Biochem Carbs Lecture 1 Flashcards
Sugars, starches, and cellulose are common
These are dietary staples
This is found in the cell walls of plants and has a structural role
Carbohydrates
Sugars and starch
Cellulose
What is the general formula for carbohydrates?
Cn(H2O)m where n greater than or equal to 3
Name the 2 categories of carbohydrates
Some also contain these 3 elements
Polyhydroxy aldehydes or ketones
Nitrogen phosphorous and sulfur
For most simple sugars, m=?
therefore, the empirical formula of simple sugars is
m=n
(CH2O)n
C5H10O5= (CH2O)5 C6H12O6= (CH2O)6
These are the simple sugars, with monomer units of more complex carbohydrates
Whats the most abundant one?
Monosaccharides
d-glucose (dextrose)
Short chains of monosaccharides joined by _______ bonds, like the disaccharide sucrose (table sugar
Glycosidic
Sugar polymers that contain 20+ monosaccharide units, like cellulose
Polysaccharides
Sugars that contain an aldehyde group are
Sugars that contain a keto group are
Aldoses
Ketoses
3,4,5,6,7 carbon sugars
tritose (?), tetrose, pentose, hexose, heptose
Names can be more specific, glucose is an ______ (has an aldehyde carbonyl group and 6 carbons
Aldohexose
D or L is assigned to which carbon?
The penultimate carbon, the chiral carbon furtherst from the carbonyl carbon
The sugars with the boxes around their names in the handout are the most common in nature. They are all in __ form
D form
These are the two most common simple sugars in nature
D-glucose D-fructose
D-ribose and 2-deoxy-ribose are components of ___
Nucleic acids
Compounds among the D-aldoses and D ketoses corresponding to the same number of atoms are _____ of each other
Diasteriomers (non mirror images)
There are ______ stereoisomers where n = number of chiral centers
2^n
The aldohexoses have how many carbon centers?
Therefore, how many stereoisomers do they have?
4
16 (2^4)
In aqueous solution, aldotetroses and all monosaccharides with 5 or more carbon atoms occur predominately as ___ structures
Cyclic
In the formation of the cyclic structures of carbohydrates, the ring structures form as a result of a general reaction between alcohols and aldehydes or ketones to form ___ and ____
Hemiacetal, kemiketal
Does hemiacetal/hemiketal formation create a new chiral center?
Yes.
With the formation of a new chiral center, two stereoisomeric forms result, what are they?
α and β anomers
Six membered ring structures are called _____
Five membered ring structures are called
Pyranoses
Furanoses
The α and β anomers of D glucose interconvert in aqueous solution by
Mutarotation
A solution of α-D-glucose and β-D-glucose forms an identical equilibrium mixture with identical __ properties
The mixture has about ____ amount of α-D-glucose and _____ of β-D-glucose
Very small amounts of what occur?
Chiral
1/3 α, 2/3 β
Open (linear chain) and five membered ring forms
Which is more stable, the α or β anomer of glucose?
β form
When switching between D and L forms of a sugar, do all of the chiral carbons have H and OH switch positions in the fischer projections?
Yes! They all do. Not just penultimate carbon
Is the pyranose ring planar?
What conformation is it?
No.
Chair conformation
The β anomer should be more stable in the chair conformation because the C-1 OH group is ___
Equatorial (axial in α)
In general, substituents in the equatorial positions are less hindered ____ly by neighboring substituents
Sterically
Monosaccharides can be oxidized by a relatively mild _____ agent.
What is an example of one?
The carbonyl group is oxidized to a ___ group
Reducing agent
Ex: Cu(2+)
carboxyl group
Sugars like glucose that reduce metal ions are called ____ sugars
Reducing sugars
_____’s reaction measures the amount of oxidizing agent reduced by a sugar. It can be used to estimate the concentration of glucose in the blood and urine (diabetes test)
What is currently used as amore sensitive measure for blood glucose levels?
Fehling’s Reaction
The enzyme glucose oxidase
Disaccharides are composed of two ___ covalently linked through a ______ bond
monosaccharides
O-glycosidic bond
The disaccharide is formed when the ____ OH of one sugared is replaced by the O of an OH group of another sugar
What is eliminated?
What is formed?
Anomeric OH group
Water (condensation reaction)
Acetal from a hemiacetal
Acetals and ketals of sugars are called ____
Glycosides
- To name disaccharides and oligosaccharides, give the configuration and the ___ C that joins the first monosaccharide unit to the second
- Name the nonreducing sugar, insert ____ and ___ to distinguish between 5 and 6 membered rings
- Name the second residue. If there is a third residue, describe the second glycosidic bond by the same conventions
Anomeric
Furano, Pyrano
_____ is a disaccharide of α-D-glucose and β-D-fructose linked by the O from the anomeric C1 of ____ to the anomeric C2 of ____
Sucrose
anomeric C1 of glucose to anomeric C2 of fructose
Since both of sucrose’s anomeric bonds are involved in glycosidic linkage, sucrose is a ____ sugar, or glycoside
Practice naming structure of sucrose in lecture (slide 16)
Nonreducing sugar
Maltose is made of two ___ residues
The O-glycosidic linkage occurs between the ____ of one glucose and the ____ of the other
D-glucose
C1 and C4
Maltose retains one free anomeric carbon, so it is a ______ sugar
The configuration of the anomeric carbon on the glycosidic link is
The glucose residue with the free anomeric carbon
can be
Reducing
α
α or β
Maltose is (name it)
Using abbreviated nomenclature, it is
α-D-glucopyranosyl-(1→4)-D- glucopyranose
Glc(α 1→4)Glc
Trehalose is the disaccharide of _____ joined through the ____ anomeric carbons of borth glucose residues
D-glucose
C1 anomeric carbons of both
Is Trehalose a reducing sugar?
Where does it play a major part?
No (no free anomeric C1s
The circulating fluids of insects
Most carbohydrates in nature are
This type is made of a single kind of monomer
This type contains two or more different types of monomers
Note: you don’t have to draw the polysaccharides
Polysaccharides
Homopolysaccharide
Heteropolysaccharide
Polysaccharides used for energy storage are
- -> in plants
- –> in animals
Starch (in plants)
Glycogen (in animals)
Polysaccharides used as structural elements are (in plants and animals)
Cellulose (in plants
Chitin and Detran (in animals)
This homopolysaccharide is amixture of amylose and amylopectin,
Amylose and amylopectin are polysaccharides of D-glucose joined by α or β ______ and α or β ______ linkages?
Starch
α 1→4 and α1→6 linkages
This homopolysaccharide is also a polymer of D-glucose, but it is more extensively branched and more compact than starch
Glycogen
This homopolysaccharide is a polysaccharide of D glucose joined by α or β ____ linkages?
β 1→4 linkages
Glycogen and starch ingested in the diet are hydrolyzed by ________,
They are enzymes in saliva and intestines that break ___ linkages
α-amylases
α1→4 linkages
In contrast to glycogen and starch, cellulose is not a digestible food source for people because they do not have enzymes to hydrolyze the ____ linkages between glucose units in cellulose
β 1→4
