membrane transport and signalling

• What is the main component of cell membranes?

  Phospholipid bilayer
• What are the two layers of the phospholipid bilayer composed of?

  Phospholipids with embedded proteins
• What does the hydrophilic phosphate end of a phospholipid do?

  Attracts water
• What does the hydrophobic lipid tail of a phospholipid do?

  Repels water
• What are the two types of membrane proteins?

  Peripheral and integral
• What does the Fluid Mosaic Model describe about cell membranes?

  They are constantly moving and changing
• What is one function of the cell membrane?

  Acts as a barrier
• What are the three functions of the cell membrane?

  1. Barrier – keeps wastes out, allows substances in
  2. Organization – packages materials in vesicles
  3. Selective Filter – semi-permeable, regulates substance movement
• What is a concentration gradient?

  Difference in concentration across a space
• What happens at equilibrium regarding particle movement?

  Particles continue to move back and forth
• What is a hypotonic solution?

  More water than in the cell
• What is a hypertonic solution?

  Less water than in the cell
• What is an isotonic solution?

  Same amount of water as in the cell
• Why is energy spent on active transport?

  Maintains internal cell environments
• How do multicellular organisms communicate?

  • Cells talk to each other
  • Neighbors have private conversations
  • Messages sent over distances
  • Public announcements for danger
• What are the types of chemical signaling?

  1. Direct Contact
  2. Paracrine
  3. Endocrine
  4. Autocrine
• What type of signaling involves chemicals that impact another cell?

  Paracrine signaling
• What type of molecules serve as recognition markers on plasma membranes?

  Glycoproteins and glycolipids
• What are plasmodesmata?

  Cell junctions in plant cells
• What are gap junctions?

  Cell junctions in animal cells
• What is the role of local regulators in cell communication?

  • Influence nearby cells
  • Growth factors stimulate multiplication
  • Paracrine signaling involves multiple cells
  • Synaptic signaling in the nervous system
• What is paracrine signaling?

  Cell acts on nearby target cells
• What is endocrine signaling?

  Long-distance signaling via hormones
• What is autocrine signaling?

  Signal impacts the same cell that released it
• What are the steps in signal transduction pathways?

  1. Reception – detection of message
  2. Transduction – receptor initiates cascade
  3. Response – activation of target
• What activates G-protein-linked receptors?

  Signal molecule attaches to receptor
• What is the role of receptor tyrosine kinases?

  Activate two kinases at a time
• What do ligand-gated ion channels do?

  Open a gate for specific ions
• What are second messengers in cell signaling?

  • Small, non-protein, water-soluble ions
  • Examples: Cyclic AMP, Calcium Ions
  • Regulate gene expression and cellular responses
• How is cyclic AMP created?

  From ATP by adenyl cyclase
• What happens when calcium ions increase in a cell?

  Muscle contraction and cell division occur
• What is the response in cell signaling?

  • Signals are amplified
  • Specific to target cells and enzymes
  • Not all cells respond to a signal
• What is the role of phosphorylation in signal transduction?

  Activates proteins in the cascade
• What is the role of protein phosphatases?

  Deactivates proteins by removing phosphate
• What is the significance of the MAPK pathway?

  Importance of modulation in signaling
• What is the function of relay molecules in signal transduction?

  Transmit signals within the cell
• What is the role of receptors in cell signaling?

  Detect specific signaling molecules
• What type of receptors are usually intracellular?

  Receptors for hydrophobic signaling molecules
• What is the function of plasma membrane receptors?

  Bind to hydrophilic signaling molecules
• What is the significance of G-protein activation?

  Triggers a cascade of cellular responses