© 2012 Pearson Education Inc. Lecture prepared by Mindy Miller-Kittrell North Carolina State University Chapter 3 Cell Structure and Function

Cell Morphology 3 main shapes Rod (bacillus) Sphere (coccus) Spiral (spirilla)

Processes of Life Growth Reproduction Responsiveness Metabolism—chemical reactions in the cell. Building up and breaking down molecules. © 2012 Pearson Education Inc.

Prokaryotes –Lack nucleus –Lack various internal structures bound with phospholipid membranes –Are small (~1.0 µm in diameter) micrometers –Have a simple structure –Include bacteria and archaea © 2012 Pearson Education Inc. Prokaryotic and Eukaryotic Cells: An Overview

Figure 3.2 Typical prokaryotic cell Ribosome Cytoplasm Nucleoid Glycocalyx Cell wallCytoplasmic membrane Inclusions Flagellum

Eukaryotes –Have nucleus –Have internal membrane-bound organelles –Are larger (10–100 µm in diameter) –Have more complex structure –Include algae, protozoa, fungi, animals, and plants © 2012 Pearson Education Inc. Prokaryotic and Eukaryotic Cells: An Overview

Figure 3.3 Typical eukaryotic cell Nucleolus Cilium Ribosomes Nuclear envelope Nuclear pore Lysosome Mitochondrion Centriole Secretory vesicle Golgi body Transport vesicles Rough endoplasmic reticulum Smooth endoplasmic reticulum Cytoplasmic membrane Cytoskeleton

Figure 3.4 Approximate size of various types of cells Chicken egg 4.7 cm diameter (47,000  m)* Virus Orthopoxvirus 0.3  m diameter Bacterium Staphylococcus 1  m diameter Parasitic protozoan Giardia 14  m length *Actually, the inset box on the egg would be too small to be visible. (Width of box would be about mm.)

External Structures of Bacterial Cells Glycocalyces –Gelatinous, sticky substance surrounding the outside of the cell –Composed of polysaccharides, polypeptides, or both © 2012 Pearson Education Inc.

External Structures of Bacterial Cells Two Types of Glycocalyces –Capsule –Composed of organized repeating units of organic chemicals –Firmly attached to cell surface –May prevent bacteria from being recognized by host –Slime layer –Loosely attached to cell surface –Water soluble –Sticky layer allows prokaryotes to attach to surfaces © 2012 Pearson Education Inc.

Figure 3.5 Glycocalyces-overview Glycocalyx (capsule) Glycocalyx (slime layer)

External Structures of Bacterial Cells Flagella –Are responsible for movement –Have long structures that extend beyond cell surface –Are not present on all bacteria © 2012 Pearson Education Inc.

External Structures of Bacterial Cells Flagella –Structure –Composed of filament, hook, and basal body –Basal body anchors filament and hook to cell wall by a rod and a series of either two or four rings of integral proteins © 2012 Pearson Education Inc.

Figure 3.7 Micrographs of basic arrangements of bacterial flagella-overview

Figure 3.8 Axial filament-overview Axial filament Endoflagella rotate Axial filament rotates around cell Outer membrane Cytoplasmic membrane Axial filament Spirochete corkscrews and moves forward

External Structures of Bacterial Cells Flagella –Function –Rotation propels bacterium through environment –Rotation reversible; can be counterclockwise or clockwise –Bacteria move in response to stimuli (taxis— phototaxis or chemotaxis) –Runs –Tumbles © 2012 Pearson Education Inc.

Figure 3.9 Motion of a peritrichous bacterium Tumble Run Tumble Attractant Run

External Structures of Bacterial Cells Fimbriae and Pili –Rodlike proteinaceous extensions © 2012 Pearson Education Inc.

External Structures of Bacterial Cells © 2012 Pearson Education Inc. Fimbriae –Sticky, bristlelike projections –Used by bacteria to adhere to one another, to hosts, and to substances in environment –Shorter than flagella –Serve an important function in biofilms

Figure 3.10 Fimbriae Flagellum Fimbria

External Structures of Bacterial Cells Pili –Special type of fimbria –Also known as conjugation pili –Longer than other fimbriae but shorter than flagella –Bacteria typically have only one or two per cell –Mediate the transfer of DNA from one cell to another (conjugation) © 2012 Pearson Education Inc.

Figure 3.11 Pili Conjugation pilus

Bacterial Cell Walls –Provide structure and shape and protect cell from osmotic forces –Assist some cells in attaching to other cells or in resisting antimicrobial drugs –Cell wall of bacteria can be targeted with antibiotics –Give bacterial cells characteristic shapes –Composed of peptidoglycan –Scientists describe two basic types of bacterial cell walls, Gram-positive and Gram-negative © 2012 Pearson Education Inc.

Figure 3.12 Bacterial shapes and arrangements-overview

Bacterial Cell Walls Gram-Positive Bacterial Cell Walls –Relatively thick layer of peptidoglycan –Appear purple following Gram staining procedure © 2012 Pearson Education Inc.

Figure 3.15a Comparison of cell walls of Gram-positive and Gram-negative bacteria Gram-positive cell wall Peptidoglycan layer (cell wall) Cytoplasmic membrane Teichoic acid Lipoteichoic acid Integral protein

Bacterial Cell Walls Gram-Negative Bacterial Cell Walls –Have only a thin layer of peptidoglycan –Bilayer membrane outside the peptidoglycan contains phospholipids, proteins, and lipopolysaccharide (LPS) –May be impediment to the treatment of disease –Appear pink following Gram staining procedure © 2012 Pearson Education Inc.

Figure 3.15b Comparison of cell walls of Gram-positive and Gram-negative bacteria Gram-negative cell wall Outer membrane of cell wall Peptidoglycan layer of cell wall Cytoplasmic membrane Lipopolysaccharide (LPS) Porin Porin (sectioned) Periplasmic space Phospholipid layers Integral proteins n Core polysaccharide O side chain (varies In length and composition) Lipid A (embedded in outer membrane) Fatty acid

Comparison of Gram positive and Gram negative cells

Bacterial Cytoplasmic Membranes Structure –Referred to as phospholipid bilayer –Composed of lipids and associated proteins –Fluid mosaic model describes current understanding of membrane structure © 2012 Pearson Education Inc.

Figure 3.16 The structure of a prokaryotic cytoplasmic membrane: a phospholipid bilayer Head, which contains phosphate (hydrophilic) Tail (hydrophobic) Phospholipid Phospholipid bilayer Integral protein Peripheral protein Integral protein Cytoplasm Integral proteins

Bacterial Cytoplasmic Membranes Function –Energy storage –Harvest light energy in photosynthetic bacteria –Selectively permeable –Naturally impermeable to most substances –Proteins allow substances to cross membrane –Maintain concentration gradient © 2012 Pearson Education Inc.

Bacterial Cytoplasmic Membranes Function –Passive processes –Diffusion –Facilitated diffusion –Osmosis –Active processes –Active transport © 2012 Pearson Education Inc.

Figure 3.20 Effects of isotonic, hypertonic, and hypotonic solutions on cells-overview Isotonic solution Hypertonic solution Hypotonic solution Cells without a wall (e.g., mycoplasmas, animal cells) Cells with a wall (e.g., plants, fungal and bacterial cells) Cell wall Cell membrane H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O H2OH2O

Cytoplasm of Bacteria Cytosol – Liquid portion of cytoplasm Inclusions – May include reserve deposits of chemicals Endospores – Unique structures produced by some bacteria that are a defensive strategy against unfavorable conditions © 2012 Pearson Education Inc.

Figure 3.23 Granules of PHB in the bacterium Azotobacter chroococcum

Cytoplasm of Bacteria Nonmembranous Organelles –Ribosomes –Sites of protein synthesis –70S—consists of 50S large subunit and 30S small subunit. –Cytoskeleton –Plays a role in forming the cell’s basic shape © 2012 Pearson Education Inc.

External Structures of Archaea Glycocalyces –Function in the formation of biofilms –Adhere cells to one another and inanimate objects Flagella –Consist of basal body, hook, and filament –Numerous differences with bacterial flagella Fimbriae and Hami –Many archaea have fimbriae –Some make fimbriae-like structures called hami –Function to attach archaea to surfaces © 2012 Pearson Education Inc.

Figure 3.26 Archaeal hami Hamus Grappling hook Prickles

Archaeal Cell Walls and Cytoplasmic Membrane –Most archaea have cell walls –Do not have peptidoglycan –Contain variety of specialized polysaccharides and proteins –All archaea have cytoplasmic membranes –Maintain chemical gradients –Control import and export of substances from the cell –Lipids lack phosphate (not phospholipids). © 2012 Pearson Education Inc.

Figure 3.27 Representative shapes of archaea-overview

Cytoplasm of Archaea –Archaeal cytoplasm similar to bacterial cytoplasm –Have 70S ribosomes –Fibrous cytoskeleton –Circular DNA –Archaeal cytoplasm also differs from bacterial cytoplasm –Different ribosomal proteins –Different metabolic enzymes to make RNA © 2012 Pearson Education Inc.

External Structure of Eukaryotic Cells Glycocalyces –Never as organized as prokaryotic capsules –Help anchor animal cells to each other –Strengthen cell surface –Provide protection against dehydration –Function in cell-to-cell recognition and communication © 2012 Pearson Education Inc.

Eukaryotic Cell Walls –Fungi, algae, plants, and some protozoa have cell walls –Composed of various polysaccharides –Plant cell walls composed of cellulose –Fungal cell walls usually composed of chitin. –Algal cell walls composed of a variety of polysaccharides. © 2012 Pearson Education Inc.

Eukaryotic Cytoplasmic Membranes –All eukaryotic cells have cytoplasmic membrane –Are a fluid mosaic of phospholipids and proteins –Contain steroid lipids to help maintain fluidity –Control movement into and out of cell © 2012 Pearson Education Inc.

Figure 3.30 Endocytosis-overview Pseudopodium

Cytoplasm of Eukaryotes Flagella –Structure and arrangement –Differ structurally and functionally from prokaryotic flagella –Within the cytoplasmic membrane –Shaft composed of tubulin arranged to form microtubules –Filaments anchored to cell by basal body –Function –Do not rotate but undulate rhythmically © 2012 Pearson Education Inc.

Figure 3.31a Eukaryotic flagella and cilia Flagellum

Figure 3.31b Eukaryotic flagella and cilia Cilia

Cytoplasm of Eukaryotes Cilia –Shorter and more numerous than flagella –Coordinated beating propels cells through their environment –Also used to move substances past the surface of the cell © 2012 Pearson Education Inc.

Cytoplasm of Eukaryotes Other Nonmembranous Organelles –Ribosomes –Larger than prokaryotic ribosomes (80S versus 70S) –Composed of 60S and 40S subunits –Cytoskeleton –Extensive network of fibers and tubules –Anchors organelles –Produces basic shape of the cell © 2012 Pearson Education Inc.