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The Plasma Membrane. Maintaining Homeostasis. Cell Membrane - Multiple names - plasma membrane, phospholipid bilayer , lipid bilayer , biological membrane -Controls what comes into the cell and what goes out, it is said to be selectively permeable

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the plasma membrane

The Plasma Membrane

Maintaining Homeostasis


Cell Membrane

- Multiple names - plasma membrane, phospholipidbilayer, lipid bilayer, biological membrane

-Controls what comes into the cell and what goes out, it is said to be selectively permeable

-cell membrane is fluid, pieces move around feely

this is called the fluid-mosaic model

- Contains proteins

* Transport (Channel and Carrier)

* Adhesion

* Recognition (Antigens)

* Receptor Sites

- Contains cholesterol to keep fluid


Biological Membranes and Maintenance of Homeostasis

Components to the Plasma Membrane

Phospholipids –Two layers, that float over one another

Chanel Proteins –allow large molecule to move into and out of the cell

Receptor Proteins – used to identify the cell type, and allows for cell to cell communication, through the use of hormones etc


Maintaining Homeostasis-

Passive Transport

Osmosis and Diffusion

Passive Transport- the unassisted movement of materials across the cell membrane that does not require energy, only for small molecules

Diffusion – the movement of materials down a concentration gradient from high concentrations to lower concentrations

Osmosis- special type of diffusion, that only refers to water moving down a concentration gradient from high to low concentrations

Large molecules are trapped inside the cell, but water can move freely into and out of the cell

For a cell to be happy or to be in equilibrium, the cell needs the same concentration of water on the inside of the cell as the outside of the cell

Solutions – homogeneous mixture of two or more substances

Solvent – the stuff the does the dissolving ( Ex: Water)

Solute- the stuff that is being dissolved ( Ex: Salt)


Types of Solutions - Hypertonic

More water inside the cell then outside the cell

Water moves out of the cell  cause the cell to shrink ( crenate)


Types of Solutions - Hypotonic

Hypo = Hippo

More water outside the cell then inside

Water moves into the cell causes it to swell


Types of Solutions - Isotonic

Same amount water inside the cell as outside

No net movement of water, water moves in and water moves out but they balance each other out


Maintaining Homeostasis- Passive Transport

Facilitated Diffusion

Facilitated Diffusion-the assisted movement of material across the cell membrane through the use of channel (membrane) proteins

-requires no energy


Maintaining Homeostasis- Active Transport

Active Transport – the assisted movement of larger molecules across the cell membrane, through channel proteins. Molecules move up the concentration gradient from low concentrations to higher concentrations, thus the process requires energy

EX: Sodium-Potassium Pump is required for proper nerve functioning


Interactive –w/ Sodium potassium pump

Just Passing Through

How Osmosis works


Cell Transport - Endo/ Exocytosis

Process used by cells to import or export large molecules into and out of the cell

Phagocytosis ( Cell Eating)- large objects, used to get rid of pathogens and to absorb large molecules

Pinocytosis ( Cell Drinking)- used so the cell can obtain solute and single molecules such as a protein