#Question id: 12374
#Unit 10. Ecological Principles
#Question id: 28040
#Unit 1. Molecules and their Interaction Relevant to Biology
Cyclic symmetries, Dihedral symmetries, Tetrahedral symmetry, Octahedral (cubic) symmetry, Icosahedral symmetry these symmetry arises as a result of
#Question id: 12745
#Unit 13. Methods in Biology
#Question id: 10903
#Unit 6. System Physiology – Plant
Materials translocated in the phloem, such as sucrose, amino acids, hormones and some inorganic ions. Some inorganic solutes that move in the phloem called mobile elements. In contrast, some are relatively immobile in the phloem.
A) Immobile elements
B) Mobile elements
i) potassium, magnesium, phosphate, and chloride
ii) caesium, zinc, magnesium and iron
iii) nitrate, calcium, sulfur, and iron
iv) potassium, calcium, cobalt and caesium
Which of the following are the correct match of mobile and immobile elements in the phloem?
#Question id: 723
#Unit 1. Molecules and their Interaction Relevant to Biology
Common structural elements in proteins such as α-helices or β-sheets are characterized by uniformly repeating, energetically favorable main chain conformations which additionally exhibit a completely saturated hydrogen-bonding network of the main chain NH and CO groups. Although polyproline or polyglycine type II helices (PPII or PGII ) are frequently found in proteins, they are not considered as equivalent secondary structure elements. Which of the following statements are correct about PP and PGs.
A. PGII -like helices form hexagonal bundles which appear to fulfill the criterion of a (largely) saturated hydrogen-bonding network of the main-chain groups
B. main chain NH and CO groups of the central PGII -helix are saturated by either intra- or intermolecular hydrogen-bonds, resulting in a self-contained hydrogen-bonding network
C. The formation of the right-handed PPI helix is possible only with proline residues because of the required cis conformation.
D. PPII helices seem to be stabilized by main chain-water hydrogen bonds (in the absence of main chain- main chain H-bonds), and tend to have a regular pattern of hydrogen bonds with water. After this, it is not surprising, that PPII helices are found mostly on the protein surface.