Chapter 8 Flashcards
What is the empirical formula for any carbohydrate? Specify what n must be greater than or equal to.
(CH2O)n, where n is greater than or equal to 3
How do we name carbohydrates?
By the number of units they contain.
What differentiates an oligosaccharide from a polysaccharide?
An oligo saccharide has 2-20 units, and a polysaccharide has more than 20 monosaccharides
Define “glycoconjugate”
A modified carbohydrate
D-Glucose and D-Fructose are two common monosaccharides. What differentiates them from each other? Include information pertaining to aldehydes and ketones within their structures, and how we refer to them.
In glucose, carbon 1 is oxidized to an aldehyde. Referred to as an aldose.
In fructose, carbon 2 is oxidized to a ketone. Referred to as a ketose.
(T/F) The aldehyde and ketone groups within carbohydrates cannot react with groups further down the carbohydrate structure.
False. Aldehydes and ketones can react with an alcohol group, forming either a hemiacetal or a hemiketal.
When aldehydes or ketones react with alcohols further down the carbohydrate structure, what happens to the overall structure of the carbohydrate?
A closing of the linear chain to form a cyclic structure occurs.
When the aldehyde group within glucose reacts with an alcohol within the carbohydrate structure, what kind of ring is formed? How do we refer to cyclic glucose?
A 6-membered ring is formed. It resembles a pyran ring, so we refer to cyclic glucose as alpha-D-glucopyranose
When the ketone group within fructose reacts with an alcohol within the carbohydrate structure, what kind of ring is formed? How do we refer to cyclic fructose?
A 5-membered ring is formed. It resembles a furan ring, so we refer to cyclic fructose as alpha-D-fructofuranose
Most monosaccharides that are at least 4 carbons or longer will predominantly be in the (linear, cyclic) form.
Cyclic
Define what an anomeric carbon is.
Anomeric carbon: The most oxidized carbon of a cyclized monosaccharide
What differentiates the alpha from the beta configuration of the anomeric carbon in ring structures? Which can be said to resemble a trans conformation? Cis?
In the alpha configuration, the alcohol group on the anomeric carbon is on the opposite side of the ring from the CH2OH group on carbon 5 (sort of like trans conformation).
In the beta configuration, the alcohol group on the anomeric carbon is on the same side of the ring from the CH2OH group on carbon 5 (sort of like cis conformation).
In hexoses, what is special about carbon 5?
In hexoses, carbon 5 is a chiral carbon that is used to designate the sugar as D or L stereoisomer. Most sugars used for energy production in the body will be in the D form.
What is a glycosidic bond?
A primary structural linkage involving monosaccharide subunits hooked together into polysaccharides
What kind of linkages are glycosidic bonds?
Acetal linkages. The sugar anomeric carbon is condensed with an alcohol. Can also form with an amine or thiol group in modified sugars
Compounds containing glycosidic bonds are sometimes called ______.
Glycosides
Name 2 compounds that are joined together with glycosidic linkages.
Lactose, sucrose.
Describe the structure of lactose, indicating which monomers it is made up of and what kind of specific bond (alpha or beta) joins those monomers.
Lactose consists of a monomer of glucose and a monomer of galactose joined together by a beta 1,4 glycosidic bond
To be metabolized for energy, the glycosidic bond of lactose must be cleaved by the enzyme lactase to release the 2 monomeric units. If you lack this enzyme, you are said to be _____ ______.
Lactose intolerant
Describe the structure of sucrose, indicating which monomers it is made up of.
Sucrose consists of a monomer of glucose (in the alpha configuration) and a monomer of fructose (in the beta configuration) joined together by a glycosidic bond.
Where do we acquire most of our dietary sucrose?
From plant material. Sucrose is the major form of carbohydrate in plants.
Define homoglycan.
A homoglycan is a polysaccharide that contains only 1 type of monosaccharide subunit repeating over and over.
Define heteroglycan.
A heteroglycan is a polysaccharide that contains more than 1 type of monosaccharide subunit
In plants and fungi, glucose is stored as _______.
In animals, glucose is stored as _______.
Starch, glycogen
Name the branched form of starch.
Amylopectin
Name the linear form of starch.
Amylose
Due to the configuration and shape of the glucose monomers, amylose forms a (left, right)-handed helical structure.
Left.
Amylose consists of glucose monomers attached by what kind of repeating linkage?
Alpha 1,4
Amylopectin consists of glucose monomers attached by what kind of linkage?
Alpha 1,6
What creates the kinked branch points within the amylopectin structure?
The alpha 1,6 linkages between glucose subunits
Glycogen is most similar to which form of starch? Amylose or amylopectin?
Amylopectin. Glycogen is much more branched, however.
Why is polymerizing glucose an important way to store excess glucose for future metabolism?
It reduces the effective osmotic pressure of keeping glucose in the monomeric form.
What role do glycosaminoglycans typically play in the body?
Structural roles. Not directly used for energy production.
Glycosaminoglycans can undergo a variety of changes. What purpose does this serve? Or rather, why is it beneficial for the body that glycosaminoglycans can be so heavily modified?
Allows for the creation of new materials for usage in connective tissue and other places in the body
When sugars covalently attach to proteins, we refer to the protein as a ______ ________.
Glycosylated protein.
When do complex glycosylation patterns occur on a protein?
Post-translationally
(T/F) Most secreted proteins aren’t glycosylated.
False. Often, the specific glycosylation patterns on membrane proteins at the cell surface are important for cell-to-cell recognition in the body.
The presence of glycosaminoglycans allows cartilage to do what essential function? Name a location in the body where this essential function is most relevant.
Allows cartilage to adopt a gel-like structure that can absorb a lot of water molecules. This structure gives cartilage the ability to compress and absorb a lot of pressure. Can release water and then spring back by re-absorbing water after the pressure is removed. Important for its function in joints.
