Cellular Transport Notes

1. Cellular Transport Notes

2. The Purpose of the Plasma Membrane is to Maintain Balance called “HOMEOSTASIS” or “To Reach Dynamic Equilibrium”” Is traffic at equilibrium? Why or why not?

3. Equilibrium occurs when molecules have spread out evenly When the concentration of a solute is equal throughout the solution

4. protein channel Layer 1 Cell Membrane Layer 2 lipid bilayer protein pump Cell Membrane Cell Wall ALLcells have a cell membrane made of proteins and lipids • SOME cells have cell membranes andcell walls – ex: plants, fungi and bacteria

5. Plant cells have a cell wall made of cellulose – that cellulose is fiber in our diet • Bacteria and fungi also have cell walls, but they do not contain cellulose • Cell membranes and cell walls are porous allowing water, carbon dioxide, oxygen and nutrients to pass through easily

6. Components of the Plasma Membrane Phospholipids: Proteins Cholesterol

7. Aka:Lipid Bilayer: 2 layers of phospholipids provides a barrier for the cell. Allows for selective permeability Phosphate head is polar (hydrophilic=water loving) b. Fatty acid tails are non-polar (hydrophobic=water fearing) Phospholipids Phospholipid Lipid Bilayer http://www.youtube.com/watch?v=Rl5EmUQdkuI&feature=fvwrel

8. Figure 8.9 Some functions of membrane proteins PROTEINS serve many functions for the plasma membrane

9. Cholesterol Molecules Makes the bilayer stronger but still flexible Holds two layers together

10. Function of the Cell Membrane: • Cell membrane separates the components of a cell from its environment—surrounds the cell • “Gatekeeper” of the cell—regulates the flow of materials into and out of cell—selectively permeable • Cell membrane helps cells maintain homeostasis—stable internal balance

11. Passive Transport • A process that does not require energy to move molecules from a HIGH to LOW concentration • Diffusion • Osmosis • Facilitated Diffusion

12. outside of cell inside of cell • Diffusion is the movement of small particles across a selectively permeablemembrane like thecell membrane until equilibrium is reached. • These particles move from an area of high concentrationto an area of low concentration.

13. Diffusion HIGH to LOW concentration

14. Where does diffusion take place in the body?

15. Osmosis is the diffusion of water through a selectively permeable membrane like the cell membrane • Water diffuses across a membrane from an area of high concentration to an area of low concentration. Semi-permeable membrane is permeable to water, but not to sugar

16. Glucose molecules outside of cell inside of cell • Facilitated Diffusion is the movement of larger molecules like glucose through the cell membrane – larger molecules must be “helped” • Proteins in the cell membrane form channels for large molecules to pass through • Proteins that form channels (pores) are called protein channels

17. diffusion of specific particles through transport proteins found in the membrane Transport Proteins are specific– they “select” only certain molecules to cross the membrane Ex: channel or carrier proteins Transports larger or charged molecules A B Facilitated diffusion (Carrier Protein) Diffusion (Lipid Bilayer) Facilitated diffusion(Channel Protein)

18. ENERGY NEEDED: Active Transport NO ENERGY NEEDED: Diffusion Osmosis Facilitated Diffusion ANALOGY:

19. Active Transport • Active transport is the movement of molecules from LOW to HIGH concentration. • Energy is required as molecules must be pumped against the concentration gradient. • 3 Types: • 1. Protein Pumps • 2. Endocytosis • 3. Exocytosis outside of cell Carbon Dioxide molecules inside of cell

20. 1. Protein Pumps -transport proteins that require energy to do work • Protein changes shape to move molecules: this requires energy! • Example: Sodium / Potassium Pumps are important in nerve responses.

22. Endocytosis and Exocytosis is the mechanism by which very large molecules (such as food and wastes) get into and out of the cell Food is moved into the cell by Endocytosis Wastes are moved out of the cell by Exocytosis

23. 2 Types of Endocytosis 1. Phagocytosis- “cell eating” Extensions of the cytoplasm surround a particle and package it within the vacuole 2. Pinocytosis- “cell drinking” Pockets form along the cell membrane, fill with liquid, and pinch off to form vacuoles within the cell

24. Solute Substance that is dissolved in a solvent to make a solution Solvent Substance in which a solute is dissolved to form a solution Solution Mixture of two or more substances in which the molecules of the substances are evenly distributed

25. Types of Solution Concentrations 1. Hypertonic 2. Hypotonic 3. Isotonic

26. Hypertonic Solutions: contain a high concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypertonic solution, the water diffuses out of the cell, causing the cell to shrivel.

27. Isotonic Solutions: contain the same concentration of solute as another solution (e.g. the cell's cytoplasm). When a cell is placed in an isotonic solution, the water diffusesinto and out of the cell at the same rate. The fluid that surrounds the body cells is isotonic.

28. Hypotonic Solutions: contain a low concentration of solute relative to another solution (e.g. the cell's cytoplasm). When a cell is placed in a hypotonic solution, the water diffusesinto the cell, causing the cell to swell and possibly explode.

29. Figure 8.12 The water balance of living cells HYPO= “More” ISO = “Equal” HYPER = “More”