Homeostasis Transport Passive Transport Passive Transport v The

Passive Transport v The movement of materials across a cell membrane WITHOUT the use

Diffusion n Movement of molecules from an area of high concentration to an area

Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW)

Diffusion across a membrane n Depends upon size, shape, and chemical makeup n Easy

Osmosis n WATER diffusion across a membrane n “Down the gradient” n Hypotonic solution

Hypotonic Solution n The solute concentration is higher inside the cell, the water concentration

Hypertonic Solution n The solute concentration is higher outside the cell, the water concentration

Isotonic Solution n The solute and water concentrations are EQUAL on both sides of

Osmosis in Red Blood Cells Isotonic Hypertonic

Facilitated Diffusion n Use of carrier proteins the assist diffusion across a membrane. n

Diffusion via ion channels n Use of membrane proteins to assist diffusion of ions

Active Transport § Uses energy (ATP) to move materials against the gradient § “Up

1. Sodium Potassium Pump n Transports sodium and potassium ions across the membrane up

2. Endocytosis n Movement of large amounts of material into the cell n Formation

Moving the “Big Stuff” Large molecules move materials into the cell by one of

3. Exocytosis n The movement of a large amount of materials out of the

Exocytosis Exocytic vesicle immediately after fusion with plasma membrane.

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Homeostasis & Transport

Passive Transport

Passive Transport v The movement of materials across a cell membrane WITHOUT the use of energy (ATP). v Four Types: n Diffusion n Osmosis n Facilitated Diffusion n Ion Channels

Diffusion n Movement of molecules from an area of high concentration to an area of low concentration.

Diffusion through a Membrane Cell membrane Solute moves DOWN concentration gradient (HIGH to LOW)

Diffusion of Liquids

Diffusion across a membrane n Depends upon size, shape, and chemical makeup n Easy to diffuse: n Small n Nonpolar

Osmosis n WATER diffusion across a membrane n “Down the gradient” n Hypotonic solution to hypertonic solution Osmosis n animation

Osmosis

Hypotonic Solution n The solute concentration is higher inside the cell, the water concentration is higher outside the cell. n Net movement = Water into the cell

Hypertonic Solution n The solute concentration is higher outside the cell, the water concentration is higher inside the cell. n Net movement = Water out of the cell n May cause Plasmolysis

Isotonic Solution n The solute and water concentrations are EQUAL on both sides of the membrane. n Equilibrium

Osmosis in Red Blood Cells Isotonic Hypertonic

hypotonic hypertonic isotonic hypotonic

Facilitated Diffusion n Use of carrier proteins the assist diffusion across a membrane. n Specific carrier proteins for specific molecules (like glucose or amino acids) n “Down the gradient”

Diffusion via ion channels n Use of membrane proteins to assist diffusion of ions across a membrane n Channel is usually specific to 1 type of ion n Common ions: n Sodium n Potassium n Chlorine n Calcium

Active Transport

Active Transport § Uses energy (ATP) to move materials against the gradient § “Up the gradient” § Low to high concentration

1. Sodium Potassium Pump n Transports sodium and potassium ions across the membrane up their gradients n Low to high concentration n Uses ATP

2. Endocytosis n Movement of large amounts of material into the cell n Formation of a vesicle from the cell membrane that will go to the lysosome for digestion n Uses ATP

Moving the “Big Stuff” Large molecules move materials into the cell by one of three forms of endocytosis

3. Exocytosis n The movement of a large amount of materials out of the cell n Vesicle fuses to the cell membrane to release contents out of the cell n Uses ATP

Exocytosis Exocytic vesicle immediately after fusion with plasma membrane.