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Cell Metabolism 5242 > Carbohydrates > Flashcards

Carbohydrates Flashcards

1
Q

Which cells utilize glucose for energy

A

ALL of them

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2
Q

The body tries to maintain blood glucose levels at what range?

A

70-100mg/dL

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3
Q

Identify the major carbohydrate constituents in the average diet.
Are they polysaccharides or disaccharides?

A

Starch, Sucrose and Lactose

Polysaccharides

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4
Q

Define the digestion of carbohydrates

A

Digestion converts dietary polysaccharides and disaccharides to their respective monosaccharides

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5
Q

Are all naturally occurring sugars in the D or L form?

A

D form

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6
Q

How can you identify the D form of glucose when written in a non cyclic fashion?

A

You look at the farthest asymmetric carbon from the carbonyl carbon and see what side the OH group is on. If it is on the right it is a D and if it is on the Left it is a L

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7
Q

The creation of a cyclic structure exists between which two carbons in a glucose molecule?

A

The aldehyde and the anomeric carbon

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8
Q

True or False
The 6 membered ring (5C + O) of glucose is considered to have a pyranose structure, while the 5 membered ring (4C + O) of fructose is considered to have a furanose structure.

A

True

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9
Q

If the hydroxyl group at position #1 points up it is a _____ form. If the hydroxyl group at position #1 points down it is a ______.

A

Beta

Alpha

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10
Q

The anomeric carbon is located on which position for glucose?
For Fructose?

A

On Carbon #1

On Carbon #2

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11
Q

Define a reducing end on a sugar molecule

A

The hydroxyl group on the anomeric carbon of a cyclized sugar is not linked to another sugar by a glycosidic bond

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12
Q

Starches can be divided into which two structural classes?

A

Amylose

Amylopectin

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13
Q

Describe the difference between Amylose and Amylopectin

A

Amylose consists of linear chains of glucose molecules all linked by α-1,4 bonds, while amylopectin has a branched character in which the linear chains of glucose molecules are occasionally linked α-1,6.

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14
Q

True or False

Starches are primarily carbohydrate storage in animals

A

False -
Starches = Plants
Glycogen = Animals

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15
Q

True or False

Glycogen resembles Amylopectin in structure

A

True

It resembles amylopectin in structure, but is more highly branched

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16
Q

Cellulose is a chief constituent of the fibrous parts of plants, and is composed of ____________in unbranched chains.

A

β-D-glucose units

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17
Q

True or False

Humans do not have any digestive enzymes that can cleave a Beta D bond (like those in cellulose) so it is indigestible

A

True

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18
Q

Name the 3 major disaccharides discussed in class

A

Sucrose, Lactose, Trehalose

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19
Q

Sucrose contains which two sugar molecules?

A

Glucose and Fructose

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20
Q

Is sucrose a reducing sugar? Why or why not?

A

No it is not because the anomeric carbons on the glucose and fructose molecules are occupied

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21
Q

What type of bond (linkage) is found in sucrose

A

alpha, beta, 1,2

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22
Q

Lactose contains which two sugar molecules?

A

Glucose and Galactose

23
Q

Is lactose a reducing sugar? Why or why not?

A

Yes, the anomeric carbon on glucose can be reduced

24
Q

Trehalose contains which two sugar molecules

A

2 Glucose molecules

25
Q

What type of bond is found in trehalose?

A

alpha, alpha 1,1

26
Q

Is Trehalose a reducing sugar? Why or why not?

A

No, the anomeric carbons are both occupied

27
Q

Digestion is catalyzed by a family of enzymes known as _______________that hydrolyze glycosidic bonds.

A

glycosidases (glycoside hydrolases)

28
Q

The saliva contains a digestive enzyme known as ____________which randomly hydrolyzes the interior __________ bonds between glucose residues within amylopectin, amylose, and glycogen converting the large polysaccharides to smaller entities.

A

salivary alpha amylase

alpha 1,4

29
Q

What bonds/areas will salivary alpha amylase likely not cleave?

A

Terminal Ends
Near branches
Alpha 1,6 bonds

30
Q

True or False

There are no digestive enzymes in the stomach that can cleave glycosidic linkages found in carbohydrates.

A

True

31
Q

Digestion in the intestine occurs in what two phases?

A

Luminal and Membrane

32
Q

Cholecystokinin acts on the exocrine cells of the pancreas to stimulate the release of _______.

A

Pancreatic alpha amylase

33
Q

Other intestinal epithelial cells produce another peptide hormone _________, in response to the low pH of the gastric contents entering the intestine.

A

secretin

34
Q

Secretin causes the pancreas to release a solution rich in _________ that helps neutralize the pH of the intestinal contents.

A

bicarbonate

35
Q

What are the final products of α-amylase action on starch?

A

Maltose, maltotriose and branched dextrins

36
Q

In the membrane phase, what 4 glycosidases are found protruding from the brush-boarder?

A

Lactase, Trehalase, Sucrase-Isomaltase complex and glucoamylase

37
Q

Lactase cleaves the ______ bond between ______ and ______ molecules.

A

β-1,4 bond between galactose and glucose in lactose

38
Q

Trehalase hydrolyzes ______bond to yield two molecules of________.

A

alpha, alpha 1,1 bond

glucose

39
Q

Glucoamylase complex functions to cleave the ______ linkages between glucose units in oligosaccharides, starting from the _______ end of the chains.

A

alpha 1,4

nonreducing

40
Q

Glucoamylase also hydrolyzes the α-1,4 bonds in maltose and maltotriose yielding _______.

A

glucose

41
Q

Alpha beta 1,2 bonds between glucose and fructose are hydrolyzed by the ______ portion of the sucrase-isomaltase complex

A

Sucrase portion

42
Q

The isomaltase portion of the sucrase-isomaltase complex cleaves which bond? What are the products of this cleavage?

A

Cleaves alpha 1,6 to give glucose and maltotriose

43
Q

Dietary fiber is composed of carbohydrates or carbohydrate derivatives that ________(can or cannot) be digested by human digestive enzymes. Colonic bacteria convert the more soluble dietary fiber to _____, _______, and ________.

A

Cannot

Gases (CO2, H2 and methane), short-chain fatty acids (acetic, propionic and butyric), and lactate

44
Q

What is the function of bile acids?

A

Emulsify fats

45
Q

Absorption of the monosaccharides takes place primarily from the ________ of the small intestine and involves the “_______ border” of the epithelial cells.

A

lumen

brush

46
Q

Monosaccharides are transported through the absorptive cells of the intestine by which two mechanisms?

A

Facilitated diffusion and by Na+- dependent facilitated transport (active transport)

47
Q

_______ and _________ are transported by SGLT-1 into absorptive intestinal epithelial cells via active transport

A

Glucose and galactose

48
Q

Fructose utilizes ________ for its absorption via facilitated diffusion.

A

GLUT-5

49
Q

What 3 sugars are transported from the intestinal epithelial cells into the portal circulation by GLUT-2?

A

Glucose, galactose, and fructose

50
Q

What is the glycemic index?

A

An indication of how rapidly blood glucose levels rise after consumption. The higher the number, the more rapidly blood glucose levels rise.

51
Q

True or False

Lactose/Lactase are osmotically active

A

True

52
Q

True or False

Lactose causes water to be drawn into the intestine

A

True

53
Q

In addition to the increase in water in the intestine, what other factors contribute to the symptoms associated with lactose intolerance?

A

Bacterial fermentation

Cell Metabolism 5242 (2 decks)

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