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GI and Nutrition > 1.4.2 Carbohydrate Metabolism > Flashcards

1.4.2 Carbohydrate Metabolism Flashcards

1
Q

What can be the symptoms of galactosemia?

A

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

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2
Q

What is lactose intolerance

A
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3
Q

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

A

ADP

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4
Q

Why is gluconeogenesis important?

A

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

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5
Q

Draw an overview map of metabolism

A
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6
Q

What reactions occur in the mitochondria matrix?

A

Citric acid cycle

Oxidative phosphorylation

Beta-oxidation

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7
Q

How is glucose an example of a futile cycle?

A

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

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8
Q

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

A

Similar to the transferase deficiency - treatment is restrict dietary galactose

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9
Q

What is heriditary fructose intolerance?

A

Lack of aldolase B - severe hypoglycemia

Liver failure can result - treat with avoiding fructose

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10
Q

What are the components of sucrose?

A

1-2 linkage between glucose and fructose

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11
Q

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

A

Lactate to pyruvate

Formation of NADH

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12
Q

Under anaerobic conditions pyruvate is converted into?

A

Lactate

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13
Q

What are the 3 principle forms of sugar transport?

A

Facilitated diffusion

Hormone sensitive transporters

Na coupled transport

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14
Q

What is this an image of?

A

β-D-Fructose

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15
Q

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

A

No

It can inhibit hexokinase but not glucokinase

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16
Q

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

A

Stim - Citrate

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

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17
Q

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

A

It will inhibit gluconeogenesis

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

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18
Q

What are the 3 components of the pyruvate dehydrogenase complex?

A

E1 - decarboxylase

E2 - dihydrolipoyl transacetylase

E3 - dihydrolipoyl dehydrogenase

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19
Q

What is essential fructosuria?

A

Lack of fructokinase

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20
Q

Describe the process of galactose metabolism?

A
21
Q

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

A

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

22
Q

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

A

Sensitive to - insulin

Found - muscle, heart, and adipose tissue

23
Q

What will inhibit the reaction of phosphoenolpyruvate to pyruvate?

A

ATP and alanine

24
Q

Insulin will inhibit

A

gluconeogenesis

25
Q

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

A

galactose-1-phosphate uridyl transferase

or

galactokinase

26
Q

How do the Km of hexokinase and glucokinase compare?

A

Hexokinase - low Km

Glucokinase - high Km

27
Q

Hexokinase is found in the muscle while glucokinase is found?

A

In the liver

28
Q

Fructose-1,6-BPase deficiency is what?

A

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

29
Q

What is the beginning reaction of the pentose phosphate pathway?

A

Glucose 6-p to 6-phosphogluconolactone

30
Q

What is the principle control step in glycolysis?

A

Phosphofructokinase

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

31
Q

Glucokinase is insulin independent or dependent?

A

Dependent

32
Q

What reactions occur in the cytosol?

A

Glycolysis

Pentose phosphate pathway

Fatty acid synthesis

Purine biosynthesis

33
Q

What are the components of lactose?

A

1-4 linkage between galactose and glucose

34
Q

The pyruvate dehydrogenase reaction is what type of reaction?

A

Irreversible

35
Q

What are some inhibitors of the PFK reaction? Why?

A

ATP

Citrate

H+ ions

These are indications that the cellular levels of energy are high

36
Q

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

A

Hormonal control

Primarily when levels are normal

37
Q

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

A

Stimulated by Acetyl CoA

Inhibited by ADP

38
Q

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

A

NADPH

Ribose-5-phosphate

39
Q

What is this an image of?

A

alpha-D-galactose

40
Q

Describe the process of maltose formation

A

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)

41
Q

Cortisol will stimulate?

A

Gluconeogenesis

42
Q

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

A

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

43
Q

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

A

Conversion of pyruvate to oxaloacetate

Oxaloacetate to phosphoenolpyruvate

44
Q

What is this an image of?

A

alpha-D-glucose

45
Q

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

A

Epinephrine and glucagon

Produce cAMP which will activate a kinase which will stimulate glycogen breakdown

46
Q

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

A

Pyruvate to acetyl CoA and production of NADH and CO2

47
Q

What are the 5 cofactors os the Pyruvate dehydrogenase complex?

A

NADH

Thiamin pyrophosphate

lipoic acid

FAD

CoASH

48
Q

Pyruvate to oxloacetate requires what cofactor?

A

biotin

49
Q

What is the principle transporter in the liver?

A

GLUT 2

GI and Nutrition (57 decks)

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