Final

Question 1

Fructose, a natural sugar in honey, is synthesized via the polyol pathway from what precursor?

Answer 1

Glucose

Question 2

What is the rate limiting enzyme in the metabolism of fructose?

Answer 2

Aldolase B

Question 3

How does fructose enter the cells? What transporter?

Answer 3

GLUT 5 Transporters

Question 4

How can fructose enter glycolysis?

Answer 4

Becomes fructose-1-P, which is then phosphorylated and can enter glycolysis as intermediates DHAP or G3P

Question 5

How is fructose phosphorylated into Fructose-1-Phosphate?

Answer 5

Primarily via Fructokinase

Fructose can also be phosphorylated by hexokinase when fructose is in higher concentrations or if glucose levels are low (becomes F6P)

Question 6

Hereditary Fructose Intolerance (HFI) is due to a deficiency in which enzyme?

Answer 6

Aldolase B

Question 7

Essential fructosuria is a deficiency in which enzyme?

Answer 7

Fructokinase

Question 8

Why is an aldolase B deficiency so severe?

Answer 8

Causes a build up of Fructose 1-P intermediate which inhibits the actions of glycogen breakdown and gluconeogenesis (hypoglycemia)

Question 9

List the 2 steps of the polyol pathway and their products

Answer 9

1 - reduction of C1 of glucose via aldose reductase to form sorbitol
2 - oxidation of C2 by sorbitol dehydrogenase to form fructose

Question 10

What is a possible downside to the polyol pathway, especially concerning diabetics?

Answer 10

Second step of the pathway (sorbitol–>fructose) is slower, and in hyperglycemic conditions, sorbitol can accumulate in susceptible tissues such as the retina and cause damage

Question 11

The use of galactose in the polyol pathway produces what initial intermediate?

Answer 11

Galacticol

Question 12

What must galacticol be converted to in order to be used in glycolysis?

Answer 12

UDP-Galactose

Question 13

What are the two major products of the Pentose Phosphate pathway?

Answer 13

2 NADPH and Ribose-5-Phosphate (nucleotide synthesis) + CO2…. from 1 glucose molecule

Question 14

4 enzymes of the non-oxidative phase of the PPP?

(non-NADPH producing)

Used to interconvert between various sugar molecules

Answer 14

isomerase (ribose –> ribulose)
epimerase (ribulose –>xyulose)
transketolase 2C (carbon chain transfer)(thiamine): xyulose to G3P
transadolase 3C (G3P —>F6P)

Question 15

Thiamine deficiency is commonly seen in what population?

Answer 15

Alcoholics

Question 16

What cofactor is needed for transketolase to work in the PPP?

Answer 16

Thiamine

Question 17

What size carbon unit does transketolase transfer in the non-ox PPP?

Answer 17

2 Carbons

Question 18

What size carbon unit does transaldolase transfer in the non-oxidative PPP?

Answer 18

3 Carbons

Question 19

What is the net result of non-oxidative PPP from 3 mols of Ribulose - 5- P?

Answer 19

2 mols fructose6P

1 mol G3P

Question 20

What molecule in RBCs requires NADPH from the PPP and acts as an antioxidant?

Answer 20

Glutathione

Question 21

Why is the PPP important for all cell types?

Answer 21

NADPH demand in all facets

Question 22

What is the rate limiting enzyme in the PPP?

Answer 22

G6P dehydrogenase, first step

Question 23

What happens if a person ingests Fava Beans while on anti-malarials?

Answer 23

The divicine in fava beans produces H202 when it interacts with antimalarials, causing hemolytic anemia (massive RBC destruction)

Question 24

Gluconeogenesis is stimulated by?

Answer 24

Glucagon

Question 25

Name three sources for gluconeogenesis (molecules).

Answer 25

Lactate, Amino Acids (usually alanine), and glycerol

Question 26

Where is the most important control point for gluconeogenesis?

Answer 26

Glucagon and Insulin’s control over the transformation between F6P and F1,6P

Question 27

A patient presents with severe fasting hypoglycemia, tests show that he lacks G6Phosphatase enzyme… Dx?

Answer 27

Von Gierks Disease

Question 28

4 precursors for nonessential amino acid synthesis

Answer 28

Pyruvate
Oxaloacetate
alpha ketoregulate
3 phosphoglycerate

Question 29

Function of Tetrahydrofolate?

Answer 29

carrier of one carbon units in several reactions of amino acids and nucleotide metabolism. Must be consumed in diet**
**know it moves methyl groups

Question 30

Long Chain fatty acids are absorbed as micelles and transported into mitochondria by?

Answer 30

Carnitine, made from lysine or ingested in diet

Question 31

Where are short chain fatty acids activated?

Answer 31

mitochondrial cytosol

Question 32

Where are medium chain fatty acids activated?

Answer 32

mitochondrial matrix (kindey, liver)

Question 33

Where are long chain fatty acids activated?

Answer 33

ER, outer mitochondrial membrane, peroxisomal membrane

Question 34

Where are very long fatty acids activated?

Answer 34

peroxisomes

Question 35

What is different about the products of odd numbered fatty acid chain beta oxidation? (product)

Answer 35

Proprionyl CoA as an additional product

Question 36

Disease with inherited absence of peroxisomes. Affects brain, liver, kidney, and is associated with an accumulation of long chain fatty acids.

Answer 36

Zellweger Syndrome

Question 37

Disease with a genetic defect in peroxisomal alpha-hydroxylase. Phytanic acid accumulates, especially in the nervous tissue). Leading to retinitis, pigmentosa, cerebral ataxia, chronic polyneuropathy.

Answer 37

Refsum Disease

Question 38

5 Ketogenic Amino Acids that can convert to acetyl coA?

Answer 38

Tryptophan, Threonine, Lysine, Isoleucine, leucine,

Question 39

3 Ketogenic Amino Acids that can convert to acetoacetate?

Answer 39

Phenylalanine, tyrosine, leucine

Question 40

After 10 days of fasting, what compound has the highest levels in the blood?

Answer 40

Beta-OH-Butyrate

Question 41

An autosomal recessive disease where medium chain fatty acids cannot be oxidized, so they are excreted?

Answer 41

MCAD deficiency - (medium chain acyl CoA dehydrogenase)