Carbohydrates

Question 1

What is the major dietary polysaccharide?

Answer 1

starch

Question 2

What do human cells synthesize to digest polysaccharides?

Answer 2

α-endoglycosidases

Question 3

Why can’t humans digest celulose?

Answer 3

we do not synthesize β-endoglucosidases

Question 4

Where does digestion of α-dextrins and disaccharides occur?

Answer 4

in small intestine

Question 5

Why is α-amylase is largely inactivated in the stomach?

Answer 5

due to the acidity, so it becomes denatured and digestion stops for a moment

Question 6

After the action of pancreatic α-amylase, _____ (fragments of poylsaccharides) are processed into disaccharide, trisachardies and oligosaccharides

Answer 6

α-dextrins

Question 7

Is Maltose a reducing sugar?

Answer 7

Yes

Question 8

Is Sucrose a reducing sugar?

Answer 8

No

Question 9

Is Lactose a reducing sugar?

Answer 9

yes

Question 10

What are the 2 components of starch?

Answer 10

amylose α-(1→4) links

amylopectin α-(1→6)

Question 11

Lactose and Sucrose can’t be broken down in the stomach because they have what bonds?

Answer 11

β(1-4) and α(1,2) respectively

Question 12

What is the difference between maltose and isomaltose?

Answer 12

isomaltose is 2 glucose with a (1,6) link

Question 13

Is there carbohydrate digestion in the stomach?

Answer 13

no

Question 14

what causes lactose intolerance?

Answer 14

a defect in specific disaccharidases in intestinal mucosa so that undigested carbohydrates enter the large intestine

Question 15

what demographic is lactose intolerance mostly seen in?

Answer 15

African and Asians ~90%

Question 16

how are glucose and galactose transported into the mucosal cell?

Answer 16

secondary active carrier mediated sodium dependent glucose transporter-1 (SGLT-1)

Question 17

how are fructose along with glucose and galactose transported into the cell?

Answer 17

sodium-independent monosaccharide transporter (GLUT5); this is a facilitated transporter (GLUT5)

Question 18

describe the exit of the 3 monosaccharides

Answer 18

they exit the mucosal cell and enter into portal circulation via GLUT-2

Question 19

Which GLUT transporters have a high affinity for glucose?

Answer 19

GLUT 1, GLUT 3

Question 20

Which GLUT transporter has a low affinity for glucose?

Answer 20

GLUT 2

Question 21

What is the km of GLUT 1?

Answer 21

1mM

Question 22

What is the km of GLUT 2?

Answer 22

15mM

Question 23

What is the km of GLUT 3?

Answer 23

1mM

Question 24

What is the km of GLUT 4?

Answer 24

5mM

Question 25

Where is GLUT 1 found?

Answer 25

human erythrocyte, all the blood-brain etc barriers

Question 26

Where is GLUT 2 found?

Answer 26

liver, kidney, pancreatic B cell

Question 27

Where is GLUT 3 found?

Answer 27

brain

Question 28

Where is GLUT 4 found?

Answer 28

adipose tissue, skeletal muscle, heart muscle

Question 29

Where is GLUT 5 found?

Answer 29

intestinal epithelium, spermatoxia

Question 30

What is different about GLUT 4 and 5?

Answer 30

GLUT 4-insulin-sensitive transporter

GLUT 5- fructose transporter

Question 31

What bonds does Maltose have?

Answer 31

α-(1→4)

Question 32

What bonds does Sucrose have?

Answer 32

α-(1→2)

Question 33

What bonds does Lactose have?

Answer 33

β-(1→4)

Question 34

What bond does amylopectin have?

Answer 34

α-(1→6)

Question 35

What do salivary and pancreatic α-amylase have activity towards?

Answer 35

only those linked by α-(1→4) bonds

Question 36

where does the final digestion occur?

Answer 36

mucosal lining of the upper jejunum

Question 37

what gases lead to flatuance?

Answer 37

methane, carbon dioxide, hydrogen