Lecture 30

Question 1

A ________ kinase deficiency leads to buildup of Galactose (Galactosemia.) At high levels, Galactose can be acted upon by ________ reductase (which has a high Km for Galactose) to form Galactitol. Galactitol build up can cause _______ in the eye.

Answer 1

A Glactose Kinase

Aldose reductase

CATARACTS.

Question 2

Classic Galactosemia is more sever than that caused by a Galactose Kinase deficiency. In classic Galactosemia, ______ is deficient, causing a buildup of _______ in the cell, rather than converting it to UDP-_______. Buildup of _______ can cause ______ damage, ______ disability, ______ in the eye, and premature _______ failure in females.

Answer 2

Galactose-1-P uridyltransferase

Galactose-1-P

UDP-Glucose

Galactose-1-P

LIVER damage

LEARNING disability

CATARACTS

OVARIAN failure in females.

Question 3

Glycogen is the storage form of Glucose with glucosyl residues linked via a(n) ______ glycosidic bond and _______ linkage at branch points (increasing the solubility of glycogen) occurring about every 8-12 _______ glycosidic bonds.

Answer 3

ALPHA 1,4

ALPHA 1,6 linkage

ALPHA 1,4 bonds.

Question 4

_____ catalyzes the reaction that adds _____ onto glycogen via the formation of an alpha-1,4 linkage, and glycogen ______ enzyme catalyzes the alpha-1,6 linkages.

Answer 4

Glycogen synthase catalyzes the reaction that adds UDP-GLUCOSE onto glycogen, and glycogen BRANCHING enzyme catalyzes the alpha-1,6 linkages.

Question 5

Glycogen is a glycoprotein that uses ______ which lays down a “primer” so that Glycogen Synthase can add UDP-glucose to the chain.

Answer 5

It uses GLYCOGENIN

Question 6

Glycogen ______ is the enzyme that catalyzes the cleavage of alpha-1,4 linkages, which require inorganic ______ and forms ______-1-phosphate.

Answer 6

Glycogen PHOSPHORYLASE

PHOSPHATE

GLUCOSE-1-Phosphate.

Question 7

Branch points are cleaved by a ______ reaction catalyzed by _______ enzyme to produce free _____. This enzyme also has _______ activity, transferring small oligosaccharides near branch points to alpha-1,4 linked chains.

Answer 7

Cleaved by a HYDROLYTIC reaction catalyzed by GLYCOGEN DEBRANCHING enzyme to produce free GLUCOSE. Also has TRANSFERASE activity.

Question 8

Lactose is a disaccharide composed of glucose and galactose linked via a ____ ___-___ glycosidic link. Lactose is not absorbed in the intestine. Digestion requires _____ reaction via lactase. Lactase insufficiency leaves bacteria to metabolize lactose to acids, carbon dioxide, and ___ which can be measured in the breath.

Answer 8

Beta 1-4 glycosidic

Hydrolysis

H2

Question 9

Glycogen accounts for about ___% of the Liver’s wet weight and is depleted after ___hrs of fasting. Muscle glycogen is not mobilized in the same way - instead, it is used during _____. Glycogen is also used differently in muscle vs the liver. In the former, it is used as a source of ____ production, whereas in the latter, it can be used to restore blood glucose levels via Glucose-__-_____ activity.

Answer 9

5%

24

Exercise

ATP

Glucose-6-phosphatase

Question 10

Glucose-6-phosphate is converted to glucose-1-phosphate in a ______ reaction (reversible or irreversible?) catalyzed by ________. Glucose-1-phosphate + ____ forms UDP-glucose and _______ which is catalyzed by UDP-glucose ________.

Answer 10

Reversible

Phosphoglucomutase

UTP

Pyrophosphate

UDP-glucose pyrophosphorylase

Question 11

REMEMBER that the _____ and ______ are the only organs that have Glucose-___-_______ activity, which converts Glucose-___-_____ to glucose.

Answer 11

Liver

Kidneys

Glucose-6-phosphatase

G-6-P