Ch. 13: Carbohydrate Structure and Function Flashcards
What are the three main groups of carbohydrates?
Simple sugars, polysaccharides, glycoconjugates
Three types of simple sugars
Monosaccharides, disaccharides, oligosaccharides
Two types of polysaccharides
Glucose homopolymers, disaccharide heteropolymers
Three types of glycoconjugates
Glycoproteins, proteoglycans, glycolipids
D vs. L-Oriented Sugars
L- last chiral group is on the left, D - last chiral group is on the right (most abundant in nature)
Alpha vs. Beta glycosidic linkages
If the H group lost from the hydroxyl is below the line of symmetry, it’s alpha; above the line of symmetry, and it’s beta
Glycosyltransferases
Enzymes that catalyze the formation of the glycosidic linage to form a glycoside
Glycobiology
The study of glycan structure and function
What is the benefit of branching in glycans?
Structural stability and ability to hold more energy
Glycan biochemistry
Conjugates are identified by liquid chromatography or mass spectroscopy
Glycan biosynthesis
Recruited from the environment or made within the cell in the ER or Golgi apparatus
Glycan diversity
Can be found on cell surface; varies within species and across species
Glycan recognition
Specific binding proteins called lectins bind to glycans to stimulate a biological response
Lectins
Do not have a high affinity for glycans, so they can be disrupted by reagents for medical applications
Oligosaccharides
Simple sugars that range from 3 to 20 branched and unbranched sugar residues
What are some examples of oligosaccharides?
Stachyose and Raffinose
Raffinose
A trisaccharide made up of 3 monomers: Galactose, glucose, and fructose
What do plants use carbs for?
Energy storage and structure (cell wall)
Cellulose
Made up of repeating units of a disaccharide called cellobiose; branching properties give rise to more structural integrity; make up the cell wall of plants
Chitin
Linear polysaccharide that is the structural component to the exoskeletons of crustaceans and insects; also found in the tissues of animals
Starch
Used by plants to store excess glucose; made up of amylose, amylopectin, and other polysaccharides
Glycogen
Used by animals to store dietary sources of glucose; contains branch points
Amylose
Amylose sugars form a structure where there are 6 sugars per helical turn; used by starch for energy storage
Penicillin
A beta-lactamase inhibitor; Penicillin inhibits bacterial enzymes called transpeptidase through irreversible binding, causing the cell wall of bacteria to disintegrate
How are some bacteria penicillin/antibiotic resistant?
Bacteria have developed two mechanisms of resistance to beta-lactam antibiotics
Proteoglycans
Two types of structures: Extracellular matrix and cell surface
Intrinsic Glycoconjugate Interactions
The whole cell is communicating with itself
Extrinsic Glycoconjugate Interactions
Communication between the whole cell and foreign cells (ie. viruses, pathogens)
Glycoconjugate Analysis: Liquid Chromatography
Peaks show the amount of each glycan species eluted over time
Glycoconjugate Analysis: Mass Spectroscopy
Peaks show the molecular mass of each glycan species in the sample
Glycoconjugate Analysis: Lectin Array
Use as a substrate; bind to a fluorescent “antigen”
Glycan cleavage
A method of structural characterization; glycans must first be separated from the protein moiety using a cleavage reaction
N-linked glycan
Removed from protein using just PNGaseF
O-linked glycan
Chemicals such as NaOH and NaBH4 strip the O-linked glycan from the sugar
What are the main functions of monosaccharides?
To produce and store energy
What are the main functions of polysaccharides in living things?
Energy storage and structural support
What molecules make up carbohydrates/glycans?
Carbon, hydrogen, oxygen
What is the ratio of carbon, hydrogen, and oxygen in carbohydrates?
1:2:1
For every one carbon, there are two hydrogens and one oxygen
What is another common name for carbohydrates?
Glycans
What is the empirical formula for carbohydrates?
(CH2O)n, where n is greater than or equal to 3
What are some examples of the functions of glycoconjugates?
- Cell-to-cell communication
- Cross-linkage between proteins
