Lecture 15 Flashcards
monosacs- two types
aldoses and ketoses
at least two hydroxyl
groups (CH2O)n
aldoses
carbonyl group comes at the end of the chain and thus represents an aldehyde group
ketoses
carbonyl group occurs within the chain and hence represents a ketone group
enatiomers
stereoisomers that are nonsuperimposable mirror images of eachother
diastereomers
Diastereomerism occurs when two or more stereoisomers of a compound have different configurations at one or more (but not all) of the equivalent (related) stereocenters and are not mirror images of each other.
Carbohydrates
Primary energy source in bread, rice and pasta
- They do not catalyze reactions.
- They do not replicate.
- They serve as signals on cells.
- They are important fuels.
- They taste good.
Glyceraldehyde
is the smallest aldose
D or L more common?
D
Epimers
differ from each other at just one asymmetric carbon
Dihydroxyacetone
is the smallest ketose
• No asymmetric carbons.
Ketoses
have 1 fewer asymmetric carbons than aldoses
Ketoses often use the same root names as aldoses but with a“ul” included in the middle of the name.
anomeric
The carbonyl carbon becomes the “anomeric” carbon
α means opposite CH2OH (carbon 6)
β means same side as CH2OH (carbon 6)
Glycosidic bonds
form when an anomeric carbon reacts with an alcohol
galactose and glucose relationship
epimers
non-reducing
This cannot form a free aldehyde or ketone
so it is called a non-reducing sugar
Maillard Reaction
Reaction of reactive carbonyl of the open forms reducing sugars with nucleophilic amino groups of amino acids at high temperature to
produce a complex mixture of substances.
Hemoglobin A1c:
N-fructosyl-valine Hemoglobin
High levels of HbA1c are a
reliable indicator of diabetes.
Polysaccharides
Cellulose, chitin, glycogen, starch
cellulose
glucose+ glucose
Wood, white cotton and paper are almost pure cellulose.
We cannot digest cellulose. Estimated 1015 kg of
cellulose is synthesized and degraded on earth
annually!!
EM of cell wall of green algae..shows rigid long cellulose fibrils.
Who can digest cellulose? •Cows (rumen full of bacteria) •Termites (endogenous and bacterial cellulase) •Biofuel companies (make cellulosic ethanol starting with fungal cellulases or acid treatment)
chitin
next to cellulose, chitin is the second most abundant polysaccharide in nature
amylose
this type of helix cannot form when there are branches
cellulose
β-D 1,4
Unbranched Starch – α amylose
Starch is insoluble in water and must be broken down by pancreatic amylases.
amylopectin
can be up to 10^6 glucose residues
α (1–>6) branch point
(one every 24-30 residues)
HIGH FRUCTOSE CORN SYRUP
cornstarch ~7-% amylopectin –> (α-amylase) —> Oligosaccharides of glucose —> (glucoamylase) –> glucose –> (glucose isomerase) —> glucose (42%) & fructose (55%)
“HFCS 55”
Glycogen
stored glucose in muscle and liver.
More branched than starch.
Glucose can be released starting at non-reducing ends.
(one every 8-14 residues)
