Description
- The graph below depicts the O2 binding curves for myoglobin and hemoglobin at pH 7.4.
a) Print or draw yourself a copy of this graph then label each of the curves as Mb (myoglobin) or Hb (hemoglobin). Why do the shapes of the two curves differ?
b) Which of these curves will differ significantly as a function of pH? Draw the new curve at pH 6.8.
c) Explain the molecular mechanism of this relationship between pH and O2 binding.
d) What is the physiological significance of the relationship between pH and O2 binding? - Draw the structure of the monosaccharide D-Mannose in its linear form. Is D-Mannose a triose, tetrose, pentose, or hexose? Is it an aldose or a ketose? Draw D-Mannose in its α-pyranose form. Draw D-Mannose in its β-furanose form.
- Below is the structure of the ketohexose sugar D-fructose in its Fisher projection form.
a) Its most stable cyclic form in solution is as a furanose. Draw the structure of β-D-fructofuranose as a Haworth projection. Number the carbons and circle the anomeric carbon. (Hint: the furan ring forms by nucleophilic attach of the C5-hydroxyl group on the carbonyl carbon.)
b) The most popular sweetener in the world today is sucrose. Sucrose is the disaccharide O-α-D-glucopyranosyl-(1→2)-β-D-fructofuranoside. Draw its structure as a Haworth projection. (Hint: this is α-D-glucose attached to β-D-fructose through an α(1→2) covalent linkage.) Is sucrose a reducing or a nonreducing sugar? - A student in a laboratory at SDSU has purified 81.0 mg of skeletal muscle glycogen. After exhaustive methylation (to methylate all free hydroxyl groups) and complete hydrolysis (to monosaccharide units), she detects 62.5 micromoles of 2,3-dimethylglucose, 62.5 micromoles of 2,3,4,6-tetramethylglucose, 373.5 micromoles 2,3,6-trimethylglucose, and 1.5 micromoles of 1,2,3,6-tetramethylglucose. What fraction of the monosaccharide units in this sample of glycogen are branch points? (Hint: the molecular weight of a glycosyl unit is 162 g/mol). How many reducing ends were originally present in this sample?
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