Fructose and Galactose Metabolism Flashcards

1
Q

Fructose provides what percentage of calories in Western diet

A

10%

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2
Q

Which sugar does not promote insulin secretion

A

Fructose

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3
Q

From what sources do we obtain free fructose

A

Honey, fruits and corn syrup

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4
Q

From which disaccharide do we obtain fructose

A

Sucrose

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5
Q

Where is fructose mainly absorbed

A

The liver

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6
Q

Apart from the liver, where else can fructose be absorbed

A

Liver and kidneys

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7
Q

Which enzyme breaks down sucrose

A

Sucrase

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8
Q

Which enzyme breaks down fructose

A

Fructokinase

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9
Q

Which enzyme breaks down fructose-1-P

A

Fructose-1-P Aldolase/ Aldolase B

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10
Q

What are the products produced after Fructose-1-P is broken down

A

DHAP and Glyceraldehyde

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11
Q

What enzyme breaks down Glyceraldehyde

A

Triokinase

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12
Q

Which 2 intermediates in fructose metabolism can go into Glycolysis, Glycogenesis or Gluconeogenesis

A

DHAP and Glyceraldehyde-3-P

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13
Q

Which 2 enzymes can break down fructose

A

Fructokinase and Hexokinase

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14
Q

Which enzyme required to break down fructose has the smaller Km

A

Fructokinase

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15
Q

At which steps is ATP utilized in fructose metabolism

A
  1. Conversion of Fructose to Fructose-1-P

2. Conversion of Glyceraldehyde to glyceraldehyde-3-P

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16
Q

Which metabolism is faster: Glucose or Fructose

A

Fructose

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17
Q

How can fructose metabolism lead to fatty acid synthesis

A

Increased fructose metabolic rate leads to increased glycolysis which results in increased pyruvate. Increased pyruvate leads to increased acetyl coA which would lead to increased fatty acid synthesis

18
Q

What is the Polyol pathway

A

The conversion of glucose to fructose

19
Q

Importance of the Polyol pathway

A

To make fructose to provide energy for spermatozoa

20
Q

Where in the body is the polyol pathway found

A

Liver, seminal vesicles, ovaries, sperm

21
Q

Which enzyme facilitates the conversion of glucose to sorbitol

A

Aldolase reductase

22
Q

Which enzyme facilitates the conversion of sorbitol to fructose

A

Sorbitol dehydrogenase

23
Q

Essential fructosuria results from a deficiency in which enzyme

A

Fructokinase

24
Q

Hereditary fructose intolerance results from a deficiency in which enzyme

A

Fructose -1- P aldolase/ Aldolase B

25
What is seen in Hereditary fructose intolerance
Fructose in blood, trapped cellular phosphate results in decreased gluconeogenesis and glycogenolysis, which leads to hypoglycemia. Can result in death.
26
Two main fates of galactose
Glucose or glycolysis
27
What molecules is the carrier for galactose
UDP
28
Four molecules that UDP obtains galactose from
Lactose, keratan sulfate, glycolipids and glycoproteins
29
Which enzyme breaks down galactose
Galactokinase
30
Which enzyme breaks down galactose-1-P
galactose-1-P uridyl transferase
31
Which enzyme breaks down glucose-1-P to glucose- 6-P
Phosphoglucomutase
32
Which enzyme breaks down glucose-6-P to glucose
Glucose-6-phosphatase
33
UDP-Galactose changes to Glycogen (glycogenesis) by what enzyme
UDP-galactose epmerase
34
Glactosemia occurs as a result of deficiency in which enzyme
Galactose-1-P uridyl transferase
35
Cateracts an result from impaired galactose metabolism because of a deficiency in which enzyme
Galactokinase
36
Which enzymes causes cateract forming because of a build up of galactose
Aldolase reductase
37
In which glands is lactose synthesized
Lactating mammary glands
38
Which enzyme is needed for lactose synthesis
Lactose synthase
39
Which protein makes lactose synthase
alpha-lactalbumin
40
Which hormone simulates synthesis of alpha lactalbumin
Prolactin
41
In which cellular organelle does lactose synthesis occur
The Golgi