Blake_Biochem_24_Carbohydrates

Question 1

Define Oligosacharides ad Polysacharides:

Answer 1

• Oligosaccharides: 3-10 monosaccharides
  
  • Glycolipids and glycoproteins
• Polysaccharides: >10 monosaccharides
  
  • Glygogen, starch, cellulose

Question 2

Three components to identify a monosaccharide:

Answer 2

• Carbon Number
• Functional group
• Stereoisomer form

Question 3

what is the seminal differnce between an aldose and a ketose?

Answer 3

• Ketoses have a ketone group: R-(C=O)-R
• Aldoses have an aldehyde group at the END: R-(C=O)-H

Question 4

Define epimer:

Answer 4

Diastereomers that differ in configuration of only one stereogenic (chiral) center

Question 5

Deliniate “D” and “L” sugars

Answer 5

• “D” sugars: OH group farthest from the carbonyl carbon is on the same side as the carbonyl oxygen
• “L” sugars: OH group farthest from the carbonyl carbon is on the opposite side of the carbonyl oxygen

Question 6

List the most biologically common monosaccharides and their C-numbers (7)

Answer 6

• Ketose:
  
  • Dihdroxyacetone, 3
  • _D-Fuctose, 6
• Aldoses
  
  • _D-glyceraldehyde, 3
  • _D-Ribose, 5
  • _D-Glucose, 6
  • _D-Mannose, 6
  • _D-Galactose, 6

Question 7

What is the difference between a Pyranose and a Furanose?

Answer 7

Pyran is a 6 membered sugar ring, Furan is a 5 membered sugar ring

Question 8

In what proportions are the different structures of glucos found in the body?

Answer 8

<1% _D-glucose (open chain)

~36% alpha-_D-glucose

~63% ß-_D-glucose

Question 9

WHat determines alpha and beta anomers of a sugar ring?

Answer 9

position of the OH at C-1 from the CH₂OH

alpha=opposite side

Beta=same side

Question 10

Name

Answer 10

Question 11

what types of bonds and what substituents make up Sucrose?

Answer 11

alpha1-ß2 bond

alpha-D-Glucopyranosyl-(1→2)-ß-D-fructofuranose

Question 12

what types of bonds and what substituents make up Lactose?

Answer 12

ß1-4 bond

ß-D-Galactopyranosyl-(1→4)-alpha-D-glucopyranose

Question 13

what types of bonds and what substituents make up Maltose?

Answer 13

alpha1-4 bond

alpha-D-glucopyranosyl-(1→4)-alpha-D-glucopyranose

Question 14

give an example of Deoxyaldose

Answer 14

a chemically modified derivative of ribose (an aldose) found in DNA is 2-Deoxy-_D-ribose

Question 15

Where are Acetylated amino sugars found?

Answer 15

They are components of glycoproteins and glycolipids [important for cell signaling, cell adhesion, immuno response]

Question 16

Where are Acidic sugars found?

Answer 16

Glycosaminoglycans and proteoglycans

Present in cell membranes and the extracellular matrix

Question 17

Give some examples of sugar alchohols:

What three facts did Theison give about sugar alcohols?

Answer 17

e.g.: Mannitol, sorbitol, xylitol

1. used as food aditives
2. gains importance in uncontrolled diabetes leading to cataracts and peripheral neuropathy
3. used in the synthesis of lipids

Question 18

Sugar esters are found where?

Answer 18

constituted the gangliosides in oligodendrocytes of the nervous system.

Question 19

Which amino acid is associated with N-Linked GlcNAc?

Answer 19

Asn is associated with this carbohydrate

Question 20

Which amino acid is associated with O-linked GalNAc

Answer 20

Ser is associated with this carbohydrate

Question 21

4 types of Glycoaminoglycans:

Answer 21

1. Chondroitin Sulfate
2. Dermatan Sulfate
3. Heparan Sulfate
4. Keratan Sulfate

Question 22

Define Proteoglycan:

Answer 22

Proteoglycans are proteins that are heavily glycosylated. The basic proteoglycan unit consists of a “core protein” with one or more covalently attached glycosaminoglycan (GAG) chain(s).

Question 23

Proteoglycan synthesis:

Answer 23

• Sugars are added to the protein one at a time, with UDP-sugars serving as the precursors (glycosyl transferases)
• Initially, a xylose residue is added to a serine in the protein
• Then two galactose residues are added, followed by a glucuronic acid (GlcUA) and an N-acetylglucosamin (GalNAc). (chondroitin sulfate)

Question 24

• why do GAGs tend to adopt highly extended conformations that occupy a huge volume relative to their mass?
• What kinds of substances do GAGs form? why is this useful to tissues?
• What other properties of GAGs help the function of the E.C. space?

Answer 24

• because polysaccharide chains are too stiff to fold up into compact structures and are strongly hydrophillic
• GAGs form porous, hydrated gels (even at low concentrations). These gells fill up the E.C. space which provides mechanical support to tissues.
• High density of negative charges attracts cations (esp Na⁺) -> osmotically active which causes large ammounts of H₂O to be pulled into the matrix. The resulting swelling pressure enables the matrix to withstand compressive forces

Question 25

where are proteoglycans synthesized?

Answer 25

Golgi Apparatus