Mammalian cell biology 1

• What are the main components of the plasma membrane?

  Specific proteins, lipids, and sugars
• What property do phospholipids have that allows them to form biomembranes?

  They are amphipathic
• What are the characteristics of phospholipid heads and tails?

  Heads are hydrophilic, tails are hydrophobic
• What happens to phospholipids in the presence of water?

  They assemble into a lipid bilayer
• How do steroids affect the plasma membrane?

  They affect membrane fluidity and act as hormones
• What role does cholesterol play in membrane fluidity?

  Reduces fluidity at moderate temperatures
• How does cholesterol affect membrane solidification?

  Avoids solidification at low temperatures
• What does lipid composition influence in membranes?

  It affects membrane curvature and identity
• What are lipid rafts?

  Membrane regions with specialized lipids and proteins
• What does fluorescent recovery after photobleaching reveal in membranes?

  Differences in membrane fluidity and protein mobility
• What does the integral membrane protein Sso1 undergo in the plasma membrane?

  2D-diffusion
• What happens to the bleached area in the plasma membrane?

  It closes due to diffusion of Sso1
• What are the bio-physical properties of lipids essential for?

  Cellular compartments
• How do membranes differ in their lipid composition?

  They provide identity to the organelle
• What is the fluid mosaic model of membranes?

  • Proteins swim in the lipid bilayer
  • A range of proteins are embedded
  • Functions include transport, enzymes, receptors
• What are the functions of membrane proteins?

  • anchorage and communication to the cytoplasm
  • anchorage at extracellular matrix
  • transport over membranes
  • cell-cell communication
• What does the extracellular matrix provide?

  • provides mechanical support
  • barrier for large molecules
  • supports cell migration
  • seperates tissue
  • involved in cellular signalling
  • consists of secreted proteins
• What is the plasma membrane's role as a barrier?

  It protects against the environment
• What type of molecules can pass through the plasma membrane?

  Uncharged and hydrophobic molecules
• What type of molecules cannot pass through the plasma membrane?

  Charged molecules
• How do membrane channels mediate transport?

  They facilitate communication and exchange
• What controls the permeability of ion channels?

  Gating mechanisms
• What types of gating can ion channels have?

  Voltage, mechanically, temperature, ligand gated
• Do channels use ATP for transport?

  No, they do not use ATP
• What do protein pumps do?

  Transport against a gradient using ATP
• What is membrane potential?

  Uneven distribution of electrical charges
• How do channels contribute to membrane potential?

  They cooperate to form membrane potential
• What is the typical membrane potential range for cells?

  -50 to -70 mV
• Do non-excitable cells change their membrane potential?

  No, they do not change
• What happens in excitable cells regarding membrane potential?

  It can dramatically change with cation influx
• What causes the membrane potential?

  Differences in ion permeability and ATP-dependent pumps