ch 1 membrane

• Physiology relates process to function
• The cell is able to have transport across membranes, which is important for the cell to survive.
• 4 functions of membranes are: physical isolation, regulation of exchange with the environment, communication between the cell and the environment, and support and structure
• molecules that move freely within the membrane are urea and cholesterol (steroid hormones).
• concentration gradient is the energy used to do simple and facilitated diffusion
• glucose goes from high outside the cell to low inside the cell
• GLUT 4 is insulin sensitive
• certain functions of proteins

  they are transporters, provide structural support, receptors, and enzymes
• endocrine cells and neurons release signals that bind to receptors
• Simple diffusion involves small hydrophobic/lipophilic molecules (ex: O2). It also involves small uncharged polar molecules (urea), large uncharged polar molecules (glucose, amino acids, and nucleotides), ions(K+, Na+, HCO3-, H+), and cholesterol based molecules (ex: steroid hormones)
• Active transport requires energy from ATP and passive transport uses energy from the concentration gradient
• examples of active transport are vesicle transport, primary active transport, and secondary active transport
• Passive transport is either simple or facilitated. Facilitated diffusion can either be channel or carrier
• primary active transport creates the concentration gradient for secondary active transport
• active transport goes from low to high concentration
• Glucose has 2 carriers: GLUT2 and GLUT4 (usually for those with insulin sensitivity/Type 2 diabetes)
• ATP is used to make the vesicle used in vesicular transport
• Endocytosis is broken into three parts: Phagocytosis is cell eating, pinocytosis is cell drinking, and receptor mediated uses receptors (ex: HIV and t cells)
• Exocytosis is when something comes out of the cell
• vesicular transport deals with large molecules
• The lumen is the Apical membrane and the ECF is the basal membrane
• Transporter and pump are common words used when describing active transport
• in secondary active transport if the pump stops working then transport stops
• In a transport graph there is a linear relationship between transport rate and plasma [glucose]. After some time, transport will reach a maximum due to saturation
• Characteristics of mediated transport

  specificity, competition, and saturation
• the Na+/K+ pump allows two k+ inside the cell and 3 na+ to be moved out the cell
• ATPases are one of the many active transporters
• primary active transport works against the concentration gradient (goes from low to high)
• Carriers have allosteric sites that aren't the binding site
• carriers are like enzymes where there is competition and saturation, which does not happen in ion channels
• Carriers are very similar to enzymes. Carriers are affected by temperature and pH, they catalyze transport processes, have specific substrates, and undergo conformational change
• carriers operate slower than channels. when the substrate binds there is a conformational change that moves it to the other side of the membrane
• channels are open from the ICF to the ECF
• most channels are ion but there are also mechanical gated, voltage gated, and ligand gated
• diffusion rate depends on lipid solubility of the molecule, available surface area, and membrane thickness
• Fick's law: (surface area x concentration gradient x permeability) / membrane thickness
• Diffusion works well with an increased surface area and within short distances
• diffusion stops when there is no concentration gradient to equilibrate
• kinetic energy is the energy required in diffusion
• symport transport is a form of cotransport and antiport is counter transport. (ex: in a H+/Na+ antiport; the H+ is being moved against the gradient