Carb chemistry

Question 1

Sugar nomenclature

Answer 1

Carbonyl group (either aldehyde- at C1 C=o,H or a ketone- at C2 C=o with a CH2OH at C1) with 2 or more alcohols,
Depending on how many Cs = triose, tertose, pentose, hexose, and heptose

All carbohydrates have an empirical formula of (CH2O)n

Glucose is an aldehyde (OHs goRLRR), fructose is the ketone of glucose LRR)
Isomers- same number of atoms but different configuration, epimers are isomers with only one single carbon config difference, diasteromers have one or more than one chiral carbon differences

Carbs are chirally active . optically active (isomers that are mirror images of each other are enantiomers), D- and L config are the absolute config and are based on the Carbon furhtest from the carrbonyl

D glucose (aka dextrose is usually in D form OH on the R)

Question 2

Monosaccharides that you have to know

Answer 2

Aldehydes:
Galactose (RLLR)
Glucose (RLRR)
Mannose(LLRR)

Ketone:
Fructose (LRR)

Isomerases can reconfigure the carbonyl group (Glucose-> Fructose via acid base catalysis)

Aldohexoses (The C-1 Carbonyl is oxidized to COO- (glucose-> gluc(uronate)
Reduction of Carbonyl creates a new alcohol (sorbitol)

Sperm use fructose (converted from glucose in seminal vesicles using D- sorbitol as the intermediate) liver removes sorbitol, diabetes-> excess sorbitol in lens, swelling

Question 3

Cyclization of sugars

Answer 3

Adding an alcohol to an Aldehyde or ketone makes it a hemi acetal or hemiketal which can then become an acetal or ketal if you add an additional R group

For five and six carbon sugars, hemiacetal and hemiketal formation happens intramolecularly to make a ring Pyranose is a 6 C ring aldose. Furanose is a 6C Ketose forming a 5 membered ring. Anomeric carbons can be alpha OH is down or B OH is up

Alpha and beta are in an equilibrium with open form linear structures (less than 1% are open form), when the OH is equatorial this allows it to be more present
B-D glucopyranose has all OH equatorial, which is why B D glucose is 2/3 of the solution

Question 4

Reducing sugars

Answer 4

Free aldehyde groups can reduce copper (Cu2+) and iron or Fe3+

Cu2O is red/yellow/green (from blue)

you can detect sugar in blood or urine via enzymes (when glucose->glucolactone it yields H2O2 which is used by peroxidases to make a oxidized Bright orange color)

Question 5

Formation of glycosidic bonds

Answer 5

glycosidic bond, when the anomeric carbon is attached to an R group rather than H, it locks it in cyclized form, and locks it in either the alpha or beta form (no more equilibrium), they become non reducing sugars and are termed glycosides

Disaccharides contain 2 sugars linked by a glycosidic bond, enzymes are specific to the type of bond of the glycosidic linkage, sucrose is a disacharide of glucos and fructose (via 1-2 glycosidic bond)

glycosyl residue is the sugar contributing the anomeric carbon (for sucrose its both)

Lactose is comprimised of galactose (glycosyl) and glucose which is the reducing sugar, its a B 1-4

maltose (derived from starch hydrolysis), 2 glucose (a1-4, has a reducing sugar)

glycosidic bond formation can make polysaccharides (major storage form of sugars within cells), plants store glucose as starch (strach includes amylose, a linear polymer with alpha 1-4 linkages and amylopectin a branched polymer with a 1-4 and a 1-6 linkages, cellulose is a structure poly sach in plants and is a bunch of linear glucose in B 1-4

Question 6

glycogen

Answer 6

Animals store glucose as glycogen (a branched polysaccharide having both a 1-4 and a1-6 linkages, the branching allows for compaction , but the two different linkages require 2 different enzymes

Question 7

Glycosidic bonds other than sugars

Answer 7

Nucleosides, anomeric carbon of ribose is bound to a purine or pyrimidine base in an N glycosidic bond

Proteins on the outer PM, extracellular space and serum contain sugars that act as binding determinants. O-linked or N-linked to serine or asparagine

Question 8

Non specific glycosylation of proteins

Answer 8

Hydrophillic surface Amino acids on proteins have nucleophiles that are added on to the anomeric Carbon of a reducing sugar. Amine of lysine forming a Schiffs base

Shiffs base has vicinal OH group and can undergo an amadori reaction (like collagen)

Non specific glycation/ glycation- high in blood glucose diabetes, leades to advanced glycation endproducts (AGEs)
The anomeric carbon of glucose forms a Schiffs base with the NH2, leads to rearrangement of the double bond in an irreversible step

Question 9

CArb digestion

Answer 9

dietary carbs include mono saccharides (glucose and fructose)
Disaccharides (sucrose and lactose)
Starch Amylose and amylopectin
glycogen and cellulose (undigestible

Digesting starch and glycogen begins with a amylase (in saliva and pancreatic juice), its an endo saccharidease attacking internal a 1-4 glycosidic linkages not at branches, yeilding maltose maltotriose, and a limit dextrin , cooking hydrates starch for easy attack

digestion is continued by a-glucosodases in small intestine, also on the wall are sucrase and lactase

Question 10

Problems of Carb digestion

Answer 10

humans lack enzymes to hydrolyze some carbs, we dont digest cellulose and that allows us to hydrate poop, lactase is not prevelant