Physiology (8)

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  • 1. Physiology The Typical Cell • typical cell: 1. nucleus 2. cell membrane 3. cytoplasm -cytosol -cytoskeleton 4. cytoplasmic organelles -membranous -non-membranous Cytoplasm • semi-fluid-like jelly within the cell • division into two subdivisions: cytosol & organelles • also contains a supportive framework of proteins: cytoskeleton Cytosol - intracellular fluid of the cell - about 55% of the cell’s volume - about 70-90% water plus: dissolved nutrients, ions, soluble & insoluble proteins, waste products, glucose, ATP amino acids, fatty acids. Cytoskeleton: • internal framework of the cell • gives the cytoplasm flexibility and strength • three major components 1
  • 2. 1. microfilaments 2. intermediate filaments 3. microtubules intermediate filaments = made up of vimentin, desmin or keratin - function: 1. impart strength 2. stabilize organelles 3. transport materials - some are specialized in specific cell types e.g.: neurofilaments - for transport of synaptic vesicles containing neurotransmitters five major groups of intermediate filaments: 1- Type I: acidic keratins (epithelial) 2. Type II: basic keratins (epithelial) 3. Type III: - vimentin (mesenchyme) - desmin (muscle) 4. Type IV: Neurofilaments (neuronal) 5. Type V: Lamins A, B, C (all cells) microtubules = repeating units of tubulin -assembly is controlled in the MTOC (microtubule organizing center) - located near the nucleus -cylinder = 13 rows of tubulin -function: 1. cell shape & strength 2. organelles: anchor & movement 3. mitosis - form the spindle (chromosome movement) 4. form many of the non-membranous organelles (cilia, flagella, centrioles) Endoplasmic reticulum (ER) = series of membrane-bound, flattened sacs in communication with the nucleus and the PM -each sac or layer = cisternae -inside or each sac = lumen -three functions: 1. synthesis 2. storage 2
  • 3. 3. transport -two types: Rough ER - outside studded with ribosomes -continuous with the nuclear membrane -protein synthesis, phospholipid synthesis -the peptide strand as it is being translated by the ribosome is fed into the RER -initial site of processing (attachment of carbohydrates) and sorting for transport to the Golgi Smooth ER – extends from the RER - free of ribosomes - many enzymes on the surface of the SER - lipid and steroid (estrogen and testosterone) biosynthesis for membranes, detoxification of toxins and drugs, vesicle formation, cleaves glucose so it can be released into the bloodstream -the amount of SER per cell can increase with drug use – cell accomodates to increase protection Mitochondria = site of energy production (ATP production) -via Cellular Respiration - breakdown of glucose into water and CO2 results in the production of ATP -initial glucose breakdown occurs in the cytosol -terminal stages occur in the mitochondria = Oxidative Phosphorylation Cellular respiration -glycolysis -citric acid cycle -electron transport chain 3
  • 4. Golgi Apparatus = stack of 3 to 20 flattened membrane sacs/cisternae • site of protein modification, and final packaging of the finished protein into secretory vesicles -> exocytosis or for use in the cytosol 4