18.6 Electric Forces in Biology

18.6 Electric Forces in Biology

• It is very similar to the field produced by two positive charges, except that the directions are reversed.
• The field is not as strong as it could be.
• The individual forces on a test charge are in opposite directions.

• We use electric field lines to visualize and analyze electric fields.

• Field lines must start on positive charges or end on negative charges in the case of isolated charges.

• The magnitude of the charge is what determines the number of field lines leaving a positive charge or entering a negative charge.

• The strength of the field is determined by how close the field lines are to each other.

• At any point in space, the direction of the electric field is related to the field line.

• Field lines are impossible to cross.

• The field is unique at any time.
• If they crossed the field would have two directions, but it would be impossible if the field is unique.

• You can view the electric field, voltages, equipotential lines, and more by moving the point around on the field.

• There is an important role for classical electrostatics in modern biology.
• Large molecule are usually charged by electricity.
• The structure and strength of the molecule is due to the electrostatic force that holds the molecule together.

• The molecule is charged.
• The double helix shows the strands of DNA that are coiled around a row of nitrogenous bases.
• The strands are connected by bonds.

• The sequence of nucleotides in the strand varies between bases.

• The symbols for the four bases are A, C, G, and T. The order of the bases in each strand is different, but the pairs are the same.
• The order of bases in cell division is preserved by the fact that C and G are always pairs.
• The distances between the base pairs must be small enough to hold them together since the Coulomb force drops with distance.

• The distance between the two strands that make up the DNA structure is about one hundredth of a second, while the distance between the individual atoms within each base is about one hundredth of a second.

• If we have so many charged molecules, why don't electrostatic forces play a bigger role in biology?
• There are other charges in the cell.

• The water molecule is the best example of charge screening.
• The 10 electrons from the oxygen atom and 2 from the hydrogen atoms are closer to the oxygen nucleus than to the hydrogen nucleus.

• Some of the electric field lines coming from a free charge will be terminated by these two centers of charge.
• Screening makes the Coulomb force a short range force.

• Inside and outside of living cells, these ion are located.
• The motion of nerve impulses through nerve axons depends on the movement of the ion through cell membranes.

• Recent studies show that electric fields in cells can be extended over larger distances, despite screening, by "microtubule" within the cell.
• The hollow tubes that guide the movement of chromosomes when cells divide, the motion of other organisms within the cell, and provide mechanisms for motion of some cells are called microtubules.

• A net separation of positive and negative charge is formed when the oxygen and hydrogen atoms share the same electrons.

• The attraction of opposite charges between molecule leads to this.