Consider following statements for catalytic mechanism of RNA polymerase

A. RNA synthesis by RNA polymerase. The reaction involves two Mg2+ ions, coordinated to the phosphate groups of the incoming nucleoside triphosphates (NTPs)

B. Three Asp residues, which are highly conserved in the RNA polymerases of all species. One Mg2+ ion facilitates attack by the 39-hydroxyl group on the phosphate of the NTP; the other Mg2+ ion facilitates displacement of the pyrophosphate, and both metal ions stabilize the pentacovalent transition state.

C. About 17 bp of DNA are unwound at any given time. RNA polymerase and the transcription bubble move from left to right along the DNA as shown, facilitating RNA synthesis. Movement of an RNA polymerase along DNA tends to create negative supercoils (overwound DNA) ahead of the transcription bubble and positive supercoils (underwound DNA) behind it.

D. The RNA polymerase is in close contact with the DNA ahead of the transcription bubble as well as with the separated DNA strands and the RNA within and immediately behind the bubble. A channel in the protein funnels new NTPs to the polymerase active site. The polymerase footprint encompasses about 35 bp of DNA during elongation.

#Question id: 11806

#Unit 6. System Physiology – Plant

sap is translocated from areas of supply, called sources, to areas of metabolism or storage, called sinks. Which of the following statements about source and sink are TRUE?

a.) Sinks include any nonphotosynthetic organs of the plant and organs that do not produce enough photosynthetic products to support their own growth or storage needs

b.) Sources include exporting organs that are capable of producing photosynthate in excess of their own needs

c.) During the growing season of the first year, storage root is a sink, when it accumulates sugars received from the source leaves. During the second growing season the same root becomes a source

d.) Roots, tubers, developing fruits, and immature leaves, which must import carbohydrate for normal development, are all examples of sources tissues

Find the correct combination of the source and sink pattern of translocation.

#Question id: 10553

#Unit 6. System Physiology – Plant

Cell walls allow plant cells to build up large internal hydrostatic pressures called

#Question id: 10554

#Unit 6. System Physiology – Plant

Transpiration is an important means of dissipating the heat input from sunlight, Heat dissipates because the water molecules that escape into the atmosphere

#Question id: 10555

#Unit 6. System Physiology – Plant

The water molecule, hydrogen–oxygen bonds form an angle of 105°, The opposite partial charges (δ– and δ+) on the water molecule lead to the formation of which bond with other water molecules,

#Question id: 10557

#Unit 6. System Physiology – Plant

The attraction of water to a solid phase such as a cell wall or glass surface known as

#Question id: 10559

#Unit 6. System Physiology – Plant

which gives water a high tensile strength,