BioChem Exam #3 Flashcards
What are the Simple Sugars (glucose, fructose) used for?
Energy
What are Complex Polymers used for?
Cellulose - structure;
Starch/Glycogen - energy storage;
Hormones, antibodies, communications, etc.
What is the general formula for Carbs?
(CH2O)n;
Come as polyhydroxy aldehydes, ketones, and their derivatives and polymers;
Classified by degree of polymerization
What are Monosaccharides?
Single units; Simple sugars; Large number of hydroxyl groups and polar; Water soluble; Taste sweet
What are Oligosaccharides?
2-10 units
What are Polysaccharides?
Many units
How are Monosaccharides named?
- “-ose” ending;
- # of carbons;
- functional group (keto or aldo);
- Combine
What is an Aldose?
Monosaccharide with the carbonyl group as an aldehyde;
On the END
What is a Ketose?
Monosaccharide with the carbonyl group as a ketone;
In the MIDDLE
What are Chiral Carbons?
Have 4 different attached groups;
Most carbs have one or more
What is there is MORE than one chiral carbon?
Means there can be more than two stereoisomers
How is the number of Stereoisomers (optical isomers) determined?
2^n, with n being the number of chiral carbons
What are Enantiomers?
Non-superimposable mirror images;
Like our hands;
Members of each pair of stereoisomers
What are Diastereiomers?
Members of different pairs of stereoisomers
What is a D sugar?
-OH on the highest numbered chiral carbon is to the RIGHT;
Predominant form
What is an L sugar?
-OH on the highest numbered chiral carbon is to the LEFT
What are Aldotrioses?
3 carbons, aldehyde end;
1 chiral;
-D-glyceraldehye
What are Aldotetroses?
4 carbons, aldehyde end;
2 chiral;
3 stereoisomers
Aldotetroses
D-erythrose;
D-threose
What are Aldopentoses?
5 carbons, aldehyde end;
3 chiral;
8 stereoisomers
Aldopentose
D-ribose;
ALL -OH on the RIGHT
What are Aldohexoses?
6 carbons, aldehyde end;
4 chiral;
16 stereoisomers
Aldohexoses
- D-glucose
- D-mannose
- D-galactose
How do you draw the fisher for Glucose?
“Right - Left - Right” for -OH’s (except bottom right for D)
What is an Epimer?
When the Fisher structure differs by ONLY ONE -OH placement
What is Mannose to Glucose?
Mannose is the C2 epimer to Glucose
OH at C2 is on the LEFT instead of right
What is Galactose to Glucose?
Galactose is the C4 epimer to Glucose
OH at C4 is on the LEFT instead of right
What does the Fischer of a KETOSE look like?
C=O is at C2;
Lose a Chiral Carbon that was at C2 in an aldehyde;
“-ulose” ending in naming
Ketoses
- Dihydroxyacetone (3 carbons)
- D-erythrulose (4 carbons)
- D-ribose (5 carbons)
- D-fructose (6 carbons)
What is D-Fructose to Glucose?
It is the KETOSE analogous to Glucose;
Only differs in that the carbonyl (C=O) is at C2
How do ring structures form?
- Reaction between the CARBONYL group and the HIGHEST number chiral carbon;
- Internal hydroxyl groups don’t move!;
- Make either a hemiacetal, acetal, hemiketal, or ketal
What is an Anomeric Carbon?
New chiral Carbon that is created in the formation of a ring structure;
From the Carbon that was in the Carbonyl;
Always on the RIGHT of the ring
How do you determine Alpha and Beta ring structures?
By the position of the -OH on the ANOMERIC Carbon (new chiral center);
Alpha = DOWN (right in fischer):
Beta = UP (left in fischer)
For Haworth, the ANOMERIC Carbon is…
on the RIGHT
For Haworth, the RING O is….
ABOVE and to immediate LEFT of the Anomeric C
For Haworth, groups to the RIGHT in fishcer are…
DOWN in the ring
For Haworth, groups to the LEFT in fischer are…
UP in the ring
For Haworth, the terminal -CH2OH of D-sugars is…
UP
all the sugars we draw!
What is Furanose?
A 5-membered ring;
Fructose, ribose
What is Pyranose?
A 6-membered ring;
Glucose
What are Conformational structures?
Some enzymes might require the CHAIR confirmation
What is Mutarotation of Monosaccharides?
- “opening and closing” of the ring structure;
- Allows the going back and forth between enantiomers (Alpha and beta confirmations);
- Beta to Open Chain to Alpha, and vice versa;
- Reversible reaction
What is the Open Chain form?
When there is a FREE aldehyde or ketone;
No bond to the highest chiral carbon is formed in this state
How often is Glucose in each enantiomer?
- About 62% Beta;
- About 38% Alpha;
- Remaining .02% open chain
Why is so little time spent in the Open Chain form?
- Rings are thermodynamically more stable;
- On average, less than 10% of molecules are ever in the the open chain
What is Isomerization of Monosaccharides?
- Under alkaline (basic) conditions,there is reversible interconversion between the ketose, aldose and epimer forms of the compounds;
- Aldose-Ketose Interconversion;
- Epimerization
Isomerization of Glucose
- Fructose (ketose) to
- Glucose (aldose) to
- Mannose (C2 epimer)
What is Oxidation of Monosaccharides?
- An ALDEHYDE can be oxidized and act to REDUCE other compound;
- It acts as a REDUCING AGEN;
- Requires a FREE aldehyde
What happens to the aldose when it is oxidized?
it becomes an Aldonic Acid
Glucose becomes gluconic acid
How can a KETONE be involved in an oxidation reaction?
Under ALKALINE (basic) conditions, ketoses can be converted to aldoses, and then be oxidized
What are Reducing Sugars?
Aldoses and ketoses that can convert to open chain form
How does Oxidation continue if it is IRREVERSIBLE?
Because the open chain and ring forms exist in equilibrium, removing open chain to be oxidized, will push equilibrium to create more open chain structures that can be used
What is Esterification of Monosaccharides?
-Addition reaction (Condensation);
-Between an alcohol and a carboxylic acid;
EX: React an alcohol (-OH group) with Phosphoric acid (H), removes a molecule of water and adds phosphate group the R group of the alcohol by a bond to the oxygen left on the acid
What are the Substitutions of Monosaccharides (derivatives)?
- Amino sugars
- Deoxysugars
- Glycoside formation
What makes an Amino Sugar?
An (-OH) group on the sugar is replaced by an AMINE group (NH3+)
What are Deoxysugars?
- An (-OH) group on the sugar is replaced by JUST a Hydrogen
- Missing an Oxygen (EX: Deoxyribose in DNA)
What is Glycoside formation?
- A SUGAR (hemiacetal/hemiketal) becomes bound to a functional group (such as an alcohol) with a glycosidic bond;
- Hydrogen on Hydroxyl group on C1 is replaced with an acetal group;
- Makes a GLYCOSIDE (acetal/ketal) and water;
- Must have the CYCLIC structure to occur
How does a Glycoside change the functionality of the monosaccharide?
- When the glycoside forms, the ring is now “locked” and won’t reopen;
- NO longer a Reducing Sugar = NON-REDUCING;
Why can’t a monosaccharide reduce after glycoside formation?
- The new glycosidic bond between the C1 (anomeric) carbon and the Oxygen of the acetal group, stabilizes the alpha and beta form (ring);
- Forms a disaccharide when the second (-OH) of the reaction is an alcohol
How do you name Disaccharides?
- Name the first sugar on the LEFT (hemiacetal or hemiketal donor)
a. D or L
b. Sugar name with “-osyl” ending
c. Ring size - Anomeric configuration (alpha/beta)
- Positions of linkages
- Name the second sugar on the RIGHT
Full name of MALTOSE
- D-glucosyl(p) - alpha (1,4) - D-glucose;
- Reducing
- We can digest
Full name of CELLOBIOSE (makes cellulose)
- D-glucosyl(p) - beta (1,4) - D-glucose;
- Reducing
- We CANNOT digest
Full name of LACTOSE
- D-galactosyl(p) - beta (1,4) - D-glucose;
- Reducing
- We can digest
Full name of SUCROSE
- D-glucosyl(p) - alpha, beta (1,2) - D-fructose
- NON-reducing (both anomeric are in the linkage)
- We can digest
What form are Oligosaccharides normally found in?
Glycoprotein with proteins;
Glycolipids with lipids
What are N-linked Oligosaccharides?
(-OH) of the sugar + (-NH2) of amide group on the protein; Carbon-Nitrogen bond; -Asparganine -Glutamine; (Remove a water to make bond)
What are O-linked Oligosaccharides?
(-OH) of the sugar + (-OH) of the protein; Carbon-Oxygen bond; -Serine (mostly) -Threonine -Tyrosine
What are HOMOpolysaccharides?
Made of 1 type of monosaccharide unit;
Usually glucose, especially for energy storage as Starch and glycogen;
Also Cellulose
What is Starch? (Homopolysaccharide)
- Major storage form of carbs in plants;
- Polyglucose (many glucose)
- Major links are ALPHA (1,4)
- Branches are ALPHA (1,6)
What are the 2 different forms of Starch?
- Amylose
- Amylopectin
Characteristics of Amylose
- Linear, Unbranched;
- Single chain of alpha (1,4) links;
- NO branches
- Forms a helix with internal Hydrogen bonding
- Relatively INSOLUBLE in H2O due to self-interacction of helix
Characteristics of Amylopectin
- Alpha (1,4) backbone with Alpha (1,6) branches
- Branched about every 20-25 residues;
- More SOLUBLE due to LESS internal H-bonding
- Digested and absorbed much quicker than amylose due to the presence of more branches that enzymes can act on
What is Glycogen? (Homopolysaccharide)
- Major form of carb storage in animals;
- HIGHLY branches about every 8-12 residues;
- Stored in LIVER and skeletal MUSCLES
What makes Glycogen a readily available energy source?
- Being HIGHLY BRANCHED makes very soluble and more allows for enzymatic breakdown and FASTER release of glucose;
- Acted upon at EACH branch
Why is the quick release of Glucose from storage needed in the body?
- Quick access to energy in the muscles during “fight or flight” responses;
- Maintenance and control of blood glucose levels by the liver when we eat
What is Cellulose? (Homopolysaccharide)
- STRUCTURAL carb found in the cell wall of plants;
- Polyglucose
- BETA (1,4);
- Linear, UNbranched
- NO nutrient value;
- NOT digested by humans;
- Very INSOLUBLE due to lots of Internal H-bonding
- Appears as sheets due to beta bonding
Why can Cows and other animals gain nutrients from Cellulose?
-Certain microorganisms that live in the intestinal tract of ruminant animals breakdown the cellulose and then the animals can utilize the products
What are HETEROpolysaccharides?
- Consists of MORE than one type of monosaccharide unit;
- Glucosaminoglycans
- Glycoconjugates
What are Glucosaminoglycans, GAGs? (Hetero)
- Long unbranched polysaccharides consisting of a repeating disaccharide unit (same 2 sugars);
- consists of an AMINO SUGAR and uronic sugar or galactose (SUGAR ACIDS, -SO4 2- derivatives);
- Highly polar due to charge-charge repulsion making them highly negative so traps water;
- Turns gel-like due to absorbed water
What are GAGs used for?
- Useful as a lubricant or shock absorber;
- Gel structure can absorb physical stress;
- Found in Cartilage and Arterial Walls
- Heparin is used as an anticoagulant