MCP - Maimone - 2/9 - Intro to Carbohydrates Flashcards
This sugar is cleaved by which glycosidase?
A. isomaltase
B. lactase
C. maltase
D. sucrase
B. Lactase
The sugar shown is lactose, which is galactose and glucose connected by a ß 1,4 linkage.
Where does the digestion of sugar begin?
The small intestine
A patient with elevated levels of serum alpha-amylase most likely has a disorder of the:
Pancreas (pancreatitis)
What metabolic pathway is used to produce NADPH for biosynthetic reactions?
Pentose Phosphate Pathway
Glycogen stored in what tissue is used to maintain blood glucose levels during fasting?
Liver
Name this sugar.
What kind of “hexose” is this sugar?
ß-D-glucose, note anomeric C is facing up.
Glucose is an aldohexose, due to the terminal aldehyde group (C1) present in the Fisher projection.
Name this sugar.
alpha-D-glucose
Anomeric C is facing down.
What sugar is this?
What two sugars make up this disaccharide?
What kind of glycosidic bond is shown?
Maltose
Made of 2 units of glucose
alpha 1-4
Name this sugar.
What two sugars make up this disaccharide?
What kind of glycosidic bond is shown?
Lactose
Made of galactose (left) and glucose (right)
beta 1-4
List the major dietary carbohydrates.
Starch (made of amylose and amylopectin), lactose and sucrose.
Name this sugar.
Galactose (alpha-D-galactose)
This is a section of what polysaccharide.
This polysaccharide is a component of what major dietary carbohydrate?
What sugars make up this molecule?
What glycosidic bonds are shown here?
Amylopectin
A component of starch.
Glucose units joined by alpha 1-4 inkages, with alpha 1-6 branches.
Name this sugar.
What kind of “hexose” is this sugar?
Fructose (beta-D-fructose)
A ketohexose (ketone on C2 in Fisher projection)
What is the difference between glycogen and amylopectin?
Glycogen has the same basic structure as amylopectin, but is more highly branched (more alpha 1-6 bonds).
Name this sugar.
What are its component units?
What glycosidic bond is present?
Isomaltose
Made of 2 units of glucose
alpha 1-6 bonds
What is this molecule?
What kind of saccharide is this?
What are the component units and glysodidic bonds involved?
What is unique about this molecule?
Cellulose
Polysaccharise, 100s to 1,000,000 etc.
Glucose residues in beta 1-4 linkages.
We cannot digest cellulose bc we don’t have the component enzyme for cleaving a beta 1-4 linkage.
Name this sugar.
What are its component units?
What glycosidic bond is shown?
Why is this sugar considered a non-reducing sugar?
Sucrose
Made of glucose and fructose
alpha 1-2 glycosidic bond
Sucrose is a non-reducing sugar because the OH’s of the 2 anomeric carbons are not free.
Salivary glands produce what glycosidase? What sugars does it break down?
Alpha-amylase, an endoglycosidase, hydrolyzes random *internal* alpha 1-4 bonds between glucose residues
Alpha amylase cleaves starch polymers into smaller polysaccharides, but is then inactivated when the bolus reaches the stomach.
Name this sugar.
What are its component units?
What glycosidic bonds are shown?
Amylose, a component of starch
Repeating glucose units
alpha 1-4 linkages
Transporters in the brush border of the intestine transport what size sugars into epithelial cells?
Monosaccharides
What is glucoamylase? Where is it found? What is its function?
Glucoamylase is an exoglycosidasethat cleaves terminal alpha 1-4 bonds between glucoses in oligosaccharides and disaccharides, for example maltose, maltotriose, alpha-dextrins, amylose, amylopectin. It’s found at the brush border.
Name this sugar.
What are the component units?
What glycosidic bonds are shown?
Maltotriose
Made of three glucose units
Connected by alpha 1-4 linkages
What are the main brush border enzymes?
Glucoamylase
Maltase
Isomaltase
Sucrase
Lactase
What dietary enzyme cleaves this molecule?
Maltase, cleaves the alpha 1-4 bond to produce glucose
Maltase also cleaves alpha 1-4 linkages in maltotriose to produce maltose and glucose.
What are alpha-dextrins?
Formed from the initial breakdown of starch by alpha-amylase.
Alpha-dextrins are an intermediate between starch and tri/oligosaccharides, made of glucose with alpha 1-4 and alpha 1-6 linkages.
What enzyme cleaves the alpha 1-6 bond in this molecule?
Isomaltase, cleaves alpha 1-6 linkages in isomaltose and alpha-dextrins to produce glucose and glucose polymers.
What enzyme cleaves this molecule?
Sucrase, cleaves the alpha 1-2 bond in sucrose to produce glucose and fructose
What enzyme produces these two sugars by cleaving a disaccharide?
Lactase (beta-galactosidase)
As the name implies, it cleaves the beta 1-4 linkage in lactose to produce galactose (down up up) and glucose (down up down)
What is lactose intolerance?
Lactose intolerance is *symptomatic* lactase deficiency.
If a person does not have the polymorphism responsible for lactase persistence, then undigested lactose in the colon is fermented by bacteria, producing lactic acid. This can cause diarrhea and other GI symptoms. It should be noted that the severity of symptoms is not correlated with specific levels of lactase.
What are the available treatments for lactose intolerance?
Dietary modification to avoid lactose.
Taking lactase enzyme before eating to help digestion.
Consuming lactase-treated products.
The oxidation of glucose to generate ATP and pyruvate is known as:
glycolysis
What is glycogen synthesis?
When glucose is converted to a storage polymer (glycogen) for later use
What is the immediate step to trap glucose into a cell once it enters?
Glucose is converted to glucose-6-phosphate
What is the major function of the pentose phosphate pathway?
To produce NADPH, needed for biosynthetic pathways. The 5 carbon sugar produced by the oxidation of glucose can also be used in making nucleotides.
