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#‼️BIOCHEMISTRY - PLE TOPNOTCH 2020 > CARBOHYDRATES > Flashcards

CARBOHYDRATES Flashcards

1
Q

Rapoport-Luebering shunt pathway

A
  • Found in RBCs where the reaction catalyzed by phosphoglycerate kinase is bypassed
  • 1,3-BPG → 2,3-BPG
    • Enzyme: Bisphosphoglycerate mutase
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2
Q

Lysosomal acid maltase deficiency

A

Pompe disease (Type II)

  • ↑ Glycogen in lysosomes
  • Juvenile onset: hypotonia, death from heart failure by age 2
  • Adult onset: muscle dystrophy
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3
Q

Essential fructosuria

A

Fructokinase deficiency

• Fructose → Fructose-1-P

• Enzyme: Fructokinase or hexokinase

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4
Q

What is the substrate of PPP?

A

Glucose-6-phosphate

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5
Q

Liver phosphorylase deficiency

A

Hers disease (Type VI)

• Hepatomegaly, mild hypoglycemia

* No liver Glycogen Phosphorylase, so no liver glycogen breakdown = glycogen accumulates there = hepatomegaly

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6
Q

Discuss this graph

A
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7
Q

most common enzyme defect in glycolysis?

A

Pyruvate kinase

  • converts PEP to pyruvate
  • presents as hemolytic anemia
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8
Q

2 steps in glycolysis produce ATP via substrate-level phosphorylation

A
  • 1,3-Bisphosphoglycerate → 3-Phosphoglycerate
    • Enzyme: Phosphoglycerate kinase
  • Phosphoenolpyruvate → Pyruvate
    • Enzyme: Pyruvate kinase
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9
Q

Differentiate PFK-1 and PFK 2

A
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10
Q

non-reducing sugar

A

Sucrose

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11
Q

Discuss the process of GLUCONEOGENESIS

A
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12
Q

Rate-limiting step of glycogenolysis

A

Shortening of glycogen chains

Enzyme: Glycogen phosphorylase

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13
Q

What type of glycolysis is utilized by:

  • Cells with mitochondria
  • Cells with adequate supply
A

AEROBIC GLYCOLYSIS AKA Embden-Meyerhof-Parnas Pathway​

End product: Pyruvate

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14
Q

Heinz bodies and bite cells are found in what disorder?

A

G6PD deficiency

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15
Q

Second Phase of PPP

A

Nonoxidative and Reversible

  • Enzymes:
    • Transketolases (Cofactor: Thiamine)
    • Transaldolases
  • Products:
    • Ribose-5 phosphate
    • Fructose-6phosphate
    • Glyceraldehyde-3phosphate
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16
Q

NADPH functions

A

o Reductive biosynthesis of fatty acids and steroids

o Glutathione reduction inside RBCs

o Cytochrome P450 monooxygenase system

o Oxygen-dependent bactericidal mechanism of WBCs

o Synthesis of nitric oxide

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17
Q
  • Flatulence and diarrhea after ingestion of dairy products
  • Seen in up to 90% of adults of African or Asian descent are lactase-deficient
A

Lactose intolerance

Lactase deficiency

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18
Q

GLUT 1 is found in ___

A

Brain, kidney, colon, placenta, RBC

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19
Q

Mono-saccharides

(Hexoses)

A

Glucose, Fructose, Galactose and mannose

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20
Q
  • Isomers that differ in configuration around only one specific carbon atom (except the carbonyl carbon)
  • Examples: glucose and galactose (differ only in position of –OH in C4), glucose and mannose (differ only in position of –OH in C2)
A

EPIMERS

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21
Q

Mono-saccharides

(Pentoses)

A

Ribose, Ribulose and Xylulose

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22
Q

What type of glycolysis is utilized by:

  • Cells without mitochondria
  • Cells without sufficient O2
A

ANAEROBIC GLYCOLYSIS

End product: Lactate

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23
Q

Muscle phosphorylase deficiency

A

McArdle syndrome (Type V)

Poor exercise tolerance, muscle cramps and myoglobinuria but no lactic acidosis, high muscle glycogen

* because muscle lacks the phosphorylase enzyme, it cannot retrive glucose residues from glycogen, leading to cramps.

* No GP in the muscle, (GP is the rate-limiting enzyme in

glycogenolysis), so no GP, no muscle glycogen breakdown

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24
Q

GLut 4 is found in ___

A

Heart and skeletal muscle, adipose tissue

“FHM” fat, heart, muscle

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25
Q

Purpose of PENTOSE PHOSPHATE PATHWAY Also known as the Hexose MonoPhosphate shunt

A

o Produces NADPH

o Produces ribose 5-phosphate required for biosynthesis of nucleotides

o Provides a mechanism for the metabolic use of 5-carbon sugars

o Take Note: Neither produces nor consumes ATP

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26
Q
  • Characterized by Deficiency in NADPH oxidase
    • Converts molecular oxygen into superoxide in leukocytes (especially neutrophils and macrophages) and used in the respiratory burst that kills bacteria
  • Severe, persistent, and chronic pyogenic infections caused by catalase-positive bacteria
A

CHRONIC GRANULOMATOUS DISEASE

*In the absence of NADPH oxidase, neutrophils will not be able to convert oxygen to superoxide, which is used to kill bacteria that they’ve engulfed.

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27
Q

Insulin is needed in ___

A

GLUT 4 transporter (“FHM” - fat, heart, muscle)

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28
Q

Important products of PPP

A

NADPH and Ribose-5-phosphate

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29
Q

Most common cause of congenital lactic acidosis

A

Pyruvate dehydrogenase deficiency

  • X-linked dominant
  • ↑ lactate (anaerobic glycolysis) + ↓ acetyl CoA (citric acid cycle) leads to brain deprived of acetyl CoA leading to psychomotor
  • retardation and death
  • Treat with ketogenic diet
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30
Q

Where does TCA occur?

A
  • In all cells with mitochondria
  • Mitochondrial matrix
    • Except: succinate dehydrogenase (inner mitochondrial membrane)
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31
Q

What are the fates of Pyruvate?

A
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32
Q

Glucose 6 phosphatase is present in ___

A

The liver but not in the muscle.

The end product of glycogenolysis in the muscle is Glucose - 6 - Phosphate

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33
Q

GLUT 5 is found in ___

A

Small intestine (lumen)

for the Absorption of fructose

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34
Q

ATP yield of Glycolysis

A
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35
Q

This final step is shared by gluconeogenesis and glycogenolysis, because both pathways yield glucose.

A

GLUCOSE-6-PHOSPHATE → GLUCOSE

Enzyme: Glucose 6-phosphatase

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36
Q

Classic galactosemia

(Galactose-1-phosphateuridyltransferase deficiency)

A

Galactose-1P + UDP-glucose → UDP-galactose + Glucose-1P

Enzyme: Galactose-1-P uridyl transferase (GALT)

  • Autosomal recessive
  • More severe symptoms
  • Galactosemia, galactosuria, cataracts, diarrhea, vomiting, jaundice
  • Poor growth in children, severe mental retardation, and liver damage
  • Premature ovarian failure in females
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37
Q

Hexokinase and glucokinase are ____

A

Isozymes

38
Q

Which step is rate-limiting step of glycolysis?

A

Fructose-6-phosphate → Fructose-1,6-bisphosphate

Enzyme: Phosphofructokinase-1

39
Q

Differentiate hexokinase from Glucokinase.

A
40
Q
  • Functional group is a ketone
  • Carbonyl carbon at any other position
  • Example: fructose
A

Ketose

41
Q

What is the rate-limiting step of Glycogenesis?

A

Elongation of glycogen chains i.e., creation of α-(1,4) glycosidic bonds Enzyme: Glycogen synthase

42
Q
  • Optical isomers or stereoisomers
  • Pairs of structures that are mirror images of each other
  • The enantiomers are designated as a D-sugar (Dextrorotatory) and an L-sugar (Levorotatory)
  • D-sugars are more common
A

ENANTIOMERS

43
Q

What are the substrates for gluconeogenesis?

A

o Intermediates of glycolysis and the TCA

o Lactate through the Cori Cycle

o Glycerol and propionyl CoA from triacylglycerols

o Carbon skeletons of glucogenic amino acids

44
Q

In this cycle, Lactate formed by glycolysis in skeletal muscle is transported to the liver where it is converted back to glucose through gluconeogenesis

A

Cori cycle

45
Q

Branching enzyme deficiency

A

Andersen disease (Type IV)

Hepatosplenomegaly,↑ polysaccharide with few branch points, death from heart or liver failure before age 5

46
Q

What are the 5 coenzymes of Pyruvate dehydrogenase (pyruvate to Acetyl CoA)?

A

o Thiamine pyrophosphate (from vitamin B 1 )

o FAD (from vitamin B 2 )

o NAD+ (from vitamin B 3 )

o Coenzyme A (contains pantothenic acid) (from vitamin B 5 )

o Lipoic acid (antioxidant)

47
Q

Carbohydrates that can act as reducing agents because they have an aldehyde group or a free ketose group

A

REDUCING SUGARS

48
Q

Insulin is not needed in ____

A

RBc, intestinal mucosa, liver, brain

49
Q

How may ATPs will be produced for every molecule of ACetyl CoA from tha TCA cycle?

A
50
Q

Galactokinase deficiency

A

Galactose → Galactose-1-P

Enzyme: Galactokinase

  • Autosomal recessive
  • Relatively mild symptoms
  • Galactosemia and galactosuria

• Cataracts in early childhood

51
Q

Where does PPP occur?

A

o RBCs and tissues that produce lipids (liver, adipose tissue, adrenals, thyroid, testes, lactating mammaries)

o In the cytosol

52
Q
  • Intolerance of ingested sucrose
  • Seen in about 10% of the Inuit people of Greenland and Canada
A

Sucrase isomaltase complex deficiency

53
Q

Glucose + Galactose

A

lactose

54
Q

Disaccharides

A
55
Q

Which step is rate-limiting in TCA cycle?

A

Isocitrate → α-ketoglutarate

Enzyme: Isocitrate dehydrogenase

56
Q

Glucose-6-phosphatase deficiency

A

Von Gierke disease (Type Ia)

↑ Glycogen in liver and renal tubule cells, hypoglycemia, lactic acidosis, ketosis, hyperlipemia

*because you do not have glucose-6-phosphatase, you cannot produce glucose, resulting to hypoglycemia.

57
Q

Most common type of glycolysis.

A

Embden-Meyerhof-Parnas pathway

58
Q

Glucose → Sorbitol

Enzyme?

Sorbitol → Fructose

Enzyme?

A

Aldose reductase

Sorbitol dehydrogenase

59
Q

Discuss the pathway for glycolysis

A
60
Q

What is the substrate and the end-products of glycolysis?

A

Glucose to 2 molecules of either pyruvate or lactate

61
Q

3 to 10 sugar units

A
62
Q

Where does glycogenesis occur?

A

o Liver and muscle

o Cytosol

63
Q

Complete oxidation of Glucose will yield how many ATPs?

A
64
Q
  • Functional group is an aldehyde
  • Carbonyl carbon at the end
  • Examples: glucose, galactose, mannose
A
65
Q

What are the products of GLYCOGENOLYSIS?

A

o Glucose in liver

o Glucose-6-phosphate in muscle

66
Q

Discuss TCA/Kreb’s/ Citric Acid Cycle

A
67
Q

Reactions catalyzed by carboxylase and requires BIOTIN as a cofactor.

A

Pyruvate → Oxaloacetate (Pyruvate carboxylase)

Acetyl CoA → Malonyl CoA (Acetyl CoA carboxylase)

Propionyl CoA → Methylmalonyl CoA (Propionyl CoA carboxylase)

68
Q

GLUT 3 is found in ____

A

Brain, placenta, kidney

69
Q

What is the rate limiting step in Gluconeogenesis?

A

Fructose 1,6-bisphosphate → Fructose 6-phosphate

Enzyme: Fructose 1,6-bisphosphatase

70
Q

SGLT 1 is found in ___

A

Small intestine and kidneys

71
Q

Which step is rate-limiting in PPP?

A

Glucose-6-phosphate → 6-phosphogluconate

Enzyme: Glucose-6-phosphate dehydrogenase (G6PD)

72
Q

Protein that serves as a primer for glycogen synthesis when glycogen is completely depleted

A

GLYCOGENIN

73
Q

What are the products of TCA?

A
  • 2 CO2
  • 1 GTP
  • 3 NADH
  • 1 FADH2
74
Q

Debranching enzyme deficiency

A

Cori disease (Type IIIa)

Fasting hypoglycemia, hepatomegaly in infancy, ↑ limit dextrin, muscle weakness

75
Q

Where does Gluconeogenesis occur?

A

o Occurs in the liver (90%) and the kidney (10%)

o Occurs in both mitochondria and cytosol

76
Q

Anaerobic Glycolysis

A
77
Q

First Phase of PPP

A

Oxidative and Irreversible

  • Glucose-6-phosphate dehydrogenase
  • Products: 2 NADPH and Ribulose-5 phosphate
78
Q

Glucode and Galactose are ___ epimers

A

C4 epimers

79
Q

Glucose + Glucose

A

Maltose

80
Q

can undergo interconversion (from α to β, and vice versa) without energy expenditure or the need for enzymes, in a process called mutarotation

A

ANOMERS

81
Q
  • Compounds that have the same chemical formula
  • Glucose, fructose, galactose, and mannose are all isomers of one another because they have the same formula C 6 H 12 O 6
A

ISOMERS

82
Q

The sugar units are linked together by ____

A

glycosidic bonds

83
Q

Glucose and Mannose are ___ epimers

A

C2

84
Q

What are the 2 shuttles for transport of NADH in the ETC?

A
85
Q
  • 1 step in glycolysis produces NADH
  • This is an oxidation reaction that passes electrons to NAD+ to make NADH
A

Glyceraldehyde-3-Phosphate → 1,3-Bisphosphoglycerate

Enzyme: Glyceraldehyde-3-phosphate dehydrogenase

86
Q

What is the substrate for TCA?

A

Acety CoA

87
Q

GLUT 2 is found in ___

A

Liver, pancreas, small intestine (basement membrane), kidney

88
Q

Hereditary fructose intolerance

A

Aldolase B deficiency

• Fructose-1-P → DHAP + Glyceraldehyde

• Enzyme: Aldolase B

  • Profound hypoglycemia and vomiting after consumption of fructose or sucrose
  • Jaundice, hemorrhage, hepatomegaly and liver failure, renal dysfunction, hyperuricemia, lactic acidosis, and death
  • Symptoms appear after weaning from milk
89
Q

Polysaccharides

A

> 10 sugar units

Glycogen, Starch, Cellulose, Inulin

90
Q

where does glycolysis occur?

A

In the cytosol of all mammalian cells

91
Q

Glucose + Fructose

A

sucrose

#‼️BIOCHEMISTRY - PLE TOPNOTCH 2020 (13 decks)

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