Carbohydrate Theory Flashcards

1
Q

Generally, what is a carbohydrate’s chemical structure?

A
  • a polyhydroxy aldehyde (R-CH=O) or ketone (R-CR’=O)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the simplest aldehyde-based carb?

And what are aldehyde-based carbs called generally?

A

glyceraldehyde

  • glycerol w/ one end OH replaced by =O
  • known as aldoses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is the simplest ketone-based carb?

And what are ketone-based carbs called generally?

A

dihydroxyacetone

  • glycerol w/ middle OH replaced by =O
  • known as ketoses
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How are carbs generally named based on the number of carbons they contain?

A

triose - 3 C

**tetrose **- 4 C

pentose - 5 C

hexose - 6 C

etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How can L or D configurations be determined via a simple, 2D

backbone-style carb structure?

What configuration are most carbs in nature?

A

Look at the last chiral carbon in the chain.

The position of the functional group (OH) on this carbon determines L or D.

Most are D in nature.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How would a 6 C aldehyde-based carb be named?

An 8 C ketone-based carb?

A

Aldohexose

Keto-octose

etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How is D-Galactose different from D-Glucose?

What does this make it in relation to glucose?

How can its structure be rememberd?

A
  • swapped OH position on C4 (left instead of right)
  • this makes it the 4-epimer of glucose
  • the OHs kind of make a G shape (according to Sipeki)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is an epimer?

A
  • an isomer that differs in configuration from its pair epimer at only one stereocenter
  • ALL other stereocenters, if there are any, are the same
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is mannose in relation to glucose?

A

a 2-epimer

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does reduction of a carb consist of?

What is the product?

A
  • aldehyde or ketone is reduced into primary or secondary alcohol, respectively
  • in other words =O becomes -OH and -H
  • makes a sugar alcohol
    ex: glucose/fructose > sorbitol
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does a sugar oxidation consist of?

What does it make (3 examples via 3 diff oxidations) ?

A
  • generally a group that has either only -OH or =O gets BOTH and becomes carboxylic
  • 1st group = -aldonic acid
  • last group = -uronic acid
  • both groups = -aldaric acid
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How is fructose different from glucose?

Using general nomenclature, what does this make it?

A
  • the =O is on C2 via a spontaneous migration
  • this makes it a ketohexose (rather than aldo-)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are some examples of important sugar alcohols and their functions in nature?

A

**ribitol **is a component of riboflavin (vit B2)

**sorbitol **is used as a sweetener for diabetics

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are some important natural sugar acids and their functions?

A

**D-glucuronic acid **and uronic acid are mucopolysaccharide components

L-ascorbic acid is vitamin C

D-glyceric acid is important to glycolysis and O2 binding in Hb

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Why don’t carbohydrates exist in the open chain form in which they are often represented?

A
  • because aldehyde and ketone groups are quite reactive
  • tend to form rings with other Os in the chain
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the two groups which bond to form the ring structure of an aldose?

And what is this kind of bond called?

A

the aldehyde and an alcohol

forms a hemiacetal

17
Q

What two groups bond to form the ring structure in ketoses?

What is this bond called?

A

ketone bonds with hydroxyl

forms hemiketale

18
Q

What is mutarotation?

A

a change in optical rotation due to shifts in equilibrium ratios of two anomers

19
Q

What is an anomer?

How are anomers denoted in chemical structure names?

A

carbohydrate epimers that differ specifically at the glycosidic OH

  • ⍺ means OH is ‘up’ (or same position as the ‘D’ OH)
  • β means OH is ‘down’ (or same position as ‘L’ OH)
20
Q

Why is beta-D-glucose the more stable than alpha?

A

all its OH groups are equatorial in chair conformation

21
Q

In what way does glucose isomerism change from open-chain to ring structure?

A
  • addition of a 5th chiral center at the aldehyde C
  • this means anomerism … ⍺ and β
22
Q

What are the general names for the two most stable carbohydrate ring structures?

A

Pyranose - 6 atom ring with one O, characteristic of aldohexoses

Furanose - 5 atoms, one O, from pentoses + ketohexoses

23
Q

What are the rules for drawing carbohydrate ring representations?

A
  1. O in ring is at top right for pyranoses, top for furanoses
  2. OH groups to right of open chain form are drawn below ring plane
  3. CH2OH group is written over ring plane for D, under for L
24
Q

What are reducing vs. non-reducing disaccharides?

A

reducing - have a free glycosidic OH group

non-reducing - no free glycosidic OH (only sucrose)

25
Q

What is glycogen?

What feature of a disaccharide unit of glycogen forms its backbone?

It contains two kinds of bonds between its monomers…what are they?

Why does the body store glycogen and not free monosaccharides?

A
  • a highly branched storage carb of many glucose units
  • axial groups of alpha-D-glucose form helical “trunk” of glycogen
  • 1-4 glucose bonds make up “trunk”, 1-6 glucose bonds make up “branches”
  • its single free glycosidic OH end makes it unreactive and it has lower osmotic effect than free monomers
26
Q

What are the two important pentoses in nucleic acids?

A

Beta-D-Ribose - RNA (shown below)

Beta-D-2-Deoxyribose - DNA (ribose minus the O on C2)