B. Glycoproteins

Sialic acid (NANA)

A 19-year-old man is seen by you with a chest infection. He admits to coughing frequently and bringing up liberal quantities of green slimy, slippery phlegm. After your examination, you reach for your pad to write a prescription for an antibiotic and then you recall that phlegm is a mixture of mucus, bacteria and sloughed epithelial cells. Its slipperiness is due to mucin, a glycoprotein with large amounts of N-linked high mannose chains Sialic acid (NANA) Glucuronic or iduronic acids Phosphorylated sugars Sulfated sugars

E. Iduronate-2-sulfatase

A 3-year-old boy is brought to the pediatrician to be evaluated for new-onset abnormal facial development and recent hyperactive and aggressive behavior. Physical examination reveals a prominent forehead and an enlarged tongue; hepatosplenomegaly; and pearly papules on the skin over the scapulae, arms, and thighs. A deficiency in which of the following characterizes this patient's most likely diagnosis? A. α-Galactosidase A B. α-L-Iduronidase C. β-Glucosidase D. Hexosaminidase A E. Iduronate-2-sulfatase F. Sphingomyelinase

Glycoproteins Glycoproteins, proteoglycans, and glycolipids all contribute to the glycocalyx. Only one of them is included as an answer choice here. Correct answer is glycoproteins.

All cells have a glycocalyx, which contains sugar molecules on the outer surface of the cell plasma membrane. Which of the following is an important component contributing to the glycocalyx? Glycoproteins Heptahelical receptors Glycerophospholipids Glycogen molecules

E. Protein tagging at the Golgi apparatus

An 18-month-old boy is being evaluated in the office for developmental delay and failure to thrive. On physical examination, he is small for his age with coarse facial features, corneal clouding, an enlarged liver, and limited mobility in both his elbows and knees. Serum testing reveals elevated plasma lysosomal enzyme concentrations. Urinalysis is normal. Cultured fibroblasts show prominent vacuolization and inclusions in the cytoplasm. A defect in which of the following characterizes the most likely diagnosis in this patient? A. Breakdown of glycosaminoglycans B. Degradation of sphingomyelin C. Glycogenolysis D. Metabolism of an essential amino acid E. Protein tagging at the Golgi apparatus

D. Protein modification

An 18-month-old girl is brought to the physician because she has a hoarse voice and is unable to roll over or sit unsupported. On physical examination, she is small for her age with club feet, coarse facial features, and enlarged gums. She is diagnosed with a condition caused by an enzymatic defect in N-acetylglucosamine-1-phosphotransferase. This child's enzymatic defect occurs in an intracellular organelle that normally performs which of the following functions? Aß-Oxidation of long-chain fatty acids B. Degradation of cellular materials C. Lipid and membrane biosynthesis D. Protein modification E. Protein synthesis

Elevated levels of acid hydrolases in the blood

An 8-month-old boy with coarse facial features, skeletal abnormalities, and delays in both growth and development is diagnosed with I-cell disease based on his presentation and on histologic and biochemical testing. I-cell disease is characterized by Oligosaccharides in the urine An inability to N-glycosylate proteins Decreased production of cell-surface O-linked glycoproteins Increased synthesis of proteoglycans

Inability to phosphorylate mannose residues

In I-cell disease or mucolipidosis type II, all of the lysosomal enzymes are missing from the lysosomes within the cells of connective tissue. The defect is caused by GDP-mannose pyrophosphorylase deficiency Mannose kinase deficiency Mannose 6-phosphate isomerase hyperactivity Inability to phosphorylate mannose residues

A. Defects in the degradation of glycosaminoglycans

Mucopolysaccharidoses are hereditary lysosomal storage diseases. What is the most important underlying cause of these diseases? A. Defects in the degradation of glycosaminoglycans B. Detestsonthe targeting of enzymes C. An increased rate of synthesis of the carbohydrate component of proteoglycans D. An insufficient rate of synthesis of proteolytic enzymes E. amountsoriore proteimally small F. The synthesis of heteropolysaccharides with an altered structure

Defects in the degradation of glycosaminoglycans

Mucopolysaccharidoses are hereditary lysosomal storage diseases. What is the most important underlying cause of these diseases? An increased rate of synthesis of the carbohydrate component of proteoglycans Defects in the degradation of glycosaminoglycans An insufficient rate of synthesis of proteolytic enzymes The synthesis of abnormally small amounts of core proteins The synthesis of heteropolysaccharides with an altered structure Defects in the targeting of enzymes to lysosomes

outside Carbohydrates are found attached on the external surface of the cell membrane.

On which surface(s) of the cell membrane are the carbohydrate part of glycoproteins or glycolipids found? Outside Inside Both outside and inside Neither side

Having a large number of very specific glycosyltranferases

The low-density lipoprotein receptor has a domain containing O-linked glycan chains. How are the sequences of the sugar residues determined? Editing the sugar sequences to replace sugars in the wrong position Controlling the availability of the different activated sugars Matching against a carbohydrate template in the ER Having a large number of very specific glycosyltranferases

D. Allow the TSHR to appear at the cell membrane

The thyroid stimulating hormone receptor (TSHR) has both N- and O- type glycosylation. What is a plausible role of this glycosylation? A. Activate intracellular second messengers B. Facilitate the export of free TSHR out of the cell C. Target the TSHR to the lysosomes D. Allow the TSHR to appear at the cell membrane

B. Charge repulsion between glycosaminoglycan chains

The underlying mechanism by which glycosaminoglycans allow for the formation of a gel-like substance in the extracellular matrix (ECM) is which of the following? A. Charge attraction between glycosaminoglycan chains B. Charge repulsion between glycosaminoglycan chains C. Hydrogen bonding between glycosaminoglycan chains D. Covalent cross-linking between glycosaminoglycan chains E. Hydroxylation of glycosaminoglycan chains

A. Loss of negative charges on the proteoglycans

Which of the following alterations would reduce the ability of cartilage to cushion weight bearing activities at joints? A. Loss of negative charges on the proteoglycans B. Loss of positive charges on proteoglycans C. Gain of negative charges on proteoglycans D. Increased acid concentration of glucuronic acid residues E. Increased concentrations of Sulfated sugars in the proteoglycans

B. Inactivation of the fucose transferase

Which of the following best describes the underlying reason for the presence of blood type On in a person? A. Amino acid substitutions in the glycosyl transferase B. Inactivation of the fucose transferase C. Frameshift mutation in the glycosyl transferase D. Differential ability to produce sugars D-galactose or N- acety galactosamine

Mannose

Which of the following is a characteristic sugar residue always found in N-linked glycoproteins, but hardly ever in O-linked glycoproteins? Xylose Ribose Sorbitol Galactose Fructose Mannose

proteoglycans which are found in all connective tissues, extracellular matrix and on the surfaces of many cells.

Which of the following is found in connective tissues? Glycolipids Proteoglycans Glycosaminoglycans Glycoproteins

They hold less amount of water. Proteoglycans hold large amounts of water.

Which of the following statements is false about proteoglycans? They hold less amount of water They possess charge They are made of amino acids and sugars Chondroitin sulfate is a proteoglycan