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Biochemistry Exam 1 > Chapter 18 (Entry of other Sugars) > Flashcards

Chapter 18 (Entry of other Sugars) Flashcards

1
Q

Entry of Fructose via the muscle

A

Very similar to metabolism of Glucose

Hexokinase is used to convert Fructose into Fructose-6-P

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2
Q

Fructokinase

A

The phosphorylation of Fructose into Fructose-1-P (which is not a metabolite in glycolysis)
Irreversible
Found in the liver

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3
Q

Fructose-1-P Aldolase

A

Catalyzes the cleavage of Fructose-1-P into Glyceraldehyde and DHAP
Reversible
Found in the liver

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4
Q

Glyceraldehyde has two pathways

A

Short: direct to GAP via the enzyme Glyceraldehyde Kinase
Long: to GAP (creating Glycerol-3-P in the process) via several steps

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5
Q

Glyceraldehyde (Short Path)

A

converted to GAP via the enzyme Glyceraldehyde Kinase
Requires 1 ATP (to phosphorylate)
Irreversible

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6
Q

Alcohol Dehydrogenase

A

Changing the aldehyde on Glyceraldehyde into a alcohol to create Glycerol
Consumes a NADH (oxidation)

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7
Q

Glycerol Kinase

A

Adds a phosphate group onto the C#3 of glycerol to create a Glycerol-3-P
Only found in the liver
Requires ATP
Irreversible

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8
Q

Glycerol Phosphate Dehydrogenase

A

Oxidizes the -OH on C#2 of Glycerol-3-P into a ketone to create a DHAP
Consumes NAD+ (reduced)

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9
Q

What is the purpose of the longer Glyceraldehyde pathway?

A

It is used to create Glycerol-3-P which is used as a backbone for triacylglycerols (and other compounds)

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10
Q

Entry of Fructose via the liver

A

Glucokinase has a low affinity for fructose to fructokinase is used

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11
Q

Entry of Glycerol

A

Occurs only in the liver

Same steps used during the long pathway to convert Glycerol to DHAP in the Fructose pathway

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12
Q

Entry of Galactose

A

Galactose is the C4 epimer of Glucose
Only metabolized in the liver
Galactokinase is used

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13
Q

Galactokinase

A

Adds a phosphate group onto the C#1 of Galactose to create Galactose-1-P
Irreversible
Requires ATP

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14
Q

Galactose-1-P Uridylyltransferase

A

Transfers a phosphate group from UDP-Glucose to create a UDP-Galactose
Glucose-1-P continues on down the pathway

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15
Q

Phosphoglucomutase

A

Transfers the phosphate group from C#1 to C#6 to create Glucose-6-P (which continues down glycolysis)

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16
Q

What enzyme epimerizes UDP-Galactose back into UDP-Glucose and vice versa

A

UDP-Galactose-4-epimerase

17
Q

If an infant has a galactose problem

A

they cannot drink their mothers milk or it will lead to mental retardation

18
Q

Dr. Luis Leloir

A

won noble prize for galactose metabolism

19
Q

Entry of Mannose

A 
Mannose is C#2 epimer of Glucose
Can use the enzyme hexokinase (muscle)
Adds phosphate group to create Mannose-6-P
Requires ATP
Irreversible
20
Q

Phosphomannose Isomerase

A

Turns Mannose-6-P into Fructose-6-P

21
Q

Mannose is primarily seen as

A

Mannose-1-P (via phosphomannose mutase)

22
Q

Aldose Reductase

A

Reduces aldoses to their corresponding sugar alcohols
Reduces Glucose to Sorbitol
Requires NADPH

23
Q

Aldose Reductase has a (high/low) Km for aldoses which means a lot of substrate is needed

A

High

High aldolase = increased activity

24
Q

Sorbitol Dehydrogenase

A

Converts Sorbitol into Fructose
Requires NAD+
Found in sperm (and several tissues)
Low concentrations can lead to damage similar to that of Type 1 Diabetes

25
Q

At which point in the glycolysis pathway does arsenate poisoning become a problem

A

During the conversion of GAP to 1,3-BPG via GAPDH
GAP mistakes arsenate as a phosphate group and creates 1-Arseno-3PG
The arsenate is then hydrolized off (no enzyme needed)

26
Q

Why is arsenate poisoning so dangerous

A

Because this causes the GADPH step to be skipped which leads to a net yield of 0 ATP through glycolysis

27
Q

Bisphosphoglycerate Mutase

A

Converts 1,3-BPG to 2,3-BPG via the movement of a phosphate group
Irreversible

28
Q

Significance of 2,3-BPG

A

it is a allosteric effector for hemoglobin

29
Q

2,3-BPG Phosphatase

A

Hydrolyzes the phosphate off of 2,3-BPG to create 3-PG
Phosphate group comes off as Pi
Irreversible

30
Q

The effect of Hexokinase deficiency on blood oxygen

A 
Low Hexokinase = low 1,3-BPG
Low 1,3-BPG = low 2,3-BFG
Low 2,3-BFG = higher affinity for O2
Blood can carry less O2 than normal 
Curve shifts to the left
31
Q

The effect of Pyruvate Kinase deficiency on blood oxygen

A 
Low Pyruvate Kinases = more 1,3-BPG (everything backs up)
More 1,3-BPG = more 2,3-BPG
More 2,3-BPG = lower affinity for O2
Blood can carry more O2 than normal
Curve shifts to the right

Biochemistry Exam 1 (8 decks)

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