crossing cell membrane

prokaryotes:

• no nucleus

• dna is in cytoplasm not nucleus

eukaryotes:

• nucleus and membrane bound organelles

• larger than prokaryotes

functions of plasma membrane:

• act as an active and selective boundary

• cell identity

• receives external signals

• transport material

CROSSING CELLS MEMBRANE

• simple diffusion

  • passive transport (no energy required)

  • movement from high to low concentration to the equilibrium

    
    

• osmosis (special type of diffusion)

  • movement of water across a semi-permeable membrane

  • from low to high solute concentration

  • continues until equilibrium

    
    

  • animal and plant cells in:

    • isotonic solution

      • no net movement across membrane

      • cells maintain a normal shape

      
      

    • hypotonic solution

      • solution with high water and low concentration solution

      • net movement of water from outside to inside the cell

      • plant cells swell dye to turgor pressure from water uptake

      • animal cells lyse (process of disintegration or dissolution)

      
      

    • hypertonic solution

      • solution with low water and high solute concentration

      • net movement of water from inside to outside the cell

      • animal cells shrink

      • plant cells become plasmolysed (the shrinkage of cells)

      
      

• facilitated diffusion

  • movement from high to low water concentration

  • no energy and through proteins

  • e.g glucose and ions- Na+/K+

    
    

• active transport

  • move molecules against gradient

  • atp energy required for transport

  • e.g. Na+/K+ pump

    
    

• bulk transport

  • moves large organic molecules in and out of cell

  • requires atp

    
    

• endocytosis

  • process: large/bulk substances enter cell without crossing plasma membrane

  • 2 main types:

    • phagocytosis: cell eating solids like pathogens engulfed by cell

    • pinocytosis: cell drinking liquids solutions are engulfed by cell

      
      

• exocytosis

  • process: large/bulk substances exit cell without crossing plasma membrane

  • Golgi-derived vesicles fuse with plasma membrane

  • contents expelled into extracellular environment.