Biochemistry Chapter 6: Carbohydrate Structure Flashcards
Anomeric carbon glucose
C1 (where the carbonyl group is)
Anomeric carbon fructose
C2 (where the carbonyl group is)
Enantiomers
are mirror images, different in orientation at every chiral carbon
diastereomers
They are molecules that have the same molecular formula and sequence of bonded atoms (constitution) but differ in the spatial arrangement of their atoms in a way that they are not mirror images of each other.
Epimers
Diastereomers thats differ at 1 chiral center
Carbons numbered starting from the
Terminal C=O or the end closest to it
Hemiacetal
Hemiketal
Pentoses and hexoses can form cyclic forms featuring what kind of group?
Hemiacetal or hemiketal
Which carbons connect to form a pyranose?
C1 and C5
Which carbons join to form a furanose?
C1 and C4
OH groups points _____ in alpha-anomers
DOWN
OH groups points _____ in beta anomers
UP
An anomer
is a type of stereoisomer that arises from the formation of cyclic structures in sugars. Specifically, anomers differ in the configuration at the anomeric carbon, which is the carbon derived from the carbonyl group (aldehyde or ketone) during the cyclization of a sugar.
Glycosidic bond creates what?
Ketal/Acetal
Sucrose is made up of what monosaccarides?
glucose + fructose, α1→β2 glycosidic bond.
Lactose is made up of what monosaccarides?
galactose + glucose, β(1→4) glycosidic bond.
Maltose is made up of what monosaccarides?
glucose + glucose, α(1→4) glycosidic bond.
Amylose
linear glucose chain with α(1→4) bonds.
Polysaccarides
long linear chains of glucose
Amylopectin
like amylose, but with α(1→6) branches every 24–30 units.
Starch (in foods) is made of what
20%–30% amylose + 70%–80% amylopectin.
Glycogen
Polysaccaride. (energy storage in humans): α(1→4) bonds with α(1→6) branches every 8–12 units.
Cellulose
indigestible fiber in plants; connected by β(1→4) bonds.
Most common carb stereochemistry system
D/L system, based on orientation of D-glyceraldehyde — in a linear Fischer projection, a D-carbohydrate is one with the bottom-most -OH group pointing to the right.
Virtually all biological carbohydrates are (D or L)?
D
How to find number of stereoisomers
2^X = number of stereoisomers where X = number of chiral centers
Each hexose will have how many enatiomers, epimers and diastereomers?
one enantiomer (differing by D vs. L).
four epimers (one epimer for each stereocenter).
14 diastereomers.
Reducing sugars
terminal C=O in aldoses can easily be oxidized to carboxylic acids. Aldoses are reducing agents/sugars. Reducing sugars = reducing agents
disaccharides where an element can be converted into a linear aldose are
reducing sugars
Are Ketose monosaccharides reducing sugars?
Yes because they can tautomerize to aldoses
Is sucrose a reducing sugar?
No
Are starch and polymers reducing sugars?
No because only one end of the sugar gets reduced
Why sucrose alpha1 - beta2 glycosidic bond?
The glucose (C1) is in the α-configuration (OH group on the anomeric carbon is trans to the CH₂OH group).
The fructose (C2) is in the β-configuration (OH group on the anomeric carbon is cis to the CH₂OH group).
Anomeric Carbon
An anomeric carbon is a carbon atom in a sugar molecule that forms a stereocenter when the sugar cyclizes
In the open-chain form of a sugar, the anomeric carbon is the carbonyl carbon of the aldehyde or ketone functional group.
In the cyclic form of a sugar, the anomeric carbon is the carbon atom bonded to the ring oxygen and a hydroxyl group.
The stereochemical designators α and β distinguish between:
epimers at anomeric carbon
Difference between AMP and cAMP
AMP = standard nucleotide with 1 phosphate group
cAMP = A modified form of AMP where the phosphate group forms a cyclic bond with both the 3’ and 5’ carbons of the ribose, creating a ring-like structure.
AMP = Plays a role in energy metabolism and nucleotide synthesis.
cAMP = second messenger
t is synthesized from ATP by the enzyme adenylyl cyclase in response to signals like hormones (e.g., epinephrine, glucagon) and activates protein kinase A (PKA), leading to various cellular responses.
α (Alpha) anomer → The OH on the anomeric carbon (C1) is
opposite (trans) to the CH₂OH group (C6).
β (Beta) anomer → The OH on the anomeric carbon (C1) is on the
same side (cis) as the CH₂OH group (C6).
Fischer projection: L Glucose
The D- or L- configuration is determined by the position of the OH group on the highest-numbered chiral carbon (which is C5 in glucose).
L-glucose → OH on C5 is on the left.
Fischer projection: D Glucose
The D- or L- configuration is determined by the position of the OH group on the highest-numbered chiral carbon (which is C5 in glucose).
D-glucose → OH on C5 is on the Right.
Hawthorn projection: L Glucose
In the Haworth projection, cyclization changes the orientation of the CH₂OH (C6) group
L-glucose → CH₂OH (C6) is below the ring.
Hawthorn projection: D Glucose
In the Haworth projection, cyclization changes the orientation of the CH₂OH (C6) group
D-glucose → CH₂OH (C6) is above the ring.
Difference between L, D and alpha beta for naming monosaccarides
The D- or L- configuration is determined by the position of the OH group on the highest-numbered chiral carbon (which is C5 in glucose).
Alpha (α) and Beta (β) anomers are determined by the orientation of the OH group on the anomeric carbon (C1) when the sugar cyclizes into a ring form.
bond that links monosaccharides together in an oligosaccharide is a special type of acetal linkage known as a
glycoside bond
