Chapter Seven Cell components structure and function Prokaryotic Lack of membrane bound organelles DNA just floating around in cytoplasm Bacteria and archea Usually single celled organisms Eukaryotic Membrane bound organelles DNA contained in a nucleus Large multicellular organisms are common Pancreatic cell a Animal cell no cell wall b Make enzymes and secrete them into the small intestine for digestion c Lots of rough ER for making proteins rough ER contains ribosomes for making transmembrane proteins or proteins that have a significant polar part and a significant non polar part d Lots of vesicles for transporting proteins out of cell Animal testis cell a Lots of smooth ER for making lipids such as testosterone b Exports lipid soluble signals Plant leaf cell a b c d Make atp and sugars Lots of chloroplasts for energy Cell shape is very rigid due to vacuole and cell wall Tobacco leaf vacuoles store nicotine Brown fat cell a Lots of mitochondria b In hibeRNAting animals and babies c Specialized mitochondria produce heat rather than atp The point of these was to show that STRUCTURE FUNCTION Cell systems 1 Nuclear transport a Things must go through the nuclear envelope to get into the nucleus b Envelope has two layers inner and outer membrane c Also a nuclear pore complex d Things going in DNA and RNA materials i All things going in need a nuclear localization signal NLS to let them in 17 amino acid long tag sometimes call molecular zip code ii Some viruses like AIDS have evolved to have their own NLS even though that s bad for the host e Things going out RNA 2 Endomembrane system a Made of smooth and rough ER and Golgi apparatus b Protein and lipid production ER c Transportation of proteins and lipids Golgi d Golgi apparatus has a cis side and a trans side i Cis side closest to ER ii Trans side closest to cell membrane iii Receives proteins lipids from vesicles from ER e Protein transportation is very tightly regulated by secretory pathway ER to Golgi to vesicle to cell membrane or where ever f Proteins need a way to get into the endomembrane system SIGNAL HYPOTHESIS PULSE CHASE EXPERIMENT used to support secretory pathway model Find some normal cells label proteins with a radioactive amino acids so their movement can be followed Add radioactive amino acids to the cells Track amino acids Record their locations o Seems like they went from ER to Golgi to secretory vesicles The Signal Hypothesis Proteins bound for the endomembrane system have a code the directs polypeptides to the ER proteins come to the ER mid production so they are partially made and then have to go to the ER 20 amino acids long Sequence binds to a signal recognition particle SRP that then binds to a receptor in the ER membrane the signal sequence gets removed once the protein arrives at the ER In the rough ER lumen protein production happens and the tag tells where the protein should go and whatnot Inside ER glycosylation adds carbohydrates to proteins Then proteins go to vesicles which take them to where ever they need to go Endocytosis breaking down proteins and recycling the bits for new proteins 3 Dynamic cytoskeleton made of Actin intermediate filaments and microtubules a Actin and myosin allow movement to occur b Cytokinesis in animals animal cells splitting in two during mitosis meiosis c Actin myosin interactions cytoplasmic streaming