Anatomy and Physiology Exam 1 Figueroa The Plasma Membrane The fluid mosaic model Membrane lipids Lipid bilayer forms the fabric of the Composed of phospholipid molecules membrane Head polar and hydrophilic philic means it likes water if water soluble Tail hydrophobic phobice means it is afraid of water insoluble in water Uncharged nonpolar It is made up of two fatty acid chains Membrane Proteins Integral proteins firmly inserted into the lipid bilayer some only protrude from only one membrane surface most are transmembrane span the entire width of the membrane and stick out both sides most are involved in transport some clump together to form channels or pores through which water soluble molecules or ions can move through others are carriers that bind to a substance and then move it through the membrane receptors Peripheral proteins are not embedded in the lipid they attach loosely to integral proteins Functions transport from one side to the other enzymatic activity substrate to produce products Receptors for signal transduction Neurotransmitters Hormones Membrane Transport Passive process no energy used Diffusion the tendency of molecules or ions to move from high concentration to low concentration along their concentration gradient passive transport occurs if lipid soluble small assisted by carrier molecule Simple Diffusion unassisted diffusion lipid soluble substances and nonpolar oxygen and carbon dioxide dependent on the concentration gradient Facilitated Diffusion assisted Limited by the number of protein channels available Amino acids ions and Glucose travel via Carriers binding to protein carriers in the membrane and ferried across for bigger molecules amino acids and glucose Channels moves through water filled protein channels ions electrolytes use channnels Osmosis the diffusion of a solvent such as water through a selectively permeable membrane Solutes attract water Occurs when the concentration of a solvent is different on opposite sides of a membrane Osmolarity total concentration of a solute in a solution Tonicity nothing happens Isotonic solutions with the same solute concentration as the cytosol Hypertonic solution has a higher solute concentration than the cytosol Hypotonic solution has a lower solute concentration loses water shrivels up gains water cell expands if RBC ruptures hemolysis Active Process Active Transport Carrier mediated facilitated diffusion Requires carrier protein that combine specifically and reversibly with the transported substance Solute pumps move solutes most ions against their concentration gradient ATP is needed Primary Active transport requires carrier proteins Antiports transport mechanism that moves two substances in opposite directions ATP is energy ATPase breaks ATP into ADP as well as transports it Ex Sodium Potassium Pump Carrier is called sodium potassium ATPase K inside the cell is 10x higher in concentration than outside of the cell Na is higher in concentration outside never have more Na inside 3 Na leaves goes out of the cell and 2 K move into the cell the result the Na K pump the Na provides energy for the Secondary Active transport Secondary Active transport transport driven indirectly by energy stored in ionic gradients created by the primary active transport pumps Symports transport mechanism that moves the substance in the same direction Glucose and Amino Acids need Na to enter Glucose has a different transporter that AAs but move in the same direction If Na goes from high low ALONE it is using facilitated diffusion If Na goes from low high in a TRANSPORTER w ATP it is using Primary Active transport if Na goes from high low w AA or Glucose it is using Secondary Active transport Vesicular Transport transport of large particle and macromolecules across the plasma membrane Ex Receptor mediated Endocytosis Phospholipid bilayer is main component of plasma membrane Exocytosis movences from the cell s interior to the extracellular space Endocytosis move substances from the outside of the cell to the inside Phagocytosis cell s eat large particles Pinocytosis the cell drinks the small particles think of the particle as a large burger you need to take bites to eat it think of the particle as a pill you don t need to break it down you just swallow it Vesicles fuse to the lysosome Cytoplasm consists of everything between the nucleus and the cell membrane Cytosol the intracellular fluid mostly water but also contains dissolved chemicals between the plasma membrane and the nuclear membrane both have a lipid bilayer Organelles structures that each perform specific functions for the cell Ribosomes the site of Protein Synthesis two major subunits made up of RNA and proteins mRNA is in the space between the two subunits Free ribosomes make proteins used in the cytosol Attached ribosomes Endoplasmic Reticulum make proteins used in membranes and for export an extensive membrane network within the cytosol Rough ER Smooth ER contains bound ribosomes has enzymes involved in metabolism of lipids and drugs NO ribosomes attached no contact between the Rough ER and the Golgi just as there is no contact between the Golgi and the cell membrane Golgi Complex modifies and sorts out proteins produced by the rough ER generates vesicles for moving molecules Protein goes from rough ER Golgi plasma membrane Protein travels in a vesicle Vesicle fuses with the plasma membrane and allows protein to exit the cell exocytosis rough ER forms the membrane of the vesicle to complete protein synthesis it MUST go through the golgi Transcription the process where a DNA sequence is copied into RNA sequence occurs in the nucleus transfers genetic info from DNA into one of 3 major classes of RNA messenger RNA mRNA ribosomal RNA rRNA transfer RNA tRNA the enzyme RNA polymerase creates the RNA molecules enzyme breaks down bonds and begins reading amino acids RNA uses U uracil rather than T thymine mRNA if the RNA sequence is meant to encode proteins it is called messenger RNA the mRNA sequence is used to make new proteins in a process called Translation occurs in ribosome tRNA transfer RNA brings amino acids to the ribosome from the cytoplasm tRNA helps to line up the correct amino acids to make a new protein Codon in mRNA Anticodon in tRNA mRNA moves nucleotides from nucleus to ribosome tRNA moves amino acids from nucleus to ribosome 3 bases nucleotides are moved read at a time 3 bases make up a codon or an anticodon Epithelium Primary Functions Protection Absorption
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