cells lect 8

• Why are eukaryote cells compartmentalized?

  To increase reaction speed and diversity
• What does cryo-electron tomography show about cells?

  How densely packed cells are
• What are the functions of membranes in cells?

  • Controlling transport
  • Concentrating enzyme activity
  • Controlling cell communication
  • Connecting cells
  • Recognising cells
• How thick are most membranes?

  5 – 10 nm thick
• What type of viruses are enclosed by membranes?

  Enveloped viruses like HIV and influenza
• What are the two types of phospholipids?

  Phosphoglycerides and sphingolipids
• How many different types of lipids have been identified in membranes?

  500 – 1000 different types
• What regulates the cell's molecular traffic?

  The plasma membrane
• Which type of molecules can pass through the membrane rapidly?

  Hydrophobic (nonpolar) molecules
• What do polar molecules require to cross the membrane?

  Specific transport mechanisms
• What are the types of transport across membranes?

  • Passive transport
  • Active transport
  • Diffusion
  • Facilitated diffusion
  • Channel protein
  • Carrier protein
• Why does a typical animal cell use energy for the Na+/K+ pump?

  To maintain solute concentrations inside the cell
• What happens if water moves into the cell unregulated?

  The cell will burst
• How do cells control intracellular osmolarity?

  By actively pumping out inorganic ions
• What are the methods for transporting large molecules?

  • Phagocytosis
  • Pinocytosis
  • Receptor-Mediated Endocytosis
• What happens during exocytosis?

  Proteins are released outside the cell
• Where are secreted proteins synthesized?

  In the rough ER
• What are signal sequences in proteins?

  Instructions for protein location in the cell
• What are the three main ways to transport proteins around the cell?

  1. Gated transport (e.g., nuclear pore)
  2. Transmembrane transport (e.g., mitochondria)
  3. Vesicular transport (e.g., motor proteins)
• What is the nuclear envelope composed of?

  Two concentric membranes
• How many nuclear pore complexes does a typical mammalian cell contain?

  3000 – 4000 NPCs
• What do nuclear pore complexes recognize?

  Nuclear localisation signals on proteins
• How many macromolecules can each NPC transport per second?

  500 macromolecules
• What are the types of motor proteins used for transport?

  • Myosin (along actin microfilaments)
  • Kinesin (along microtubules)
  • Dynein (along microtubules)
• What is required for motor protein movement?

  Energy and ATP
• What role do kinesin and dynein play in neurons?

  Transport neurotransmitters
• How do motor proteins help zebrafish change color?

  By transporting pigment molecules along microtubules
• What do myosin motor proteins transport?

  Vesicles and organelles
• What is the role of myosin in muscle contraction?

  It walks down actin filaments
• How do chromatophores change color rapidly?

  By changing shape due to muscle fibers