carb overview

Carbohydrates are a special class of organic molecule that have which groups in it?

1. An alcohol(s)

2. Either an aldehyde or a ketone group

What is a sugar called?

A saccharide

A single saccharide is called what?

Monosaccharide

Two monosaccharides bonded together forms what?

Disaccharide

When 3-9 monosaccharides are linked in a chain together what is this called?

Oligosaccharide

When there’s more than 9 monosaccharides bound together, what is this called?

Polysaccharides (STARCHES)

When a carbohydrate contains a ketone group at the very end of the molecule, what is it called?

Ketose

When a carbohydrate contains an aldehyde group at the very end of the molecule, what is it called?

Aldose

How many carbons do carbohydrates usually contain?

3-7

(Triose, Tetrose, Pentose, hexose, heptose)

Larger, simple carbohydrates with at least 5 carbons have a natural tendency to do what?

Cyclize into a ring structure

What happens to the stability of a carbohydrate when it’s in a ring structure?

The carbohydrate becomes more stable

Can carbohydrates cyclize and de-cyclize back into linear form?

Yes

Carbohydrates serve what 4 important roles?

1. Energy source

2. Structural functions

3. Binding points

4. Signaling

What is the carbohydrates role as an energy source?

The metabolism of glucose to produce ATP

What is the carbohydrates role as a structural function?

Component of nucleic acids (DNA and RNA) and cell walls

What do carbohydrates serve as binding points for?

Proteins and cells

What is the carbohydrates a role in signaling?

Specific sugars presented on cell surfaces can produce particular biological responses between cells

In regards to a Fischer projection, are all naturally occurring monosaccharides D or L isomers?

D isomers

Linear aldose monosaccharides tend to form cyclic structures via what?

Via a chemical reaction between the aldehyde functional group of a molecule and the alcohol group on the same molecule

When an aldose monosaccharide forms a ring, what is this new functional group called?

A hemiacetal

Linear ketose monosaccharides tend to form a cyclic structure via what?

A chemical reaction between the ketone functional group of the molecule and an alcohol group on the same molecule

When a linear ketose monosaccharide forms a ring what is this new functional group called?

Hemiketal

What are three 6-carbon sugars (hexoses) that undergo glycolysis to form ATP and other energy rich compounds?

1. Glucose

2. Fructose

3. Galactose

What is glucose?

The universal fuel for human cells and the source of carbon for the synthesis of most other compounds in the body

What is fructose?

Known as the “fruit sugar” because it is the main sugar found in fruits

What is galactose?

A monosaccharide that binds with glucose to form the disaccharide lactose

What are ribose/deoxyribose?

5-carbon (Pentose) components of nucleotides for RNA/DNA structure

What is a Fischer projection?

A simplified drawing to represent 3D molecules in their OPEN chain form

In a Fischer projection what is coming towards you and what is curving away from you?

The functional groups come towards you

The carbon spine curves away from you

Which carbon in the Fischer projection determines if a carbohydrate is L or D isomer?

The last chiral carbon on the bottom of the chain

What, with the chiral carbon, determines if a carbohydrate is D or L isomer?

The position (left or right) of the hydroxyl group attached to the chiral carbon

What is the position of the hydroxyl group if the carbohydrate is a D isomer?

The hydroxyl group is to the right of the last carbon

What is the position of the hydroxyl group if the carbohydrate is an L isomer?

The hydroxyl group is to the left of the chiral carbon

What is chirality?

The property of a molecule that makes it non-superimposable on its mirror image

What makes a chiral carbon?

When the carbon is bonded to four different atoms or groups

Are almost all carbohydrates chiral?

Yes

Chiral molecules can have many sterocenters. What are sterocenter?

For the purpose of this lecture they are simply chiral carbons

Stereocenters result in multiple enantiomers. What are enantiomers?

Pairs of molecules that are exact mirror images of each other, but cannot be perfectly overlapped

Enantiomers are a special kind of isomer called what?

Stereoisomer

What is the 2ⁿ rule?

Calculates the maximum possible number of unique 3D shapes (stereoisomers) a molecule can have

(n=chiral carbons present)

If gluocse has 4 stereocenters, how many possible isomers of glucose are there?

16

What is the optical activity of enantiomers?

When a pure solution of one enantiomer tends to cause polarized light to rotate in equal but opposite directions

The rotary implication only holds true for which carbohydrate?

Glyceraldehyde

(+) and (-) are scientifically factual and used when?

When describing the optical activity of enantiomers

D and L carbohydrates are named based on what?

Their structure on a Fischer projection

What are the bonds between monosaccharides called?

Glycoside bonds

How are disaccharides formed?

From a reaction between the hemiacetal/hemiketal of one monosaccharide and the alcohol group of another monosaccharide

Why are disaccharides a condensation reaction?

Because water is one of the products

What two configurations can disaccharides be in?

Alpha or beta

Most carbohydrates that humans can digest contain, which kind of bonds?

Alpha glycosidic bonds

What are polysaccharides?

Polymers of monosaccharides

What structure can polysaccharides be in?

Can be in linear chains or branches

What are two common polysaccharides found in nature?

Starch and cellulose

Starch and cellulose are polymers of which molecule?

Glucose

Cellulose is found in what?

Plants

Cellulose is composed of which bonds?

Beta linkages

Are beta linkages digestible?

No

Starch is found in what?

Plants and animals

Starch is composed of what kind of bonds?

Alpha linkages

Are alpha linkages digestible?

Yes

What is glycogen?

Heavily branched form of starch found in the human body

Glycogen is the main form of what?

Storage of glucose

Is glycogen non-osmotic or osmotic?

Non-osmotic

What makes glycogen non-osmotic?

It can be stored in cells without disrupting the overall osmotic balance

Where is glycogen mainly stored?

Liver and muscles

What are glycosaminoglycans (GAGs)?

Repeating chains of disaccharides composed of glucose or galactose that have been modified

What is the polarity of GAGs?

Highly polar molecules that attract water

What do GAGs often serve as?

Structural components

What are GAGs linked together by?

A central linear protein core called a proteoglycan

What are 3 examples of GAGs

1. Hyaluronic acid

2. Chondroitin

3. Heparin

What does hyaluronic acid do and where is it found?

It acts as another structural function of binding collagen and is found in bones and joints

What does chondroitin do and when is it found?

It acts as another structural function of binding collagen and is found in bones and joints

What are glycoproteins?

Proteins that have been glycosylated (addition of sugars to a protein)

What 3 purposes do glycoproteins serve?

1. Immune system functions (innate and adaptive)

2. Structural purposes (collagen)

3. ABO blood group surface recognition of erythrocytes

Cell-cell signaling/recognition works via what?

Via glycoproteins presented on cell membranes

How is ATP formed?

When glucose, galactose, and fructose undergo glycolysis