Cell Membrane! List 3 characteristics of cell membranes. What is the difference between passive and active transport? What is osmosis? How is it different from diffusion?

Time can impact fluidity of the cell membrane… Membrane Structure & Function The Plasma Membrane: --the fluid mosaic model -- semi-permeable -- lipids and proteins – main components --fluid portion is a double layer of phospholipids, called the phospholipid bilayer Time can impact fluidity of the cell membrane…

Jobs of the cell membrane Isolate the cytoplasm from the external environment Regulate the exchange of substances Communicate with other cells Identification

Phospholipid bilayer Phospholipids contain a hydrophilic head and a nonpolar hydrophobic tail Cholesterol – decreases fluidity and prevents the phospholipids from becoming closely packed Glycolipids & Glycoproteins – short chains of sugar units that bind to lipids or proteins. Used for cell-to-cell recognition (binding).

Proteins embedded in membrane serve different functions Channel Proteins - form small openings for molecules to diffuse through Carrier Proteins- binding site on protein surface "grabs" certain molecules and pulls them into the cell Cell Recognition Proteins - ID tags, to identify cells to the body's immune system Receptor Proteins - molecular triggers that set off cell responses (such as release of hormones or opening of channel proteins) Enzymatic Proteins - carry out metabolic reactions

Transport Across Membrane Passive Transport: 1. Simple Diffusion - molecules move from areas of high concentration to areas of low concentration, down a concentration gradient 2. Osmosis – diffusion of water 3. Facilitation Diffusion - diffusion that is assisted by proteins (channel or carrier proteins)

Osmosis affects the turgidity of cells, different solution can affect the cells internal water amounts

Which way will the water move Which way will the water move? Sucrose is too large to pass through the membrane. Label each beaker as being a hypertonic, hypotonic, or isotonic solution.

Active Transport pinocytosis for extracellular fluid, Active Transport - involves moving molecules "uphill" against the concentration gradient, which requires energy Endocytosis - taking substances into the cell pinocytosis for extracellular fluid, phagocytosis for solids Receptor-mediated endocytosis – specific molecules Exocytosis - pushing substances out of the cell, such as the removal of waste Sodium-Potassium Pump - pumps out 3 sodiums for ever 2 potassium's taken in against gradient

Water Potential Predicting the movement of water into or out of plant cells. Measures the tendency of water to leave one place in favor of another place. Water will always move in the direction of the lower water potential. Any solute will lower the water potential.

Solute Potential What is the solute potential of a 1.0 M sugar solution at 22 oC under standard atmospheric conditions? Suppose you calculate the water potential of a solution inside a bag as -6.25 bars and the water potential of the solution surrounding the bag as -3.25 bars. Which direction will the water flow? Explain.

Reminders Finish lab analysis questions Review cell membrane and water potenital… quiz on Thursday. Read Chapter – Introduction to Metabolism Metabolism Catabolic vs. anabolic pathways Energy (potential vs. Kinetic vs. Chemical) 1st and 2nd Laws of Thermodynamics Endergonic vs. exergonic reactions ATP Phosphorylation Chart 8.12