Chapter 7, Problem 29DAP

(a)

Summary Introduction

To determine:  The meaning of “fractional solubility test”.

Introduction: The ABO blood typing in humans was first identified in 1901. In 1924, it is determined that gene for ABO antigen is present at a same locus and three different alleles were controlling the structure of A, B and O antigen. Later in 1960, work of W.T.J Morgan shows the complete structures of A, B, and O antigen.

Explanation of Solution

Explanation:

In this test, sample is dissolved in different variety of a solvents. Morgan does not dissolve whole sample in one solvent, but he dissolves fraction of samples in different solvent. After dissolving sample in different solvent, the dissolved sample particle and undissolved sample particle were analyzed. By comparing these solvent through fractional solubility test, researcher can determine whether there is any difference in the  composition of dissolved and undissolved sample.

(b)

Summary Introduction

To explain: The reason why analytical value obtained from fractional solubility test of a pure substance be constant, and those of an impure substance not be constant

Introduction: The ABO blood typing in humans was first identified in 1901. In 1924, it is determined that gene for ABO antigen is present at a same locus and three different alleles were controlling the structure of A, B and O antigen. Later in 1960, work of W.T.J Morgan shows the complete structures of A, B, and O antigen.

Explanation of Solution

Explanation:

Fractional solubility test is used to determine the component of a sample. The analytical value acquired from fractional solubility test of a pure substance is constant. Whereas the impure substance are not constant. This is because all molecules are same for a pure substance, so the composition of dissolved fraction is same as the composition of the undissolved fraction.

The impure substances contains a mixture of different compounds. If researcher dissolves impure substance in different solvent, various components may dissolve while remaining components may not dissolve. As a result the dissolved and undissolved fractions of the impure substance have different compositions. Thus, the analytical value obtained from the fractional solubility test of an impure substances are not constant.

(c)

Summary Introduction

To explain: The reason that why it important for Morgan’s studies especially for addressing given problem 2, that this activity assay be quantitative rather than simply qualitative.

Introduction: The ABO blood typing in humans was first identified in 1901. In 1924, it is determined that gene for ABO antigen is present at a same locus and three different alleles were controlling the structure of A, B and O antigen. Later in 1960, work of W.T.J Morgan shows the complete structures of A, B, and O antigen.

Explanation of Solution

Explanation:

Quantitative assay determines that no activity is lost at the time of degradation process. Quantitative assay determines the intact molecular structure of a compound. Loss of any part of a molecular structure would give un-interpretable molecular structures. Qualitative assay only determines the existence of an activity.

(d)

Summary Introduction

To determine: Which findings of blood group structure by Morgan’s are consistent with known blood group structure.

Introduction: The ABO blood typing in humans was first identified in 1901. In 1924, it is determined that gene for ABO antigen is present at a same locus and three different alleles were controlling the structure of A, B and O antigen. Later in 1960, work of W.T.J Morgan shows the complete structures of A, B, and O antigen.

Explanation of Solution

Explanation:

Result 1 shows that type B antigen contains three molecules of galactose, whereas type A antigen and type B antigen contain two molecules of galactose. This finding of Morgan’s was correct as type B antigen contains highest number of galactose units as compared to type A and O antigen.

Result 2 shows that type A antigen contain two molecules of amino sugar that is (N-acetyl galactosamine and N-acetyl glucosamine, whereas type B and type O antigen contains only one molecule of amino sugar (N-acetyl glucosamine). This finding of Morgan’s was also correct as type A antigen contains more number of amino sugars.

Result 3 given by Morgan’s was not correct as the ratio glucosamine and galactosamine in type A antigen is $1:1$ and in type B antigen is $1:0$.

Thus, only result 1 and result 2 of Morgan’s show consistency.

(e)

Summary Introduction

To determine: The way in which researcher explains the discrepancies in between Morgan’s data and known structures.

Introduction: The ABO blood typing in humans was first identified in 1901. In 1924, it is determined that gene for ABO antigen is present at a same locus and three different alleles were controlling the structure of A, B and O antigen. Later in 1960, work of W.T.J Morgan shows the complete structures of A, B, and O antigen.

Explanation of Solution

Explanation:

The samples used were probably impure or partly degraded. The first two finding’s of Morgan’s were accurate. This is because the technique used for first and second finding was roughly quantitative, and sensitive. Whereas, in third finding, the method used by Morgan was more quantitative. Hence, the values obtained by Morgan were different from the known values. The difference obtained in both the values is due to the use of impure and degraded substances.

(f)

Summary Introduction

To determine: Whether the enzyme prepared from T foetus is an endoglycosidase or exoglycosidase.

Introduction: The ABO blood typing in humans was first identified in 1901. In 1924, it is determined that gene for ABO antigen is present at a same locus and three different alleles were controlling the structure of A, B and O antigen. Later in 1960, work of W.T.J Morgan shows the complete structures of A, B, and O antigen.

Explanation of Solution

Explanation:

The enzyme prepared from Trichomonas foetus for cleaving O antigen is exoglycosidase. This is because this enzyme removes the sugar present at the outer surface of an antigen type O. The endoglycosidase enzyme would cleave the bond present in between the molecules. This cleavage results in the release of three molecules that is galactose, N-acetyl glucosamine, and N-acetyl galactosamine. If the activity of an enzyme is not inhibited by these three sugars, then it might be considered as the enzyme was exoglycosidase. Also fucose is the only sugar that inhibits the O-antigen degradation.

(g)

Summary Introduction

To describe: The reason that why does fucose fail to prevent their degradation by Trichomonas foetus enzyme and also determine the produced structure.

Introduction:

The ABO blood typing in humans was first identified in 1901. In 1924, it is determined that gene for ABO antigen is present at a same locus and three different alleles were controlling the structure of A, B and O antigen. Later in 1960, work of W.T.J Morgan shows the complete structures of A, B, and O antigen.

Explanation of Solution

Explanation:

The enzyme isolated from the Trichomonas foetus is considered as exoglycosidase, which act as the removal of terminal sugar. The cleavage of type A antigen results in the release of N-acetylgalactosamine unit, whereas the cleavage of type B antigen, results in the release of galastose unit. But, in type O antigen, the cleavage of this antigen results in the release of fucose unit. The release of fucose prevents further degradation of type O antigen, as fucose is the only sugar that prevents further degradation of type O antigen. Hence, the O antigen would be the product as the degradadtion is halted at fucose.

(h)

Summary Introduction

To determine: Which of the results in (f) and (g) are consistent with structure given in figure 10-14.

Introduction:

The ABO blood typing in humans was first identified in 1901. In 1924, it is determined that gene for ABO antigen is present at a same locus and three different alleles were controlling the structure of A, B and O antigen. Later in 1960, work of W.T.J Morgan shows the complete structures of A, B, and O antigen.

Explanation of Solution

Explanation:

The (f) and (g) results are coherent with the antigen structures. In antigen structure D-fucose molecule and L-galactose molecule that protect against degradation  were not present. Thus, the N-acetylgalactosamine is the only sugar which  prevents the degradation of type A antigen and galactose prevents further degradation of type B antigen. D-fucose molecule prevents the degradation of type O antigen, whereas L-galactose molecule prevents the degradation of type B- antigen.