Mammalian cell biology 8

• what percentage of your body is muscle

  40
• what percentage of muscle is protein

  20
• what percentage of muscle is actin

  12-15
• what do thick filaments consist of

  myosin 2
• what do thin filaments consist of

  F-actin
• mechanism of contraction

  1. stimulus from neuron spreads over the plasma membrane of the muscle cell
  2. depolarisation of membrane releases calcium from the sarcoplasmic reticulum into the cytoplasm
  3. binding of calcium to the troponin complex releases the block of the myosin binding site on actin
  4. myosin binds actin and walks towards the Z-disc
  5. calcium is removed by calcium pumps and myosin releases the actin filament and slide back
• features of flagellum

  • one or few per cell
  • function in cell locomotion
  • propeller-like motion
  • 10-40 beats per second
  • used to move cells
  • e.g. motility of sperm cells
• features of cilia

  • usually many per cell
  • fluid in function and particle transport
  • back and forth beating
  • 12-20 beats per second
  • used to move liquids and remove particles
• what is an axoneme

  the core of the cilium/flagellum made from microtubules
• what is a basal body

  • anchors the cilium/flagellum at the cell
  • centrioles form basal body of flagella
• what does intraflagellar transport support

  • the formation and function of the cilium
  • rafts travel along the axoneme
  • kinesin and dynein drive the bidirectional transport
• what does dynein do in cilia

  • dynein slides microtubules against each other
  • motor activity against the protein bridges between the tubules cause bending
• cilia in the body

  • brain ependymal cilia
  • retinal photoreceptor connective cilia
  • respiratory cilia
  • renal monocilia
  • sperm flagellum
  • fallopian tube cilia
• what are non-motile primary cilia

  • detect signals that govern cell proliferation
  • sense flow and bending - this triggers various regulation pathways
  • primary cilia are essential for developmental processes
• motile cilia

  generating flow, cleaning surfaces 
• non-motile cilia

  sensing environmental cues
• examples of non-motile cilia

  • dendritic knob of olfactory neuron
  • stimulus results in membrane depolarisation
  • rods and cones in the eye retina
  • rhodopsin discs are found in the cilium