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Chapter 3: Cell Structure and Function Processes of Life 1. Growth2. Reproduction3. Responsiveness4. Metabolism5. Cellular Structure*The activity of any of these functions can vary over time. Eukaryotic and Prokaryotic Cells: An Overview Cell Theory- Eukaryotes- can be single celled or part of a multicellular organism, and share general characteristics: Prokaryotes- single celled organisms and share general characteristics: Prokaryotes are divided into two major groups based on the sequence of base pairs in their ribosomal RNA; bacteria and archaea 1 External Structures of Bacterial Cells Glycocalyces-Functions of the Glycocalyx: 1. 2. 3. Flagella (bacterial) -A long whip-like structure that allows the bacteria to be motile -Composed of three major parts: 1. 2. 3. -The hook and the rod and rings of the basal body allow the filament to rotate 360o. -Differences in the proteins that make up the flagella allow for classification of species into groups called serovars (strains of a single species). -Flagella can be arranged on the bacterial cell in various ways -polar-peritrichous-Spirochetes (spiral shaped bacteria)-The major function of the flagella is locomotion -these actions are in response to external stimuli: 1. phototaxis2. chemotaxis3. positive taxis4. negative taxis2 Fimbriae and Pili- proteinaceous filamentous extensions of the cell Fimbriae- Pili- Prokaryotic Cell Walls Bacterial cell walls -the primary polymer of the bacterial cell wall is peptidoglycan, a polysaccharide. -this polymer consists of alternating monomer units, both similar to glucose: NAG: N-acetylglucosamine NAM: N-acetylmuramic acid -chains of NAG and NAM are attached to other chains by crossbridges of four amino acids (tetrapeptides) -there are two basic types of bacterial cell walls; gram negative and gram positive. -Gram Positive Cell Walls -Gram Negative Cell Walls -Bacteria without Cell Walls -Mycoplamsa- 3 Bacterial Cytoplasmic Membranes Structure-composed of a phospholipid bilayer which can contain various other types of molecules. Function- controls what enters and leaves the cell, selective permeability -Passive processes 1. diffusion- 2. osmosis1. isotonic2. hypertonic3. hypotonic-Active processes- substances move across the membrane using cellular energy (ATP) 1. active transport2. group translocation- Cytoplasm of Bacteria Cytosol- liquid portion of the cytoplasm InclusionsEndospores and Sporulation- 4 Nonmembranous Organelles -ribosomes-differentiated by sedimentation rate (S= Svedberg units) -prokaryotes have 50S and 30S subunits which make a 70S ribosome -eukaryotes have 60S and 40S subunits which make a 80S ribosome -cytoskeleton-formed by the internal fibers of the cell -some round cells may not have a cytoskeleton. Archaeal External and Internal Structures Glycocalyces- Flagella-Differences between archaea and bacteria flagella Fimbriae and HamiCell Walls and Membranes-Archaeal cell walls lack peptidoglycan Both Gram (+) and Gram (-) forms exist -Archaeal membranes lack phosphate groups on lipids, and have stronger hydrocarbon linkages. CytoplasmRibosomes and enzymes are similar to eukaryotes Endosymbiotic Theory Because of the similarities of mitochondria and chloroplasts to bacteria, it is thought that larger anaerobic prokaryotes engulfed smaller aerobic prokaryotes, and began a symbiotic relationship which evolved into eukaryotic cells. 5