Lecture 19

Question 1

State and describe the 3 types of isomers

Answer 1

Constitutional: the order of atoms changes

Configurational: have chiral bonds (this is how they form diastereomers and enantiomers)

Conformational: have reversible rotation changes

Question 2

What type of isomer are tautomers?

Answer 2

tautomers are constitutional isomers

Question 3

What are fisher projections? where does the carbon numbering on these projections begin?

Answer 3

linear drawings of carbohydrates

Carbon numbering starts at the carbonyl (Double bond to O) end of the aldose

Question 4

Stereoisomers have the same _____ but different _____ ______. State the 2 “types of isomers” that are considered to be stereoisomers.

Answer 4

connectivity

spatial organizations

Both Configurational and Conformational isomers are stereoisomers
(constitutional isomers are the only type of isomer that is not considered to be a stereoisomer)

Question 5

What type of carbon do configurational isomers feature?

Answer 5

chiral carbons

Question 6

Compare enantiomers (what do these create) and diastereomers
(include similarities)

Answer 6

Enantiomers: the mirror images that occur at ALL chiral centers in a structure
These occur at all chiral carbons and Form D and L forms of the same molecule

Diastereomers: are NOT mirror images overall
These require multiple chiral centers)

Both are configurational isomers

Question 7

Define Haworth Projections

Answer 7

Haworth Projections: the cyclical versions of carbohydrates (another method of drawing their structures)

Question 8

Compare anomers and Epimers (differences and similarities)

Answer 8

Anomers: differ at the anomeric carbon ONLY (alpha vs beta)

Epimer: differs ANYWHERE besides the anomeric carbon (same alpha or beta but different somewhere else)

Both are diastereomers

Question 9

Write out the 7 steps in this lecture

Answer 9

7 steps

Question 10

True or False:

Conformational Isomers have irreversible rotation changes. explain.

Answer 10

FALSE

Conformational isomers have REVERSIBLE rotation changes

Question 11

In conformational isomers, what determines if the structure will be “boat or chair” form? what term describes this influence?

Answer 11

The larger functional groups on the molecule

This is an example of steric hindrance

Question 12

What is formed when one or more hydroxyl is replaced on a monosaccharide?

Answer 12

glycosides

Question 13

Describe how following modified chemical modifications are achieved if you start with an unmodified monosaccharide:

Fucose:

Esters:

Oxidation and REduction:

N-linkages:

O-linkages:

Answer 13

Fucose: weird one

Esters: phosphorylation

Oxidation and REduction: Alcohols

N-linkages: AA’s and nucleotides

O-linkages: Methylation/Toxins

Question 14

State the 2 tautomers that we need to know from this lecture

Answer 14

Ribose (aldose)

Ribulose (ketose)

These are the same number of atoms but Ribose has a =O group at C1, while Ribulose has a =O group at C2

Question 15

Define Anomeric carbon

Answer 15

Anomeric Carbon: the Carbon atom that is 1 position clockwise from the Carbonyl

Question 16

When converting from fisher to haworth structures, what determines whether the structure is considered to be in the alpha or beta configuration?

Answer 16

Alpha configurations have the OH that used to be the C=O, pointing DOWN

Beta configurations have the OH that used to be the C=O, pointing UP

Question 17

State the galactose derivative that is the only L-monosaccharide that is made and used by mammals

Answer 17

Fucose (“its the weird one”)

Question 18

What monosaccharide modification adds a negative charge and forms important reactive intermediates in carbohydrate metabolism

Answer 18

Phosphorylation

Question 19

True or False:

ATP is a phosphorylated sugar. explain.

Answer 19

True

ATP is ADP (sugar) with another phosphate on it

Question 20

The monosaccharide modifications of oxidation and reduction are very similar in that they both occur at the carbonyl. Which of these creates acids, lactones, and alditols? Which of these can create sorbitol and cause cataracts and which is used in diabetes urine tests?

Answer 20

Oxidation of reducing sugars at the carbonyl makes acids and lactones
Oxidation is used in diabetes urine tests

Reduction at the carbonyl makes alditols
Reduction can create sorbitol and cause cataracts

Question 21

What type of modified monosaccharide is found in branched polysaccharides? how is this modified monosaccharide formed?

Answer 21

Amino sugars

Amino sugars are formed via N-linkages

Question 22

Describe the type of linkage that Methylation is formed with. How does this compare to amino sugars?

Answer 22

Methylation is achieved through O-linkages

This uses the same reaction that is used to create polysaccharides in the formation of Amino sugars, HOWEVER, Methylation does not use a sugar

Question 23

State the 8 essential Monosaccharides (4 regular, 1 oddball, 3 Amino sugars)

Answer 23

"regular":
D-Glucose
D-Galatose
D-Mannose
D-Xylose

“oddball”:
L-Fucose

Amino Sugars:
GlcNAc
GalNac
Sialic Acid

Question 24

For the following disaccharide, state the 2 monosaccharides that are linked in order to form it:
(indicate which positions link together)

Maltose

Answer 24

Maltose = Alpha-D-Glucose (C1 position) + Alpha-D-Glucose (C4 position)

Question 25

For the following disaccharide, state the 2 monosaccharides that are linked in order to form it:
(indicate which positions link together)

Lactose

Answer 25

Lactose = Beta-D-Galactose (C1 position) + Beta-D-Glucose (C4 position)

Question 26

For the following disaccharide, state the 2 monosaccharides that are linked in order to form it:
(indicate which positions link together)

Sucrose

Answer 26

Sucrose = Alpha-D-Glucose (C1 position) + Beta-D-Fructose (C2 position)

Question 27

State the 3 roles of polysaccharides

Answer 27

1. Glucose Storage
2. Structure
3. Protein Diversity

Question 28

Compare Amylopectin/Glycogen with Amylose in terms of their structure. Also include what role of polysaccharides they are most involved in

Answer 28

Amylopectin/Glycogen are branched

Amylose is unbranched

Both of these are involved in the glucose storage role of polysaccharides

Question 29

Name the 2 polysaccharides that are involved in the “structure” role of polysaccharides. Which of these has alpha and beta bonds and which of these is considered the “universal structural polysaccharide?

Answer 29

Cellulose: Has alpha bonds (forms a helical structure) and beta bonds (forms a beta sheet looking structure
(these bonds all occur at once to give it it’s rigidity)

Chitin: is considered the universal structural polysaccharide

Question 30

N-links and O-links contribute to the role of protein diversity that polysaccharides are involved in. What AA’s do these 2 linkages lead to?

Answer 30

N-Linked = Asn only

O-linked = Ser or Thr

Question 31

Compare Glycoproteins, Glycosaminoglycans, and Mucins in terms of their “protein to sugar composition” and locations in the body they are found.

Answer 31

Glycoproteins: Protein > Sugar (by weight)
Found on membrane proteins (in cell adhesion) and on soluble proteins (in cell signaling)

Glycosaminoglycans: Protein < Sugar (by weight)
In repeating disaccharide units to form the sugar component of proteoglycans

Mucins: Protein < Sugar (by weight)
In mucus to provide lubrication (protection + hydration)

Question 32

What type of polysaccharide decorates cell membranes and are used to recognize self/non-self cells? Give an example of this in action.

Answer 32

Glycolipids

A, B, and O antigens are just sugars added to blood cell surfaces

Question 33

How are altidols formed from monosaccharides? What about the process that makes acids and lactones?

Answer 33

reduction at the carbonyl makes altidols

Oxidation at the carbonyl makes acids and lactones