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MEH > Session 2 > Flashcards

Session 2 Flashcards

1
Q

What is the purpose of the phosphorylation of glucose?

A

Makes the sugar anionic so prevents it crossing the cell membrane, increases the reactivity of the sugar so it can be metabolised, allows formation of compounds with high phosphoryl-group transfer potential that can transfer phosphate group to ADP.

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2
Q

What is the purpose of the phosphorylation of glucose?

A

Makes the sugar anionic so prevents it crossing the cell membrane, increases the reactivity of the sugar so it can be metabolised, allows formation of compounds with high phosphoryl-group transfer potential that can transfer phosphate group to ADP.

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3
Q

Which monosaccharide does not contain a chiral centre?

A

Dihydroxyacetone

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4
Q

Which monosaccharide does not contain a chiral centre?

A

Dihydroxyacetone

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5
Q

What is the normal concentration of blood glucose?

A

~5 mmol/L

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6
Q

What level of blood glucose indicates untreated diabetes?

A

> /= 7.0 mmol/L

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7
Q

What makes a disaccharide non-reducing?

A

If the aldehyde/ketone groups of both sugars are involved in forming the glycosidic bond.

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8
Q

Where is glycogen synthesised?

A

The liver and skeletal muscle.

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9
Q

What is produced when starch is hydrolysed?

A

Glucose and maltose

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10
Q

Why can humans not digest cellulose?

A

The human GI tract does not produce enzymes that are able to hydrolyse beta-1,4 linkages

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11
Q

What type of reaction is glycolysis?

A

Catabolic

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12
Q

Where does glycolysis take place?

A

The cytoplasm

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13
Q

How much glucose does the CNS require?

A

approx. 140g/24 hours

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14
Q

What type of bond does pancreatic amylase hydrolyse?

A

a-1,4 bonds

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15
Q

What type of bond does isomaltase hydrolyse?

A

a1-6 bonds

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16
Q

What is primary lactase deficiency?

A

A lack of lactase enzyme caused by the absence of lactase persistence allele. Only occurs in adults.

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17
Q

What is secondary lactase deficiency?

A

A lack of lactase enzymes caused by damage to the epithelial lining of the small intestine. It is generally reversible and can occur in infants and adults.

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18
Q

What is congenital lactase deficiency?

A

A lack of lactase enzymes caused by an autosomal recessive defect in lactase gene, preventing infants from digesting breast milk. It is extremely rare.

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19
Q

Which two transporters are involved in the absorption of monosaccharides?

A

Sodium-glucose-transporter-1 (SGLT1)

Glucose transporter-2 (GLUT2)

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20
Q

Which glucose transporter is insulin-regulated?

A

GLUT4

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21
Q

What is the function of hexokinase?

A

To phosphorylate glucose

22
Q

What is the function of hexokinase?

A

To phosphorylate glucose

23
Q

What is the function of phosphofructokinase-1?

A

The phosphorylation of fructose

24
Q

What is the function of pyruvate kinase?

A

Converts phosphoenolpyruvate to pyruvate

25
Q

What is the function of glycerol-3-phosphate dehydrogenase?

A

To form glycerol phosphate from dihydroxyacetone phosphate

26
Q

Why is glycerol phosphate required?

A

It is important to triglyceride and phospholipid biosynthesis

27
Q

What is the function of bisphosphoglycerate mutase?

A

Convert 1,3- bisphosphoglycerate to 2,3-bisphosphoglycerate

28
Q

What is the function of 2,3- bisphosphoglycerate?

A

Produced in red blood cells

Regulator of haemoglobin O2 affinity (promotes release)

29
Q

How can glycolysis indicate cancer?

A

Rate of glycolysis up to 200 times greater in cancer

Measure uptake of fluorinated glucose analog with a PET scan.

30
Q

What is the general formula of carbohydrates?

A

(CH2O)n where n>3

31
Q

What are the allosteric regulators of phosphofructokinase?

A

Inhibitors: ATP, Citrate

Stimulators: AMP, fructose-2,6-bisphosphate

32
Q

What are the hormonal regulators of phosphofructokinase?

A

Inhibitor: Glucagon

Stimulator: Insulin

33
Q

What is the regulator of hexokinase?

A

Glucose-6-phosphate by product inhibition

34
Q

What is the regulator of pyruvate kinase?

A

It is stimulated by a high insulin to glucagon ratio

35
Q

Why is pyruvate sometimes reduced to lactate?

A

To allow NADH to be oxidised to NAD+, allowing glycolysis to continue (producing ATP) when there is an inability to use NADH for oxidative phosphorylation

36
Q

What is the amount of lactate produced without major exercise?

A

40-50g/24 hours

37
Q

How much lactate is produced when doing strenuous exercise?

A

30g/5 min

38
Q

When is someone in lactic acidosis?

A

Above 5 mM in the blood

Blood pH lowered

Concentrations of lactic acid detected in urine

39
Q

What is the function of fructokinase?

A

The phosphorylation of fructose to fructose-1-P

40
Q

What is the function of aldolase?

A

To convert fructose-1-P to glyceraldehyde and DHAP

41
Q

What is the function of triose kinase?

A

The phosphorylation of glyceraldehyde to glyceraldehyde-3-P

42
Q

What is the function of TPI?

A

The conversion of DHAP to glyceraldehyde-3-P

43
Q

Name the cause of essential fructosuria

A

Lack of fructokinase enzyme

44
Q

Name the cause of fructose intolerance

A

Lack of aldolase

45
Q

What is the function of galactokinase?

A

The phosphorylation of galactose to galactose-1-P

46
Q

What is the function of galactose-1-P uridyl transferase?

A

The conversion of UDP-glucose + galactose-1-P to glucose-1-P + UDP galactose

47
Q

What is the function of UDP-galactose 4’-epimerase?

A

The conversion of UDP-galactose to UDP-glucose

48
Q

Why is UDP-galactose important?

A

It is required for synthesis of glycoproteins & glycolipids

49
Q

What is the function of aldose reductase?

A

The reduction of galactose to galactitol

50
Q

What is the function of glucose-6-P dehydrogenase?

A

The oxidation of glucose-6-P to 6-phosphogluconoacetone

51
Q

What is the rate limiting enzyme of the pentose phosphate pathway?

A

Glucose 6-phosphate dehydrogenase

MEH (5 decks)

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