AIPGME 2012 BIOCHEMISTRY MCQ QUESTIONS SOLVED WITH REFERENCES

Thanks to all my students in TMCAA who have taken effort to post me the questions for discussion .Any one who can find missed question can add up so that i can complete the list  .You can forward  future entrance question to my mail or in this blog for discussion.

1. The function of a gene is determined by

a.southern blot

b.western blot

c.inserting in trangenic mice

d. inserting as a knock out gene

Knockout : Remove complete or part of the gene from the genome
Knockin : inserting external elements in to the genome like GFP/RFP or LacZ
Transgenic : over expressing particular gene in in vivo, similar way like overexpressing proteins in mammalian cells

When researchers isolate human genes with unknown functions, they can create knockout mice with these genes and observe the results. Instead of creating merely the mouse equivalent of the human gene, researchers are able to reproduce and express actual human genes and their corresponding proteins in mice. Subsequent offspring will inherit not only the instructions coded by their original mouse genome, but also the traits coded for by the inserted human DNA. This helps researchers understand health and disease by observing how genes work in cells.
Knockout mice have many benefits. They not only allow researchers to determine gene function and understand diseases at the molecular level, but they also aid scientists in testing new drugs and devising novel therapies.

http://www.ornl.gov/sci/techresources/Human_Genome/faq/compgen.shtml

Transgenic Mice

One of the simplest ways to study gene function in a mouse is exogenous expression of a protein in some or all tissues. For this type of genetic modification, a new piece of DNA is introduced into the mouse genome. This piece of DNA includes the structural gene of interest, a strong mouse gene promoter and enhancer to allow the gene to be expressed and vector DNA to enable the transgene to be inserted into the mouse genome

Currently, the phrase "transgenic mouse" generally refers to any mouse whose genome contains an inserted piece of DNA, originating from the mouse genome or from the genome of another species, and the term includes the standard transgenic mouse as well as a knockin or knockout mouse http://www.cellmigration.org

According to my opinion Inserting as knock out gene is the best option

2. In Immune complex formation structure of protein involved is

 

               a) Primary

               b) Secondary

               c) Tertiary

              d) Quaternary

Tertiary structure ,the immunoglobulin fold is the domain involved which is a tertiary structure.Even though Ig Has more than one polypeptide chain .For its functional fulfillment domain is needed which is a tertiary structure.

Covalently-connected tertiary domains

In this class of protein, domains are usually formed as modules covalently "strung together" on a single polypeptide chain. The individual chains of antibodies are like this, strings of immuno-globulin domains. However, light and heavy chains then combine to produce hetero-multimers, which may even associate into higher complexes, as with IgM [http://swissmodel.expasy.org]

Higher Levels of Protein Organization
Primary structure of a protein refers to the covalent structure of a protein. It includes amino acid sequence and location of disulfide (cystine) bonds. Higher levels of
protein organization refer to noncovalently generated conformational properties of the primary structure. These higher levels of protein conformation and organization
are defined as the secondary, tertiary, and quaternary structures of a protein. Secondary structure refers to the local threedimensional
folding of the polypeptide
chain in the protein. The polypeptide chain in this context is the covalently interconnected atoms of the peptide bonds and a carbon
linkages that sequentially link the
amino acid residues of the protein. Side chains are not considered at the level of secondary structure. Tertiary structure refers to the threedimensional
structure of
the polypeptide. It includes the conformational relationships in space of the side chains and the geometric relationship between distant regions of the polypeptide chain.
Quaternary structure refers to the structure and interactions of the noncovalent association of discrete polypeptide subunits into a multisubunit protein. Not all
proteins have a quaternary structure.[Text book of Biochemistry with clinical correlation Thomas M Devlin  ]

I had got another reference recently       this from page 1351  Clinical laboratary medicine by
 kenneth d macclatchey  . This is what is refered 

3. Amylin is secreted by:

     

               a.alpha cells

               b.beta cells

               c .gamma cells

               d .delta cells

Amylin, or Islet Amyloid Polypeptide (IAPP), is a 37-residue peptide hormone secreted by pancreatic β-cells at the same time as insulin

4. All except occurs on Decrease in liver glucose level :

            a.inhibition of PFK2

            b.Activation of Fructose 2,6bisphosphatase

             c.increase in glucagon

             d.increase in Fructose2,6bis phosphate

When there is an abundant supply of glucose, the concentration of fructose 2,6-bisphosphate increases, stimulating glycolysis by activating phosphofructokinase-1 and inhibiting fructose 1,6-bisphosphatase. In the fasting state, glucagon stimulates the production of cAMP, activating cAMP-dependent protein kinase, which in turn inactivates phosphofructokinase-2 and activates fructose 2,6-bisphosphatase by phosphorylation. Hence, gluconeogenesis is stimulated by a decrease in the concentration of fructose 2,6-bisphosphate, which inactivates phosphofructokinase-1 and relieves the inhibition of fructose 1,6-bisphosphatase.[Harper 28^th edition]

 Answer is increase in Fructose2,6bis phosphate

5.After 12-24 hrs starvation, what will not happen?

 

       A. Increase free fatty acid

      B. increase ketone bodies.

     C. decreased glycogen

     D. decreased serum protiens.

Table 16–2. Plasma Concentrations of Metabolic Fuels (mmol/L) in the Fed and Fasting States

Fed 40 Hours Fasting 7 Days Starvation Glucose 5.5 3.6 3.5 Free fatty acids 0.30 1.15 1.19 Ketone bodies Negligible 2.9 4.5

By 12-24 hours the glycogen store is depleted ,So no point of decrease in glycogen after 24 hours.Eventhough I could not find decrease in serum  Protein it is obvious that plasma protein synthesis decrease in starvation.