August 27-28, 2014

 Selectively permeable barrier between the cell and the environment.

What does ‘selectively permeable’ mean?

 Selectively permeable barrier between the cell and the environment. What does ‘selectively permeable’ mean? Only some materials can cross the membrane Selective permeability is necessary for the cell to maintain the correct internal environment for physiological functions.

 Phospholipids ◦ Make up the majority of the membrane ◦ Arranged in a bilayer, with hydrophilic heads outside, and hydrophobic tails inside

 Phospholipids ◦ Make up the majority of the membrane ◦ Arranged in a bilayer, with hydrophilic heads outside, and hydrophobic tails inside Hydrophilic = ___________ Hydrophilic molecules are __________ like water. Hydrophobic = ____________ Hydrophobic molecules are __________ like oil.

 Phospholipids ◦ Make up the majority of the membrane ◦ Arranged in a bilayer, with hydrophilic heads outside, and hydrophobic tails inside Hydrophilic = water loving Hydrophilic molecules are polar like water. Hydrophobic = water fearing Hydrophobic molecules are nonpolar like oil.

 Phospholipids The structure of phospholipids is the key to their function! Hydrophilic heads can interact with watery external environment and watery cytoplasm. Hydrophobic tails reduce the diffusion of water and other charged or polar substances across the membrane.

 Cholesterol ◦ Makes the cell membrane more rigid and less permeable to water  Proteins ◦ Act as enzymes, pores, carriers, and hormone receptors, and structural elements

 Glycoproteins and Glycolipids ◦ Glyco = sugar! ◦ Influence cell interactions (e.g. identifying cell as ‘self’) and molecule transport

Talk with a partner then share as a class  Scholar on the left answers … ◦ What are the 4 membrane components? ◦ Which component has most functions? Why?  Scholar on the right answers … ◦ Name 4 functions of membrane proteins ◦ Which two components are primarily responsible for reducing fluid loss through the cell? What do those components have in common?

 ____________ a dissolving agent (water, usually)  ____________ substances dissolved in a solution  ____________ watery environment outside cells  ____________ lower solute concentration  ____________ higher solute concentration  ____________ equal solute concentration

 Solution: a dissolving agent (water, usually)  Solute: substances dissolved in a solution  Interstitial fluid: watery environment outside cells  Hypotonic: lower solute concentration  Hypertonic: higher solute concentration  Isotonic: equal solute concentration

Transport of materials across the cell membrane can be characterized as passive or active.

Passive mechanisms require NO ENERGY from the cell. ALL passive mechanisms transport molecules down their concentration gradient. Active mechanisms require energy from the cell.

Diffusion is the net movement of molecules down their concentration gradient. Results from the random movement of molecules. Diffusion animation

 Simple Diffusion – diffusion directly across the cell membrane or through membrane pores. Only works for tiny OR non-polar molecules. Examples:

 Simple Diffusion – diffusion directly across the cell membrane or through membrane pores. Only works for tiny OR non-polar molecules. Examples: fats, fat-soluble vitamins, O 2, CO 2, Cl -

 Simple Diffusion – diffusion directly across the cell membrane or through membrane pores. Only works for tiny OR non-polar molecules. Examples: fats, fat-soluble vitamins, O 2, CO 2, Cl - Osmosis is simple diffusion of water.

 Facilitated diffusion - diffusion using a protein carrier; used for large polar molecules ◦ Example: glucose

Filtration occurs when water and solutes are pushed through a membrane by hydrostatic (fluid) pressure. Water and solutes move down pressure gradient. Process by which blood is filtered in the kidney.

Wait 30 sec, then show answer with your fingers  What 2 things do all passive transport mechanisms have in common? 1)Membrane proteins are always involved and no energy is required 2)Membrane proteins are always involved and energy is required 3)Molecules move down a gradient and no energy is required 4)Molecules move down a gradient and energy is required

Wait 30 sec, then show answer with your fingers  What 2 things do simple and facilitated diffusion have in common? 1)Membrane proteins are always involved and no energy is needed 2)Membrane proteins are always involved and energy is required 3)Molecules move down their concentration gradient and no energy is needed 4)Molecules move down their concentration gradient and energy is required

How is each molecule transported? Show 1) Simple diffusion through lipids 2) Simple diffusion through protein pores 3) Facilitated diffusion using carrier proteins a) Water b) CO 2 c) Glucose d) Cl -

How is each molecule transported? Show 1) Simple diffusion through lipids 2) Simple diffusion through protein pores 3) Facilitated diffusion using carrier proteins a) Water - 2 b) CO c) Glucose - 3 d) Cl - - 2

Use the picture to answer. In which direction will ions diffuse? 1) into the cell 2) out of the cell In which direction will osmosis occur? 1) into the cell 2) out of the cell

Use the picture to answer. In which direction will ions diffuse? 1) into the cell 2) out of the cell In which direction will osmosis occur? 1) into the cell 2) out of the cell

Active transport requires the use of energy (ATP) to transport material across the cell. Active transport is used for ◦ Solutes moving against the concentration gradient - or - ◦ Very large substances

 Solute Pumping (aka active transport) Membrane proteins (called solute pumps) use ATP to carry solutes against their concentration gradient. Examples: amino acids and most ions

 Exocytosis - movement of materials out of the cell by vesicle Examples: hormones, neurotransmitters, mucus, some wastes

 Endocytosis – movement of materials into the cell by vesicle

◦ Phagocytosis (cell eating) – white blood cells engulf bacteria, dead cells, and foreign debris ◦ Pinocytosis (cell drinking) – used to take up droplets of fats and dissolved proteins Animation

Many diseases are caused by malfunctions in cell membrane transport. Examples:  Cystic Fibrosis: a Cl - channel is missing, causing Cl - to build up within the cell  Familial hypercholesterolemia – cholesterol receptors on cell membrane missing, so cholestrol builds up in the blood  Burned tissue ‘weeps’ fluids, proteins, ions, etc.

Draw a detailed picture of the cell membrane. Include, and label:  The structural components  Phospholipids, cholesterol, membrane proteins, glycoproteins, glycolipids  The transport mechanisms  Simple diffusion, osmosis, facilitated diffusion, solute pumping, exocytosis, pinocytosis, phagocytosis When done, compare with a neighbor, but don’t add to it.