The Cell (Plasma) Membrane Gateway to the Cell

Functions of Cell Membrane 1. Protective barrier Regulates transport in & out of cell (selectively permeable) Allows cell recognition 4.Maintain 4.Maintain ion concentration

Cell Membrane The cell membrane is flexible and allows a unicellular organism to move

Homeostasis Balanced internal condition of cells Balanced internal condition of cells Also called equilibrium Also called equilibrium Maintained by plasma membrane controlling what enters & leaves the cell Maintained by plasma membrane controlling what enters & leaves the cell

Structure of the Cell Membrane

hydrophilic Polar heads are hydrophilic “water loving ” hydrophobic Nonpolar tails are hydrophobic “water fearing” Cell Membrane Makes membrane “Selective” in what crosses

Phospholipid Bilayer

Fluid Mosaic Model (Lots of different types of molecules that assemble to form a function)

Cell Membrane Hydrophobic molecules pass easily; hydrophillic DO NOT phospholipid bilayer The cell membrane is made of 2 layers of phospholipids called the lipid bilayer

Small molecules and larger hydrophobic molecules move through easily. e.g. O 2, CO 2, H 2 O Semipermeable Membrane

Ions, hydrophilic molecules larger than water, and large protein molecules do not move through the membrane on their own. Semipermeable Membrane

Solutions Solutions are made of solute and a solvent Solutions are made of solute and a solvent Solvent – The liquid part. It does the dissolving. Solvent – The liquid part. It does the dissolving. Solute – The thing being dissolved. Salt and sugar are solutes. Solute – The thing being dissolved. Salt and sugar are solutes.

Types of Transport Across Cell Membranes 1.Diffusion 2.Osmosis 3.Facilitated Diffusion 4.Active Transport

Diffusion Requires NO energy Requires NO energy Solutes move from area of HIGH to LOW concentration Solutes move from area of HIGH to LOW concentration

Diffusion: Draw this

Diffusion of Liquids

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

Osmosis Diffusion of water across a membrane Diffusion of water across a membrane Moves from HIGH water potential (low solute) to LOW water potential (high solute) Moves from HIGH water potential (low solute) to LOW water potential (high solute) Diffusion across a membrane Semipermeable membrane

Diffusion of H 2 O Across A Membrane High H 2 O potential Low solute concentration Low H 2 O potential High solute concentration

Osmosis: Draw this

Types of Solutions Hypotonic – concentration of solute is higher INSIDE the cell. Hypotonic – concentration of solute is higher INSIDE the cell. Hypertonic – concentration of solute is higher OUTSIDE the cell. Hypertonic – concentration of solute is higher OUTSIDE the cell. Isotonic – concentrations of solutes is the same inside and outside the cell Isotonic – concentrations of solutes is the same inside and outside the cell

Plant and Animal Cells put into various solutions

Facilitated Diffusion  Doesn’t require energy  Uses transport proteins to move high to low concentration Examples: Glucose or amino acids moving from blood into a cell.

Proteins Are Critical to Membrane Function

Facilitated Diffusion Molecules will randomly move through the pores in Channel Proteins.

Facilitated Diffusion Some Carrier proteins do not extend through the membrane. Some Carrier proteins do not extend through the membrane. They bond and drag molecules through the lipid bilayer and release them on the opposite side. They bond and drag molecules through the lipid bilayer and release them on the opposite side.

Three Forms of Transport Across the Membrane

Active Transport  Requires energy or ATP  Moves materials from LOW to HIGH concentration  AGAINST concentration gradient

Sodium-Potassium Pump 3 Na+ pumped in for every 2 K+ pumped out; creates a membrane potential

Think/Pair/Share Work with a partner to create different situations that can be classified as diffusion. Work with a partner to create different situations that can be classified as diffusion. Do the same for osmosis. Do the same for osmosis.