Cell Transport Mechanisms

Moving molecules across the Cell Membrane Two methods: Passive Transport Active Transport

Passive Transport Allows molecules to ____________ according to natural laws of physics Everything tends towards___________ Three types of passive transport mechanisms: - - -

Passive Transport – Diffusion This forces molecules to move from areas of ________ concentration to areas of ________ concentration _________a ___________________ “_______________” High Concentration Low Concentration Movement of molecules is __________ When they bump into each other, they _________________ When they are __________ concentrated, they bump into each other _____________________

Passive Transport – Diffusion When molecules have reached equal concentrations in both locations, diffusion ends. Molecules _________ moving, but they move in ______________ equally. _________________. = ___________

Diffusion across a Membrane Examples: small molecules (CO 2,O 2 ) small lipids alcohol Prediction?

Passive Transport – Osmosis Moves ________ molecules across cell membrane (into or out of cells) Molecules still move down the concentration gradient Purple dots are solutes, not water molecules

Passive Transport – Osmosis Predict Results

Passive Transport – Osmosis Osmotic Pressure – Pressure created by the presence of water in the cell …cell _______or ________ Example: Blood cell in low/high salt solutions

Passive Transport – Osmosis Animal Cell Plant Cell Hypertonic Solution: Conc. of solutes outside cell is ________ 5% salt 2% salt Water _______ cell

Passive Transport – Osmosis Isotonic Solution: Conc. of solutes outside cell is _________inside cell Animal Cell Plant Cell 5% salt Water ____________cell _____________ _____ _______ ______________

Passive Transport – Osmosis Hypotonic Solution: Conc. of solutes outside cell is _________ Animal Cell Plant Cell 2% salt 5% salt Water ________ cell

Passive Transport – Facilitated Diffusion Molecules still move down the concentration gradient, but cannot pass phospholipids on their own. Rely on __________ imbedded in membrane to “________” them across Proteins are specific to _____________________________________ _____________ ______________ Examples: water salt ions glucose

Active Transport Moves molecules __________ the concentration gradient from areas of _________ concentration to areas of __________ concentration. Restores ________ Takes _______ to “go _______” _____________ move molecules into or out of cell ______ gradient. Outside CellInside Cell

Active Transport Exocytosis Moving molecules _____cells Endocytosis Moving molecules ________ cells ___________: “cellular _________” ___________: “cellular _________”

Endocytosis Molecules move into a “pocket” of the cell membrane

Endocytosis “Pocket” pinches off the membrane into cytoplasm

Endocytosis ________ has now formed and can move around inside cell

Exocytosis _______ pinches off ________________

Exocytosis Free vesicle migrates towards cell membrane

Exocytosis Vesicle contacts cell membrane and begins to fuse with it

Exocytosis As vesicle becomes part of plasma membrane, contents spill out of cell

Endocytosis and Exocytosis These two processes occur at roughly the same rate = ______________ ______________ ______________