Lecture 1 Outline (Ch. 7) I.Plasma Membrane A. bilayer B. fluidity C. proteins II.Transport across membranes A.Simple diffusion B.Osmosis & Facilitated diffusion C.Active transport D.Bulk transport III.Preparation for next lecture

Membrane structure

Experiment to determine membrane fluidity: marked membrane proteins mixed in hybrid cell Membrane structure

cell can alter fatty acid tail saturation  affects fluidity cholesterol keeps membrane fluid at different temperatures Membrane structure

1915, knew membrane made of lipids and proteins Where to place proteins? Lipid layer 1 Lipid layer 2 Proteins

freeze fracture proteins intact, one layer or other two layers look different Membrane structure

cell membrane – amphipathic- hydrophilic & hydrophobic membrane proteins that are inserted, also amphipathic Membrane structure hydrophilic hydrophobic

“fluid mosaic model” – 1970s Integral Peripheral Glycoproteins Glycolipids fluid – phospholipids move around mosaic – proteins embedded in membrane Membrane structure

Based on what we just discussed, of the following choices, which is true of cell membranes? A.Membranes are hydrophobic inside the cell B.Phospholipid tails are hydrophilic C.Membrane proteins are amphipathic D.Fluidity is static (not able to change) E.Proteins are sandwiched between the two lipid layers

Membrane Proteins

Remember secondary and tertiary protein structure?! Membrane Proteins

Hydrophobicity plot: determine hydrophobic/hydrophilic for each region of a protein

Membrane Proteins What would a hydrophobicity plot look like for this protein?

Transport Across Membranes Types of transport: A.Passive transport 1. simple diffusion 2. osmosis & other facilitated diffusion B.Active transport C. Bulk transport Keep track: Is Energy Required? Direction of Movement?

Selectively Permeable Membranes Small, non-polar molecules can move by simple diffusion

Selectively Permeable Membranes Large or charged molecules need help crossing membrane

Use transport proteins - channel or carrier proteins Facilitated Diffusion DOWN concentration gradient - Large, charged, polar (sugar, ions, water) NO ENERGY required

osmosis – movement of water across cell membrane water moves via special channels called aquaporins Passive Transport - Osmosis water moves into/out of cell until solute concentration is balanced osmosis is a type of diffusion

tonicity – # solutes in solution in relation to cell - isotonic – equal solutes in solution - hypertonic – more solutes in solution animal cell plant cell - hypotonic – fewer solutes in solution Passive Transport - Osmosis

equal solutes in solution as in cell more solutes in solution, than in cell fewer solutes in solution, than in cell In each situation below, does water have net movement, and which direction: Isotonic? Hypertonic? Hypotonic?

Paramecium example regulate water balance water into contractile vacuole – water expelled pond water hypotonic Passive Transport - Osmosis

Scenario: in movie theater, long movie. You are: drinking water You are: eating popcorn What happens to your blood? becomes hypotonic to cells kidneys – remove water body excretes water becomes hypertonic to cells kidneys – uptake water body retains water Passive Transport - Osmosis

Facilitated diffusion….. A.Requires energy and is up the conc. gradient B.Requires energy and is down the conc. gradient C.Does not require energy and is up the conc. gradient D.Does not require energy and is down the conc. gradient

Active Transport - Usually ions or large molecules (Na +, K +, glucose) uses transport carrier proteins/pumps UP/AGAINST concentration gradient ENERGY IS required

ATP used, pump H + ions *gradients – used by cell for energy potential Active Transport Ex. proton (H + ) pump Pump H + across inner membrane! - Usually ions or large molecules (H +, Na +, K +, glucose) uses transport carrier proteins/pumps UP/AGAINST concentration gradient ENERGY IS required

Exocytosis Bulk Transport – all types require energy!

phagocytosis – “food” in pinocytosis – water in Molecules moved IN  endocytosis Bulk Transport Molecules moved OUT - exocytosis

Self-Check Type of transport Energy required? Movement direction? Examples: Simple diffusionnodown conc. gradientO 2, CO 2, non- polar molecules Osmosis Facilitated diffusion Active transport Bulk transport

Things To Do After Lecture 1… Reading and Preparation: 1.Make sure you are ready for lab 1 this week 2.Re-read today’s lecture, highlight all vocabulary you do not understand, and look up terms. 3.Read chapter 7, focus on material covered in lecture (terms, concepts, and figures!) 4.Ch. 7 Test Your Understanding: #1-4, 6 (correct answers in back of book) 5.Skim next lecture (ch. 8) “HOMEWORK” (NOT COLLECTED – but things to think about for studying): 1.Draw and label a phospholipid bilayer including integral and peripheral proteins. 2.Name three molecules that easily cross membranes; name three molecules that are blocked by cell membranes. 3.Describe diffusion and osmosis – then, how is active transport different?