14 - Carbohydrates Flashcards Preview

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Flashcards in 14 - Carbohydrates Deck (19):
1

What is the most abundant biomolecule in nature?

Carbohydrates

2

What are four cellular functions of carbohydrates? (broadly)

Energy
Structure
Communication
Precursor for other biomolecules

3

Carbohydrates are a direct link between ____ and ____

Solar energy and chemical bond energy

4

What is the most basic component of a carbohydrate (eg. the lowest molecular formula)

Can be thought of as a carbon and H2O (CH20)

5

What is a monosaccharide

Aldehyde or ketone derivatives of straight chain polyhydroxyalcohols containing a minimum of 3 C atoms

6

How can different monosaccharides be differentiated?

By their carbonyl functional group (eg. aldehyde or ketone, aldoses and ketoses)

Or by number of C atoms (eg. triose, nonose etc.)

Put together you can have things like aldotrioses

monosaccharides are also in D or L forms (stereoisomers), the D form is much more common than L.. By convention the assymetric carbon most distal from the carbonyl group (O=C-H) gives the D or L notation.

7

What are the names of carbohydrates with different C numbers? (3 to 9)

A hint, ribose is a pentose

Triose
tetrose
pentose
hexose
heptose
nonose

8

What is the organic chem equivalent for D and L in monosaccharides?

D = R
L = S (think left)

9

What is the difference between enantiomer and diastereomer monosaccharide stereoisomers?

Enantiomers are exact mirror images shown in Fischer diagrams, diastereomers are not complete mirror images.

10

What are epimers?

Stereoisomers that differ in arrangement at a single chiral carbon. An example is D-glucose and D-galactose. D-mannose is a epimer to D-glucose as well, but not to D-galactose

11

How do cyclic monosaccharides occur and what are two types are made?

When a hydroxyl group in a sugar reacts with the aldehyde or ketone groups. They form either:

hemiacetals (aldehyde + OH)
hemiketals (ketone + OH)

12

What is the anomeric carbon atom?

It's the chiral carbonyl carbon in a cyclic sugar. The anomeric carbon can either be α or β, depending on if the hydroxyl group is on the right/down (R) or the left/down (L)

On Haworth structures (showing ring as 2D, not 3D like in conformational structures) the hydroxy group is down in α and up in β

13

What kind of rings are formed in monosaccharide cyclization? (2 types)

All rings have an oxygen in them, the carbon clockwise of the oxygen is the 1' anomeric carbon.

Furan rings have 5 members (4 C and 1 O)
Pyran rings have 6 members (5 C and 1 O)

The monosaccharide names for these two types are furanose and pyranose

14

Converting linear depiction of cyclical sugars to cyclical.

The whole thing 'timbers' down, but there's a catch, groups depicted on the right point up and groups depicted on the left point down.

15

Conformation of the pyranose rings

The pyranose ring is like a cyclohexane except it hase an O instead of a 5' C. It can be in boat or chair conformation, if the substituents are in certain position, steric crowding can occur in the boat position.

16

The anomeric carbon is α/β when..?

The anomeric carbon is alpha or beta depending on if it's D or L.

If it is D, then it is α when the OH group on the 1' C is pointing opposite of the CH2OH at the end (eg. at C6), when OH is pointing down

β in D sugars when the OH group is pointing up

α in L when OH pointing up
β in L when OH pointing down

D, alpha down, beta up
L, alpha up, beta down

17

What is mutarotation?

Mutarotation is when the alpha and beta forms of monosaccharides are readily interconverted when dissolved in water. it is spontaneous and at equilibrium in water with furanose and pyranose ring structures. The open chain structure can participate in redox reactions

18

What does Benedict's reagent test for?

Benedicts reagent tests for reducing sugars, but will only detect monosaccharides because these can turn linear and reduce the copper in Benedict's. All aldoses and ketoses can react, aldoss because they can form open chain, and ketoses can reduce because of isomerization.

Reduction of copper causes colour change in solution

19

What are amino sugars?

In amino sugars a hydroxyl group (usually on carbon 2) is replaced with an amine group