The mechanisms that regulate the loading of sucrose from the apoplast to the sieve elements by the sucrose–H+ symporter await characterization. Possible regulatory factors include the following:

a) The solute potential or, more likely, the turgor pressure of the sieve elements

b) Sucrose concentration in the apoplast

c) The available number of symporter protein molecules

Which one of the mechanism that involve to regulate the loading of sucrose?

#Question id: 870

#Unit 1. Structure and Function of Biomolecules

Choose correct statements about ‘Protein Disulfide Isomerase’ in protein folding

A. Oxidized PDI catalyzes the rearrangement of a polypeptide’s non-native disulfide bonds via disulfide interchange reactions to yield native disulfide bonds.

B. Reduced PDI catalyzes the initial formation of a polypeptide’s disulfide bonds through the formation of a mixed disulfide.

C. Protein disulfide isomerase contains the conserved active site motif of Cys-Xaa-Xaa-Cys found in thioredoxin and shares a similar role to the Dsb family of proteins found in E. coli.

D. Under more reducing conditions with thiols in the active site the enzyme reshuffles disulfides (isomerase) in target proteins.

#Question id: 871

#Unit 1. Structure and Function of Biomolecules

According to ‘Energy–entropy phenomenon’ for protein folding correct combinations of possible conformations

#Question id: 872

#Unit 1. Structure and Function of Biomolecules

Which of the following statements is not true about HSP 70 family.

A. They have a molecular weight near 70,000 and are abundant in cells stressed by elevated temperature.

B. Bind to regions of unfolded polypeptides that are rich in hydrophilic residues

C. Hsp70 proteins not  block the folding of certain proteins that must remain unfolded untill they have been translocated across a membrane.

D.) It releases polypeptides in a cycle that uses energy from ATP hydrolysis.

#Question id: 873

#Unit 1. Structure and Function of Biomolecules

Intrinsically disordered proteins have properties that are distinct from classical structured proteins

A. Are characterized by sequences rich in certain polar and charged amino acids (Gln, Ser, Pro, Glu, Lys, Gly, and Ala)

B. Ordered proteins tend to participate in signaling and regulation, whereas Intrinsically disordered proteins are involved largely in catalytic reactions, transport processes, and structural functions.

C. Nearly half of all prokaryotic proteins contain long disordered segments, whereas only a few percent of eukaryotic proteins do.

D. Often adopt a specific secondary or tertiary structure when they bind to other molecules such as ions, organic molecules, proteins, and nucleic acids.

#Question id: 874

#Unit 1. Structure and Function of Biomolecules

Fates of misfolded proteins, according given figure

#Question id: 875

#Unit 1. Structure and Function of Biomolecules

Why positive phi angles less common than negative Phi angles in proteins contain L amino acid?