7.3 Cell Boundaries. Regents Biology. Originally prepared by Kim B. Foglia. Revised and adapted by Nhan A. Pham

Transcription

1 7.3 Cell Boundaries Originally prepared by Kim B. Foglia. Revised and adapted by Nhan A. Pham

2 Don t look at your reading guide/textbook or talk with each other yet! Write down one thing you know/remember about cellular transport Pass the sheet onto the next person

3 Objectives Identify the main functions of the cell membrane and cell wall Explain the movement of molecules into and out of cells Explain simple diffusion, facilitated diffusion, and osmosis Compare and contrast passive transport and active transport.

4 The Size of Cell Cells live in a fluid environment. Tissue fluids constantly bathe each of the cells in your body. To function efficiently, a cell must be: a) large b) medium c) small d) any size

5 Why? To maximize the surface areato-volume ratio. How is this good for the cell? It takes much less time and effort for materials to enter and exit the cell.

6 The Plasma Membrane

7 Model of the Plasma Membrane

8 The Plasma Membrane acts as a boundary regulates what enters and leaves the cell (water, amino acids, glucose, etc.) is selectively permeable*

9 Consists of mostly lipid, with protein and carbohydrate Lipid molecules in a double layer hydrophobic (nonpolar) tails toward the center of membrane and hydrophilic (polar) heads directed outward

10 The Cell Membrane

11 This arrangement of phospholipids into 2 layers is spontaneous and without energy spent. The membrane is fluid w/ lipid and proteins moving within it. Fluid-mosaic Model 1972, J. Singer & G. Nicolson proposed Fluid Mosaic Model

12 Diffusion is the random movement of particles that results in the net movement of particles from high to low concentration Dynamic Equilibrium movement but there is no net change

13 Simple Diffusion Movement of particles from HIGH to LOW concentration (down concentration gradient) passive transport since no energy is needed Very slow!!! diffusion

14 Osmosis diffusion of water into and out of cells across a selectively permeable membrane.

15 Concentration of water Direction of osmosis (diffusion of water) is determined by difference in solute concentration in and out of cell - Hypertonic more solute (less water) - Hypotonic less solute (more water) - Isotonic equal solute (equal water)

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17 Osmosis in Plants

18 Passive Transport What sort of substances can pass through the plasma membrane? - small - nonpolar - lipids, lipid-soluble substances Their passage across the membrane is AUTOMATIC from HIGH to LOW concentration (DOWN concentration gradient) The cell does NO work Ú PASSIVE Transport!

19 Molecules that will pass through the membrane without aid - small (hydrophobic) molecules (hydrocarbons and O 2 ), (soluble in the lipid bilayer) - uncharged molecules And those that WON T - large polar (uncharged) molecules (sugar) - ions ( H +, Na +, Cl - )

20 Facilitated Diffusion What about stuff (ions, sugars, amino acids) that cannot dissolve in the lipid bilayer and too large to squeeze through? Protein channels are larger gates through which these particles can cross. Proteins facilitate the movement. 1. channel proteins (including ion channels) 2. carrier proteins

21 Passive Transport

22 Ion Channels

23 Protein Channels

24 Receptor Proteins

25 Active Transport Cells may need to move molecules against concentration gradient Like what? involves carrier proteins conformational shape change transports solute from one side of membrane to other Energy (ATP) is needed!

26 Active Transport Animations

27 Fish in salt water has more salt OUTSIDE.

28 Fish in fresh water has more salt INSIDE.

29 Active Transport

30 Other Means of Transport Not all substances enter a cell through its membrane Endocytosis enter Exocytosis exit

31 Exocytosis

32 Endocytosis

33 Exocytosis

34 Endocytosis

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