Carbohydrates

Question 1

Which cells utilize glucose for energy

Answer 1

ALL of them

Question 2

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

Answer 2

70-100mg/dL

Question 3

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

Answer 3

Starch, Sucrose and Lactose

Polysaccharides

Question 4

Define the digestion of carbohydrates

Answer 4

Digestion converts dietary polysaccharides and disaccharides to their respective monosaccharides

Question 5

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

Answer 5

D form

Question 6

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

Answer 6

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

Question 7

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

Answer 7

The aldehyde and the anomeric carbon

Question 8

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.

Answer 8

True

Question 9

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 ______.

Answer 9

Beta

Alpha

Question 10

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

Answer 10

On Carbon #1

On Carbon #2

Question 11

Define a reducing end on a sugar molecule

Answer 11

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

Question 12

Starches can be divided into which two structural classes?

Answer 12

Amylose

Amylopectin

Question 13

Describe the difference between Amylose and Amylopectin

Answer 13

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.

Question 14

True or False

Starches are primarily carbohydrate storage in animals

Answer 14

False -
Starches = Plants
Glycogen = Animals

Question 15

True or False

Glycogen resembles Amylopectin in structure

Answer 15

True

It resembles amylopectin in structure, but is more highly branched

Question 16

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

Answer 16

β-D-glucose units

Question 17

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

Answer 17

True

Question 18

Name the 3 major disaccharides discussed in class

Answer 18

Sucrose, Lactose, Trehalose

Question 19

Sucrose contains which two sugar molecules?

Answer 19

Glucose and Fructose

Question 20

Is sucrose a reducing sugar? Why or why not?

Answer 20

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

Question 21

What type of bond (linkage) is found in sucrose

Answer 21

alpha, beta, 1,2

Question 22

Lactose contains which two sugar molecules?

Answer 22

Glucose and Galactose

Question 23

Is lactose a reducing sugar? Why or why not?

Answer 23

Yes, the anomeric carbon on glucose can be reduced

Question 24

Trehalose contains which two sugar molecules

Answer 24

2 Glucose molecules

Question 25

What type of bond is found in trehalose?

Answer 25

alpha, alpha 1,1

Question 26

Is Trehalose a reducing sugar? Why or why not?

Answer 26

No, the anomeric carbons are both occupied

Question 27

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

Answer 27

glycosidases (glycoside hydrolases)

Question 28

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.

Answer 28

salivary alpha amylase alpha 1,4

Question 29

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

Answer 29

Terminal Ends Near branches Alpha 1,6 bonds

Question 30

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

Answer 30

True

Question 31

Digestion in the intestine occurs in what two phases?

Answer 31

Luminal and Membrane

Question 32

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

Answer 32

Pancreatic alpha amylase

Question 33

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

Answer 33

secretin

Question 34

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

Answer 34

bicarbonate

Question 35

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

Answer 35

Maltose, maltotriose and branched dextrins

Question 36

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

Answer 36

Lactase, Trehalase, Sucrase-Isomaltase complex and glucoamylase

Question 37

Lactase cleaves the ______ bond between ______ and ______ molecules.

Answer 37

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

Question 38

Trehalase hydrolyzes ______bond to yield two molecules of________.

Answer 38

alpha, alpha 1,1 bond glucose

Question 39

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

Answer 39

alpha 1,4 nonreducing

Question 40

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

Answer 40

glucose

Question 41

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

Answer 41

Sucrase portion

Question 42

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

Answer 42

Cleaves alpha 1,6 to give glucose and maltotriose

Question 43

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 ________.

Answer 43

Cannot Gases (CO2, H2 and methane), short-chain fatty acids (acetic, propionic and butyric), and lactate

Question 44

What is the function of bile acids?

Answer 44

Emulsify fats

Question 45

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

Answer 45

lumen brush

Question 46

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

Answer 46

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

Question 47

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

Answer 47

Glucose and galactose

Question 48

Fructose utilizes ________ for its absorption via facilitated diffusion.

Answer 48

GLUT-5

Question 49

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

Answer 49

Glucose, galactose, and fructose

Question 50

What is the glycemic index?

Answer 50

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

Question 51

True or False | Lactose/Lactase are osmotically active

Answer 51

True

Question 52

True or False | Lactose causes water to be drawn into the intestine

Answer 52

True

Question 53

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

Answer 53

Bacterial fermentation