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“Anatomy” and Function of Prokaryotes I • Cell Size Shape and Arrangement • Prokaryote “Anatomy” Overview • Cytoplasmic Matrix and Structures • Membranes (plasma; outer; internal) Cell Shape and Arrangement Cell Shape and Arrangement star rectangle pleomorphic = irregular hypha = thin tubes prosthecate = appendage Multicellular Organization? Not every cell is alike; nor just members of a colony. Bacillus subtilis Proteus mirabilis Myxobacterium sp. Prokaryote “Anatomy” Overview Cell envelope: Collectively all the structures outside from the plasma membrane. Cytoplasmic Matrix and Structures • • • • Cytoplasmic proteins Ribosomes Nucleoid Inclusion Bodies – – – – – – – – Glycogen (C) Poly-β-hydroxybuterate (C) Cyanophycin (N) granules Carboxysomes (RuBPcase) Gas vacuoles (vesicles) Polyphosphate granules Sulfur granules Magnetosomes Fig 3.10 Inclusion Bodies Gas Vacule = buoyancy Magnetosomes = orientation (freeze fracture SEM) (TEM) Ribosomes • Subunits made of proteins and ribosomal ribonucleic acids (rRNA). • 30S and 50S must bind together to form a complete and functional ribosome. • The two subunits “sandwich” messenger RNA (mRNA). • As it moves along the mRNA, the genetic code is “translated” into a polypeptide by the directed polymerization of amino acids. • Transfer RNAs (tRNA) shuttle the amino acids to the ribosome as needed. • Hence, ribosomes are responsible for protein synthesis. Nucleoid • The compact form of the bacterial circular chromosome (0.5 to 5 Mega base pairs (Mbp). • DNA supercoils forming ~ 60 loops. • Histone-like proteins centrally anchor loops. • Active growing cells may have >1 nucleoid; loops uncoil and extend for gene expression. Plasma Membrane • Membrane lipids are amphipathic. • Membranes are lipid bilayers (hydrophilic outside and hydrophobic inside) • Stabilized by hopanoids & long-chain saturated fatty acids. • Functions: – – – – – Selective permeable bearer into (out of) cytoplasm. Transport for nutrients, excretion, secretion Sensing the environment & signaling a response Metabolic processes (respiration; photosynthesis …) Secretion Plasma Membranes Internal Membranes • Invagination of plasma membrane. • Shaped into vesicles, tubules, or lamellae. • “mesosomes” are small; simple; unknown function (possibly chromosome replication) • Photosynthetic and Nitrifying bacteria have complex folded lamellae; increase surface area for certain metabolic.