Cellular Transport

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Transport Factors (Types)

1. Passive Transporta) Diffusionb) Osmosis

2. Active Transporta) Carrier Proteinsb) Endocytosis

1) Pinocytosis2) Phagocytosis

c) Exocytosis1) Secretory Vesicles2) Excretory Vacuoles

Diffusion<---> Osmosis

Diffusion is the tendency of objects in high concentration (state of order) to flow to an area of low concentration (state of disorder).

Facilitative Transport --> transport proteins

Osmosis is diffusion through a semipermeable membrane. Hypotonic--H2O low inside

Hypertonic-- H2O high inside

Isotonic-- H2O equal on inside/outside

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Active Transport

Ion assisted transport Molecules or ions help the substance getting transported to get across the membrane.

Receptor Site (gate) assisted transport The shape and attractions of the receptor (gate) help the substance getting transported to get across the membrane.

Energy assisted transport Energy to help transport substances is received from ATP, helping the substance getting transported to get across the membrane.

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Semipermeable Membrane

Smaller molecules are free to pass through the membrane equally in both directions <-->. Diffusion Rules!

Larger molecules are not free (or are greatly slowed down) to pass through the membrane in either direction.

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Transport Protein (facilitative)

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ATP energy assist Sodium (Na) and

Potassium (K) are at equilibrium (diffusion). This nerve cell would be inactive.

The receptor site (sodium pump) collects sodium (Na) ions. ATP activated the “sodium” pump.

Sodium gets transported against the diffusion gradient and potassium (K) load onto the carrier molecule and go inside the cell

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Hypertonic Solution

The solutes on the outside of the cell are in higher concentrations, water is in low concentration.

The concentration of water is higher inside the cell.

The result is that water flows ________ the cell.

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Isotonic Solutions

The concentration of solute is equal on both sides of the cell.

The concentration of water is equal on both sides of the cell.

The flow of water is ______.

Hypotonic Solutions

Concentrations of solutes are greater inside the cell, water concentration is lower

Concentrations of water are higher outside the cell.

The result is that water flows _______ the cell.

Pinocytosis

Molecules come in contact with the cell’s bilipid layer.

The bilipid layer responds by folding in.

The substance is completely surrounded by the cell membrane, which goes into the cell.

The cell membrane breaks up and the molecules are now inside the cell.

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Phagocytosis Similar to pinocytosis

but often involves larger molecules.

Note that cell membrane becomes a food vacuole that remains intact.

After digestion the food vacuole becomes a excretory vesicle.

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