactose to glucose 1-P

Answer 34

galactose1-P uridyltransferase (GALT)

Question 35

serves as donor of galactose for lactose synthesis, glycoproteins, glycolipids, and glycosaminoglycans

Answer 35

UDP-galactose

Question 36

if galactose is not in diet, _____ converts UDP-glucose to UDP galactose

Answer 36

epimerase

Question 37

epimerase does what and what is this necessary for

Answer 37

UDP glucose to UDP galactose | necessary for "milking mother" along with lastose synthesi, glycoproteins, glycolipids, and glycosaminoglycans

Question 38

galactokinase deficiency causes

Answer 38

cataracts in early life

Question 39

deficiency of galactokinase causes what enzyme to be more and to produce what byproduct that causes what disease process

Answer 39

aldolase reductase more active causing overproduction of galactitol causing cataracts

Question 40

Symptoms of GALT deficiency

Answer 40

``` cataracts in early life N,V,D (post lactose ingestion) failure to thrive, lethargy, hypotonia liver damage mental retardation ```

Question 41

pentose phosphate pathway generates

Answer 41

NADPH and ribulose 5-P

Question 42

NADPH produced by pentose phosphate pathway provides reducing power for

Answer 42

Biosynthesis of FA/cholesterol | detox reactions

Question 43

oxidative phase of pentose phosphate pathway is

Answer 43

irreversible

Question 44

oxidative phase of pentose phosphate pathway generates

Answer 44

NADPH, 5-C ribulose 5-P, and CO2

Question 45

intermediates of pentose phosphate to get to ribulose 5-P are

Answer 45

6-phosphoglucono-alpha-lactone and 6-phosphogluconate

Question 46

what enzyme catalyzes irreversible oxidation of G6P to 6-phosphogluconolactone and what is coenzyme and what does coenzyme produce

Answer 46

glucose 6-P dehydrogenase (G6PD) which uses NADP+ as coenzyme to produce NADPH

Question 47

types of pathways that require NADPH

Answer 47

detoxification and reductive synthesis

Question 48

what tissues have pentose phosphate active?

Answer 48

liver endocrine glands (ovaries, testes, and adrenal cortex) early embryo and rapidly dividing cells lactating mammary

Question 49

liver uses pentose pathway to make

Answer 49

FA/cholesterol synthesis

Question 50

endocrine glands use pentose pathway to make

Answer 50

cholesterol and steroid hormone synthesis

Question 51

early embryo and rapidly dividing cells use pentose pathway for

Answer 51

ribose-5-P for nucleic acid synthesis

Question 52

lactating mammary uses pentose pathway for what

Answer 52

FA biosynthesis

Question 53

role of NADPH in RBCs

Answer 53

get rid of ROS

Question 54

role of NADPH in phagocytic cells

Answer 54

create ROS

Question 55

highest level of G6PD is found in ____ to generate NADPH

Answer 55

phagocytes

Question 56

superoxide radicals are produced by

Answer 56

phagocytic cells

Question 57

ROS can attack

Answer 57

proteins, membrane lipids, and DNA

Question 58

major antioxidant in cells is

Answer 58

glutathione

Question 59

reduced states of glutathione contains

Answer 59

sulfhydryl group (GSH)

Question 60

glutathione does what

Answer 60

prevents oxidative damage by reducing H2O2 to water

Question 61

H2O2 requires what enzyme to turn into 2H2O

Answer 61

glutathione peroxidase

Question 62

NADPH is used by glutathione reductase to

Answer 62

restore oxidized glutathione to its original reduced state

Question 63

individual with G6PD deficiency have:

Answer 63

decreased ability to produce NADPH, thus decreased ability to keep glutathione functional

Question 64

occurs within hours of exposure to oxidative stress

Answer 64

episode hemolytic anemia

Question 65

most common triggers for hemolytic anemia

Answer 65

viral and bacterial infections

Question 66

patients with low levels of G6PD activity is likely to have

Answer 66

chronic hemolytic anemia

Question 67

drugs that may induce ROS production which produces hemolytic anemia are

Answer 67

antimalarials, sulfonamide antibiotics, or foods such as fava bean

Question 68

most common inborn error of metabolism

Answer 68

G6PD deficiency

Question 69

G6PD genetics are

Answer 69

X-linked, recessive disorde. so males are more likely to get

Question 70

additional oxidative stressors cause

Answer 70

someone with G6PD deficiency who is asymptomatic to become symptomatic

Question 71

insoluble masses caused by oxidation of SH groups related to glutathione

Answer 71

Heinz bodies

Question 72

prototype of the disease. the oldest cells have the lower enzyme activity level therefore removed in hemolytic episode

Answer 72

G6PD A (moderate)

Question 73

Class II (Mediterranean)

Answer 73

G6PD deficiency is more severe and enzyme has decreased stability

Question 74

Class I (rare)

Answer 74

is most severe. Anemia often occurs even in absence of oxidative stress