membrane transport and cell signalling

• What are the two models for facilitated diffusion?

  Pore (channel) and Carrier
• What does a pore (channel) model allow to pass through the membrane?

  Impermeable species
• What is facilitated diffusion?

  Passive transport using transport proteins
• What is the role of ionophores?

  Facilitating ion movements
• How does simple diffusion differ from facilitated diffusion?

  Simple diffusion occurs through lipid, facilitated uses proteins
• What is the direction of particle movement in passive transport?

  Down their concentration gradient
• What is required for active transport?

  Energy (ATP)
• What is primary active transport?

  Transport needing direct energy source
• How does secondary active transport differ from primary active transport?

  Secondary uses gradients, primary uses direct energy
• What is the function of the Na/K ATPase?

  Maintains membrane potential
• What is diffusion?

  Movement from high to low concentration
• What is osmosis?

  Diffusion of water across a membrane
• What are the two types of endocytosis?

  Pinocytosis and Phagocytosis
• What is phagocytosis?

  Engulfing large particles into vesicles
• What is receptor-mediated endocytosis?

  Endocytosis using receptors to recognize molecules
• What is exocytosis?

  Release of vesicle contents outside the cell
• What is the role of SNARE proteins in exocytosis?

  Mediating vesicle fusion with the membrane
• What factors affect membrane transport?

  Phospholipid bilayer properties
• What is the permeability of the membrane to water?

  Permeable to water
• What is facilitated diffusion?

  Diffusion down concentration gradient with help
• What are the types of transport across membranes?

  • Passive Transport:
  • Simple diffusion
  • Facilitated diffusion
  • Osmosis
  • Active Transport:
  • Primary active transport
  • Secondary active transport
  • Endocytosis
  • Exocytosis
• What are the differences between primary and secondary active transport?

  • Primary Active Transport:
  • Direct energy source (ATP)
  • Moves ions against their gradient
  • Secondary Active Transport:
  • No direct energy source
  • Uses gradients of other molecules
• What are the types of endocytosis?

  1. Pinocytosis (cell drinking)
  2. Phagocytosis (cell eating)
  3. Receptor-mediated endocytosis
• What is the significance of the Na/K ATPase in cells?

  • Maintains membrane potential
  • Essential for secondary active transport
  • Consumes significant cellular energy
• What is the role of vesicles in exocytosis?

  • Transport substances out of the cell
  • Fuse with plasma membrane
  • Release contents like hormones or waste
• How does the structure of the phospholipid bilayer affect transport?

  • Hydrophobic center restricts polar molecules
  • Allows non-polar molecules to pass
  • Small uncharged molecules can diffuse
• Why is it important to stop or reduce cell signaling?

  Overstimulation causes problems in cellular functions
• What are the five main methods to stop or reduce signaling?

  • Receptor desensitization
  • Receptor internalization
  • Enzymatic degradation of signals
  • Receptor downregulation
  • Signal sequestration
• What type of molecules bind to intracellular receptors?

  Small and hydrophobic signal molecules
• What do nuclear receptors regulate?

  They regulate gene expression
• What do DNA-binding domains contain?

  Multiple Zinc fingers
• Who was Viktor Yushchenko?

  • Ukrainian politician
  • Campaigned against Viktor Yanukovych
  • Diagnosed with dioxin poisoning in 2004
• What is the significance of GPCRs in the genome?

  They encode over 2% of the genome
• How many different GPCRs are there?

  Over 1000 different GPCRs
• What percentage of drugs target GPCRs?

  Over 40%
• What are the families of GPCRs?

  • Family A: Rhodopsin/β2-adrenergic receptors
  • Family B: Glucagon/VIP/calcitonin receptors
  • Family C: Metabotropic neurotransmitter/calcium receptors
  • Families D, E, and F: Less characterized
• What is notable about Family A of GPCRs?

  It is well studied with known crystal structures
• How does GPCR distribution reflect ligand diversity?

  • Classical small molecules and neurotransmitters
  • Peptides
  • Large glycoprotein hormones
  • Protease ligands
  • Light activation of GPCRs
• What is the general structure of GPCRs?

  • Seven transmembrane domains (TM1 to TM7)
  • Extracellular and intracellular loops
  • N-terminus and C-terminus regions
• What do animal cells depend on for communication?

  Multiple extracellular signals