Topic 12: Carbohydrates Flashcards
What makes a sugar L vs D
From its structure, if the –OH group attached to the bottom-most asymmetric center (the carbon that is second from the bottom) is on the right, then, the compound is a D- sugar. If the –OH group is on the left, then, the compound is a L-sugar
What is mutrotation?
Mutarotation involves the conversion of an anomeric form of a sugar into another form, specifically between the alpha and beta anomers. This process is a result of the rotation of the plane of polarized light, which is why it’s called “mutarotation
What is a glycosidic bond
A glycosidic bond, also known as a glycosidic linkage, is a chemical bond in the form of a covalent connection that connects a carbohydrate (sugar) molecule to another group, which might be another carbohydrate or not
Describe the function and structure of glycogen, cellulose and starch
Cellulose is a major polysaccharide of glucose found in plants, and is an important component of the plant cell wall. Cellulose is an unbranched polymer of glucose residues joined by thousands of β-1,4 linkages.
Glycogen and starch are the primary storage forms of glucose in animals and plats
Starch is also a homopolymer of glucose, of which there are two forms. Amylose, the unbranched type of starch, consists of glucose residues in a 𝛼-1,4-linage, while amylopectin, the branches form, as about 1 𝛼-1,6-linkages per 30 𝛼-1,4 linkages, in similar fashion to glycogen but a lower degree of branching.
Starch is fully digestible, and is an essential part of the human diet.
Glycogen, also called animal starch, is the most common homopolymer in animals. It is a large, branched polymer of glucose residues. Most of the units are linked by 𝛼-1,4-glycosidic bonds, but the branches are formed by 𝛼-1,6-glycosidic bonds, present about once in 12 units
Glycogen serves as the carbohydrate storage fuel, similar to the function of starch in plants. Some of the glucose from starches in our diet is used immediately as fuel, and some is stored as glycogen for later use
Amylopectin, amylose, and glycogen are rapidly hydrolyzed by 𝛼-amylase, an enzyme secreted by the salivary glands and the pancreas
What do O-linked and N-linked refer to
O-linked” refers to a type of glycosidic linkage in the context of glycosylation, a biochemical process where carbohydrate (sugar) molecules are covalently attached to other biomolecules, such as proteins or lipids. O-linked glycosylation specifically refers to the attachment of sugar molecules to the hydroxyl (-OH) groups of certain amino acid residues in proteins. This process involves the formation of an O-glycosidic bond, where the sugar molecule is linked to the protein through an oxygen atom in the hydroxyl group.
“N-linked” refers to a specific type of glycosidic linkage in the context of glycosylation, a biochemical process in which carbohydrate (sugar) molecules are covalently attached to other biomolecules, such as proteins. N-linked glycosylation involves the attachment of sugar molecules to the amino group (nitrogen atom) of the amino acid asparagine (Asn) in proteins
N-linked oligosaccharides of glycoproteins are complex branched polymers. N-acetylglucosamine is linked to a protein via the side-chain N of an asparagine residue in a particular 3-amino acid sequence.
