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TLS Online TPP Program

#Question id: 14753

German scientist Adolf Fick discovered that the rate of diffusion is directly proportional to the concentration gradient (∆cs /∆x)—that is, to the difference in concentration of substance s (∆cs ) between two points separated by the distance ∆x. According to Fick’s first law,

#Unit 6. System Physiology – Plant
  1. The movement of molecules by diffusion always proceeds nonspontaneous, down a gradient of concentration or chemical potential, until equilibrium is reached, movement of molecules is termed passive transport
  2. The rate of accumulation (or depletion) of concentration within the volume as proportional to the local curvature of the concentration gradient
  3. A substance will diffuse faster when the concentration gradient becomes steeper (∆cs is large) or when the diffusion coefficient is increased
  4. A cell membrane potential to standard potential and to the activities of the electroactive, relates the effective concentration
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TLS Online TPP Program

#Question id: 3828

#Unit 3. Fundamental Processes

Why does E. coli need both DNA polymerase III and DNA polymerase I?
TLS Online TPP Program

#Question id: 3829

#Unit 3. Fundamental Processes

Why is only one copy of DNA made per cell division cycle in eukaryotes despite the presence of multiple origins of replication?
TLS Online TPP Program

#Question id: 3830

#Unit 3. Fundamental Processes

Why is DNA damage in skin cells from exposure to excessive UV light not completely reversed by photoreactivation?
TLS Online TPP Program

#Question id: 3831

#Unit 3. Fundamental Processes

State whether the following statements is true/false regarding DNA replication.

1. In E. coli replication begins at the origin of replication and proceeds in one direction until the entire circular DNA molecule has been copied.

2. The chromosome of the fruit fly (D. melanogaster) is about twice as large as the E. coli chromosome.

3. Prokaryotic DNA replication occurs in two steps. First, ATP provides a phosphate to the growing DNA chain. This is followed by addition of a nucleoside.

4. DNA polymerase III is the largest DNA polymerase in E. coli.

5. The β subunits of E. coli DNA polymerase form a sliding clamp that surrounds the DNA strands at the replication fork.
TLS Online TPP Program

#Question id: 3832

#Unit 3. Fundamental Processes

You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). Which two classes of DNA do these different samples represent?
TLS Online TPP Program

#Question id: 3833

#Unit 3. Fundamental Processes

Regarding DNA replication, which, if any, of the following statements is incorrect?