Passive and Active Transport Cell Transport Passive and Active Transport

Consists mainly of phospholipids with membrane proteins attached. RECALL: CELL MEMBRANE: Consists mainly of phospholipids with membrane proteins attached. Major Function: Control what enters and leaves (semi-permeable)the cell in order to maintain homeostasis (balance) within the cell. This is called Cell Transport.

Cell Transport : Movement of Substances Across the Membrane Cells must bring in nutrients and other materials, like food and oxygen and remove wastes such as carbon dioxide. These processes occur at the cell membrane. PHOSPHOLIPID BILAYER

https://www.youtube.com/watch?v=RPAZvs4hvGA (ed puzzle video) 2 TYPES OF CELL MEMBRANE TRANSPORT: https://www.youtube.com/watch?v=RPAZvs4hvGA (ed puzzle video) * PASSIVE * ACTIVE

Passive Transport Movement of particles down the concentration gradient From high concentration to low concentration Occurs until balanced

3 TYPES OF PASSIVE TRANSPORT Diffusion Facilitated Diffusion Osmosis

FACILITATED DIFFUSION Requires NO Energy! OSMOSIS Requires NO Energy! https://www.youtube.com/watch?v=IaZ8MtF3C6M

1. Simple Diffusion – moving substances from areas of high concentration to low concentration; molecules tend to spread out. This process requires no energy.

Animation : How Diffusion Works

Skittles Diffusion Activity Instructions: 1. Place your Skittles™ in the petri dish as shown below 2. Add water to your petri dish to cover the Skittles™ about half way. 3. Closely observe the changes in the petri dish for 5 minutes. 4. Draw the table below in your notebook and record your observations. Draw the diagram below in your notes and using colored pencils, color in the final results on the diagram.

Facilitated Diffusion – The movement of charged/polar or ion molecules with the help of carrier proteins used as passageways.. Requires NO ENERGY! (no conformation change)

Animation - How Facilitated Diffusion Works http://highered.mheducation.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html

OSMOSIS - movement of water molecules and ONLY WATER from areas of high concentration to low concentration. with the help of aquaporins (integral proteins) https://www.youtube.com/watch?v=eQsAzXr0UCU Aquaporins – specialized membrane channels that allow water to move very rapidly across the cell membrane. RBC’s Kidneys plants

Aquaporin: channel protein that allows passage of H2O

Animation: How Normal Osmosis Works

SALT SUCKS There are 3 types of solutions that affect Osmosis: - Hypertonic (high solute, low solvent) - Hypotonic (high solvent, low solute) - Isotonic (equal parts of solute and solvent) SALT SUCKS Recall that a Solution includes Solvent (usually water)+ Solute (can be anything else i.e. sugar, salt, etc.) = Solution

Affects of Different Solutions during Osmosis:

External environments can be hypotonic, isotonic or hypertonic to internal environments of cell Turgid Pressure – force within the cell that pushes the plasma membrane against the cell wall caused by osmotic flow from low concentration outside the cell into the vacuole (higher solute concentration) - Healthy Plant Flaccidity – (means loose/weak) is when a plant is put into a hypertonic solution and the plant loses water. Plasmolysis – when the cytoplasm peels away from the cell wall leaving gaps, plant cell shrinks and crumbles.

Hypertonic solution A solution with a greater solute concentration compared to another solution. 5% NaCl 95% H2O solution 3% NaCl 97% H2O Red Blood Cell Water moves OUT!

Hypotonic solution A solution with a lower solute concentration compared to another solution. 1% Na 99% H2O solution Water moves IN! 3% Na 97% H2O Red Blood Cell

Isotonic solution A solution with an equal solute concentration compared to another solution. 3% Na 97% H2O solution 3% Na 97% H2O Water moves IN & OUT @ same rate! Red Blood Cell

Active Transport Movement of large, bulky particles against the concentration gradient From low concentration to high concentration Energy is needed for Active Transport. Energy is defined as the ability to do work.

Active Transport – movement of molecules from areas of low concentration to high concentration and requires energy (ATP) This is easy !!! This is hard work!!!

Adenosine Triphosphate (ATP) - energy storing compound containing Adenine, Ribose and three Phosphate groups mostly synthesized in the mitochondria Energy is stored in the bonds between the Phosphates. When a bond is broken between the phosphates, energy is released – usually to drive endergonic reactions. Endergonic = absorptioin of energy Exergonic = loss of energy Adenosine diphosphate Adenosine monophosphate

Types of Active Transport * Electrogenic Pumps generate voltage across the cell membrane. BULK TRANSPORT OF MATERIALS: Endocytosis - Phagocytosis - Pinocytosis * Exocytosis 25

1. Protein Pumps - requires energy to do work Proton Pump 1. Protein Pumps - requires energy to do work Na+/K+ Pump Push protons (H+) across membrane Eg. mitochondria (ATP production) – cellular respiration Pump Na+ out, K+ into cell Important to Nerve transmission

Animation-How the Sodium-Potassium Pump Works

Bulk Transport Transport of proteins, polysaccharides, large molecules Endocytosis: take in macromolecules, form new vesicles Exocytosis: vesicles fuse with cell membrane, expel/remove contents

Types of Endocytosis Phagocytosis: “cellular eating” - solids Pinocytosis: “cellular drinking” - fluids Receptor-Mediated Endocytosis: Ligands bind to specific receptors on cell surface. Ligand – one molecule binds to another (usually larger) molecule)

Osmoregulation Control solute & water balance Contractile vacuole: “bilge pump” forces out fresh water as it enters by osmosis Eg. paramecium caudatum – freshwater protist

How Organisms Deal with Osmotic Pressure https://www. youtube Paramecium (protist) removing excess water video Bacteria and plants have cell walls that prevent them from over-expanding. In plants the pressure exerted on the cell wall is called turgor pressure. A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over- expanding. Salt water fish pump salt out of their specialized gills so they do not dehydrate. Animal cells are bathed in blood. Kidneys keep the blood isotonic by removal of excess salt and water.

Understanding Water Potential

Water potential equation: ψ = ψS + ψP Water potential (ψ): The measure of the relative tendency of water to move from one area to another, and is commonly represented by the Greek letter Ψ (Psi). H2O moves from high ψ (water potential)  low ψ (water potential). Water potential equation: ψ = ψS + ψP Water potential (ψ) = free energy of water Solute potential (ψS) = solute concentration (osmotic potential) Pressure potential (ψP) = physical pressure on solution; turgor pressure (plants) Pure water: ψP = 0 MPa Plant cells: ψP = 1 MPa

Calculating Solute Potential (ψS) ψS = -iCRT i = ionization constant (# particles made in water) C = molar concentration R = pressure constant (0.0831 liter bars/mole-K) T = temperature in K (273 + 0C) The addition of solute to water lowers the solute potential (more negative) and therefore decreases the water potential.

Where will WATER move? From an area of: higher ψ  lower ψ (more negative ψ) low solute concentration  high solute concentration high pressure  low pressure

Which chamber has a lower water potential? Which chamber has a lower solute potential? In which direction will osmosis occur? If one chamber has a Ψ of -2000 kPa, and the other - 1000 kPa, which is the chamber that has the higher Ψ?

Sample Problem Calculate the solute potential of a 0.1M NaCl solution at 25°C. If the concentration of NaCl inside the plant cell is 0.15M, which way will the water diffuse if the cell is placed in the 0.1M NaCl solution?