Question

1. Describe ONE way the Proton Motive Force (PMF) is produced and Describe TWO ways it is used to do work in bacteria.

2. What is meant by the terms below as they pertain to DNA replication?

Bi-directional

Asymmetrical

Semi-conservative

Proofreading

Answer 1

1a. The proton motive force or PMF is composed of two components, (i) Hydrogen ion gradient across the mitochondrial membrane, and (ii) the mitochondrial membrane potential. The proton-motive force is reported to be generated by an electron transport chain located in mitochondria. The PMF acts as a proton pump and helps in pumping protons out of the membrane, creating a charge difference. The electrochemical gradient results in the generation of PMF and it can also be defined as the measure of the potential energy accumulated as a combination of the proton gradient and voltage gradient generated across a membrane.

1b. Uses-

· The pmf can be utilized as a driving force in the flagellar rotation in bacteria.

· It can be used in the transportation of substrates or nutrients in or out of the bacterial cell.

· The pmf also controls the function of the ATP synthase complex.Protons are translocated and in the process,and it generates ATP from ADP.

2. a. Bidirectional replication.

It is a type of replication that occurs in DNA where the replication proceeds in both direction from the origin of replication and generates 2 replication forks in opposite directions. Theta mode of replication describes the bidirectional replication clearly.

b. The replication fork is reported to be asymmetrical as the DNA replication occurs in a semiconservative way with the aid of DNA polymerase. The replication fork is usually Y shaped and the new daughter strands are formed from the fork.

c. Semi-conservative replication can be defined as the mode of replication in which the two polynucleotide strands separate. Both strands serve as the template for the synthesis of a new strand. The free nucleotides are added from the 3’OH end. In this mode of replication, each daughter strand has half of the DNA from the parental strand and half of the DNA strand is newly-formed.

d. As DNA is the genetic material the process of DNA relplication should be accurate and error free. The mistakes that occurs during the process is corrected by the proof reading activity (nuclease activity) of the DNA polymerase. The incorrect base is usually removed and corrected during proof reading.