Question:
Kjeldahl analysis provides an accurate measurement of the content of food protein since only proteins in foods will be measured
True or false
Answer
False
This is rather not true because we know that the method does not give accurate percentage it gives only approximate calculation and would rather be accurate estimate of the nutritional value of nitrogenous substances in food and not the protein content alone
Explanation
In general, the Kjeldahl method permits the available nitrogen to be precisely determined and not protein, in the plant or even soil by involving three successive phases which are
Digestion of the organic material which helps convert nitrogen into HNO3.
Distillation of the released Ammonia into an absorbing surface or medium.
Lastly, the volumetric analysis of the Ammonia that results from the first process which is the digestion.
With this in mind, we can thus conclude that the method does no provide an accurate measure of protein content and does not only determine the protein content in food.
Question:
If enzymatic inhibitors result in their lines of enzymatic Lineweaver-Burk plots having a fixed y-intercept (1/Vmax) and changed slopes and x-intercepts, then these inhibitors for the enzymatic reactions are considered:
a. Competitive
b. Uncompetitive
c. Non-competitive
d. Post-competitive
Answer
a. Competitive
The Lineweaver-Burk plot can distinguish competitive, non-competitive and uncompetitive inhibitors which is created by plotting the inverse initial velocity (1/V0) as a function of the inverse of the substrate concentration (1/[S]).
Explanation
Basically speaking, competitive inhibitors have the same y-intercept as uninhibited enzyme because Vmax is mot affected by competitive inhibitors the inverse of Vmax also doesn’t change and rather what happens is that there are different slopes and x-intercepts between the two data sets. In this sense, to clarify things we would say that this happens when the binding of an inhibitor prevents binding of the target molecule of the enzyme, also known as the substrate.
Question:
Viscosity is defined as the internal friction of a fluid or its tendency to resist flow, which has several different units corresponding to different materials. Which one of the following units is not expressed correctly:
a. Pa·s
b. mPa·s
c. (N.s)/m2
d. kg/m·s
e. N/cm-2
Answer
e. N/cm-2
As already been said, the viscosity of a fluid is the measure of its resistance to gradual deformation by shear stress or tensile stress.
Explanation
In general terms, viscosity describes how resistant the given substance is to any form of deformation that is often informally referred to as thickness.
This unit N/cm-2 is rather used to measure pressure
Some of the units that are used in measurement of viscosity are:
Centipoise (cP)
Gram per centimeter second (g/(cm·s))
Kilogram per metre second (kg/(m·s))
Newton second per square metre (N·s/m²)
Pascal-second (Pa·s), Poise (P)
Question:
For an antibody (IgG), which of the following does not exist in its structure:
a. Peptide chain
b. Disulfide bonds
c. DNA chain
d. Variable binding site
Answer
c. DNA chain
In general an antibody fro instance the IgG antibodies are large molecules of about 150 kDa made of four peptide chains which normally contain two similar class γ heavy chains of about 50 kDa and two identical light chains of about 25 kDa,which means in other words, they are tetrameric quaternary structure
Explanation
There is the basic structure of any antibody and the variable parts which keep changing from one class of antibodies to the others,though in general their making is the same. The antibody consists of four polypeptides- two heavy chains and two light chains joined to form a “Y” shaped molecule. Also, the amino acid sequence in the tips of the “Y” varies greatly among different antibodies and this is what distinguishes antibodies in different classes where also this variable region, composed of 110-130 amino acids, give the antibody its specificity for binding antigen.
Question:
Water activity is always half value of the corresponding moisture content
True or false?
Answer
False
Water activity can simply termed to be water available to attract another material wheereas moisture content can be said to be the amount of water in a given material
Explanation
Since we know that water activity is the water available to attract another material and moisture content can be said to be the amount of water in a given material, then the statement can not hold true always because every material is not uniform or rather materials are not homogeneous. The reason this is not always half or as described is that for a given humidity value, a sorption isotherm would indicate a corresponding content of water at a given constant temperature. Again, in case the materials composition changes or the quality of the material, then sorption behavior will ultimately change
