Chapter 5 The Plasma Membrane

The Cell Membrane: OUTSIDE INSIDE HYDROPHILIC HEAD HYDROPHOBIC TAIL TRANSPORT PROTEIN

The cell membrane is referred to as a PHOSPHOLIPID BILAYER

The Plasma Membrane It contains two layers of phospholipids It contains two layers of phospholipids The hydrophobic (water-hating) tails face each other like peanut butter and jelly. The hydrophobic (water-hating) tails face each other like peanut butter and jelly. The hydrophilic heads face the watery exteriors of the bilayer The hydrophilic heads face the watery exteriors of the bilayer Sometimes fats, proteins, and other carbohydrate molecules float around the bilayer like ice cubes in water. They are not stationary. Sometimes fats, proteins, and other carbohydrate molecules float around the bilayer like ice cubes in water. They are not stationary.

A Gallery of Membrane Proteins Passive transporters- channels that allow specific thing to enter the cell without inputting energy. Passive transporters- channels that allow specific thing to enter the cell without inputting energy. Go to: Go to:

A Gallery of Membrane Proteins Active Transporters- channels that allow specific thing to enter the cell with the input of energy (ATP) Active Transporters- channels that allow specific thing to enter the cell with the input of energy (ATP)

Diffusion Diffusion: The movement of molecules to an area of high concentration [  ] to an area of low concentration [  ] until the concentration is the same everywhere. Diffusion: The movement of molecules to an area of high concentration [  ] to an area of low concentration [  ] until the concentration is the same everywhere.

Osmosis Water may constantly pass into and out of cells through these plasma membranes (lipid bilayers). This uninterrupted flow of water through these membranes is called OSMOSIS. Water may constantly pass into and out of cells through these plasma membranes (lipid bilayers). This uninterrupted flow of water through these membranes is called OSMOSIS. Water has the free pass to travel in and out of organisms and cells. So water is called a solvent. Water has the free pass to travel in and out of organisms and cells. So water is called a solvent.

Why do I “melt” when salt is poured on me? Because water always goes to where there is more “stuff”

Hypotonic Hypotonic- having a lower concentration of solutes Hypotonic- having a lower concentration of solutes

Hypertonic Hypertonic- having a higher concentration of solutes Hypertonic- having a higher concentration of solutes

What about fish? Do either of these fish need to “drink” the water to survive? Who will it be? We drink the water because there is more “stuff” in the ocean than in us. Therefore, we must drink the water to recover the water we lose to osmosis.

Other Transport Mechanisms Membranes are selectively permeable - -(they only let specific stuff pass to the other side) Membranes are selectively permeable - -(they only let specific stuff pass to the other side)

Passive Transport Substances move DOWN their concentration gradient into or out of the cell (a person going down a water slide) Substances move DOWN their concentration gradient into or out of the cell (a person going down a water slide) No extra energy is required to perform passive transport. No extra energy is required to perform passive transport.

Active Transport Substances move through transport proteins but AGAINST the concentration gradient. Cells use free energy (usually from ATP) to do this. It requires extra energy. Substances move through transport proteins but AGAINST the concentration gradient. Cells use free energy (usually from ATP) to do this. It requires extra energy.