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Chapter 4 Prokaryotic Cell

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Presentation on theme: "Chapter 4 Prokaryotic Cell"— Presentation transcript:

1 Chapter 4 Prokaryotic Cell
Functional Anatomy of Prokaryotic and Eukaryotic Cells Bio 205

2 Prokaryotic Cells Comparing Prokaryotic and Eukaryotic Cells
Prokaryote comes from the Greek words for prenucleus. Eukaryote comes from the Greek words for true nucleus.

3 Prokaryote Eukaryote Paired chromosomes, in nuclear membrane
One circular chromosome, not in a membrane No histones No organelles Peptidoglycan cell walls Binary fission Paired chromosomes, in nuclear membrane Histones Organelles Polysaccharide cell walls Mitotic spindle

4 Average size: µm  µm Basic shapes:

5 Most bacteria are monomorphic
Unusual shapes Star-shaped Stella Square Haloarcula Most bacteria are monomorphic A few are pleomorphic (variable shapes during life cycle) Figure 4.5

6 Arrangements Pairs: diplococci, diplobacilli Clusters: staphylococci
Chains: streptococci, streptobacilli

7 Glycocalyx Outside cell wall Usually sticky
A capsule is neatly organized A slime layer is unorganized & loose Extracellular polysaccharide allows cell to attach Capsules prevent phagocytosis Figure 4.6a, b

8 Flagella Outside cell wall Made of chains of flagellin
Attached to a protein hook Anchored to the wall and membrane by the basal body Figure 4.8

9 Flagella Arrangement Figure 4.7

10 Brownian Motion Flagella motion

11 Motile Cells Rotate flagella to run or tumble
Move toward or away from stimuli (taxis) Flagella proteins are H antigens (e.g., E. coli O157:H7)

12 Axial Filaments Endoflagella In spirochetes
Anchored at one end of a cell Rotation causes cell to move Figure 4.10a

13 Fimbriae Fimbriae allow attachment
Pili are used to transfer DNA from one cell to another Figure 4.11

14 Cell Wall Prevents osmotic lysis Made of peptidoglycan (in bacteria)
Figure 4.6a, b

15 Peptidoglycan Polymer of disaccharide N-acetylglucosamine (NAG) & N-acetylmuramic acid (NAM) Linked by polypeptides Figure 4.13a

16 Figure 4.13b, c

17 Gram-positive cell walls Gram-negative cell walls
Thin peptidoglycan No teichoic acids Outer membrane Thick peptidoglycan Teichoic acids In acid-fast cells, contains mycolic acid

18 Gram-Positive cell walls
Teichoic acids: Lipoteichoic acid links to plasma membrane Wall teichoic acid links to peptidoglycan May regulate movement of cations Polysaccharides provide antigenic variation Figure 4.13b

19 Gram-Negative Outer Membrane
Lipopolysaccharides, lipoproteins, phospholipids. Forms the periplasm between the outer membrane and the plasma membrane. Protection from phagocytes, complement, antibiotics. O polysaccharide antigen, e.g., E. coli O157:H7. Lipid A is an endotoxin. Porins form channels through membrane

20 Gram Stain Mechanism Crystal violet-iodine crystals form in cell
Gram-positive Alcohol dehydrates peptidoglycan CV-I crystals do not leave Gram-negative Alcohol dissolves outer membrane and leaves holes in peptidoglycan CV-I washes out

21 Atypical Cell Walls Mycoplasmas Lack cell walls
Sterols in plasma membrane Archaea Wall-less, or Walls of pseudomurein (lack NAM and D amino acids)

22 Damage to Cell Walls Lysozyme digests disaccharide in peptidoglycan.
Penicillin inhibits peptide bridges in peptidoglycan. Protoplast is a wall-less cell Gram-positive cell. Spheroplast is a wall-less Gram-negative cell. L forms are wall-less cells that swell into irregular shapes. Protoplasts and spheroplasts are susceptible to osmotic lysis.

23 Plasma Membrane Figure 4.14a

24 Plasma Membrane Phospholipid bilayer Peripheral proteins
Integral proteins Transmembrane proteins Figure 4.14b

25 Fluid Mosaic Model Membrane is as viscous as olive oil.
Proteins move to function Phospholipids rotate and move laterally Figure 4.14b

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