Introduction to Carbohydrates* Flashcards

1
Q

define monosaccharide, disaccharide, oligosaccharide, and polysaccharide

A

• monosaccharide
– 1 sugar residue (ex: glucose)

• disaccharide
– 2 sugars covalently bound together (ex: lactose,
sucrose, maltose, isomaltose)

• oligosaccharide
– 2-15 sugars covalently bound in a linear or branched chain (ex: α-dextrins)

• polysaccharide
– many sugars covalently bound in a linear or branched polymer (ex: glycogen, α-amylose, amylopectin)

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2
Q

recognize glycosidic linkages (for example: α1,4 vs β1,4 vs α1,6, etc.)

A

alpha = trAns to CH2OH

Beta = cis

For numbers, count the carbons

See pg. 3 lecture 1 (not notes)

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3
Q

recognize the structures (in cyclic form) of glucose, galactose, fructose, maltose, isomaltose, lactose, sucrose, maltotriose, α-dextrins, amylose, amylopectin, glycogen, and cellulose.

A

See pgs. 4 - 8

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4
Q

list the major dietary carbohydrates

A

Main carbs:

Starch

Lactose = milk

Sucrose = table sugar

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5
Q

describe how and where the major dietary carbohydrates are digested

A

Monosaccharides are transported into bloodstream via intestinal epithelial cells.

• Endoglycosidases (ex: α-amylase) cleave
internal glycosidic bonds in sugar polymers
• Exoglylcosidases (ex: glucoamylase) cleave terminal glycosidic bonds in sugar polymers
• Disacharidases (ex: maltase) cleave glycosidic bonds in disaccharides

Specificity of Glycosidases is based on structure of glycosidic linkage

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6
Q

describe the causes of lactose intolerance and its treatment

A

Lactose intolerance = lactase deficiency

75% of ADULT world

• Undigested lactose moves to colon where bacteria digest it. Digestion products may cause diarrhea, nausea, abdominal cramps, bloating, and gas.

Lactose Intolerance - Treatment
•  Modification of diet to avoid dairy
•  Consuming lactase treated dairy
products
•  Taking lactase enzyme tablets prior to consuming dairy products
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7
Q

discuss the basic functions of the major carbohydrate metabolism pathways (glycolysis,
citric acid cycle, gluconeogenesis, glycogen synthesis, glycogenolysis, and the pentose phosphate pathway) and their relationships to one another

A

see pgs. 16 - 21

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8
Q

Why isn’t Cellulose digested?

A

We cannot digest Cellulose because we do not have an enzyme that can digest a glucose-glucose beta 1,4 linkage.

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9
Q

Describe the roles and specificities of α-amylase and the various intestinal glycosidases involved.

A
  • α-Amylase (endoglucosidase) in pancreas & saliva hydrolyzes random internal α1,4 bonds in STARCH.
  • Carbohydrates must be cleaved to monosaccharides before they can be transported into epithelial cells.

• Epithelial cells synthesize and secrete glycosidases that remain attached to brush border
– they cleave oligosaccharides and disaccharides to monosaccharides.

  • Monosaccharide transporters in brush border (apical membrane) move monosaccharides into cells
  • Monosaccharide transporters in basolateral membrane move monosaccharides into bloodstream.

Review pgs 10 - 11.

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