3.1 Cell Theory Water Most important compound in living organisms Polar molecule with an unequal distribution of charge Hydrogen Bond attraction of opposite charges forms a weak bond forms between water molecules 3.4 Diffusion and Osmosis

3.1 Cell Theory Adhesion – attraction between unlike substances Cohesion – attraction between like substances Capillarity – Due to adhesion & cohesion water is pulled up through tiny tubes Surface Tension – caused from cohesion 3.4 Diffusion and Osmosis

3.1 Cell Theory Requires more heat to increase its T than do most other common liquids Loses a lot of heat when it cools Due to the hydrogen bonds Insulator that helps maintain a steady environment when conditions fluctuate (homeostasis) 3.4 Diffusion and Osmosis

3.1 Cell Theory How Polarity Makes Water act Strange 8&list=PLJicmE8fK0Ehrg3meytY7DT8LJiwuU3Th&index= 65

3.1 Cell Theory The cell membrane is a barrier that separates a cell from the external environment. 3.3 Cell Membrane

3.1 Cell Theory Cell membranes are composed of two phospholipid layers. 3.3 Cell Membrane

3.1 Cell Theory Cell membranes are composed of two phospholipid layers. The cell membrane has two major functions. – –forms a boundary between inside and outside of the cell – –controls passage of materials cell membraneoutside cell inside cell 3.3 Cell Membrane

3.1 Cell Theory Cell membranes are composed of two phospholipid layers. The cell membrane is selectively permeable Some molecules can cross the membrane while others cannot. 3.3 Cell Membrane

3.1 Cell Theory Cell membranes are composed of two phospholipid layers. The cell membrane is selectively permeable. Some molecules can cross the membrane while others cannot. 3.3

3.1 Cell Theory Materials move across membranes because of concentration differences. 3.4 Diffusion and Osmosis

3.1 Cell Theory Molecules move down a concentration gradient. From High to Low concentration 3.4 Diffusion and Osmosis

3.1 Cell Theory Molecules move in RANDOM STRAIGHT line until they run into another particle and are deflected Movement continues until they reach equilibrium equal concentration throughout the space Movement never STOPS – maintains equilibrium Concentration, Temperature, & Pressure affect rates of diffusion 3.4 Diffusion and Osmosis

3.1 Cell Theory Passive transport does not require energy input from a cell 1.Facilitated Diffusion 2.Diffusion Through Ion Channels 3.Osmosis Molecules move down the concentration gradient Diffusion 3 types of diffusion 3.4 Diffusion and Osmosis

3.1 Cell Theory Some molecules can only diffuse through transport proteins. Facilitated diffusion is diffusion through channel proteins. High to low concentration 3.4 Diffusion and Osmosis Channel Protein

3.1 Cell Theory Diffusion through Ion Channels Na+ sodiumK+ potassium Ca 2 + calciumCl- chloride (not soluble in lipids) Ion channels allow ions to diffuse into and out of cell Ion channels are either open all the time or gates which open in response to stimuli 1. stretching of cell membrane 2. electrical signals 3. chemical signals 3.4 Diffusion and Osmosis

3.1 Cell Theory Solution = A mixture in which a solute is dissolved evenly in a solvent Solute – What gets dissolved Solvent – What does the dissolving Water is the universal solvent Because its polar Dissolves both positive and negative solutes 3.4 Diffusion and Osmosis

3.1 Cell Theory Osmosis is the diffusion of water molecules across a semipermeable membrane 3.4 Diffusion and Osmosis

3.1 Cell Theory Hypotonic Concentration of dissolved substances (solute) is lower in the solution outside the cell than inside the cell What Happens: Water moves through the membrane into the cell Cell swells Cytolysis – cell bursts (animal cells) Turgor Pressure – plant cells 3.4 Diffusion and Osmosis

3.1 Cell Theory Hypertonic Concentration of dissolved substances outside the cell is higher than inside the cell What Happens: Water flows out of cell Plant cells – loss of turgor pressure – Plasmolysis – wilting 3.4 Diffusion and Osmosis

3.1 Cell Theory Isotonic Concentration of solute in solution is the same outside as inside the cell – equilibrium What happens: Water diffuses at the same rate in and out of the cell Maintaining equilibrium - homeostasis 3.4 Diffusion and Osmosis

3.1 Cell Theory Active transport requires energy input from a cell and enables a cell to move a substance against (up) the concentration gradient. Powered by chemical energy (ATP). Cells use active transport to maintain homeostasis. Active transport occurs through transport protein - pumps (carrier proteins) EX: Na-K pump 3.5 Active Transport

3.1 Cell Theory A cell can import and export large materials or large amounts of material in vesicles Cells use energy to transport material in vesicles. Endocytosis - process of taking material into the cell. Phagocytosis – endocytosis of solid particles. Pinocytosis – endocytosis of liquids 3.5Active Transport

3.1 Cell Theory A cell can import and export large materials or large amounts of material in vesicles Cells use energy to transport material in vesicles. Exocytosis is the process of moving material out of the cell. 3.5Active Transport