Fructose and Galactose Metabolism Flashcards
Fructose provides what percentage of calories in Western diet
10%
Which sugar does not promote insulin secretion
Fructose
From what sources do we obtain free fructose
Honey, fruits and corn syrup
From which disaccharide do we obtain fructose
Sucrose
Where is fructose mainly absorbed
The liver
Apart from the liver, where else can fructose be absorbed
Liver and kidneys
Which enzyme breaks down sucrose
Sucrase
Which enzyme breaks down fructose
Fructokinase
Which enzyme breaks down fructose-1-P
Fructose-1-P Aldolase/ Aldolase B
What are the products produced after Fructose-1-P is broken down
DHAP and Glyceraldehyde
What enzyme breaks down Glyceraldehyde
Triokinase
Which 2 intermediates in fructose metabolism can go into Glycolysis, Glycogenesis or Gluconeogenesis
DHAP and Glyceraldehyde-3-P
Which 2 enzymes can break down fructose
Fructokinase and Hexokinase
Which enzyme required to break down fructose has the smaller Km
Fructokinase
At which steps is ATP utilized in fructose metabolism
- Conversion of Fructose to Fructose-1-P
2. Conversion of Glyceraldehyde to glyceraldehyde-3-P
Which metabolism is faster: Glucose or Fructose
Fructose
How can fructose metabolism lead to fatty acid synthesis
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
What is the Polyol pathway
The conversion of glucose to fructose
Importance of the Polyol pathway
To make fructose to provide energy for spermatozoa
Where in the body is the polyol pathway found
Liver, seminal vesicles, ovaries, sperm
Which enzyme facilitates the conversion of glucose to sorbitol
Aldolase reductase
Which enzyme facilitates the conversion of sorbitol to fructose
Sorbitol dehydrogenase
Essential fructosuria results from a deficiency in which enzyme
Fructokinase
Hereditary fructose intolerance results from a deficiency in which enzyme
Fructose -1- P aldolase/ Aldolase B
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.
Two main fates of galactose
Glucose or glycolysis
What molecules is the carrier for galactose
UDP
Four molecules that UDP obtains galactose from
Lactose, keratan sulfate, glycolipids and glycoproteins
Which enzyme breaks down galactose
Galactokinase
Which enzyme breaks down galactose-1-P
galactose-1-P uridyl transferase
Which enzyme breaks down glucose-1-P to glucose- 6-P
Phosphoglucomutase
Which enzyme breaks down glucose-6-P to glucose
Glucose-6-phosphatase
UDP-Galactose changes to Glycogen (glycogenesis) by what enzyme
UDP-galactose epmerase
Glactosemia occurs as a result of deficiency in which enzyme
Galactose-1-P uridyl transferase
Cateracts an result from impaired galactose metabolism because of a deficiency in which enzyme
Galactokinase
Which enzymes causes cateract forming because of a build up of galactose
Aldolase reductase
In which glands is lactose synthesized
Lactating mammary glands
Which enzyme is needed for lactose synthesis
Lactose synthase
Which protein makes lactose synthase
alpha-lactalbumin
Which hormone simulates synthesis of alpha lactalbumin
Prolactin
In which cellular organelle does lactose synthesis occur
The Golgi
