CHAPTER 7 INSIDE THE CELL 2 10 2014 characteristics of all cells nucleic acids that store transmit information proteins that perform cell functions carbs that provide chemical energy carbon support identity selectively permeable plasma membrane cell morphology form science eukaryotic cells have a membrane bound compartment nucleus prokaryotes don t phylogeny tribe source organisms divided into 3 domains of 1 Bacteria 2 Archaea 3 Eukarya o Bacteria Archaea are prokaryotic contain long thin fibers that perform a variety of roles in cells some have a cytoskeleton formed from protein filaments smaller than eukaryotes o Eukarya are eukaryotic larger than prokaryotic cells diffusion alone does not suffice as mode of transport decreased SA V ratio reducing rate of exchange between cell and environment prokaryotes all lack a membrane bound nucleus but contain plasma membrane chromosome and protein synthesizing ribosomes o prokaryotes that perform photosynthesis contain extensive internal membranes chromosome large DNA molecule contains information w small number of proteins provides structural support o genes segments of DNA that contain information for making functional RNAs o DNA double helix coils on itself by use of enzymes to form compact supercoiled structure o nucleoid location structural organization of the supercoiled chromosome genetic material of DNA loops partitioned into distinct domains plasmids common in prokaryotes contain genes but are physical independent of cellular chromosome o extremely rare in eukaryotes ribosomes macromolecular machines complex structures composed of subunits containing RNA and protein molecules perform specialized tasks organelles membrane bound compartment inside cell that contains specialized enzymes structures o limited in bacteria archaea prominent and plentiful in eukaryotes o store and compartmentalize Ca2 ions other key molecules compartmentalization separates incompatible chemical rxns and facilitates efficient chemical rxns localizes high concentrations of substrates within organelles reduces distance of diffusion of substrate replacements cluster enzymes that work together o hold magnetite crystals help cell sense respond to magnetic field o organize enzymes that synthesize complex C compounds from CO2 o sequester enzymes that generate chemical energy from NH4 ions cytoplasm all the contents of the cell within the membrane nucleus excluded o lipid bilayer membrane proteins allow passage of only molecules ions necessary for life cell wall tough fibrous layer surrounding plasma membrane cytoskeleton present extensively in eukaryotes o resists pressure of increased water volume inside cell o protects cell gives it shape rigidity glycolipids lipids that contain carbohydrate groups o many bacteria have another protective layer outside cell wall made of lipids polysaccharides 2 10 2014 flagella structure grown from plasma membrane made from 40 proteins o propels cells through water w a long helical filament fimbriae needlelike projections that extend from plasma membrane and facilitate attachment to other cells surfaces o more numerous than flagella o cover entire surface of cell establish many infections bc can attach bacteria to surfaces cytosol fluid portion btwn plasma membrane and organelles o reduces effect of total SA V with respect to exchange of waste nutrients nucleus contains chromosomes functions for information storage and administration o nuclear envelope double membrane w pore like openings linked to fibrous proteins o nuclear lamina lattice like sheet composed of fibrous proteins linked to nuclear envelope o nucleolus region where RNA molecules are made and ribosomal subunits assembled ribosomes manufacture proteins not organelles bc do not have membranes endoplasmic reticulum membrane enclosed factory composed of the rough part RER and smooth part SER o rough endoplasmic reticulum ribosomes synthesize proteins plasma membrane cell exterior o smooth endoplasmic reticulum enzymes catalyze rxns involving lipids through synthesis of needed lipids or organelle lumen interior of the rough ER new proteins fold and process proteins produced have a variety of functions breaking down poisonous lipids molecules makes phospholipids contains calcium ions Ca2 that signal trigger activities of cell Golgi apparatus collection of flattened vesicles cisternae o modifies and packages proteins central vacuole present only in animal cells o regulates cytoplasm composition creates internal pressure and stores cell compounds chloroplast present only in plant cells contain chlorophyll and convert solar energy to chemical energy o contain membranous sacs called thylakoids surrounded by a fluid called stroma 2 10 2014 SEE PAGE 117 OF TEXTBOOK eukaryotic cytoskeleton Microfilaments are responsible for cell locomotion and the cell s structural characteristics Microtubules serve as intracellular highways for transporting vesicles and organelles they are also required for cellular locomotion via flagella and cilia Intermediate filaments are rope like structures that anchor organelles and intercellular junctions called desmosomes They are specialized for bearing tension
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