Based on Figure 1, a GlcNAc residue in the glycan chain is linked to a mannose residue by:A.a glycosidic bond between carbon 1 of GlcNAc and carbon 4 of mannose.B.a glycosidic bond between carbon 1 of mannose and carbon 4 of GlcNAc.C.a glycosidic bond between carbon 1 of GlcNAc and carbon 3 of mannose.D.a glycosidic bond between carbon 1 of mannose and carbon 3 of GlcNAc.

O-linked D-mannose can form a glycosidic bond with any sugar that has a free anomeric carbon. Therefore it could theoretically form a glycosidic bond with all of the following sugars EXCEPT:A.galactose.B.ribose.C.lactose.D.sucrose.

Passage 6 (Questions 30-35)O-GlcNAcylation, the addition of an N-acetyl-glucosamine group (O-GlcNAcyl) to a serine or threonine residue of a protein, has been identified in over 3,000 different proteins. Disruptions of O-GlcNAcylations have been implicated in major health conditions, including diabetes, cancer, and neurodegenerative diseases. The mechanism for O-GlcNAcylation is depicted in Reaction 1, with the forward reaction being catalyzed by O-GlcNAc transferase (OGT) and the reverse reaction by O-GlcNAcase (OGA).Reaction 1Reaction 1Interested in the substrate specificity of OGT, researchers conducted kinetic assays to determine kinetic parameters of OGT against 26 UDP-GlcNAc analogs. Analogs differed from UDP-GlcNAc at C2, C4, and C6 of the glucosamine ring. Figure 1 shows four select analogs.Figure 1 UDP-GlcNAc and select analogsThe results of the study revealed that modifications to the substituents of these carbons are generally not tolerated with roughly 15% of the analogs being recognized and accepted by OGT. The kinetic results of UDP-GlcNAc and the four analogs shown in Figure 1 are shown in Table 1.Table 1 Kinetic Parameters of UDP-GlcNAc and Select Analogs Kinetic Constants   UDP-GlcNAc   Analog A   Analog B   Analog C   Analog D Km (µM) 8.5 141.8 369 282.1  No activity Vmax (µM/min)1.3 2.8 3.2 3.7  No activity  Despite the low recognition rate by OGT, tolerance patterns of UDP-GlcNAc analogs emerged that may indicate the molecular locations of substrate-enzyme interactions. Based on these patterns, researchers suspect the presence and orientation of C4 and C6 hydroxyl groups, as well as the C2 N-acetyl group, play a crucial role in OGT specificity.Adapted from: X. Ma, P. Liu, H. Yan, et al., "Substrate Specificity Provides Insights into the Sugar Donor Recognition Mechanism of O-GlcNAc Transferase (OGT)." PLoS ONE. ©2013 Ma et al.Question 31The non-covalent interactions occurring between N-acetyl-glucosamine functional groups and OGT are most likely:A.hydrogen bonds.B.glycosidic bonds.C.ionic salt bridges.D.hydrophobic interactions.

Which of the following carbohydrates has a glycosidic linkage?FructofuranoseGlucopyranoseMaltoseβ−D−fructose

Glycosidic linkage

Observe the following figure and identify A and B bonds in the diagrammatic representation of a portion of glycogenA = 1-4 α - glycosidic bonds, B = 1-4 α-glycosidic bondsA = 1-1 α - glycosidic bonds, B = 1-1 α-glycosidic bondsA = 1-6 α - glycosidic bonds, B = 1-4 α-glycosidic bondsA = 1-4 α - glycosidic bonds, B = 1-6 α-glycosidic bonds