Cell Transport Mechanisms

Moving molecules across the Cell Membrane

Two methods:

Passive Transport

Active Transport

Passive TransportAllows 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 (CO2,O2)small lipidsalcohol

Prediction?

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

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 acrossProteins are specific to _____________________________________

_____________ ______________

Examples: watersaltionsglucose

Active TransportMoves 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 Cell Inside Cell

Active Transport

ExocytosisMoving molecules _____cells

EndocytosisMoving 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

ExocytosisVesicle 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

=__________________________________________