Q: About the structure of a membrane associated peptide


 

(P-15) A 42-amino acids peptide related to the extracellular Alzheimer amyloid deposits has the last few residues immersed in the membrane bilayer. Based on your knowledge about membrane proteins, which of the following sequences most probably identifies the last five amino acids in this 42 residue peptide?

 

a)     Ala-Glu-Phe-Arg

 

b)     Val-Val-Ile-Ala

 

c)      Asp-Ser-Gly-Tyr

 

d)     Lys-Val-His-His-Gln

 

e)     Asp-Val-Gly-Ser

 

 

Q: About alpha-Helix structure


Biochemistry Question P-14

 

Side view of an alpha-helix

Side view of an alpha-helix

 

 

 

 

 

This amino acid has a profound effect in the secondary structure of proteins, because when present in the amino acid sequence, it disrupts the a-helix structure:

 

a)     Alanine

 

b)     Glycine

 

c)      Proline

 

d)     Serine

 

e)     tryptophan

 

(The answer in this post)

 

Top view of an alpha-helix

Top view of an alpha-helix

 

Extended Match Question about Protein Structure.


It is possible to distinguish different structural levels in the structure of proteins:

 

a)      Primary Structure

 

b)      Secondary Structure

 

c)      Suprasecondary structure

 

d)     Tertiary Structure

 

e)      Quaternary Structure

 

 

(P-09) This structural level refers to the non covalent association of discrete polypeptide subunits into a multi subunit protein. (Not all proteins have this structural level)

 

Answer: ___

 

(P-10) It can be defined as the sequence of amino acids in a polypeptide chain, read from the amino terminal amino acid to the carboxyl terminal amino acid.

 

Answer: ___

 

(P-11) This structural level is not affected during the denaturation of  proteins.

 

Answer:___

 

(P-12) In Sickle Cell anemia, the amino acid glutamic acid, in the position 6 of the beta chains of Hemoglobin is changed by valine. This disorder is an example of an alteration in this structural level

 

Answer:___

 

(P-13) Pr P c (normal protein) and  Pr PSc (abnormal) Prions proteins are very similar proteins.  Pr PSc, related with Creudtzfel-Jacob Disease, fatal insomnia and other human and animal diseases (as mad cow disease), can induce changes in the  structure of Normal Pr Pc protein.  One striking difference between both proteins, that share the same amino acid sequence, is the fact that Pr PSc shows high Beta strand content and low alpha-helix content, while  Pr Pc shows high alpha-helix content and low beta strand content.  Beta strand and alpha helix are types of  this structural level

 

Answer: ___

 

 

Q: About Protein Electrophoresis


 

Choose the correct electrical  migration of the proteins A,B,C and D in an electric field, knowing that the buffer solution in which are diluted the proteins has a pH of 6,4 and the isoelectric points of the proteins are:

 

 A = 5.2;  B = 6.4; C = 7.0; D = 9.2

 

a)     A will migrate to the positive pole, B will not migrate and C and D will migrate to the negative pole.

 

b)     A will migrate to the negative pole, B will not migrate and C and D will migrate to the positive pole.

 

c)      A and B will migrate to the negative pole and C and D will migrate to the positive pole

 

d)     A and B will migrate to the positive pole and C and D will migrate to the negative pole

 

e)     A will migrate to the negative pole, B and C will not migrate and D will migrate to the positive pole.

 

Q: About Collagen Synthesis


Question about Proteins P-07

 

Hydroxyproline

Hydroxyproline

 

Collagen presents in its structure modified amino acids as hydroxyproline and hydroxylysine. The formation of these amino acids from their precursors, is post-trancriptional, and occurs in enzymatic reactions that require as cofactor the following compound:

 

a)     Ascorbic acid

 

b)     Citric Acid

 

c)      Folic Acid

 

d)     Lipoic acid

 

e)     Panthotenic acid

 

About Protein Classification


 

From Ethan Hein in Flickr

 Helices in a protein

 

Q: A protein X is formed by two chains with 80 amino acids in one chain and 58 in the other. These two chains are linked by disulfide bonds and all the essential amino acids are present in the structure, but not all the non-essential amino acids.  With this information, we can say that this protein is:

 

a) a globular protein

 

b) a fibrous protein

 

c) a conjugated protein

 

d) an incomplete protein

 

e) a complete protein

 

f) a hormone

 

g) an enzyme

 

 

     Answer