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What are the physiological roles of carbohydrates?

Sources of energy
Energy storage
Structural roles
Cellular interaction
Cellular identification
Information transfer (DNA RNA)


What is the empirical formula of carbohydrates?

Where n > or equal to 3


What are the two major classes of carbohydrates?

Aldoses- have aldehyde groups CHO (double bonded O)
Ketoses- have ketose groups
A C attached to two CH2OH’s and a double bonded oxygen


Memorize the 6 common monosaccharide sugars



What are epimers?

Sugars that differ at a single chiral center (H and OH are switched around)

Ex: C3 epimer of _______
H and OH at third carbon are switched


What happens to carbohydrates of 5 carbons or longer in solution?

They tend to be cyclized
Wrap in a circle


What is the formation of the cyclical structure of carbohydrates a result of?

A reaction of alcohol with either:
- An aldehyde (aldoses) to form hemiacetal
- A ketone (ketoses) to form hemiketal

Look at diagrams on slide 8


What are the two forms of cyclized carbohydrates?

Six-membered sugar ring is a pyranose
Five-membered sugar ring is a furanose


What bonds form to create cyclized structures of carbohydrates?

The free hydroxyl of C-5 and the aldehyde group of C-1


What two stereoisomers are produced by C-1 in cyclizing?
(α and β)

Alpha and beta stereoisomers are produced
α is where the H is above the OH on C-1 on the very right of the molecule
β is where the OH is above the H on C-1 on the very right of the molecule

Alpha and beta are anomers of eachother

On slide 10


What is mutarotation?

Where the α and β configurations interconvert through a linear intermediate
Change in configuration

Diagram on slide 12


Is a carbohydrate is swapped from D to L how does that affect the α and β of the cyclized form?

It will change the α to β or vice versa

Ex: β-L-Fucose has H over OH on C-1

Do practice naming on slide 15


How do plants use glucosinate and myrosinase as defence?

The myrosinase acts on glucosinolate to produce glucose and isothiocyanate which has a sharp and bitter taste
This bitter taste functions to discourage herbivores from eating plant

Slide 16


How do reducing agents work with monosaccharides?

Monosaccharides can be oxidized by mild oxidizing agents like Iron and copper
When this happens the carbonyl group (CHO) is oxidized to a carboxyl group (COOH)

Allows for quantifications of sugars present in blood or urine


What is a gylcosidic bond?
What are the two types?

Primary structural linkage in all polymers of monosaccharides

O-glycosidic bonds occur through oxygen
N-glycosidic bonds occur through nitrogen


How do you name disaccharides?

You put both monosaccharides involved in the linkage together with their beta or alpha configurations and their ring types of either puran or Duran and in between you out the linkage (C1-C4, etc)


What is the reducing end of a polymer?

The end of the chain with a free anomeric carbon (carbon at end with O and H bonded


What generates higher order carbohydrate structures?

The action of glycosyltransferases
These use monosaccharides that are activated through linkage with UDP


When naming disaccharides, what do you put at the end of each individual monosaccharides name?

For the non reducing residue, you put “osyl” at the end
This is the monosaccharide you put first in the name
For the reducing sugar, you put “ose”
At the ends
This is the monosaccharide you put second in the name


What is the difference between galactose and glucose?

Galactose has the hydroxyl group above H on carbon 4 (far left)
Glucose has the hydroxyl group below H on Carbon 4 (far left)

Diagram on slide 22


What are some of the biological function of polysaccharides?

Energy storage, structural roles, cushioning and lubrication, etc


What are homopolysaccharides and heteropolysaccharides?

Homo- polymers containing a single type of monosaccharide
Hetero- polymers containing more than one type of monosaccharide

Both can be branched or unbranched
(Branched being a stacked section of sugars branching from main group)
Slide 24


How is glucose stored in plants compared to animals?

Plants- it’s formed in polymeric forms as starch
Animals- it’s formed in polymeric forms as glycogen

Start and glycogen are both heavily hydrated structures


What is starch?

A mixture of two molecules, amylose (unbranched) and amylopectin (branched)
Found in plants and fungi


Where is glycogen stored?

Structurally identical to amylopectin with higher frequency of branch points (10 residues)

It is stored in the liver and skeletal muscles of animals
Liver to power rest of body and skeletal muscle to power muscles
It’s present in all cells but most prevalent in muscle and liver


What is the structure of amylose and amylopectin?

Amylose- linear polymer of glucose residues through α(1-4) bonds
Amylopectin- consists of α(1-4) linked glucose residues with α(1-6) branch points every 24-30 residues

Diagram on slide 26


What does the greater frequency of branching allow for glycogen?

It allows for rapid mobilization in times of need for energy


What is cellulose?

Primary component of plant cells (fiber)
It is a linear, homopolysaccharide of glucose residues
Linear arrangement of β(1-4) glycosidic residues
Cannot be cut by amylase


What is chitin?

Primary component of hard exoskeletons (insects, lobsters)
Linear, homopolysaccharide of N-acetylglucosamine residues


What is the difference between cellulose and chitin?

The replacement of hydroxyl group at C2 with acetlyated amino group