BSC 2010C Lecture Notes - Lecture 7: Pinocytosis, Endocytosis, Vacuole
Bulk Transport
Large molecules are packaged in vesicles and transported in bulk
Endocytosis (into cell)
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Exocytosis
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Endocytosis
Three types:
Phagocytosis
Cell engulfs large particle (often food)
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Uses Pseudopodia to create vacuole
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Vacuole fuses with lysosome filled with digestive enzymes
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Pinocytosis
Vesicles pinch into cell
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Cell absorbs drops of extracellular matrix
Drops contain dissolved molecules
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Forms small vesicles
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Non-specific
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Receptor- Mediated Endocytosis
Special type of pinocytosis
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Membrane proteins have receptor sites exposed to extracellular
matrix
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Occurs at receptor sites
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Specific Substances
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Receptor sites bind to specific solutes
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Exocytosis
Transporting out of the cell
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Vesicles from Golgi fuses with cell membrane
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Contents spill out into extracellular matrix
Waste products, hormones
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Vesicle membrane becomes part of cell membrane
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Tonicity
The ability of a solution to cause a cell to gain or lose water
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Depends on solute concentration and water concentration of the solution
compared to solute concentration and water concentration in cell
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A solution is both solvent (water) and solute
As solution concentration increases, water concentration decreases
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As solution concentration decreases, water concentration increases
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Equal concentration of water and solute is called isotonic
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Water concentration of the solution equal water concentration in the cell
Cell and solution are isotonic
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No net movement of water
Water diffuses in and out of cell, but in equilibrium
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Water concentration in the solution is greater than in the cell
Solute concentration of the solution is less than solute concentration
in the cell
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The solution is hypotonic compared to the cell
The cell is hypertonic compared to the solution
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Water diffuses into the cell from the solution
Cells swells up, becomes turgid and will eventually lyse
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Water concentration in the cell is greater than water concentration in the
solution
Solute concentration of the solution is greater than solute
concentration in the cell
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The cell is hypotonic compared to the solution
The solution is hypertonic compared to the cell
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Water will diffuse out of the cell into the solution
Cell will shrivel up (crenate)
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Factors that affect rate of diffusion:
Concentration gradient
Larger gradient à faster diffusion•
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Temperature
Increased temp à faster diffusion•
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Molecule size
Smaller molecules à faster diffusion•
Larger molecules à slower diffusion•
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Electrical gradient
Charge à faster diffusion•
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Pressure gradient•
Increased pressure à faster diffusion
Membrane Structure and Function
Wednesday, February 28, 2018
10:14 AM
Document Summary
Large molecules are packaged in vesicles and transported in bulk. Vacuole fuses with lysosome filled with digestive enzymes. Membrane proteins have receptor sites exposed to extracellular matrix. The ability of a solution to cause a cell to gain or lose water. Depends on solute concentration and water concentration of the solution compared to solute concentration and water concentration in cell. A solution is both solvent (water) and solute. Equal concentration of water and solute is called isotonic. Water concentration of the solution equal water concentration in the cell. Water diffuses in and out of cell, but in equilibrium. Water concentration in the solution is greater than in the cell. Solute concentration of the solution is less than solute concentration in the cell. The solution is hypotonic compared to the cell. The cell is hypertonic compared to the solution. Water diffuses into the cell from the solution. Cells swells up, becomes turgid and will eventually lyse.
