Mpharm Bio

• • GLUT-1 : High affinity - uniport, in many cells with high constitutive glucose requirements
  • GLUT-2 : Low affinity, acts as a glucose sensor in liver and pancreas because only notices glucose levels when high after a meal
  • GLUT-3 : High affinity, found on neurons
  • GLUT-4 : Insulin sensitive transporter, allows fat and muscle to increase glucose uptake in response to insulin
  • GLUT - 5 : fructose specific transport, found in intestinal epithelial cells
• Rate of Transport


  The smaller the molecule, the fewer its favourable interactions with water, the more rapidly diffuses across the lipid bilayer

  Rate = J P = permeability coefficient

  J = -P (C1 - C2)
• Important ATPase membrane transporters


  • Na+/K+ ATPase - important for osmotic balance and resting potentials. P type ATPase ubiquitous to all body cells
  • Ca2+ ATPase - important intracellular signalling molecules, normally sequester Ca2+ in intracellular stores
  • H+ ATPase - important for secretion of HCl into stomach lumen
• Na+/Glucose Transporters - Active Transport of Glucose


  • SGLT-1 - intestinal mucosa - glucose absorption
  • SGLT-2 - in proximal convoluted tubule - glucose reabsorption
• Other important co-transporters

  • Serotonin reuptake transporter (SERT) - Na+ gradient used to drive serotonin uptake from synaptic clefts (serotonin = important neurotransmitter in brain). Inhibited by serotonin-specific reuptake inhibitors (SSRIs, e.g. Fluoxetine - Prozac)
  • Na+/I+ cotransporter - drives iodine uptake in thyroid gland. Important for thyroid hormone production
• Important Exchangers

  • Na+/Ca2+ exchanger - Ca2+ influx into the cytoplasm of cardiac muscle cells drives contraction. Important for the removal of Ca2+ ions after muscle contraction
  • Cl-/HCO3- cotransporter - Important for exchange of CO2 from blood to exhaled air in lungs.
• Nernst Equation


  Force tending to drive up an ion across a membrane -- due to electrical membrane potential AND due to concentration gradient of ion.

  At equilibrium V= 62log10(Co/Ci)

  V = membrane potential - millivolts

  Co = ion concentration outside cell

  Ci = ion concentration inside cell

  Assume ion carries a single positive charge and the temperature is 37 degrees Celsius
• Microbial Mechanism Models


  • Valinomycin - carrier mechanism. Increased permeability of K+ ions. Cyclic peptide. Surface rich in methyl groups. Ring interlined with nitrogen and oxygen - well suited for chelating cations. Interior space best accommodates K+ ions.
  • Gramicidin - pore mechanism. Amino acid chain. Cation specific pore - not specific to ion - conducts Na+, K+, H+, NH4+. Causes distribution of K+ and Na+ between environment and cell interior to break down. 2 molecules must line up to form pore
• What are the main interactions between cells in multicellular organisms?

  Cell adhesion molecules and extracellular matrix
• What is the role of cell adhesion molecules?

  They facilitate interactions between cells
• Name one type of junction that facilitates cell interactions.

  Tight junctions
• What is the function of tight junctions?

  Prevent leakage of molecules between cells
• What do desmosomes do?

  Join intermediate filaments of adjacent cells
• What is the purpose of gap junctions?

  Allow small molecules to pass between cells
• What do adherens junctions connect?

  Actin bundles in neighboring cells
• What is the role of the basal lamina?

  Supports and scaffolds epithelial tissue
• What is the composition of the basement membrane?

  Collagen IV and laminin
• What is the extracellular matrix (ECM)?

  A fibrous network of proteins and polysaccharides
• What are glycosaminoglycans (GAGs)?

  Hydrated gel-like substances in ECM
• What is the function of fibroblasts?

  Produce components of the ECM
• How does collagen contribute to the ECM?

  It provides structural support and strength
• What is the basic structural unit of collagen?

  A triple helix
• How does the ECM impact drug metabolism resistance?

  It interacts with cells to regulate gene expression
• What diseases are associated with changes in ECM components?

  Alzheimer's and Parkinson's disease
• What therapeutic potential does the ECM have in cancer treatment?

  It can be a target for therapeutic interventions
• What are the functions of the extracellular matrix?

  • Holds cells and tissues together
  • Active role in embryogenesis
  • Involved in wound healing
  • Facilitates cell migration
• What are the types of cell junctions and their functions?

  • Tight junctions: Prevent leakage between cells
  • Adherens junctions: Connect actin bundles
  • Desmosomes: Join intermediate filaments
  • Gap junctions: Allow ion movement and signaling
  • Hemidesmosomes: Anchor cells to basal lamina
• What are the components of the basement membrane?

  • Thin, dense layer of ECM
  • Composed of collagen IV and laminin
  • Provides structural support
  • Regulates cell behavior
• What is the significance of the ECM in health and disease?

  • Regulates gene expression
  • Impacts drug metabolism resistance
  • Associated with diseases like Alzheimer's
  • Potential therapeutic target in cancer
• What are the roles of cadherin and integrin in cell junctions?

  • Cadherin: Connects cells to each other
  • Integrin: Connects cells to the substratum
• What is the role of the ECM in embryogenesis and wound healing?

  • Provides structural support
  • Facilitates cell migration
  • Regulates cellular activities
• What are tissues in multicellular organisms?

  Communities of cells working together
• How does the role of a tissue depend on its cells?

  It depends on the types of cells present
• What is the function of goblet cells in the gastrointestinal tract?

  Secrete lubricating mucus
• Why is proper regulation of cell division rates essential?

  It is essential for tissue maintenance and repair
• What is polarity in the context of tissue organization?

  Orientation of particular cells in their place
• What influences the arrangement of cells in a tissue?

  External signals from neighboring cells
• What is the process of cell division crucial for?

  Long-term tissue survival
• How do cell turnover rates vary in tissues?

  They vary widely between different cell types
• Which cells in the adult mammal brain rarely divide?

  Neurons