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Biochemistry I > SCT II - Carbohydrate Metabolism II > Flashcards

SCT II - Carbohydrate Metabolism II Flashcards

1
Q

Glycogen

A

POLYSACCHARIDE
1. Polymer of Glucose
2. α-1,4-glycosidic bonds

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2
Q

Blood-glucose level (mM)

A

5 mM

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3
Q

What enzyme catalyzes glycogenolysis?

A

GLYCOGEN PHOSPHORYLASE
Cleaves α-1,4-glycosidic bonds

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4
Q

What does glycogen phosphorylase need?

A
  • Does NOT need ATP = REVERSIBLE
  • Uses Inorganic Phosphate
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5
Q

What enzyme catalyzes the conversion of G-1-P to G-6-P?

A

Glucose-1-Phosphate
to | Phosphoglucomutase
Glucose-6-Phosphate

REVERSIBLE

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6
Q

Which enzyme catalyzes the conversion of G-6-P to Glucose?

A

Glucose-6-Phosphate
to | Glucose-6-Phosphatase
Glucose

Found in Endoplasmic Reticulum

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7
Q

Name the two debranching enzymes and their funciton

A

4-α-D-Glucanotransferase
Linearizes branched molecule

Amylo-α-1,6-Glycosidase
Breaks α-1,6-Glycosidic bond

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8
Q

Why do we store glycogen instead of glucose?

A

Glycogen is not as osmotically active

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9
Q

Why don’t we store excess glucose as fat instead of glycogen?

A

Glycogen is easier to breakdown than fat, which requires oxygen

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10
Q

Does insulin activate glycogenolysis or glycogenesis?

A

Glycogenesis, as it dephosphorylates (uses kinases)

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11
Q

Does glucagon activate glycogenolysis or glycogenesis

A

Glycogenolysis, as it phosphorylates (uses phosphatases)

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12
Q

What is cross regulation in glycogenolysis or glycogenesis

A

Cross-regulation ensures that both processes don’t take place at the same time

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13
Q

What is the allosteric regulation of phosphorylase in muscle and liver?

A

LIVER
Mediated by the AMP/ATP ratio
- High AMP = Glycogenolysis
- High ATP = Glycogenesis

MUSCLE
Mediated by glucose
- Glucose inhibits Glycogen Phosphorylase (inhibits Glycogenolysis)

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14
Q

What is the difference when Epinephrine binds to its β-adrenergic receptor or α-adrenergic receptor?

A

β-adrenergic
1. Increases [cAMP]i
2. cAMP activates glycogenolysis

α-adrenergic
1. Splits PIP2 to IP3 & DAG
2. IP3 & DAG release Ca2+ from ER
3. Ca2+ activates glycogenolysis via activation of glycogen phosphorylase

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15
Q

What is the bifunctional function of epinephrine?

A

Muscle: induces glycogenolysis & glycolysis
Liver: inhibits glycolysis in liver

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16
Q

How much NADPH is released through pentose phosphate pathway?

A

2

17
Q

Name the phases and their products of the pentose phosphate pathway?

A

Non-Oxidative Phase
2x NADPH

Oxidative Phase
Pentoses & C3 C4 C6 C7 compounds

18
Q

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

A

Glucose-6-Phosphate
to | Glucose-6-Phosphate Dehydrogenase
Pentose-Phosphate

NADP+ to NADPH+H
CO2 OUT

19
Q

What is the difference between NAD and NADP?

A

NAD
Used for catabolic pathways

NADP
Used for anabolic pathways

20
Q

In the oxidative stage of the pentose phosphate pathway, how are isomerases and epimerases utilized?

A

Ribose-5-Phosphate
to | Phosphopentose Isomerase
Ribulose-5-Phosphate
to | Phosphopentose Epimerase
Xylulose-5-Phosphate

21
Q

What are the uses of NADPH from the pentose phosphate pathway?

A

RBC & Brain
Reduce glutathione

Fatty Acid Synthesis
Reducing agent

22
Q

What are the uses of CO2 from the pentose phosphate pathway?

A

Liver
Uses 20-30% CO2 for metabolic pathways

23
Q

What are the uses of the pentose phosphate pathway for the muscle?

A

Muscle
Receive glycolytic intermediates (for glycolysis)
Utilize TCA cycle

24
Q

How can glucose be converted to fructose?

A

Glucose
+
NADPH+H+
to | Reduction
to | Aldose Reductase
Sorbitol
+
NADP+

Sorbitol
+
NAD+
to | Oxidation
to | Sorbitol Dehydrogenase
Fructose
+
NADH+H+

25
Q

Which enzyme is responsible for the formation of lactate? And what are its two subunits?

A

Lactose Synthase:
1. Galactosyl transferase
2. α-Lactalbumin

26
Q

Which substance activates lactose synthase?

A

Prolactin hormone

27
Q

What substance do we add in order to make an insoluble substance soluble to urea?

A

UDP-Glucouronic Acid

28
Q

Which enzyme is used in the oxidation of UDP-glucose to UDP-glucuronic acid?

A

UDP-Glucose
to | **UDP-Glucose Dehydrogenase*
UDP-Glucuronic Acid

29
Q

Which enzyme do humans lack in order to form Vitamin C (L-Ascorbic Acid)?

A

Gulonolacton Oxidase

Biochemistry I (12 decks)

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