Chapter 2 Cell biology.pptVIP

Chapter 2 Cell Biology 3. Their cell wall almost always contain the complex polysaccharide peptidoglycan The cell wall of the bacterial cell is a complex, semi-rigid structure that is responsible for the characteristic shape of the cell. The cell wall surrounds the underlying, fragile plasma (cytoplasmic) membrane and protects it and internal parts of the cell from adverse changes in the surrounding environment. Almost all prokaryotes have cell walls. Structure of cytoplasmic membrane Function of cytoplasmic membrane 2.4 Cellular genetic information Bacterial Chromosome Supercoiling and chromosome structure Chromosomal copy number Plasmids 1. Permeability barrier -prevents leakage and function as gate way for transport of nutrients into and out of the cell. 2. Protein anchor- site of many proteins involved in transport, bioenergetics, and chemotaxis. 3. Energy conservation- site of generation and use of the proton motive force. Function of membrane Intracellular membrane system Bacteria cells don’t contain membrane-enclosed organelles. However, bacteria may have specialized invaginations of the cytoplasmic membrane. Their function may be to provide a larger membrane surface for greater metabolic activity. Structure of Mesosome Mesosome may be involved in wall formation during division or play a role in chromosome replication and distribution to daughter cells. It may also be involved in secretory processes Micrograph of a bacterium showing the nucleoid region (green) within the cytoplasm where the bacterial chromosome occurs The bacterial chromosome is a circular DNA macromolecule except in Streptomyces where it is linear and Rhodobacter sphaffoides, which has two separate chromosomes. Bacterial chromosome The bacterial chromosome is usually a single covalently closed circular molecule. The term nucleoid is used to describe aggregated DNA in the prokaryotic cell. Range of genome sizes in virous groups of organisms and the organellesof eukary