Lecture 7 - Carbohydrates, fats, nucleic acids

Question 1

Basic carbohydrate nomenclature

Answer 1

Basic structure - (CH₂O)ₙ

Triose - 3C
Tetrose 4C
Pentose - 5C
Hexose - 6C
Heptose - 7C

Monosaccharide - One monomeric unit
Disaccharide - 2 monomeric units
Oligosaccharide - 2-20 monomeric units
Polysaccharide - >20 monomeric units
Glycoconjugates - sugar connected to lipid/proteins

Question 2

Aldoses and ketoses: what are they?

Answer 2

Aldoses (aldehyde) - double bond oxygen (=O) at the end of the carbon chain

Ketoses (ketones) - double bond oxygen (=O) in the middle of the carbon chain

Question 3

What determines L/D monosaccharide form?

Answer 3

The form is based on the chiral carbon that is the furthest from the aldehyde/ketone group

D isomers are more common in nature

Question 4

Formation of hemiacetals and acetals

Answer 4

An alcohol group binds to a carbon, forming a hemiacetal (the O binds to the carbon and its hydrogen moves to the aldehyde group and binds to it)

An alcohol group binds to a carbon, forming an acetal (the two sugars bind through one of the oxygens and the other oxygen binds with two hydrogens, forming water)

Question 5

Formation of hemiketals and ketals

Answer 5

An alcohol group binds to a carbon, forming a hemiketal (the O binds to the carbon and its hydrogen moves to the ketone group and binds to it)

An alcohol group binds to a carbon, forming a ketal (the two sugars bind through one of the oxygens and the other oxygen binds with two hydrogens, forming water)

Question 6

Haworth and chair formations: what are they both and which is more realistic

Answer 6

Haworth - typical illustration of macromolecules
Chair - curved bonds connecting the atoms

Chair is much more realistic

Question 7

Hemiacetals and isomer formation

Answer 7

Hemiacetals form two anomers on the C1 based on whether the OH-group is above or below the carbon

Question 8

Pentose/hexose nomenclature

Answer 8

Pyranoses - 5C + O
Furans - 5-ringed compounds

Question 9

The two types of polysaccharides

Answer 9

Homoglycans - made of only one type of sugar
Heteroglycans - made up of different sugars

Question 10

Glucose storage in animals and fungi and plants

Answer 10

Animals/fungi - glycogen
Plants - starch (amylose/amylopectin)

Question 11

Amylose: what is the glucose linkage?

Answer 11

D-glucose linked by 1,4-glycosidic bonds

Question 12

Amylopectin: what is the glucose linkage, what is the structure, and what is its effect?

Answer 12

D-glucose is linked by 1,4-glycosidic bonds but may be branched occasionally (every 24-30 carbons) due to 1,6-glycosidic bonds

Branches increase compactness, faster degradation can occur

Question 13

Glycogen: what is the glucose linkage, what is the structure, and what is its effect?

Answer 13

D-glucose is linked by 1,4-glycosidic bonds but often branches (every 8-12 carbons) due to 1,6-glycosidic bonds

Branches increase compactness, faster degradation

Question 14

Structural polysaccharides

Answer 14

Cellulose - the most abundant biochemical on earth. Contain 1,4-glycosidic bonds and remain straight with little to no branching

• Forms fibrils which associate into a high strength insoluble polymer

Question 15

Carbohydrate-protein linkages

Answer 15

Serine/threonine can bind to sugars through their OH group

Asparagine can bind to sugars through its N-group forming an N-glycosidic linkage