Phosphate Ester Formation

• Hydroxyl group + H3PO4 --> Phosphate Ester

• Phosphate esters are important compounds in carbohydrate metabolism.

Phosphate ester formation

-D-glucose-1-phosphate

Sugar and phosphate combinations are the basis for nucleotides involved in DNA / RNA,

energy carrying molecules (ADP & ATP), and chemical messengers (cAMP)

Amino Sugar Formation

• Hydroxyl group is replaced by an amino group --> Aldosamine– Important in cartilage polysaccharides and red blood cell

markers (ABO)– There are 3 important, naturally-occurring amino sugars.

• In each the amino group is on C#2.

Amino sugar formation

Glucosamine and hyaluronic acid act as the backbone for the formation of proteoglycans

found in the structural matrix of joints

Glycosidic bonds: The hydroxyl group and a hydroxyl group

of another sugar or other compound can join together, splitting out water to form a glycosidic bond.

R-OH + HO-R'   R-O-R' + H2O

glycosidic linking helps form disaccharides, oligosaccharides, and polysaccharides

from rings of monosaccharides

Acting hemiacetal Acting as an alcohol

Disaccharide formation

Alpha () or beta () describes the –OH orientation on C #1.The numbers represent the C # connections on the Haworth projection

Disaccharides

• Formation of disaccharides is like glycoside formation (condensation rxn)– Monosaccharide + alcohol --> glycoside + H2O

• Monosaccharide + monosaccharide --> disaccharide + H2O• Disaccharide glycosidic linkage Reducing? Human Digestion• Maltose (1-4) yes easily• Cellobiose (1-4) yes no• Lactose (1-4) yes usually• Sucrose (1-2) no yes

Common Disaccharides:

Milk sugar: galactose and glucose

connected

Sucrose: -Glucose and -Fructose, (12) glycosidic linkage

(14) glycosidic linkage of 2 D-Glucose molecules

Polysaccharides (glycan)

• Variations– Homopolysaccharides vs. Heteropolysaccharides– Length of chain– Type of Glycoside Linkage– Degree of Branching

• Properties– NOT sweet– No positive Tollens or Fehling’s test– Limited water solubility– Colloids form readily

Storage Polysaccharidesenergy source

(homopolysaccharides)

Starch (plants)

amylose (15-20%)straight-chain-glucose polymer

(~1000 G) amylopectin (80-85%)

branched chain (~100,000 G)

glucose polymer (~100,0000 G)

Starch + H2O --> glucoseNutritional value

Glycogen (animals)

Highly branched

glucose polymer(~1,000,000 G)

Glucose <==> Glycogen

(stored in liver

& muscle)

Cellulose

Structural Polysaccharides (homopolysaccharides)

Cellulose (cell wall)

straight chain -glucose

polymer

Chitin (exoskeleton)

N-acetyl amino derivative of glucose

Cotton and wood are primarily cellulose(14) glycosidic bonds of two glucose rings

create linear but angled bonding.

Our enzymes cannot match this bond angle structure

to hydrolyze cellulose into cellobiose subunits or break that down to glucose

Acidic Polysaccharides(heteropolysaccharides)

• Hyaluronic acid– Joint lubricant

• Heparin– Anticoagulant

Acidic polysaccharides associated with the connective tissue of joints give hurdlers such as these the flexibility needed to accomplish their task.

Hyaluronic acid: heteropolysaccharide – 2 different glucose derivatives:Glucuronic acid plusN-acetyl--D-GlucosamineAlternates (13) and (14) linkage

Glycolipids & Glycoproteins

• These form when glycosidic linkages connect monosaccharides with lipids &/or proteins.

• Very important molecules for cell recognition processes

Dietary Considerations

• A balanced diet ~ 60% carbohydrate– Simple carbs = mono & disaccharides– Complex carbs = polysaccharides

– Starch– Cellulose

• Natural vs. Refined Sugars– Natural: a mixture of sugar and other compounds– Refined: 100% sugar molecules

• Glycemic effect: due to the rate of carbohydrate digestion– Glycemic index

Glycemic Index:Measures the rate that specific

carbohydrates are hydrolyzed into glucose.

Slow release of glucose into blood = good

Quick release of glucose into blood / overproduction of insulin = bad