Unit C Cycling of Matter in Living Systems

 Plasma membrane, semi permeable membrane  Protective layer between environment & cell’s fragile contents (“biological barrier”)  Maintains equilibrium (balance) inside cell  Structure  Phospholipid bi-layer (head and tail)  Contains embedded proteins for transport and chemical reactions  “Fluid Mosiac Model”

 Semi-permeable/Selectively permeable= only certain solutes are SELECTED to cross membrane  Cells use the following to help transport materials:  Energy (ATP)  Theory of Brownian motion  Natural concentration gradient  End result always equilibrium

 Solute  Substance that is dissolved in a solution Eg. Glucose, salt, Potassium, Iron, oxygen, carbon dioxide

 Brownian Motion  Particles are constantly moving in random motion

 Concentration Gradient  Difference of concentrations of solutes/water between 2 areas  Determines direction water or solutes will move  Brownian motion (random movement) means particles (solutes/water) will naturally flow to an area where they are less concentrated

 Passive Transport  Active Transport

 Natural movement of particles/water from an area of high concentration to area of low concentration (DOWN the concentration gradient)  Does NOT require energy  3 types of Passive Transport 1. Diffusion 2. Osmosis 3. Facilitated Diffusion

 Movement (high to low) of SOLUTES (fatty acids, glycerol, CO2, O2)  Rate of diffusion  how long it takes for diffusion to occur  Can be altered by adding energy (eg stirring or heating) to speed up movement of particles

 Movement (high to low) of WATER  If a solute is too big, has a charge or not soluble then it won’t pass by diffusion so water moves instead  Can predict water movement based on the solute concentrations inside and outside of cell  3 conditions that are relative to each other: ▪ Isotonic ▪ Hypertonic ▪ Hypotonic

 When two solutions have same concentrations of solutes  Solutes/Water will move between solutions but no net change in amount of either will occur

 Two solutions differ in concentration of solutes/water  The one with more solutes is hypertonic to one with less  The solution with less solute is hypotonic to one with more solutes  Water concentration of the hypertonic solution is less than water concentration of hypotonic solution so net movement of water is from hypotonic to hypertonic solution

 Movement (high to low) of larger SOLUTES (glucose) that need the help of PROTEIN FACILITATOR  Channel Protein ▪ Creates channels or pores for small water particles to move  Carrier Protein ▪ Attach to larger molecules, changes shape and physically moves molecules across membrane

 Movement of particles from an area of low concentration to area of high concentration (AGAINST the concentration gradient)  Requires ATP (adenosine triphosphate) energy  Use carrier proteins as a “pump”  3 types of Active Transport 1. Endocytosis 2. Exocytosis 3. Protein Carriers

 Bringing large particles INTO cell  Engulfs large particle using a vesicle sac to surround, contain then “pinch” off  E.g. Ameoba getting food

 Getting large particles OUT of cell  Vesicle surrounds particle and fuses with cell membrane then ruptures and contents leave cell

 Movement (low to high) of larger SOLUTES (glucose) that need the help of PROTEIN Carrier  Carrier Protein ▪ Attach to larger molecules, changes shape and physically moves molecules across membrane

 Passive Transport  Does not require energy  Movement DOWN/WITH concentration gradient  Transports smaller, water soluble particles (CO2, O2, H2O, glucose)  Includes diffusion, osmosis, facilitated diffusion  Active Transport  Requires energy  Movement UP/AGAINST concentration gradient  Transport of larger particles & ions (Al, Fe, Ca)  Includes protein carriers, endocytosis, exocytosis

 Transport of materials in/out of cells critical  Ability to transport materials must be at maximum  Larger the cell the more:  Volume it has  Molecules will be needed to carry out life functions  Distance molecules has to travel from cell to surface increases

 As a cell size increases its surface to volume ratio decreases (SA/V)  Meaning that there is less cell membrane to do transport but more cell to get materials to

 The greater the surface to volume ratio the more efficient the cell is at transportation  Size is the limiting factor of cells  Smaller cell with greater SA/V ratio require less molecules to diffuse across the membrane with more membrane to do it

 Oxygen exchange  Oxygen is obtained form the surrounding environment such as water or blood (depends on the cell) and DIFFUSES across the cell membrane.  More membrane more diffusion (Surface area= increases by the 2 ).  A big cell needs more oxygen than a little cell (volume= increase by the 3 )  Big cell has relatively small surface area compared to its volume i.e. the surface area: volume ratio is small.  Larger cells become limited by the rate of gas exchange.

 Obtaining nutrient (glucose)  Excretion of waste molecules ( urea, ammonia, carbon dioxide).