Chapter 4 Lecture Outline-1 - Tagged.pdf

Chapter 4 Functional Anatomy of Prokaryotic and Eukaryotic Cells 1 Functional Anatomy of Typical Prokaryotic Cells Average size - Why do we need to know this? Measured in microns (μm) Ex - ~ 2.0 μm diameter X ~ 8 μm length Majority of bacteria are monomorphic, but some bacteria are pleomorphic 2 C...

Chapter 4 Functional Anatomy of Prokaryotic and Eukaryotic Cells 1 Functional Anatomy of Typical Prokaryotic Cells Average size - Why do we need to know this? Measured in microns (μm) Ex - ~ 2.0 μm diameter X ~ 8 μm length Majority of bacteria are monomorphic, but some bacteria are pleomorphic 2 Cell Shape of Typical Prokaryotic Cells 1. Coccus 2. Bacillus Coccobacillus 3. Spiral Vibrio Spirillum Spirochete Figure 4.4 - Spiral Bacteria 3 Spiral-Shaped Prokaryotes: Spirilla vs Spirochetes Spirilla Rigid cells Short/thick cells Loosely-coiled cells Cells move via Flagella Spirochetes Flexible cells Longer/thin cells Tightly-coiled cells Cells move via Endoflagella 4 Cell Arrangement of Typical Prokaryotic Cells Pairs: “diplo-” Diplococci, diplobacilli Clusters: “staphylo-” Staphylococci Chains: “strepto-” Streptococci, streptobacilli Groups of four: Tetrads Cube-like groups of eight: Sarcinae 5 Prokaryotic Cell Structure Figure 4.6 6 7 Glycocalyx May or may not be present Layer external to the cell wall Viscous and gelatinous Made of polysaccharide or polypeptide Two types of glycocalyces: Capsule  Capsule  Thick, organized & tightly attached to cell wall  Slime Layer  Thin, unorganized & loose attached to cell wall 8 Glycocalyx - Capsule Bacterium attaches to host tissue due to “stickiness” of capsule Makes bacterium look bigger  escapes phagocytosis Examples of encapsulated bacteria:  Streptococcus mutans  Streptococcus pneumoniae Bacterium Capsules 9 Flagella May or may not be present Filamentous appendages external to the cell Movement/propel bacteria Made of protein called flagellin Flagellin proteins:  Arrange themselves into filaments; many filaments make-up a flagellum  Can act as “H antigens” and help distinguish among different subspecies/strain of bacteria  Ex - Escherichia coli O157:H7 Various arrangements Figure 4.7 10 11 Flagellum Three parts: 1. Filament - outermost region 2. Hook - attaches to the filament 3. Basal body - anchors flagellum May be found in some bacilli and in all spirilla type of bacteria Figure 4.8 b 12 Axial Filaments Found in Spirochetes Also called endoflagella Internal to the cell (intracellular) and anchored at one end Made of proteins Rotation of endoflagella  cell moves in corkscrew/spiral motion Rotating Endoflagellum Outer Membrane of The Cell Wall Cell Membrane Spirochete - Figure 4.10 Spirochete Cross-Section 13 Fimbriae and Pili Fimbriae  External to cell  Made of proteins  Hair-like appendages that allow for attachment Figure 4.11 Pili  External to cell  Made of proteins  Involved in “twitching” motility & DNA transfer from one cell to another; Ex - conjugation pilus 14 15 The Cell Wall Outermost layer if no glycocalyx (capsule) present Prevents osmotic lysis and protects the cell membrane Contains peptidoglycan (rows of carbohydrates connected to proteins) Some bacteria have more peptidoglycan in their cell walls than others  called Gram-Positive bacteria Some bacteria have less peptidoglycan in their cell walls than others  called Gram-Negative bacteria 16 Gram-Negative vs Gram-Positive Bacteria 17 Gram-Positive vs Gram-Negative Bacteria Gram-Positive Cell Wall  Thick peptidoglycan layer  Teichoic acids  No outer membrane  Sensitive to Penicillin Gram-Negative Cell Wall  Thin peptidoglycan layer  No teichoic acids  Outer membrane with Lipopolysaccharide (LPS)  Resistant to Penicillin 18 Gram-Negative Bacteria & Lipopolysaccharide (LPS) Major component of outer membrane of Gram-Negative cell wall LPS contains lipids & carbohydrates  3 components of LPS: 1. Lipid A  Functions as a toxin 2. Core polysaccharide  Joins Lipid A & O polysaccharide 3. O polysaccharide  Functions as an antigen Gram-Negative Bacterium 19 Gram Staining: Differential Staining of Gram-Positive vs Gram-Negative Bacteria 20 Gram Staining: Differential Staining of Gram-Positive vs Gram-Negative Bacteria Table 4.1 21 Atypical Cell Walls Genus Mycobacterium Have a waxy lipid (mycolic acid) “bound” to peptidoglycan Use acid-fast stain instead of Gram stain Genus Mycoplasma Lack cell walls Domain Archaea No peptidoglycan present in cell wall The lipid-rich cell wall of Mycobacterium tuberculosis 22 The Plasma (Cell) Membrane Deep to the cell wall Phospholipid bilayer that encloses the cytoplasm Peripheral proteins on the membrane surface Integral & transmembrane proteins penetrate the cell membrane 23 Functions of Plasma Membrane 1. Transport - allows for passage of some molecules, but not others  “selective permeability” 2. Site of ATP production 3. Site of photosynthesis 24 Movement of Materials across Cell Membranes Passive Transport Movement of solutes from area of high  low concentration Does this process require energy? Active Transport Movement of solutes from area of low  high concentration Does this process require energy? 25 Passive Transport Passive Processes: Simple diffusion Facilitated diffusion Osmosis Isotonic solution Hypotonic solution Hypertonic solution Figure 4.18 26 27 Cytoplasm & Ribosome The substance inside the plasma membrane 80% water plus proteins, carbohydrates, lipids & ions No organelles present, except for ribosomes Bacterial ribosomes are called 70 S ribosomes  Sites of protein synthesis  Composed of 2 subunits: o Large subunit o Small subunit 28 The Nucleoid & Plasmids Nucleoid “Nucleus-like” region Contains the bacterial chromosome  Circular thread of DNA  supercoiled/compacted; contains the cell's genetic information; not surrounded by nuclear membrane Plasmids Small, extrachromosomal genetic elements Carry “non-crucial” genes that play a role in adaptability & survival  Ex - genes for antibiotic resistance & production of toxins 29 Inclusion Bodies (Reserve Deposits) Structures that store reserve materials in cytoplasm Examples: 1. 2. 3. 4. Metachromatic granules - phosphate reserves Polysaccharide granules - energy reserves of glycogen & starch Lipid inclusions - energy reserves of fat Carboxysomes - enzyme reserves involved in photosynthesis 30 Endospores Formed inside the cell Are specialized “resting” form of cells; seen in only few bacteria Produced by Genus Bacillus and Genus Clostridium Produced when nutrients are depleted; for survival Contain bacterial cell’s genetic material Resistant to desiccation, heat, chemicals, and radiation Sporulation: endospore formation (resting cell state) Germination: endospore returns to active cell state 31 32 An Overview: Prokaryotic Cells vs Eukaryotic Cells Prokaryote One circular chromosome, not in a membrane No organelles* 70 S ribosomes Peptidoglycan in cell walls Unicellular Divide by binary fission * except for ribosomes Eukaryote Paired chromosomes in a nuclear membrane Membrane-bound organelles 80 S ribosomes Polysaccharide in cells walls (if cell wall present) Unicellular & multicellular Divide by mitosis 33 Eukaryotic Cell Structure Figure 4.22 34 Eukaryotic Cell Structure Cell Wall  Found in plants, algae (Kingdom Protista), and fungi  Made of carbohydrates:  Cellulose - in plants  Chitin - in fungi  Structure and protection of the cell 35 Eukaryotic Cell Structure Cell Membrane  Has sterols (a type of steroid) bound to cell membrane  Has carbohydrates - for attachment and cell-to-cell recognition  Capable of endocytosis:  Phagocytosis - engulfing particles  Pinocytosis - engulfing fluids and dissolved substances Ribosomes - site of protein synthesis  Ex - 80 S ribosome 36 Eukaryotic Cell Organelles Nucleus  Double membrane structure (nuclear envelope) that contains the cell's DNA Endoplasmic Reticulum (ER)  Folded transport network  Rough ER - studded with ribosomes; sites of protein synthesis  Smooth ER - no ribosomes; site of cell membrane, fat, and hormone synthesis 37 Eukaryotic Cell Organelles Golgi Complex  Modifies, sorts & packages proteins from the ER Lysosomes  Vesicles formed by the Golgi Complex  Contain digestive enzymes Vacuoles  Cavities in the cell formed by the Golgi complex  Bring food into cells; provide storage 38 Eukaryotic Cell Organelles Mitochondria  Double membrane  Contain inner folds (cristae) and fluid (matrix)  Involved in cellular respiration (ATP production) Chloroplasts  Locations for photosynthesis  Contain flattened membranes that contain chlorophyll pigment Centrosomes  Form the mitotic spindle  Critical role in cell division 39