METABOLISM OF MONOSACCHARIDES AND DISACCHARIDES

Question 1

is the process of adding a phosphate group to a molecule. It is a reversible process, meaning that phosphate groups can be removed from molecules.

Answer 1

Phosphorylation

Question 2

The major source of fructose is ____, which, when cleaved, releases equimolar amounts of fructose and glucose.

Answer 2

sucrose

Question 3

phosphorylates glucose in most cells of the body and several additional hexoses can serve as substrates for this enzyme.

Answer 3

Hexokinase

Question 4

provides the primary mechanism for fructose phosphorylation

has a low Km for fructose and a high Vmax

found in the liver, kidney, and the small intestinal mucosa and converts fructose to fructose 1- phosphate, using adenosine triphosphate (ATP) as the phosphate donor.

Answer 4

Fructokinase

Question 5

fructose1-phosphate is cleaved into dihydroxyacetone phosphate (DHAP) and glyceraldehyde, which are then further metabolized to produce pyruvate

Answer 5

IN GLYCOLYSIS:

Question 6

pyruvate is converted to DHAP and glyceraldehyde, which are then combined to form fructose 1-phosphate.

Answer 6

IN GLUCONEOGENESIS:

Question 7

is the metabolic pathway that results in the production of glucose from noncarbohydrate sources, such as pyruvate, lactate, and certain amino acids.

Answer 7

Gluconeogenesis

Question 8

is the metabolic pathway that results in the breakdown of glucose into pyruvate, yielding energy in the form of ATP.

Answer 8

Glycolysis

Question 9

Synthesis of Glucose

More energy required

Liver and Kidneys

Answer 9

GLUCONEOGENESIS

Question 10

Breakdown of Glucose

Less energy required

All cells

Answer 10

GLYCOLYSIS

Question 11

The rate of fructose metabolism is more rapid than that of glucose because the trioses formed from fructose 1-phosphate bypass ____the major rate-limiting step in glycolysis

Answer 11

phosphofructokinase-1,

Question 12

a benign condition

Answer 12

Fructokinase deficiency (Essential fructosuria):

Question 13

:severe disturbance of liver and kidney metabolism

First appear when a baby is weaned from milk and begins to be fed food containing sucrose or fructose.

Answer 13

Aldolase B deficiency (Hereditary Fructose Intolerance)

Question 14

the C-2 epimer of glucose- is an important component of glycoproteins.

Answer 14

Mannose

Question 15

phosphorylates mannose to form mannose 6-phosphate.

Answer 15

Hexokinase

Question 16

isomerizes mannose 6-phosphate to fructose 6-phosphate.

Answer 16

Phosphomannose isomerase

Question 17

The conversion of glucose to fructose via sorbitol is a two-step process:

Answer 17

Aldose reductase
Sorbitol dehydrogenase

Question 18

reduces glucose to sorbitol. This enzyme is found in many tissues, including the liver, kidneys, and nerves.

Answer 18

Aldose reductase

Question 19

oxidizes sorbitol to fructose. This enzyme is found in the liver, ovaries, and seminal vesicles

Answer 19

Sorbitol dehydrogenase

Question 20

The major dietary source of galactose is ____(galactosyl β-1,4-glucose) obtained from milk and milk products.

Answer 20

lactose

Question 21

converts galactose to galactose 1-phosphate.

Answer 21

Galactokinase

Question 22

Galactose 1-phosphate cannot enter the glycolytic pathway until it is first converted to____

Answer 22

uridine diphosphate (UDP)-galactose.

Question 23

is a nucleotide, which is a type of molecule that is involved in many cellular processes, including metabolism and energy production.

Answer 23

UDP

Question 24

The enzyme that converts galactose 1-phosphate to UDP-galactose is ____

Answer 24

galactose 1- phosphate uridylyltransferase (GALT)

Question 25

The enzyme that converts UDP-galactose to UDP-glucose is called ____

Answer 25

UDP-hexose 4- epimerase.

Question 26

is a sugar molecule that is used to build many important biological molecules. These molecules include lactose, glycoproteins, glycolipids, and glycosaminoglycans.

Answer 26

UDP-galactose

Question 27

is a genetic disorder that is caused by a deficiency in the enzyme galactose 1-phosphate uridylyltransferase (GALT).

Answer 27

Classic galactosemia

Question 28

is the enzyme that converts galactose 1- phosphate to UDP-galactose.

Answer 28

GALT

Question 29

Causes elevation of galactose in blood (galactosemia) and urine (galactosuria)

Causes galactitol accumulation if galactose present in diet

Elevated galactitol can cause cataracts

Treatment is dietary restriction

Answer 29

Galactokinase Deficiency

Question 30

is a sugar that is found in milk. It is made up of two other sugars: galactose and glucose.

Answer 30

Lactose

Question 31

The enzyme____ transfers galactose from UDP-galactose to glucose, forming lactose.

Answer 31

lactose synthase

Question 32

is found in many tissues of the body

Answer 32

Protein A

Question 33

is only found in milk-producing mammary glands

Answer 33

protein B

Question 34

is caused by a lack of the enzyme lactase, which is needed to break down lactose into galactose and glucose.

Answer 34

Lactose intolerance