Complex Carbohydrates Flashcards
Glycoconjugates have a core of ___ or ___
Protein or lipid
What 3 groups make up glycoconjugates?
Glycoproteins
Proteoglycans
Glycolipids
Glycosaminoglycans are heteropolysaccharides that are consituents of the ______ ______.
Extracellular matrix
What are some of the general functions of protein glycosylation?
- Assist in folding
- Aid in solubility
- Stabilize against denaturation and degradation
- Target proteins to subcellular locations
- Recognition signals for lectins
What are lectins?
Proteins that have high selectivity and high affinity for specific carbohydrates, bind carbs
Protein glycosylation that is N-linked occurs on which amino acid residue?
Asparagine (Asn, N)
Protein glycosylation that is O-linked occurs on which amino acid residue?
Serine
Describe how a sugar moiety is added to a protein via N-linked glycosylation.
The sugar moiety (may be branched) is built onto a molecule of dilochol phosphate, which is a lipid carrier imbedded in the ER membrane. This process begins on the cytoplasmic side of the ER membrane by using UDP activated sugars to build the oligosaccharide on dilochol phospate. The sugar precursor is then flipped to the inside of the ER where oligosaccharide synthesis is completed. The entire moiety is then transferred to the protein as a whole sugar in the ER after the protein has been translated.
N-linked glycosylation only occurs in the _______ (organelle).
ER
In N-linked glycosylation, the sugar moiety is transferred to a molecule of ____ ____ (2wds) which is located in the ____ _____ (2wds).
Dilochol Phosphate
Er Membrane
The presence of ____ in a sugar moiety on a protein indiates the protein will be retained in the ER.
Glucose
Explain how glucosylation regulates protein exit from the ER.
In a normally folded protein, hydrophobic residues should not be accessible inside the ER b/c they will reside inside the protein core. Improperly folded proteins may have hydrophobic sites exposed and Glucosyl-transferase can recognize these hydrophobic sites and add glucose to any sugar moieties in this site. Chaperones then bind to the protein and prevent the proteins transport from the ER.
Presence of _____ directs proteins to lysosomes.
Mannose-6-Phosphate
What is I-cell disease?
This is a lysosomal storage disease that results from an inability to generate mannose 6 phosphate that results in inability to target proteins for lysosome. Result is insufficient enzymes in lysosomes and thus accumulation of undigested products in lysosomes. Lack of mannose 6 phosphate results in secretion of lysosome enzymes (fusion of endosome w/ membrane, release of contents).
Where does O-linked glycosylation occur?
In ER, Golgi and cytoplasm
Complete the table.
Complete the table.
Complete the table.
Complete the table.
Bombay phenotype occurs in individuals that lack the _____ enzyme.
Fucosyltransferase
What is the Bombay phenotype?
When an individual does not have functional fucosyltransferase enzyme, their genotype is hh so they lack the ability to load H antigen onto the surface of their blood cells. As such, they will produce any A or B gene products in accordance with their genotype but they will not be able to express those antigens because the H antigen is the substrate for making A and B antigens. As such, they present as O phenotypically when they may be genotypically different. They will only be able to receive blood from O donors (or other Bombay individuals) because they need blood that is hh.
Mucus is greater than ___% weight in carbohydrates.
50
Proteoglycan
Sub-category of glycoprotein that contains mucopolysaccharides or glycosaminoglycans where majority of mass is carbohydrate based
Where does formation of proteoglycans occur?
Glogi
Glycosaminoglycans are carbohydrates that contain ____ groups and ____.
Amino acid groups
Sulfates
What are the 4 classes of glycosaminoglycans.
Hyaluronate
Chondroitin 4-Sulfate
Keratan Sulfate
Heparin
Of the 4 classes of glycosaminoglycans, what is special about hyaluronate?
Only glycosaminoglycan that is not found attached to protein core and lacks sulfonation
