Lecture 11 - Carbohydrates

Question 1

what are carbohydrates?

Answer 1

-sugar, saccharides

Question 2

what is a monosaccharide?

Answer 2

singel sugar molecules

Question 3

what are polysaccharides/glycans?

Answer 3

polymeric sugar

Question 4

carbohydrates are all _____

Answer 4

-polyalcohols

Question 5

is every carbon chiral?

Answer 5

yes

except C=O at the end of the chain

Question 6

why are sugars with 5 or 6 carbons most important biochemically?

Answer 6

-they can cyclize

Question 7

how do sugars cyclize?

Answer 7

-via the formation of hemiacetals or hemiketals into rings

Question 8

what is special about 5 or 6 member rings?

Answer 8

-almost no ring strain

Question 9

what are 5 atom ring sugars called?

Answer 9

furanose

Question 10

what are 6 atom ring sugars called?

Answer 10

pyranose

Question 11

in anomeric forms of cyclic sugars, why is one of the atoms always an O?

Answer 11

came from the attacking OH

Question 12

What happens to the original C=O during cyclization?

Answer 12

becomes -OH hanging off side of ring

Question 13

what are the two optical isomers?

Answer 13

-alpha (below)
-beta (above)
anomeric forms

Question 14

cyclic sugars are ____ in solution and there is only _____ between

Answer 14

• metastable
• slow interchange
• anomeric forms

Question 15

how can sugars be modified?

Answer 15

covalently

Question 16

what can glycosidic bonds be made into? how?

Answer 16

• an amine (N-linked) or alcohol (O-linked)

- via the anomeric carbon

Question 17

polysaccharides (glycans)
purpose:
ex:

Answer 17

• structural

- cellulose, chitin

Question 18

glycosaminoglycans
purpose:
ex:

Answer 18

• viscous or lubricating agent

- vitreous humor (eye)

Question 19

proteoglycans
purpose:
ex:

Answer 19

• structural

- cartilage

Question 20

peptidoglycans
purpose:
ex:

Answer 20

• structural

- bacterial cell walls

Question 21

glycoproteins
purpose:
ex:

Answer 21

• modifies protein properties

- most proteins are glycosylated

Question 22

how are disaccharides formed?

Answer 22

-when a glycosidic bond is formed between one sugar (via its anomeric carbon) and one -OH group on another sugar

Question 23

whate are teh two anomeric forms of disaccharides?

Answer 23

1. lactose = galactose + glucose

2. sucrose = glucose + fructose

Question 24

what is cellulose?

Answer 24

the key structural fiber for plants

Question 25

what are examples of polysaccharide?

Answer 25

cellulose
chitin
starch
glycogens

Question 26

what is chitin?

Answer 26

-major component of the exoskeleton of insects, mollusks, arthropods

Question 27

what is starch?

Answer 27

• storage polysaccharide found in chloroplasts

- mixture of amylose + amylopectin

Question 28

what are glycogens?

Answer 28

• storage polysaccharides in animals

- more heavily branched than amylopectin

Question 29

what is an example of a glycoaminoglycan?

Answer 29

-hyaluronic acid

Question 30

what are the characteristics of hyaluronic acid?

Answer 30

• repeats of disaccharide containg a C6 uronic acid and a N-acetyl-glucosamine
• heavily anionic, forming viscous gels

Question 31

where are proteoglycan complexes found?

Answer 31

cartilage

Question 32

where are peptidoglycans found?

Answer 32

bacterial cell walls

Question 33

many proteins are modified by _______

Answer 33

glycosylation

Question 34

how does N-link modification work?

Answer 34

via Asn

Question 35

how does O-linked modification work?

Answer 35

-via Ser or Thr

Question 36

what do oligosaccharides do on cell surface?

Answer 36

-mediate recognition

Question 37

what is the function of oligosaccharides linked to proteins/lipids exposed on cell surface?

Answer 37

-serve as cell markers for recognition purposes

Question 38

What are oligosaccharides on cell surface recognized as?

Answer 38

antigenic determinants