Cell Transport Maintaining Balance Homeostasis process of maintaining
Cell Transport
Maintaining Balance • Homeostasis – process of maintaining the cell’s internal environment • Cannot tolerate great change • Boundary between cell and the environment • What provides this?
Plasma Membrane • Fluid Mosaic Model • Selective Permeability • Phospholipid bilayer – Hydrophobic; Fatty Acid Tail – Polar Head; Hydrophilic
• Cholesterol – Provides stability • Transport Proteins • Carbohydrates • Other Proteins – Cell recognition (immune system)
Recall Following Terms • Solution • Diffusion • Concentration gradient • Results in uniform concentration
Osmosis • Cells try to reach equilibrium • Diffusion of water across a selectively permeable membrane; 3 results – Isotonic – Hypertonic Tonicity – Hypotonic
Isotonic • Solute concentration of solution equal to that of cell • No net water movement
Hypertonic • Solute concentration of solution higher than cell • More dissolved particles outside of cell than inside of cell • Hyper = more (think hyperactive); Tonic = dissolved particles • Water moves out of cell into solution • Cell shrinks
Hypotonic • Solute concentration of solution lower than cell • Less dissolved particles outside of cell • Hypo = less, under (think hypodermic, hypothermia); Tonic = dissolved particles • Water moves into cell from solution • Cell expands (and may burst)
Active vs. Passive • Active vs. Passive Transport • Passive requires no energy from the cell • Active requires cells to use energy, usually ATP
Passive Transport • Have to move with the concentration gradient • Diffusion • Osmosis • Facilitated Diffusion- involves use of transport proteins but still follow rule of diffusion
Active Transport • Movement of materials against concentration gradient • Transport proteins • Endocytosis – cell takes in material • Exocytosis – expulsion or secretion of materials from cell
Pinocytosis Phagocytosis
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