Chapter 7 Definitions/Concepts

Question 1

Carbohydrates

Answer 1

Structural and protective unit of cell walls of bacteria and plants, connective tissue of animals, and participate in recognition and adhesion between cells. Can be covalently attached to proteins or lipids.

Question 2

Polysaccharide

Answer 2

20 or more monosaccharide units.

Question 3

Monosaccharide Characteristics

Answer 3

Soluble in water, taste sweet and form colorless crystalline structures. Contain an unbranched carbon chain that can be an open-chain or closed-cyclic.

Question 4

Closed-cyclic bond

Answer 4

Carbon of the carbonyl forming a bond with one of the hydroxyl oxygens.

Question 5

Aldose

Answer 5

Carbonyl group is found at the end of the unbranched carbon chain forming an aldehyde.

Question 6

Ketose

Answer 6

Carbonyl found at any position other then the end, forming a ketone.

Question 7

Monosaccharide Composition

Answer 7

Composed of at least three carbons. They all contain one or more asymmetric carbon except ketotriose.

Question 8

Monosaccharide Stereoisomers

Answer 8

Determined by the hydroxyl group on the chiral carbon furthest away from the carbonyl. The D form is more common for carbohydrates.

Question 9

L Stereoisomers

Answer 9

Are not as common among carbohydrates. Act more like fiber because in humans there is not was to facilitate transfer into cells.

Question 10

D-Ketoses

Answer 10

Four and five carbon ketoses are named inserting a “-ul” into the name of the corresponding aldose. All carbonyls are on the 2 carbon.

Question 11

Cyclic Monosaccharides

Answer 11

Aldotetroses and all monosaccharides with five or more carbons occur predominately as cyclic structures. Through aldolcondensation they form either a hemiacetal or hemiketal resulting in an additional chiral carbon.

Question 12

Chiral Carbon Transformation Through Aldolcondensation

Answer 12

When a hemiketal or hemiacetal is formed it forms an additional chiral carbon that can be either alpha or beta. Alpha if the hydroxyl is pointing down and beta if it is pointing up.

Question 13

Pyranoses

Answer 13

Six membered ring structure, can be formed by aldoses as well. Exists in two chair conformations. Boat conformation is not usually seen because of bulky substituents.

Question 14

Furanoses

Answer 14

Aldohexoses form a furanose. A five membered ring. Not as stable as the pyranoses.

Question 15

Monosaccharide Reducing Agents

Answer 15

Monosaccharides with a carbonyl carbon are capable of reducing other species at the same time as they are being oxidized.

Question 16

Non-Reducing Sugars

Answer 16

Some disaccharides that form linkages at the anomeric carbon to prevent the interconversion to the linear form.

Question 17

Glycosidic Bonds

Answer 17

Formed between the anomeric carbon and another atom from another molecule. In disaccharides the anomeric carbon is usually linked to an O from another sugar.

Question 18

Polysaccharides

Answer 18

Can be homo or heater. Form linear branched chains. Don’t have a definite molecular weight because there is no specific stoping signal to end synthesis.

Question 19

Homopolysaccharides As Fuel Stores

Answer 19

Starch- fuel storage in plants, found in granules.
Glycogen- fuel storage in animals, found in granules in liver and muscle.
Dextrans -fuel storage in bacteria and yeast..

Question 20

Strach

Answer 20

Two types, amylose and amylopectin.

Question 21

Amylose

Answer 21

Long and unbranched, D-glucose connected by alpha 1-4 linkages

Question 22

Amylopectin

Answer 22

Long and branched, D-glucose connected by alpha 1-4 linkages and alpha 1-6 linkages at branch points.

Question 23

Dextrans

Answer 23

D-glucose chains connected by alpha 1-6 linkages and all have alpha 1-3 branches. Some also have alpha 1-2 or 1-4 branches.

Question 24

Glycogen

Answer 24

More highly branched then amylopectin. When used one monosaccharide is removed from one of the branched non-reducing ends.

Question 25

Homopolysaccharides As Structural Components

Answer 25

Cellulose and Chitin

Question 26

Cellulose

Answer 26

Found in plant cell walls. Linear unbranched structures with beta 1-4 linkages. No enzyme to break bond, can't be used as fuel source.

Question 27

Chitin

Answer 27

Found in exoskeletons from anthropoids composed of beta 1-4 linkages but no with D-glucose.

Question 28

Polysaccharide Sterics

Answer 28

Free rotation around the glycosidic bonds hindered by hydroxyl groups. Hydrogen bonding on the hydroxyl groups direct the 3D structure.

Question 29

Starch Structure

Answer 29

The most stable conformation of amylose is a tight helix stabilized by hydrogen bonds. Has 60 degree angles creating a left-handed helix with 6 residues per turn.

Question 30

Heteropolysaccharides As Structure

Answer 30

Peptidoglycan and Agar

Question 31

Peptidoglycan

Answer 31

Found in bacteria cell walls. Alternating NAM and NAG beta 1-4 linkages cross linked by short polypeptides with L and D stereochemistry.

Question 32

Lyoszyme

Answer 32

Catalyzes the breakdown of heteropolysaccharides.

Question 33

Agar

Answer 33

In some red algae, composed of L and D galactose with C3-C6 ether linkages with branched and unbranched components.

Question 34

Heteropolysaccharides in the Extracellular Matrix

Answer 34

Found in extracellular space with fibrous proteins in an interlocking meshwork. Called glycosaminoglycans and are linear with repeating disaccharide units.

Question 35

Hyaluronate

Answer 35

Most common glycosaminoglycan found in joint fluid, cartilage and tendons.

Question 36

Glycoconjugates

Answer 36

Proteins or lipids with covalently attached carbohydrates that serve an informal role. Can serve as labels or mediate cell-cell and cell-extracellular matrix interactions.

Question 37

Proteoglycans

Answer 37

Found in the extracellular matrix. Contains a membrane or secreted protein, a polysaccharide and the linkage between them. Has a trisaccharide bridge.

Question 38

Glycoproteins

Answer 38

Proteins covalently attached to one or more oligosaccharides. The saccharide portion can function as recognition site. Not in the extracellular matrix. Attached via the hydroxyl oxygens of S or T or the amide of N. Can be homo or heater and branched or unbranched.

Question 39

Glycolipids

Answer 39

Membrane lipids with a hydrophilic saccharide head group.

Question 40

Trisaccharide Bridge

Answer 40

Links an amino acid or extracellular protein to the glycosaminoglycan. Ex. Syndecan

Question 41

Syndecan

Answer 41

Binds extracellular proteins via an attached carbohydrate. Once bound it presents the protein to the membrane receptors to trigger events intracellularly.

Question 42

Sugar Contains Information

Answer 42

Can hold far more information then proteins and can only be read by the proteins that interact with it.

Question 43

Lectins

Answer 43

Proteins which bind carbohydrates with high affinity and specificity. Function in cell to cell recognition, signaling, adhesion and intracellular targeting. Found in the liver and can identify plasma proteins that need to be replaced or destroyed.

Question 44

Lectins in Inflammation

Answer 44

Lectins that mediate cell-cell recognition are called selectins. P-selectin in the PM of capillary endothelial cells slow T lymphocyte movement. At inflammation site intern proteins tightly bind glycoproteins causing the lymphocytes to stop and move through the capillary wall.

Question 45

Lectin-Carbohydrate Interactions

Answer 45

Lectins have submolecular complementarity. Many sugars have polar and less polar sides, the polar side hydrogen bonds with the lectin. The other side forms hydrophobic interactions with non polar residues. They all have a high binding affinity.