Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
75 Cards in this Set
- Front
- Back
|
Empirical formula of carbs:
|
(CH2O)n
|
|
|
What is a monosaccharide?
|
A carbon chain w/ a carbonyl and 2 or more hydroxyls.
|
|
|
How are monosaccharides numbered?
|
From the carbonyl end.
|
|
|
What are the 2 types of monosaccharides?
|
-Ketose (ketone)
-Aldose (aldehyde) |
|
|
What is ea; ketose or aldose?
-Glucose -Fructose |
glucose = aldose
fructose = ketose |
|
|
How many carbons long is the last physiolog significant carbohydrate?
|
7
|
|
|
definition of chiral
|
carbon w/ 4 different groups attached
|
|
|
isomers in general are:
|
compounds with the same atoms but different arrangements.
|
|
|
What is dextrose?
|
D-glucose
|
|
|
What are anomers?
|
Compounds that differ in carbonyl carbon configuration.
|
|
|
What are epimers?
|
Compounds that differ in configuration at ONLY ONE SINGLE carbon other THAT IS OTHER than the carbonyl carbon.
|
|
|
What are enantiomers?
|
isomers that exist as mirror images (d/l glyceraldehyde)
|
|
|
What are diastereomers?
|
isomers differing in configuration, but that are NOT mirror images. (b/c have more than one chiral center)
|
|
|
What are the 5 most important monosaccharides to know?
|
-Ribose
-galactose -glucose -mannose -Fructose |
|
|
What are 2 important epimers of Glucose? At what carbon do they differ in configuration?
|
-galactose-> C4
-mannose -> C2 |
|
|
what is the relationship of fructose and glucose?
|
isomers; fructose is a ketose, glucose an aldose.
|
|
|
how does ribose compare to the other important monosaccs to know?
|
it has 5 carbons, not 6
|
|
|
what is a 3-carbon monosacch?
|
glyceraldehyde
|
|
|
which carbon determines whether a carb is L or D?
|
the carbon farthest from the carbonyl or ketone carbon.
|
|
|
What is gluconic acid (gluconate)?
|
Glucose with the C1 carbonyl oxidized to carbonic acid.
|
|
|
What is glucuronic acid (glucuronate)?
|
glucose with its C6 alcohol end oxidized into a carbonyl group.
|
|
|
What does reduction of the carbonyl end of a monosacch create?
|
A polyol
|
|
|
What product results from oxidizing glucose to a polyol?
|
Sorbitol
|
|
|
What cofactor is necessary to produce sorbitol from glucose?
|
NADP+ - gets reduced as glucose is oxidized to the polyol sorbitol.
|
|
|
What are 2 points of clinical relevance to sorbitol?
|
-Diabetic cataracts
-Seminal vesicles (precursor to fructose, sperm fuel) |
|
|
For sperm to convert glucose to sorbitol requires how many NADPH?
|
2
|
|
|
By what mechanism are monosaccharides cyclized?
|
Intramolecular hemiacetal or hemiketal formation.
|
|
|
What forms a
-pyranose -furanose |
Pyranose - cyclization of a 6-carbon aldose
Furanose - cyclization of a 6-carbon ketose or 5-carbon aldose. |
|
|
What 2 configurations result from cyclization?
|
Alpha or beta - referring to whether the OH group C1 is above/below the ring plane.
|
|
|
How is the OH configured in
-Alpha config? -Beta config? |
A = down
B - up |
|
|
What is the predominant anomer in a glucose solution?
|
B-glucopyranose - the most stable configuration because all OH groups are equatorial.
|
|
|
Why is hemiacetal/ketal the mechanism used in cyclization?
|
It increases the carbon's susceptiblty to intramolec. nucleophilic attack.
|
|
|
So in cyclization of glucose, what attacks what?
|
C5 -OH group attacks C1 C=O group.
|
|
|
What is a reducing sugar?
|
A saccharide with a free aldehyde group capable of reducing compounds like Fe3+ or Cu2+
|
|
|
What is a glycosidic bond?
|
The result of a functional group covalently binding the anomeric carbon of a ring.
|
|
|
What is the CLASSIC nonreducing sugar? What does its structure consist of?
|
Sucrose - glucose + fructose
|
|
|
How many members are in the ring structures of
-Glucose -Fructose |
Glucose = 6-membered
Fructose = 5-membered |
|
|
Why exactly is sucrose a nonreducing sugar?
|
Both anomeric carbons of glucose/fructose are linked to each other.
|
|
|
Why is the glycosidic bond in sucrose "alpha"1-2, not alpha-beta?
|
Because the "1" carbon is alpha and that is what determines the naming.
|
|
|
What is a disaccharide?
|
2 sugars linked by a glycosidic bond.
|
|
|
What are the 3 most common disaccharides, and what are their linkages?
|
Sucrose - a1,2 (glu/fru)
Lactose - B1-4 (glu/galact) Maltose - a1-4 (glu/glu) |
|
|
So how do maltose and lactose differ from sucrose?
|
The latter is nonreducing, the other 2 are reducing.
|
|
|
What is a complex polysaccharide?
|
A polymer of multiple sugars linked together by glycosidic bonds.
|
|
|
Why are polysaccharides important?
|
They constitute the major storage form of carbohydrates.
|
|
|
In what form do plants store sugar?
|
Starch
|
|
|
What are the 2 types of starch?
|
1. Amylose
2. Amylopectin |
|
|
What is the key difference between amylose and amylopectin?
|
Amylose = linear w/ a-1,4 links
Amylopectin = branched w/ a-1,4 and a-1,6 links. Branches every 10-12 residues. |
|
|
What is the major structural molecule in plants? What type of links, so similar to what storage polysaccharide?
|
Cellulose - B-1,4 linkages
-Similar to amylose (linear) |
|
|
Why is cellulose important?
|
Animals cant digest it b/c they lack the enzymes for catalyzing the hydrogen bond created by this stereochemistry.
|
|
|
How do animals store glucose?
|
As glycogen
|
|
|
What plant storage polysacch. does glycogen resemble?
|
Amylopectin - has both linear a-1,4 and branched a-1,6 links.
|
|
|
For glycogen, what is its unique
-Advantage -Disadvantage |
Adv: allows for compact storage of lots of glucose
Dis: mixed linkages require two diff. enzymes for breakdwn |
|
|
What type of glycosidic bond is found in nucleosides? What sugar?
|
N-glycosidic - Ribose sugar bound to a purine/pyrimidine
|
|
|
What type of glycosidic bonds are found in membrane sugars? What protein residues?
|
O-linked (Serine) or
N-linked (Asparagine) |
|
|
What bad thing happens with sugars and proteins?
|
Non-specific glycosylation
|
|
|
what is the most common type of non-specific glycosylation?
|
Sugar reacts w/ primary NH3 of lysine to form a SCHIFF'S BASE
|
|
|
What can happen to a schiff's base?
|
Contains a hydroxyl group that can undergo an Amadori rearrangement.
|
|
|
Why is an amadori rearrangemnet bad?
|
Its last step is irreversible so you're left with an undo-able glycosylated protein.
|
|
|
What disease is non-spcf glycosylation a problem espec?
|
Diabetes - results in AGE (advanced glyc. endproducts)
|
|
|
Which sugar is table sugar?
|
Sucrose
|
|
|
What are the important dietary carbs to remember?
|
Glu/Fru (mono)
Suc/Lac (di) Amylopectin/Amylose (starch) Glycogen/Cellulose (undigestble) |
|
|
What sugar is in legumes?
|
Raffinose
|
|
|
Why is raffinose important?
|
bacteria digest it in the intestines which causes gas.
|
|
|
What enzyme catalyzes the first step of starch/glycogen digestion?
|
Alpha-amylase in saliva and pancreatic juice in stomach
|
|
|
What does a-amylase do?
|
An endosaccharidase; attacks the a-1,4 linkages.
|
|
|
What are the products of a-amylase digestion?
|
Maltose, maltotriose, and a-limit dextrin.
|
|
|
What is the 3 next enzymes in starch digestion?
|
a-glucosidase, sucrase, lactase
|
|
|
What 3 sugars result from digestion that mammalian cells use for fuel?
|
Glucose
Galactose Fructose |
|
|
What kind of transport is required for enterocytes to take up Glu/Galact/Fructose?
|
Glucose - active
Galactose - active Fructose - passive |
|
|
What transporter does fructose use to get into enterocytes?
|
GLUT5
|
|
|
What transports Glu/Galactose into enterocytes?
|
SLGT-1
|
|
|
What is the mechanism of SLGT-1 operation?
|
It is facilitated active transport - uses the Na gradient established by an ATP pump on the basolateral membrane.
|
|
|
How do all 3 sugars pass from enterocytes into the blood stream? What specific transporter?
|
Via passive diffusion through GLUT2
|
|
|
What are 2 relatively common problems with carb metabolism?
|
1. Lactose insufficnecy - in children; decreases w/ age
2. Lack of enzymes for cellulose and Raffinose |
|
|
Why is the inability to digest cellulose good?
|
It provides fiber in feces that keeps it hydrated.
|
