#Question id: 5324
#Unit 8. Inheritance Biology
In eusocial insects, males develop from unfertilized eggs while females develop from fertilized eggs. The ultimate consequence of this difference is that
#Question id: 9181
#Unit 9. Diversity of Life Forms
Turnover of water in temperate lakes during the spring and fall is caused by which of the following?
#Question id: 870
#Unit 1. Molecules and their Interaction Relevant to Biology
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: 1201
#Unit 4. Cell Communication and Cell Signaling
Epinephrine binds to the same type of receptors in liver, fat, and smooth muscle cells. Yet in liver, glycogen breaks down; in fat, triacylglycerols break down; and smooth muscle cells relax. How can the same hormone produce three such different responses?
#Question id: 722
#Unit 1. Molecules and their Interaction Relevant to Biology
The structure of alpha helix is stabilized by hydrogen bonds between the hydrogen atom attached to the electronegative nitrogen atom of a peptide linkage and the electronegative carbonyl oxygen atom of the fourth amino acid on the amino-terminal side of that peptide bonds. Within the helix, every peptide bond (except those close to each end of the helix) participates in such hydrogen bonding. Each successive turn of the helix is held to adjacent turns by three to four hydrogen bonds, conferring significant stability on the overall structure. Which of the following are correct statements regarding these findings?
A. At the ends of a helical segment, there are always three or four amide carbonyl or amino groups that participate in this stabilised helical pattern of hydrogen bonding.
B. Helix ends are exposed to the surrounding solvent, where they hydrogen-bond with water, or other parts of the protein may cap the helix to provide the needed hydrogen-bonding partners.
C. Helix can form in polypeptides consisting of either L- or D-amino acids but a D-amino acid will disrupt a regular structure consisting of L-amino acids, and vice versa.
D. The most stable form of a helix consisting of L-amino acids is left-handed.
E. 310 helix occupies similar place as turns in Ramachandran plot due to its confirmation