Question

OUTLINE the differences in the envelope structures of Gram-positive and Gram-negative bacteria. You may use diagrams or a table.

Describe the behavior of chemotaxis in bacteria. Make sure to mention how the flagella contributes and how they can move toward good things and away from bad things.

DESCRIBE the Endosymbiotic Theory and OUTLINE the evidence to support

Answer 1

Chemotaxis is the movement of an organisms towards or away from a chemical. Positive chemotaxis is a movement towards a chemical i.e a substrate. Negative chemotaxis is movement away from a chemicals i.e repellent. Chemotaxis is thus a response to chemicals in the environment and requires that the cell has some form of sensory system. Prokaryotic movement can be divided into runs where the organism moves in one direction (caused by counterclockwise flagellar rotation) and twiddles where the organisms randomly tumbles (caused by clockwise rotation of the flagella). Where there is no gradient of attractant or repellent the organism moves in a random way with a large number of twiddles however, in the presence of a gradient the runs become longer and twiddles less frequent as the organism experience higher concentration of attractant or repellent.

Endosymbiotic theory - A wide variety of evidence support the theory that small prokaryotes began living in larger host cell. These cell likely gain entry to the host as the undigested prey, or internal parasites. It states that the organelles in eukaryotic cell were once prokaryotic microbes. Mitochondria and chloroplast are the same size as prokaryotic cell divides by binary fission and they both have their own DNA which circular in shape.