Processes of Life. GrowthReproductionResponsivenessMetabolism. Prokaryotic Cells. Comparing Prokaryotic and Eukaryotic CellsProkaryote comes from the Greek words for prenucleus.Eukaryote comes from the Greek words for true nucleus.. ProkaryoteOne circular chromosome, not in a membraneNo histo
1. Chapter 4 Porkaryotic Cell Structure and Function
2. Processes of Life Growth
3. Prokaryotic Cells Comparing Prokaryotic and Eukaryotic Cells
Prokaryote comes from the Greek words for prenucleus.
Eukaryote comes from the Greek words for true nucleus.
4. Comparing Prokaryotes and Eukaryotes
5. Comparing Prokaryotes and Eukaryotes
6. Average size: 0.2 -1.0 µm ? 2 - 8 µm
.5 µm 2 µm
Cocci – round
Bacilli – rod
10. External Structures of Prokaryotic Cells Glycocalyces
Fimbriae and pili
11. Glycocalyces Gelatinous, sticky substance surrounding the outside of the cell
Composed of polysaccharides, polypeptides, or both
12. Capsule Composed of organized repeating units of organic chemicals
Firmly attached to cell surface
Protects cells from drying out
May prevent bacteria from being recognized and destroyed by host
13. Slime Layer Loosely attached to cell surface
Protects cells from drying out
Sticky layer that allows prokaryotes to attach to surfaces
14. Flagella Are responsible for movement
Have long structures that extend beyond cell surface
Not all prokaryotes have flagella
Filament capable of rotating 360ş
15. Arrangements of Bacterial Flagella Peritrichous: distributed throughout the surface of the bacterium
16. Arrangements of Bacterial Flagella Monotrichous: a single flagella at one end.
17. Arrangements of Bacterial Flagella Lophotrichous: many flagella located at one end of the bacterium.
18. Function of Bacterial Flagella Rotation propels bacterium through environment
Rotation can be clockwise or counterclockwise; reversible
Bacteria move in response to stimuli (taxis)
Runs – movements of cell in single direction for some time due to counterclockwise flagellar rotation; increase with favorable stimuli (positive chemotaxis, positive phototaxis)
Tumbles – abrupt, random, changes in direction due to clockwise flagellar rotation; increase with unfavorable stimuli (negative chemotaxis, negative phototaxis)
19. Function of Bacterial Flagella
20. Fimbriae and Pili Nonmotile extensions
Sticky, proteinaceous, bristlelike projections
Used by bacteria to adhere to one another, to hosts, and to substances in environment
May be hundreds per cell and are shorter than flagella
Serve an important function in biofilms
21. Pili Long hollow tubules
Longer than fimbriae but shorter than flagella
Bacteria typically only have one or two per cell
Join two bacterial cells and mediate the transfer of DNA from one cell to another (conjugation)
22. Prokaryotic Cell Wall Provides structure and shape and protects cell from osmotic forces (cell bursting from excess water uptake).
Assists some cells in attaching to other cells or in eluding antimicrobial drugs
Animal cells do not have; can target cell wall of bacteria with antibiotics
23. Bacterial Cell Wall Most have cell wall composed of peptidoglycan; a few lack a cell wall entirely.
Peptidoglycan composed of sugars, NAG, and NAM
Chains of NAG and NAM attached to other chains by tetrapeptide crossbridges
Bridges may be covalently bonded to one another
Bridges may be held together by short connecting chains of amino acids
24. Peptidoglycan Polymer of disaccharide N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM)
25. Peptidoglycan NAG and NAM are linked by polypeptides
26. Gram-Positive Cell Wall Relatively thick layer of peptidoglycan
Contains unique polyalcohols called teichoic acids
Some covalently linked to lipids, forming lipoteichoic acids that anchor peptidoglycan to cell membrane
Polysaccharides provide antigenic variation
Acid-fast bacteria contain up to 60% mycolic acid
helps cells survive desiccation (drying out).
Example: Mycobacterium tuberculosis – causative agent of TB
27. Gram-positive Cell Wall
28. Gram-Negative Cell Walls Have only a thin layer of peptidoglycan.
Bilayer membrane outside the peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS)
29. Union of lipid with sugar
Also known as endotoxin
Lipid portion known as lipid A
Dead cells release lipid A when cell wall disintegrates
May trigger fever, vasodilation, inflammation, shock, and blood clotting
Can be released when antimicrobial drugs kill bacteria LPS
30. Periplasmic Space Located between outer membrane and cell membrane
Contains peptidoglycan and periplasm
Contains water, nutrients, and substances secreted by the cell, such as digestive enzymes and proteins involved in transport
31. Prokaryotic Cytoplasmic Membrane Referred to as phospholipid bilayer; composed of lipids and associated proteins
Approximately half the membrane is composed of proteins that act as recognition proteins, enzymes, receptors, carriers, or channels
32. Phospholipid Bilayer of Cytoplasmic Membrane
33. Cytoplasmic Membrane Function Controls passage of substances into and out of the cell; selectively permeable
Functions in energy storage
Harvests light energy in photosynthetic prokaryotes
34. Control of Substances Across Cytoplasmic Membrane Naturally impermeable to most substances
Proteins allow substances to cross membrane
Occurs by passive or active processes
Maintains a concentration gradient and electrical gradient
Chemicals concentrated on one side of the membrane or the other
Voltage exists across the membrane
35. Passive Processes of Transport Diffusion: movement of small, non-polar molecules into and out of the cell.
Facilitated diffusion: movement of ions or polar molecules into and out of the cell with the aid of a transport protein.
Osmosis: movement of water into and out of the cell based on the solutes present in the surrounding solution.
36. Effects of Solutions on Organisms
37. Overview of Passive Transport
38. Active Processes of Transport Active Transport
Utilizes permease proteins and expends energy (typically in the form of ATP)
39. Cytoplasm of Prokaryotes Cytosol – liquid portion of cytoplasm
Inclusions – may include reserve deposits of chemicals
Ribosomes – sites of protein synthesis
Cytoskeleton – plays a role in forming the cell’s basic shape
Some bacterial cells produce dormant form called endospore.
Protective structure that allows some bacteria to survive adverse conditions.
40. Endospores Tough, outer coat protects from extreme conditions;
Dormant, non-reproductive form of bacteria.
Very few bacteria can form endospores.
41. Chapter 4: Case Study #1 - Massive Tissue Death in a Diabetic Patient
On 23 November 1997, a 52-year old male diabetic entered the hospital with massive necrosis of the tissue of the foot (Figure 1), as well a large bubble within the tissue. A patient background demonstrated a history of high blood sugar due to poor diet and lack of insulin administration. This resulted in arteriosclerosis (blockage of blood vessels) within the patient. Bacteria were cultured from the foot. Bacteria grew only under anaerobic conditions and produced endospores. A gram stain revealed the presence of a gram positive cell wall.
1. Describe a gram positive cell wall.
2. Describe the structure and function of an endospore.
3. Is an endospore a reproductive structure? Explain.
42. Chapter 4: Case Study #2 – No chips and dip for me, thanks…. A multi-state outbreak of bloody diarrhea with at least 30 culture-confirmed cases in California, Oregon, and Washington was linked to eating a nationally distributed five-layer dip. The onset of symptoms occurred between 10 and 23 January 2000. The implicated product was manufactured by Senor Felix’s Mexican Foods (Baldwin Par, CA). The dip consisted of layers of beans, salsa, guacamole, nacho cheese, and sour cream. The dip was made without the addition of food preservatives.
The cause of this outbreak was revealed to be Enterohemorrhagic E. coli (E. coli O157:H7). This is a gram-negative organism causes bloody diarrhea and no fever. EHEC can cause hemolytic-uremic syndrome and sudden kidney failure. It uses bacterial fimbriae, is moderately-invasive and possesses a phage-encoded Shiga toxin that can elicit an intense inflammatory response (Wiki). It also possesses an endotoxin that illicit further inflammation of the colon. The flagella of E. coli have a peritrichous arrangement. E. coli and related bacteria possess the ability to transfer DNA, which allows genetic material to spread horizontally through an existing population.
1. Describe the structure of a gram negative cell wall in detail.
2. What is an endotoxin and where is it found? Do both gram negative and gram positive organisms produce endotoxins? Explain.
3. What is the function of fimbriae?
4. What is the function of a flagella? Describe a peritrichous arrangement.
5. What structure allows a bacterium to transfer DNA from one cell to another?