Biochem - Carbohydrate Digestion

Question 1

How many units make up:

1. monosaccharides
2. oligosaccharides
3. polysaccharides

Answer 1

Question 2

Name the sugar

Answer 2

mannose

Question 3

name the sugar

Answer 3

D-Ribose

Question 4

name the sugar

Answer 4

D-Galactose

Question 5

name the sugar

Answer 5

D-Glucose

Question 6

name the sugar

Answer 6

D-Fructose

Question 7

Maltose

1. What two monosaccharides compose maltose
2. How are they linked together
3. Where is maltose derived from

Answer 7

1. 2 alpha-D-glucose
2. alpha 1,4 glycosidic link
3. maltose is derived from starch

Question 8

Sucrose

1. What two monosaccharides compose sucrose
2. How are they linked together

Answer 8

1. alpha-D-glucose + beta-D-fructose
2. Glc-alpha-1-2Fru

Question 9

Lactose

1. What two monosaccharides compose Lactose
2. How are they linked together

Answer 9

1. Beta-D-Gal + Alpha-D-Glc
2. Beta-1,4 glycosidic link

Question 10

Starch

1. is this a homopolysaccharide, heteropolysaccharide, or a glycoconjugate?
2. where is it commonly found?
3. How are the components linked together?
4. name the two types and how they are different

Answer 10

1. homopolysaccharide
2. main storage of plant sugar
3. linked with alpha glucose
4. Amylose - 1,4 glc links - helical configuration
   Amylopectin - 1,4 glc & 1,6 glc - branched structure

Question 11

Glycogen

1. is this a homopolysaccharide, heteropolysaccharide, or a glycoconjugate?
2. where is it commonly found?
3. How are the components linked together?

Answer 11

1. homopolysaccharide
2. main glc storage form in animals
3. 1,4 and 1,6 alpha

Question 12

Cellulose

1. is this a homopolysaccharide, heteropolysaccharide, or a glycoconjugate?
2. where is it commonly found?
3. How are the components linked together?
4. Why can’t humans digest this?

Answer 12

1. homopolysaccharide
2. chief constituent of plant cell walls
3. linked by Beta-1,4 linkage
4. Humans lack cellulase, which is needed to hydrolyze Beta-1,4 bonds

Question 13

Heteropolysaccharides

1. Are these branched or unbranched?
2. List the common components of heteropolysaccharides
3. What are the most abundant heteropolysaccharides int he body?
4. Describe the charge of the most abundant heteroploysaccharides

Answer 13

1. long unbranched containing a repeating disaccharide unit
2. Disaccharide unit of a modified sugar and a uronic acid
   Such as: N-acetylgalactosamine (GalNAc) or N-acetylglucosamine (GlcNAc)
   &
   Glucuronate or iduronate
3. Glycosaminoglycans (GAGs)
4. highly negative charged molecules

Question 14

Hyaluronates, chondroitin 4- and 6-sulfates, keratan sulfates, dermatan sulfates, and heparin & heparan sulfates are examples of….

Homopolysaccharides
Heteropolysaccharides

Glycoconjugates

Answer 14

Heteropolysaccharides

Question 15

What are the three main types of glycoconjugates?

Answer 15

Proteoglycans

Glycoproteins

Glycolipids

Question 16

1. Where are proteoglycans found?
2. Vaguely describe their composition

Answer 16

1. Found in the extracellular matrix
2. GAG chains linked to core porteins

Question 17

Give some examples of glycoproteins

Answer 17

antibodies, blood types (A, B, AB, O), hormones (FSH, LH, TSH)

Question 18

Where are some prominent places that glycolipids reside?

Answer 18

nerve tissues (brain), cell membranes, gangliosides

Question 19

1. How are monosaccharides absorbed by the intestinal lining?

Answer 19

facilitated diffusion

Question 20

Maltase

1. What type of bond does it cleave?
2. What is its substrate
3. What are its products?

Answer 20

1. alpha 1,4 bonds
2. malto-oligosaccharides
3. glucose

Question 21

Sucrase

1. What type of bond does it cleave?
2. What is its substrate
3. What are its products?

Answer 21

1. Hydrolyzes sucrose and maltose
   alpha 1,4(glc-glc) and alpha-beta 1,2(glc-fru)
2. sucro and malto-oligosaccharides
3. glucose and fructose

Question 22

Isomaltase

1. What type of bond does it cleave?
2. What is its substrate
3. What are its products?

Answer 22

1. alpha 1,6 bonds (glc)
2. alpha-dextrins
3. glc

Question 23

Lactase

1. What type of bond does it cleave?
2. What is its substrate
3. What are its products?

Answer 23

1. Beta-glycosidases
2. Lactose
3. Glc and Gal

Question 24

Trehalase

1. What type of bond does it cleave?
2. What is its substrate
3. What are its products?

Answer 24

1. Trehalose
2. Trehalose
3. glc

Question 25

Monosaccharide absorption Describe how monosaccharides are absorbed? 1. Which ion-pump makes this possible and where is it located? 2. Describe how the gradient allows glucose and galactose to asborb 3. How does fructose absorb 4. How do all 3 monosaccharides enter the blood stream?

Answer 25

1. The Na+/K+ pump; It is pumps Na out of the intestinal cell and into the interstitial space 2. Na/K pump creates a strong gradient for Na to enter the intestinal cell from the lumen. glc and gal symport with sodium 3. facilitated diffusion 4. exit intestinal cell across the basolateral membrane via facilitated diffusion on the GLUT2 transporter

Question 26

Describe where the following glucose transporters are found and briefly describe their function. 1. GLUT 1 2. GLUT 2 3. GLUT 3 4. _GLUT 4_ 5. GLUT 5

Answer 26

1. Many tissues; basal transport and BBB 2. Liver, islet beta cells, kidney, small intestine (GI), low affinity, high capacity [perhaps **2** limit absorption] 3. Neurons; basal transport in neurons 4. _skeletal muscle, heart, fat; insulin responsive transport_ 5. small intestine, sperm, testes; fructose transport