What is the key difference between photoheterotrophs and photoautotrophs?
a. Photoautotrophs only use bacteriochlorophyll; photoheterotrophs only use chlorophyll a.
b. Photoheterotrophs produce oxygen as a by-product; photoautotrophs do not.
c. Photoheterotrophs use hydrogen sulfide for reducing power; photoautotrophs do not.
d. Photoheterotrophs use organic compounds as their carbon source; photoautotrophs use carbon dioxide as their carbon source.
Answer: d. Photoheterotrophs use organic compounds as their carbon source; photoautotrophs use carbon dioxide as their carbon source.
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Supercoiling is important for DNA structure, because
A) it holds together the antiparallel strands of DNA in the double helix. B) it provides energy for transcription. C) it condenses the DNA so that it can fit inside the cell. D) it prevents RNA from pairing with DNA in the double helix.
________ bonds hold the hydrogens to the oxygen within a water molecule, and ________ bonds attract one water molecule to other water molecules
A) Ionic; hydrogen B) Hydrogen; ionic C) Hydrogen; covalent D) Covalent; hydrogen E) Ionic; covalent
Each of the following is a characteristic of calmodulin except
A) It binds two calcium ions at each end of the protein. B) When activated by calcium ion binding, it wraps around proteins that have calmodulin binding sites. C) It can activate specific kinases and phosphatases. D) It has a very high affinity for calcium ions, and binds calcium ions irreversibly. E) All are characteristics of calmodulin.
What is the pH difference (?pH) across a membrane at 310 K if the membrane potential is -0.15 V and the overall Gibb's free energy change across the membrane is -19 .0 kJ mol-1? (R = 8.315 J K-1 mol-1; F = 96,485 J V-1 mol-1)
A) 5.44 B) 2.3 C) 0.74 D) 1.4