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Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells.

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Presentation on theme: "Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells."— Presentation transcript:

1 Chapter 4: Functional Anatomy of Prokaryotic and Eukaryotic Cells

2 Prokaryote Eukaryote One circular chromosome, not in a membrane No histones No membrane-bound organelles Complex cell walls (peptidoglycan in bacteria) Binary fission Paired chromosomes, in nuclear membrane Histones bound to DNA Membrane-bound organelles Simpler cell walls (polysaccharide) Mitosis Pre-nucleus True nucleus

3 Prokaryotic Cells: Morphology Average size: µm in diameter µm in length Basic shapes/morphologies: Coccus (spherical) Bacillus* (rod-shaped) Spiral Coccobacillus

4 Pairs: diplo- diplococci diplobacilli Chains: strepto- streptococci streptobacilli Clusters: staphylo- staphylococci Prokaryotic cells: Arrangements

5 Prokaryotic cells: Structures external to the cell wall

6 Capsule: Glycocalyx firmly attached to the cell wall Sticky outer coat Polysaccharide and/or polypeptide composition Aids in attachment of cell to a substrate Helps prevent dehydration Impairs phagocytosis (host defense mechanism) Prokaryotic cell structures: Glycocalyx Figure 4.6a

7 Cellular propellers Three basic parts Filament: Made of chains of flagellin protein Hook Basal body: anchor to the cell wall and membrane Rotation in the basal body propels the cell Figure 4.8 Prokaryotic cell structures: Flagella

8 Figure 4.7 ( flagella at both poles) (tuft from one pole) (flagella distributed over the entire cell) Flagella Arrangement Prokaryotic cell structures: Flagella

9 Figure 4.9 Taxis: movement toward or away from a stimulus -chemotaxis -phototaxis Prokaryotic cell structures: Flagella Motility

10 Prokaryotic cell structures: Flagella Motile E. coli with flourescently-labelled flagella from the Roland Institute at Harvard

11 Axial filaments= endoflagella Spirochete movement Anchored at one end of a cell Contained within an outer sheath Rotation causes cell to move Spiral/corkscrew motion Figure 4.10a Prokaryotic cell structures: Axial Filaments

12 Composed of protein pilin Fimbriae allow attachment to surfaces/other cells Few to hundreds per cell Pili are used to transfer DNA from one cell to another Longer, 1-2 per cell Figure 4.11 Prokaryotic cell structures: Fimbriae and Pili

13 Prokaryotic cells: The cell wall

14 Main functions of the cell wall Prevents osmotic lysis Helps maintain cell shape Point of anchorage for flagella Contains peptidoglycan (in bacteria) Prokaryotic cell structures: Cell Wall

15 Macromolecular network: Polymer of a repeating disaccharide unit (backbone) Backbones linked by polypeptides Prokaryotic cell structures: Cell Wall Peptidoglycan (or murein) Figure 4.13a

16 Prokaryotic cell structures: Gram-positive Cell Walls Gram-positive cell wall Thick PG layer; rigid structure Teichoic acids: Lipoteichoic acid links PG to plasma membrane Wall teichoic acid links PG sheets Polysaccharides & teichoic acids are cellular antigens

17 Figure 4.13b, c Gram-negative cell wall Prokaryotic cell structures: Gram-negative Cell Walls Thin PG layer Surrounded by an outer membrane Protection from phagocytes, some antibiotics Periplasm (contains PG, degradative enzymes, toxins) Lipopolysaccharide (LPS) O polysaccharide antigen Lipid A is called endotoxin Porins (proteins) form channels through membrane

18 Thick peptidoglycan Teichoic acids Thin peptidoglycan No teichoic acids Outer membrane Lipopolysaccharide Porins Gram-positive cell walls Gram-negative cell walls Prokaryotic cell structures: Cell Walls

19 Gram stain mechanism Step 1: Crystal violet (primary stain) Enters the cytoplasm (stains) both cell types Step 2: Iodine (mordant) Forms crystals with crystal violet (CV-I complexes) that are too large to diffuse across the cell wall Step 3: Alcohol wash (decolorizer) Gm +: dehydrates PG, making it more impermeable Gm -: dissolves outer membrane and pokes small holes in thin PG through which CV-I can escape Step 4: Safranin (counterstain) Contrasting color to crystal violet

20 Mycoplasma Smallest known bacteria Lack cell walls Sterols in plasma membrane protect from lysis Acid-fast cells (Mycobacterium and Nocardia genera) Mycolic acid (waxy lipid) layer outside of PG resists typical dye uptake Archaea Wall-less, or Walls of pseudomurein (altered polysaccharide and polypeptide composition vs. PG) Prokaryotic cell structures: Cell Wall Atypical Cell Walls

21 Lysozyme attacks disaccharide bonds in peptidoglycan Penicillin inhibits peptide cross-bridge formation in peptidoglycan Bacteria with weakened cell walls are very susceptible to osmotic lysis Prokaryotic cell structures: Cell Wall Damage to Cell Walls

22 Prokaryotic cells: Structures internal to the cell wall

23 Phospholipid bilayer Proteins Fluid Mosaic Model Membrane is as viscous as olive oil Proteins move to function Phospholipids rotate and move laterally Figure 4.14b Prokaryotic cell structures: Plasma Membrane

24 Main function: selective barrier Selective permeability allows passage of select molecules Small molecules (H 2 O, O 2, CO 2, some sugars) Lipid-soluble molecules (nonpolar organic) Prokaryotic cell structures: Plasma Membrane

25 Passive processes do not require energy (ATP)— involves movement down a concentration gradient Simple diffusion: Movement of a solute from an area of high concentration to an area of low concentration Facilitated diffusion: Solute combines with a transporter protein to move down its gradient Osmosis: Diffusion of water down its gradient Diffusion continues until the solute is evenly distributed (state of equilibrium) Movement across membranes: Passive Processes

26 Prokaryotic cell structures: Plasma Membrane Osmosis: Movement of water across a selectively permeable membrane from an area of higher water concentration to an area of lower water concentration Water moving down its concentration gradient Figure 4.18

27 Osmotic lysis Plasmolysis Figure 4.18c-e Prokaryotic cell structures: Plasma Membrane [sol] solution = [sol] cell [sol] solution > [sol] cell [sol] solution < [sol] cell Isotonic solution [sol] cell = concentration of solute inside the cell Hypotonic solution* Hypertonic solution Three types of osmotic solutions:

28 Prokaryotic cell structures: Plasma Membrane Active transport of substances requires a transporter protein and ATP Solute movement up/against its concentration gradient Important when nutrients are scarce Movement across membranes: Active Transport Processes

29 Cytoplasm: substance inside plasma membrane 80% water, contains mainly proteins, carbohydrates, lipids, inorganic ions and low-molecular weight compounds Chromosomal DNA: single circular string of double- stranded DNA attached to the plasma membrane Located in the “nucleoid” area of the cell Plasmids: small, circular, extrachromosomal DNA Genes encoded typically not required for survival under normal conditions Prokaryotic cell structures: Other Internal Structures

30 Ribosomes: machinery for protein synthesis (translation) Tens of thousands of ribosomes per cell Prokaryotic cell structures: Other Internal Structures Complete 70S ribosome

31 Prokaryotic cell structures: Other Internal Structures Type: Metachromatic granules (volutin) Polysaccharide granules Lipid inclusions Sulfur granules Carboxysomes Gas vacuoles Magnetosomes Contents: Phosphate reserves (for ATP generation) Energy reserves Ribulose 1,5-diphosphate carboxylase for CO 2 fixation Protein covered cylinders Iron oxide (destroys H 2 O 2 ) Inclusions: Reserve deposits

32 Prokaryotic cell structures: Other Internal Structures Endospores Specialized resting cells (metabolically inactive) Resistant to desiccation, heat, chemicals Can remain dormant for thousands of years Bacillus, Clostridium genera only (Gram-positive) Sporulation: Endospore formation Triggered by deficiency of a key nutrient Germination: Return to vegetative state Triggered by physical/chemical damage to endospore’s coat

33 Stained pus from a mixed anaerobic infection

34 Functional Anatomy of Eukaryotic Cells Figure 4.22

35 Contain cytoplasm, enclosed by plasma membrane Move in a wavelike motion Figure 4.23 Functional Anatomy of Eukaryotic Cells: Flagella and Cilia

36 Figure 4.23a, b

37 Cell walls Plants, algae, fungi Polysaccharide; simpler than prokaryotic cell walls Glycocalyx Carbohydrates extending from animal plasma membrane Anchored to cell membrane Strengthens surface, aids in attachment Functional Anatomy of Eukaryotic Cells: Cell Walls and Glycocalyx

38 Functional Anatomy of Eukaryotic Cells: Plasma Membrane Similar to prokaryotic PM structure and function: Phospholipid bilayer Peripheral proteins Integral proteins EXCEPT, they contain Sterols (complex lipids, help strengthen membrane) Site for endocytosis (phagocytosis and pinocytosis) Selective permeability Passive transport processes Active transport processes

39 CytoplasmSubstance inside plasma membrane and outside nucleus CytoskeletonMicrofilaments, intermediate filaments, microtubules Contains organellesSpecialized functions (nucleus, ER, Golgi complex, mitochondria, lysosomes, ribosomes) Functional Anatomy of Eukaryotic Cells: Cytoplasm

40 Larger, denser than prokaryotic Eukaryotic ribosomes: 80S Prokaryotic ribosomes: 70S Membrane-bound pool (attached to ER) Free pool (in cytoplasm) Functional Anatomy of Eukaryotic Cells: Ribosomes

41 Functional Anatomy of Eukaryotic Cells: Nucleus Storage for almost whole cell’s genetic information Enclosed by nuclear envelope Proteins bound to DNA (histones and nonhistones) Figure 4.24

42 Functional Anatomy of Eukaryotic Cells: Mitochondrion Contains DNA and ribosomes (70S) Double membrane Inner membrane folds: cristae Portion inside of inner membrane: matrix Proteins involved in respiration and ATP production in cristae and matrix Chloroplasts: enzymes for light- gathering necessary for photosynthesis Figure 4.27

43 Endosymbiotic Theory Theory on evolution of eukaryotic cells’ organelles Prokaryotes: byo Eukaryotes: ~2.5 byo Mitochondria and chloroplasts share properties with prokaryotes Reproduce independently of cell Size/shape Circular DNA Their ribosomes are 70S


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