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METABOLISMZ > HANDOUT: OTHER PATHWAYS OF SUGAR METABOLISM > Flashcards

HANDOUT: OTHER PATHWAYS OF SUGAR METABOLISM Flashcards

1
Q

What are the other pathways of sugar metabolism?

A

Pentose phosphate pathway
Fructose metabolism
galactose metabolism
Synthesis of Glycosides, Lactose, glycolipids and glycoproteins

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2
Q

Where can fructokinase be seen?

A

Liver
Intestine
Kidney

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3
Q

What is the function of fructokinase?

A

facilitate phosphorylation from fructose to F1P

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4
Q

Fructokinase vs Glucokinase

A

Fructokinase:
- doesn’t act on glucose
- Not insulin-dependent

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5
Q

Fructose-1-phosphate is cleaved into ________ by __________.

A

DHAP and Glyceraldehyde by aldolase B.

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6
Q

Why can fructose flood the pathways in the liver?

A

Because it bypasses PFK1 regulatory enzyme, therefore fructose undergo rapid glycolysis thus the permission to flood the liver.

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7
Q

What will the flooding of fructose in the liver lead to?

A

increased FA synthesis
Increased. FA esterification
increased VLDL
increased TAG
increased LDL

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8
Q

What can be synthesized from Polyol pathway?

A

Fructose

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9
Q

What step is the polyol pathway?

A

This is the first step wherein the sugar is reduced into sugar alcohol (i.e. Glucose to sugar alcohol sorbitol)

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10
Q

What facilitates the conversion of sugar into sugar alcohol in the polyol pathway?

A

Aldose reductase

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11
Q

Where can polyol pathway be found and what is its function there?

A

Seminal vesicles –> produce fructose for seminal fluid

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12
Q

How do spermatozoa use fructose?

A

major fuel source when in seminal fluid.

It will switch into glucose when in the female reproduct tract.

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13
Q

Enumerate the process of polyol pathway from glucose to fructose

A

Glucose –> (reduced)sorbitol –> (oxidize) fructose

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14
Q

How is aldose reductase activity harmful in the eye?

A

It is in the eye where alcohols are synthesized:
Glucose –> sorbitol
Galactose –> Galactitol

Therefore, increased blood glucose or galactose concentration would lead to higher synthesis than they are removed.

EFFECT: High osmotic pressure within the lens

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15
Q

What is deficient in essential fructosuria?

A

Fructokinase

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16
Q

What is essential fructosuria?

A
  • Benign condition.
  • fructokinase deficiency.
  • fructose can’t be taken up by liver cells
  • fructose shows up in liver & blood. Therefore have high levels of fructose there.
  • eventually, 90% of fructose is metabolized (which is likely due to alternative pathways).
17
Q

What is deficient in fructose intolerance?

A

fructose 1-Phosphate aldolase

18
Q

What accumulates in fructose intolerance?

A

fructose-1-phosphate

(since it wasn’t cleaved)

19
Q

Describe fructose intolerance

A

This is dietary. There’s just so much fructose our body can metabolize. Hence, this is malabsorption., wherein fructose is not metabolized.

There’s a severe hypoglycemia in the patient. In young children, this is due to prolonged fructose ingestion which may lead to death

20
Q

What is deficient in hereditary fructose intolerance?

A

Fructose-1-phosphate alsolase (aldolase B)

21
Q

What accumulates in hereditary fructose intolerance?

A

fructose-1-phosphate

22
Q

describe hereditary fructose intolerenace

A

F1P accumulates due to deficiency in Aldolase B. With that, the available Phosphate enzyme decreases, inhibiting gluconeogenesis and glycogenolysis. Therefore, patient will be hypoglycemic. Also, these accumulations may lead to enzymes blocking the tissue.

23
Q

What damages can hereditary fructose intolerance bring about?

A
  • enzyme block damage –> accum of F1P in tissues –> liver damage, Jaundice —> cirrhosis, ascites.
  • can also result to renal tubular damage
  • hypoglycemia
24
Q

How much galactose per kg can infants ingest?

A

1g of glucose per kg
(can metabolize more than adults can)

25
Q

What could be deficient in galatosemia?

A
  1. Galactokinase
  2. Galactose-1-phosphate uridyltransferase
26
Q

Galactosemia with galactokinase deficiency can lead to what manifestation?

A

cataract

27
Q

Galatosemia with Galactose-1-Phosphate uridyltransferase can lead to what manifestation?

A

severe disease such as liver failure

28
Q

What happens in galactosemia?

A

Inability to transform Galactose (from lactose) to glucose

29
Q

Where is PPP active?

A

Liver
Adipose Tissue
Lactating Mammary glands
Adrenal cortex

30
Q

Where is PPP found?

A

cytosol

31
Q

What are the functions of PPP?

A

Source of:

  1. NADPH + H (REDUCTIVE BIOSYNTHETIC PROCESSES: FA, Cholesterol, Steroid Hormone)
  2. Pentose (NUCLEOTIDES: Nucleic Acids, Coenzymes)
32
Q

PPP and use of ATP

A

PPP neither use nor produce ATP

33
Q

What is the common site of glycolysis and HMP shunt?

A

G6P

34
Q

What links Glycolysis and HMP shunt?

A

transketolase
transaldolase

35
Q

Which part can molecules re-enter in PPP & glycolysis (vice versa)?

A

F6P

36
Q

Characteristic differences of glycolysis and PPP

A

METABOLISMZ (7 decks)

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