Chap 21

Question 1

structure of carbohydrates in general.

Answer 1

• Ketoses – ch2oh-co-R
• Aldoses – coh-R
• hexoses (6) pentoses (5)

Question 2

optical rotation

Answer 2

• Polarize light in a different plane. D bends light right. L bends light left

Question 3

Stereoisomers formula

Answer 3

• Number of Chiral centers^2

Question 4

Fisher project

Answer 4

• Wedges come out and dashed lines go in

Question 5

difference between D- and L- sugars, and which one predominates in nature.

Answer 5

• In D (most common), chiral center farthest from the OH group faces right, in L it faces left.

Question 6

able to find the anomeric carbon

Answer 6

• C that is bonded to 2 O molecules. C1 in aldoses, C2 in ketoses
• Anomers – alpha = OH on bottom. Beta = OH on top

Question 7

to predict if a sugar will undergo mutarotation, or will be a reducing sugar.

Answer 7

• When the sugar reaches equilibrium between open-chain, close-chain forms (alpha and beta) in a solution. This changes the optical rotation.
• Reducing sugars can open, if it has an OH on the anomeric carbon
  o All monosaccharides, Lactose (glucose-galactose) and Maltose (glucose-glucose). Not sucrose (fructose-glucose) because O bonds with both anomeric carbons, so they can’t open.

Question 8

Can ketoses be reducing sugars??

Answer 8

• Yes, it can be converted to an aldose, then reduced by adding an O to the acyl group

Question 9

Sucrose, Lactose, Maltose

Answer 9

sucrose=glucose and fructose, lactose= galactose and glucose maltose= glucose and glucose

Question 10

Why is cartilage so “springy”?

Answer 10

• Polysaccharides hold 2x their mass in water, which acts as a shock absorber and lubricant. When pressed together, the charges repel one another as well.

Question 11

blood-type antigens and what they are made of.

Answer 11

• All have N acetyl glucosamine – D glucose – L fructose
  o Type O – no extra side chain
  o Type A – extra N-acetyl D-galactosamine
  o Type B – Extra D-galactose

Question 12

celllulose and chitin

Answer 12

• Cellulose - All glucose polymer, alternating alpha and beta linkages.
  o In plants
• Chitin – Same as cellulose with an amino acid and acetyl group.
  o Exoskeletons

Question 13

starch and glycogen bond numbers

Answer 13

• Glycogen – protein core (glycogenin), branch every 11 +/- 3 glucose.
• Starch – Amylopectin core, branched form of starch. Branch every 27 +/- 3 glucose.