2 I. Introduction to Cell Transport All living cells need to be able to:Take in oxygen and nutrientsGet rid of wastesCell transport= moving materials in and out of a cellThe cell membrane separates the inside of the cell from the outside.It allows some things to enter and blocks other things
3 A. Cell Membrane Structure Phospholipid Bilayer- double layer of phospholipids enclosing the cellEach phospholipid is made of a glycerol bonded to 2 fatty acids and a phosphate group.Phosphate group is polar (hydrophilic)Fatty acids are non-polar (hydrophobic)Bilayer:Exterior and interior surface: polar headsInternal part: non-polar tails
5 B. Membrane Proteins Proteins embedded in or thru the lipid bilayer. Integral proteins- are embedded in the lipid bilayer.Peripheral proteins- are loosely held on the surface.
6 B. Membrane ProteinsMembrane proteins can be used to transport materials thru the membrane, serve as chemical signals or receptors of chemical signals.Membranes also can contain cholesterol (animal cells) and glycoproteins containing carbohydrates.
7 C. Fluid Mosaic ModelDescribes the cell membrane as a fluid rather than a solid.Phospholipids and some proteins are able to move laterally within each other.This creates a mosaic that is able to change its shape and form.
8 D. Selective Permeability Due to its structure, polarity, and proteins, the cell membrane regulates what can pass in or out of the cell.this maintains a stable internal environment (homeostasis)Factors that determine a substances’ ability to pass thru the membrane:SizeShapePolarityChargeChemical make-up
10 A. Solution Lingo Solution= combination of solute and solvent Solute= Substance being dissolvedSolvent= thing substance is dissolved inUniversal solvent= water*Solute dissolves in the solventConcentration Gradient= A difference in concentrations within a system
11 B. Particle MovementBrownian motion- constant random motion of all particles.
12 C. Passive TransportMovement across the membrane requiring no additional energy from the cell.Types:DiffusionFacilitated DiffusionOsmosis
13 1. DiffusionNet movement of particles from areas of high concentration to low concentration.Particles will have NET movement towards low concentration until concentration is equal throughout the system (Dynamic Equilibrium)Particles will continue to move, but there will be no NET movement.
16 2. Facilitated Diffusion Diffusion of particles thru the cell membrane w/ the assistance of membrane proteins.Carrier proteinsIntegral proteins that change shape to move large molecules thru the lipid bilayer.
18 Ion channelsintegral proteins that provide a tube for dissolved ions to pass thru the lipid bilayer.Ex. Na+ ion channel
19 Important!***movement thru the proteins involves kinetic E, but no cellular E because the particles are moving with the concentration gradient.
20 3. Osmosis The diffusion of water across a membrane. particles dissolved in water are solutes; water is the universal solvent.water will have a net movement (opposite of solute movement)Types of solutions:Hypertonic solution- aqueous solution with a higher concentration of solute than the cell.particles will move into the cellwater will rush out of the cellCauses plasmolysis (wilting) in plant cells.
21 ii. Hypotonic SolutionSolution with a lower concentration of solute than the cell.particles will move out of the cellwater will move into the cell causing it to swellcauses Turgor Pressure in plant cellsCan cause cytolysis (bursting) of animal cells
22 iii. Isotonic solutionEqual concentration of solute in the solution and the cell.net movement of water and solute is equalcell is in dynamic equilibrium w/ the solution
26 How Cells Deal with Osmosis How do cells like paramecium that live in water, not blow up?Contractile vacuoles – organelles that remove water from the cell.
27 D. Active TransportMovement of substances against the concentration gradient. (low to high)Requires the use of cellular E.Necessary to maintain homeostasis in non-isotonic environments
28 Carrier Proteins (pumps) Integral proteins that force particles against the concentration gradientATP (E) is used to change the shape of the protein.ex. Na+/K+ ion pumpUses ATP to keep a high concentration of Na+ outside the cell and K+ inside the cell.Keeps an unbalanced charge on opposite sides of the membrane allowing for the transmission of electrical signals.
30 EndocytosisProcess by which cells ingest large particles or large amounts of solution.membrane pinches off around material creating a vacuole which often joins w/ lysosomes to digest the material.TypesPinocytosis- ingesting large amounts of fluid or solutes.Phagocytosis- ingesting large particles or whole cells.ex. White blood cells, Ameoba
31 Exocytosis Release of large particles from the cell excretory vesicles carrying proteins, wastes or other large particles fuse w/ the cell membrane releasing the material extra-cellularly.
33 Endocytosis vs. Exocytosis Which is endocytosis? Exocytosis?
34 Questions Write out the questions and answer in complete sentences. How is selective permeability related to passive and active transport?Describe two differences between active and passive transport.