Chapter 7

Question 1

What are the physiological roles of carbohydrates?

Answer 1

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

Question 2

What is the empirical formula of carbohydrates?

Answer 2

(CH2O)n

Where n > or equal to 3

Question 3

What are the two major classes of carbohydrates?

Answer 3

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

Question 4

Memorize the 6 common monosaccharide sugars

Answer 4

Aight

Question 5

What are epimers?

Answer 5

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

Question 6

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

Answer 6

They tend to be cyclized

Wrap in a circle

Question 7

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

Answer 7

A reaction of alcohol with either:

• An aldehyde (aldoses) to form hemiacetal
• A ketone (ketoses) to form hemiketal

Look at diagrams on slide 8

Question 8

What are the two forms of cyclized carbohydrates?

Answer 8

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

Question 9

What bonds form to create cyclized structures of carbohydrates?

Answer 9

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

Question 10

What two stereoisomers are produced by C-1 in cyclizing?

α and β

Answer 10

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

Question 11

What is mutarotation?

Answer 11

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

Diagram on slide 12

Question 12

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

Answer 12

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

Question 13

How do plants use glucosinate and myrosinase as defence?

Answer 13

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

Question 14

How do reducing agents work with monosaccharides?

Answer 14

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

Question 15

What is a gylcosidic bond?

What are the two types?

Answer 15

Primary structural linkage in all polymers of monosaccharides

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

Question 16

How do you name disaccharides?

Answer 16

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)

Question 17

What is the reducing end of a polymer?

Answer 17

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

Question 18

What generates higher order carbohydrate structures?

Answer 18

The action of glycosyltransferases

These use monosaccharides that are activated through linkage with UDP

Question 19

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

Answer 19

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

Question 20

What is the difference between galactose and glucose?

Answer 20

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

Question 21

What are some of the biological function of polysaccharides?

Answer 21

Energy storage, structural roles, cushioning and lubrication, etc

Question 22

What are homopolysaccharides and heteropolysaccharides?

Answer 22

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

Question 23

How is glucose stored in plants compared to animals?

Answer 23

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

Question 24

What is starch?

Answer 24

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

Question 25

Where is glycogen stored?

Answer 25

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

Question 26

What is the structure of amylose and amylopectin?

Answer 26

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

Question 27

What does the greater frequency of branching allow for glycogen?

Answer 27

It allows for rapid mobilization in times of need for energy

Question 28

What is cellulose?

Answer 28

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

Question 29

What is chitin?

Answer 29

Primary component of hard exoskeletons (insects, lobsters)

Linear, homopolysaccharide of N-acetylglucosamine residues

Question 30

What is the difference between cellulose and chitin?

Answer 30

The replacement of hydroxyl group at C2 with acetlyated amino group

Question 31

What are the difference in α and β linkages in terms of chain formation?

Answer 31

α forms hollow helical structure (compact accessible storage)
β forms long straight chains
(Rigid supportive high tensile strength)

Question 32

How are sugars related to blood group antigens?

Answer 32

Sugars are covalently linked to lipid molecules to form glycolipids
Glycolipids form blood group antigens

Diagram on slide 32

Question 33

What are glycoproteins compared to proteoglycans?

Answer 33

Glycoproteins- proteins with covalently attached sugars
Protein is largest component by weight
Proteoglycans- protein component is linked to a particular carbohydrate called glycosaminoglycan
Carbohydrate is biggest component by weight

Question 34

What do sugars attach to on proteins?

Answer 34

• the slide nitrogen of the side chain of an asparagine (N-linked)
• the hydroxyl oxygen of the aids chain of serine or threonine (O-linked)

Question 35

What is Erythropoietin (EPO)?

Answer 35

EPO is a glycoprotein that stimulates production of red blood cells
Glycosylation is essential for the biological action of EPO
Increases oxygen carrying capacity
Has three N-linked and O-linked glycosylations