1.4.2 Carbohydrate Metabolism

Question 1

What can be the symptoms of galactosemia?

Answer 1

Failure of neonates to thrive - vomiting and diarrhea result from ingestion of milk

Can also develop blindness - due to precipitation of byproduct in the lens

Question 2

What is lactose intolerance

Answer 2

Question 3

Phosphoenolpyruvate carboxykinase, and its role in gluconeogenesis, is inhibited by?

Answer 3

ADP

Question 4

Why is gluconeogenesis important?

Answer 4

Because hours after a meal the blood glucose levels in a person will return to a fasting state, and there needs to be a means of getting glucose to the brain

Question 5

Draw an overview map of metabolism

Answer 5

Question 6

What reactions occur in the mitochondria matrix?

Answer 6

Citric acid cycle

Oxidative phosphorylation

Beta-oxidation

Question 7

How is glucose an example of a futile cycle?

Answer 7

Glucose enters a cell and is phosphorylated by hexokinase. The phosphorylation leads to the inability of glucose-6-p molecule to exit the cell. The enzyme G-6-Pase can then dephosphorylate the molecule and it just goes around and around and around

Question 8

UDP-galactose-4-epimerase deficiency can result in?

Answer 8

Similar to the transferase deficiency - treatment is restrict dietary galactose

Question 9

What is heriditary fructose intolerance?

Answer 9

Lack of aldolase B - severe hypoglycemia

Liver failure can result - treat with avoiding fructose

Question 10

What are the components of sucrose?

Answer 10

1-2 linkage between glucose and fructose

Question 11

What is the first reaction in the formation of glucose from lactate?

Answer 11

Lactate to pyruvate

Formation of NADH

Question 12

Under anaerobic conditions pyruvate is converted into?

Answer 12

Lactate

Question 13

What are the 3 principle forms of sugar transport?

Answer 13

Facilitated diffusion

Hormone sensitive transporters

Na coupled transport

Question 14

What is this an image of?

Answer 14

β-D-Fructose

Question 15

Can G-6-P inhibit both glucokinase and hexokinase?

Answer 15

No

It can inhibit hexokinase but not glucokinase

Question 16

Fructose-1,6-Bisphosphatase, and its role in gluconeogenesis, is stimulated and inhibited by?

Answer 16

Stim - Citrate

Inhibited - F-2,6-BP, AMP, ADP

Question 17

How will F-2,6-BP affect gluconeogenesis?

Answer 17

It will inhibit gluconeogenesis

Inhibits the reaction of F-1,6-BP to F-6-P

Question 18

What are the 3 components of the pyruvate dehydrogenase complex?

Answer 18

E1 - decarboxylase

E2 - dihydrolipoyl transacetylase

E3 - dihydrolipoyl dehydrogenase

Question 19

What is essential fructosuria?

Answer 19

Lack of fructokinase

Question 20

Describe the process of galactose metabolism?

Answer 20

Question 21

F-1,6-BP can also act as an allosteric regulator, how?

Answer 21

F-1,6-BP can also “feed forward” in the reaction to stimulate the conversion of phosphoenolpyruvate to pyruvate.

Question 22

The GLUT-4 transporter is sensitive to what? What tissues is it found in?

Answer 22

Sensitive to - insulin

Found - muscle, heart, and adipose tissue

Question 23

What will inhibit the reaction of phosphoenolpyruvate to pyruvate?

Answer 23

ATP and alanine

Question 24

Insulin will inhibit

Answer 24

gluconeogenesis

Question 25

Galactosemia is caused by a lack of one of which two enzymes?

Answer 25

galactose-1-phosphate uridyl transferase or galactokinase

Question 26

How do the Km of hexokinase and glucokinase compare?

Answer 26

Hexokinase - low Km Glucokinase - high Km

Question 27

Hexokinase is found in the muscle while glucokinase is found?

Answer 27

In the liver

Question 28

Fructose-1,6-BPase deficiency is what?

Answer 28

Severely inhibited gluconeogenesis and severe hypoglycemia. May be lethal in newborn

Question 29

What is the beginning reaction of the pentose phosphate pathway?

Answer 29

Glucose 6-p to 6-phosphogluconolactone

Question 30

What is the principle control step in glycolysis?

Answer 30

Phosphofructokinase Conversion of F-6-P to F-1,6-BP

Question 31

Glucokinase is insulin independent or dependent?

Answer 31

Dependent

Question 32

What reactions occur in the cytosol?

Answer 32

Glycolysis Pentose phosphate pathway Fatty acid synthesis Purine biosynthesis

Question 33

What are the components of lactose?

Answer 33

1-4 linkage between galactose and glucose

Question 34

The pyruvate dehydrogenase reaction is what type of reaction?

Answer 34

Irreversible

Question 35

What are some inhibitors of the PFK reaction? Why?

Answer 35

ATP Citrate H+ ions These are indications that the cellular levels of energy are high

Question 36

What are the controlling mechanisms of glycogen metabolism? (formation)

Answer 36

Hormonal control Primarily when levels are normal

Question 37

Pyruvate carboxylase, used in gluconeogenesis, is stimulated by what? Inhibited by what?

Answer 37

Stimulated by Acetyl CoA Inhibited by ADP

Question 38

What is produced in the pentose phoshate pathway? (2)

Answer 38

NADPH Ribose-5-phosphate

Question 39

What is this an image of?

Answer 39

alpha-D-galactose

Question 40

Describe the process of maltose formation

Answer 40

A hemiacetal group on one carbon ring interacts with an alcohol group on another ring to produce a glycosidic bond. (loss of water also occurs)

Question 41

Cortisol will stimulate?

Answer 41

Gluconeogenesis

Question 42

Phosphofructokinase has a second reaction that produces what? And what is the role of that product?

Answer 42

Produces F-2,6-BP which acts as a potent stimulator for the forward glycolysis reaction

Question 43

Since the reaction to convert pyruvate to phosphoenolpyruvate is not allowed, how does the cell get past this to generate glucose for gluconeogenesis?

Answer 43

Conversion of pyruvate to oxaloacetate Oxaloacetate to phosphoenolpyruvate

Question 44

What is this an image of?

Answer 44

alpha-D-glucose

Question 45

What are the controlling mechanisms of glycogen metabolism? (breakdown)

Answer 45

Epinephrine and glucagon Produce cAMP which will activate a kinase which will stimulate glycogen breakdown

Question 46

What is the reaction carried out by the pyruvate dehydrogenase complex?

Answer 46

Pyruvate to acetyl CoA and production of NADH and CO2

Question 47

What are the 5 cofactors os the Pyruvate dehydrogenase complex?

Answer 47

NADH Thiamin pyrophosphate lipoic acid FAD CoASH

Question 48

Pyruvate to oxloacetate requires what cofactor?

Answer 48

biotin

Question 49

What is the principle transporter in the liver?

Answer 49

GLUT 2