Metabolism VII

Question 1

How can fructose bypass the rate limiting step of glycolysis?

Answer 1

It can avoid use of the enzyme PFK by conversion to glyceraldehyde which enters glycolysis (p.104)

Question 2

Describe the symptoms of galactokinase deficiency.

Answer 2

Accumulation of galactitol if galactose is present in the diet causes galactose in the blood and urine. It also causes infantile cataracts and may initially present as failure to track objects or develop a social smile. It is a relatively mild condition. (p.105)

Question 3

What is the inheritance pattern of galactokinase deficiency and classic galactosemia?

Answer 3

Both disorders are autosomal recessive (p.105)

Question 4

What enzyme is absent in classic galactosemia?

Answer 4

Galactose-1-phosphate uridyltransferase (p.105)

Question 5

Describe the pathology of classic galactosemia.

Answer 5

Damage is caused by accumulation of toxic substances including galactitol with accumulates in the lens of the eye (p.105)

Question 6

What are the symptoms of classic galactosemia?

Answer 6

Failure to thrive, jaundice, hepatomeagly, infantile cataracts, mental retardation (p.105)

Question 7

What is the treatment of classic galactosemia?

Answer 7

To exclude galactose and lactose (galactose + glucose) from diet (p.105)

Question 8

What is sorbitol?

Answer 8

The alcohol counterpart to glucose which can be trapped inside the cell (p.105)

Question 9

What enzyme is used to produce sorbitol?

Answer 9

Aldose reductase (p.105)

Question 10

How is sorbitol converted to fructose?

Answer 10

Sorbitol dehydrogenase converts sorbitol to fructose (p.105)

Question 11

What conditions can occur due to a sorbitol dehydrogenase deficiency?

Answer 11

Tissues with an insufficient amount of this enzyme are at risk for intracellular sorbitol accumulation which causes osmotic damage and may result in cataracts, retinopathy, and peripheral neuropathy as seen with chronic hyperglycemia in diabetics (p.105)

Question 12

How are high blood levels of galactose converted to osmotically active alcohol forms?

Answer 12

Via aldose reductase (p.105)

Question 13

What tissues have both aldose reductase and sorbitol dehydrogenase?

Answer 13

Lens, liver, seminal vesicles (p.105)

Question 14

What tissues have only aldose reductase?

Answer 14

Schwann cells, retina, and kidneys (p.105)

Question 15

What is the pathology associated with a lactase deficiency?

Answer 15

Loss of brush border enzyme (p.105)

Question 16

Which form of amino acids are found in proteins?

Answer 16

Only the L-form (p.106)

Question 17

What are essential amino acids?

Answer 17

Must be supplied in the diet (p.106)

Question 18

Name the three glucogenic essential amino acids.

Answer 18

Methionine, Valine, Histamine (p.106)

Question 19

Name the four essential glucogenic/ketogenic amino acids.

Answer 19

Isoleucine, Phenylalanine, Threonine, Tryptophan (p.106)

Question 20

Name the two acidic amino acids.

Answer 20

Aspartic acid and glutamic acid are negatively charged at body pH (p.106)

Question 21

What is the most basic amino acid?

Answer 21

Arginine (p.106)

Question 22

Which basic amino acid has no charge at body pH?

Answer 22

Histamine (p.106)

Question 23

Which two basic amino acids are required during periods of growth?

Answer 23

Arginine and Histamine (p.106)

Question 24

Which two amino acids are prevalant in histones which bind negatively charged DNA?

Answer 24

Arginine and Lysine (p.106)

Question 25

What is the purpose of the urea cycle?

Answer 25

To break down amino acids to form metabolites (e.x. pyruvate, acetyl CoA) which can serve as metabolic fuels (p.106)