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What is the general formula for a carbohydrate?
Cx(H2O)y
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What is the basic unit of a carbohydrate?
Simple sugar or monosaccharide
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What does the name 'simple sugar' mean?
Will not undergo acid hydrolysis to form smaller units
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What are 2 common examples for simple sugars?
D-glucose and D-fructose
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Both glucose and fructose also exist as which other structure of compounds?
Cyclic
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What is the definition of a dissacharide?
2 simple sugars linked by a covalent glycosidic bond
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What is a covalent glycosidic bond?
A specific type of ther linkage (R-O-R) between the OH on the anomeric carbon of a sugar to any other alcohol (usually another sugar molecule)
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Where does sucrose come from?
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What is sucrose made up of?
Glucose and fructose
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What is lactose made up of?
Glucose and galactose
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Where does maltose come from?
Starch enzymatic hydrolysis
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What is maltose made up of?
2 glucose molecules
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What is the definition of an oligosaccharide?
3-10 monosaccharides linked together
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What is raffinose made up of?
Trisaccharide of galactose, glucose and fructose
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What is stachyose made up of?
A tetrassacharide of glucose, fructose, and galactose
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What is a common use of oligosaccharides?
Used as prebiotics, or promoters of desirable intestinal flora
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What are 2 examples of prebiotics?
- Oligofructose (2-8) units
- Inulin (9-64) units
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What are polysaccharides?
- Longer chain length polymers, found in nature
- A variety have food applications
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What are some examples of polysaccharides?
- Starch
- Cellulose
- Glycogen
- Pecton
- Xanthan gum
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What is the role of carbohydrates in nature?
- Energy sources as starch for germination of seeds
- Structural components as cellulose and hemicellulose in plants (including trees)
- Ready supply of energy as mono and disaccharides
- Short term supply of energy in muscles (as glycogen)
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What are mono and disaccharides used for in food functionality?
- Sweetening agents
- Coloring agents (caramel color)
- Viscosity enhancers
- Flavor production (caramellization, Maillard rxn)
- Flavor carriers (plated flavors, like vanilla on sugar)
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What are oligosaccharides used for in food functionality?
Prebiotics
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What are polysaccharides used for in food fuctionality?
- Thickening and/or gelling agents
- Emulsion stabilizers
- Water holding/binding agents
- Production of edible films
- Encapsulation of flavors
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How are carbon chains numbered in sugars?
From the carbonyl end down
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The C3 to C7 portions of monosaccharides are known as what?
Polyhydric alcohols
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What is the carbonyl group of a monosaccharide?
An aldehyde or ketone
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What is the simplest monosaccharide?
Glyceraldehyde
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What is the absolute reference to determine D or L configuration of sugars?
Glyceraldehyde
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Why was glyceraldehyde chosen to be the reference compound for determining D and L configuration?
- It has only one chiral carbon
- Most sugars have more than 1 chiral carbon
- The D or L designation of sugars is based solely on the configuration of the n-1 carbon, i.e. on the carbon one before last, when counting from the carbonyl group
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What are enantiomers?
Mirror images, or any D vs. L configuration of the same sugar
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What are epimers?
- Changes at any carbon other than the n-1 carbon, for example for the same molecular formula
- (As at C2 in D glucose vs D mannose)
- All epimers are considered different sugars
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How are monosaccharides classified?
May be classified as to chain length and functional group type
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What are ketoses?
6C ketones, like fructose
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What are aldohexoses?
6C aldehydes, like glucose
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How are monosaccharides generally represented for simplicity?
- As linear molecules
- In reality (both in crystals and, predominantly, in solution) they are cyclic
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What do sugars form to become cycles?
Hemiacetals and hemiketals
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How does the chair form of beta glucose form?
- The double bond oxygen becomes an alcohol
- The alcohol oxygen becomes an ether
- C1 becomes the center of a hemiacetal (A carbon wtih both an ether and alcohol on the same carbon)
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How is cycle closure catalyzed?
By an acid
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What is the anomeric carbon?
The new chiral carbon formed at C1 where the cycle closes
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What are the alpha and beta forms of monosaccharides called?
Anomers
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What happens when a monosaccharide is dissolved in solution?
A dynamic equilibrium is set up between the 3 possible forms of the monosaccharide (open chain, alpha anomer, beta anomer)
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What is mutarotation?
Changes in optical rotation, when a pure type of sugar is dissolved in water
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What does mutarotation result from?
- the opening of one form, coming to equilibrium with the opposite anomer via the open chain form
- it may crystallize into the 5 member ring or into the 6 member ring
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What is the breakdown of glucose equilibria?
- 62% alpha pyranose
- 37% beta byranose
- <1% open chain
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What is fructos mutarotation like?
A 5 member ring (furanose)
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In general, 6 carbon aldoses tend to form which cyclic rings in mutarotation?
Pyranose rings
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In general, 6 carbon ketoses tend to form which cyclic rings in mutarotation?
Furanose rings
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The crystalline form of simple sugars is always what?
Cyclical
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The aldehyde group on aldose is a strong agent for what?
Reducing
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All monosaccharides are which kinds of sugars?
Reducing sugars
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What is a reducing sugar?
Capable of reducing metal ions and being oxidized to carboxylic acids (redox reaction)
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What does Fehling's reagent react with?
Only reacts with free aldehyde groups (showing presence of reducing sugars)
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Why is fructose considered a reducing sugar?
- Fructose is a ketose, thus no free aldehyde group
- Still considered a reducing sugar since it goes through a rearrangement when in basic conditions (enolization)
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How is reducing power of a sugar lost?
- If the OH on the anomeric C is covalently bound to another group
- The glycosidic link is formed, and the cycle cannot open up anymore, thus no free aldehyde can be regenerated
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Is sucrose a reducing sugar?
NO - due to its glycosidic bond, where both anomeric carbons are tied up in making the bond
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Is maltose a reducing sugar?
Yes
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Is lactose a reducing sugar?
Yes
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