Chapter 4 Prokaryotic cell

Bacteria are prokaryotic organisms DNA is not enclosed within a membrane DNA is not associated with histone proteins ( no nucleosomes) No membrane bound organelles. Cell walls – peptidoglycan Divide by binary fission

Curved rod Bent rod Loose spiral Tight spiral

Glycocalyx Capsule – gelatinous substance – outside the cell wall. Polysaccharides Contribute to the virulence Protect bacteria from phagocytosis Capsulated Streptococcus pneumoniae – pneumonia Uncapsulated – destroyed by WBCs

Streptococcs mutans – surface of teeth Tooth decay Flagella long filamentous Movement – motile Rotate their flagella to swim Exhibit chemotaxis Positive chemotaxis – towards substances Negative chemotaxis - move away

Spirochetes Treponema pallidum syphilis

Fimbriae Gram - bacteria have hair like structures. Shorter thinner than flagella Numerous Attachment – virulence Neisseria gonorrhoeae – fimbriae – Mucous membrane – colonize the area No fimbriae – cannot colonize

Pili One or two pili Longer than fimbriae Used for conjugation Join two bacterial cells together for DNA transfer

Cell wall Protects internal structures and plasma membrane Made up of peptidoglycan Glycan – sugar – repeating units of disaccharide N-acetylmuramic acid N-acetylglucosamine Peptido-peptide-amino acids Rows are sugars are cross linked by amino acid chains.

Lipoprotein Phospholipid lipopolysaccharide Lipid A Endotoxin Septic shock

Mycoplasma has no cell walls Cell wall can be damaged Antibiotic penicillin Stops the formation of peptide cross bridges in peptidoglycan Lysozyme-enzyme-tears, saliva, mucus Breaks the bond between sugar molecules. Gram- more resistant – outer membrane Gram+ more sensitive – peptidoglycan is exposed to the environment

Plasma membrane Encloses the cytoplasm Phospholipids and proteins No sterols – exception is mycoplasma Phospholipids are arranged in a bilayer Proteins are inserted Structure – fluid mosaic

Plasma membrane – selectively permeable (semipermeable) Damaged by alcohol, polymyxin Molecules constantly cross the membrane Nutrients get into the cell Waste products move out of the cell Active process and passive process

Passive process – molecules move from an area of high concentration to low concentration. Energy is not used. Active process – molecules move from an area of low concentration to high concentration Energy is used. Passive process Simple diffusion, facilitated diffusion, osmosis

Simple diffusion – molecules move from an area of high concentration to low concentration. CO2 and O2 cross the membrane by means of simple diffusion. Facilitated diffusion – molecules move from an area of high concentration to low concentration. Energy is not used. Transport proteins are used.

Osmosis – movement of water molecules from an area of high concentration of water to an area of low concentration of water through a selectively permeable membrane. hypotonic – solute concentration lower outside the cell. Water moves into the cell. Cell swells up and breaks down. Osmotic lysis. Cell walls are damaged – bacteria undergo osmotic lysis.

Hypertonic – solute concentration is higher outside the cell. water moves out of the cell. Plasma membrane shrinks away from the cell wall. Plasmolysis Most bacteria cannot survive in a hypertonic environment

Active process Active transport - molecules move from an area low concentration to high concentration. Energy is used. Transport proteins are involved. Ribose, histidine Group translocation – molecules move from an are low concentration to high concentration. Energy is used. Transport proteins are involved. While the molecule is being transported, it is chemically altered. Glucose transported across the membrane, phosphate is added.

Cytoplasm – carbohydrates, proteins, lipids, ribosomes, DNA, inclusions Nuclear area (nucleoid) – long circular, double stranded DNA – chromosome Genetic information needed for the structure and function of the cell. Some bacterial cells – small circular DNA – plasmid Plasmids make the bacterium resistant to antibiotics.

Ribosomes – two subunits Each subunit is made up of proteins and ribosomal RNA. 70S ribosomes – smaller, less dense than 80S ribosomes Protein synthesis

Inclusions – organic or inorganic Metachromatic granules – phosphate – used by the cell to make ATP. Corynebacterium diphtheriae Polysaccharide granules – glycogen or starch Lipid inclusions – hydroxybutyric acid Bacillus, Mycobacterium Sulfur granules – Thiobacillus – uses sulfur for energy.

Carboxysomes – enzyme – ribulose diphosphate carboxylase. Needed for photosynthesis Cyanobacteria – photosynthetic bacteria Gas vacuoles – hollow cylinders covered by protein. Float at a certain depth in water - light

Endospores Clostridium and Bacillus Dormant stage of the cell Resistant to hostile environmental conditions Heat, UV light, disinfectant, desiccation Nutrient depletion sporulation

Endospores – dehydrated DNA, RNA, ribosomes, enzymes, dipicolinic acid, calcium ions. Stay dormant for thousands of years. When conditions are favorable, spores germinate into vegetative cells. Sporulation is not reproduction. One cell – one spore – germinates into a single cell. No increase in the number of cells