8.2 Cell Transport. **The cell must move different substances into and out of the cell. **8.2 discusses the different methods of cell transport

Transcription

1 8.2 Bellringer.. (1)In your own words, define passive, active, and transport Now, imagine sitting in a boat that is moving downstream with the current. Then, imagine a small motor to move the same boat upstream against the current. (2)Determine which action shows passive transport and which shows active transport (3)Which requires an input of energy?

2 8.2 Cell Transport **The cell must move different substances into and out of the cell This happens in a variety of ways. Sometimes the cell has to use energy, sometimes they do not **8.2 discusses the different methods of cell transport

3 Passive Transport Diffusion passive transport of substances DOWN a concentration gradient (from high to low concentration) Concentration gradient one area has a higher concentration than another area Equilibrium when a space is filled evenly Diffusion is simplest type of passive transport Some substance diffuse through lipid bilayer Others though transport proteins

4 Diffusion Cell membrane is selectively permeable Nonpolar interior of lipid bilayer repels ions and most polar molecules These substances are prevented from diffusing across membrane Very small or nonpolar molecules can diffuse across the membrane down their concentration gradient

5 Simple Diffusion Moves small, nonpolar molecules directly through lipid bilayer Ex- O2 CO2

6 Diffusion

7 Model of Diffusion

8 Facilitated Diffusion Moves ions and polar molecules that simple diffusion cannot Transport proteins help these substances diffuse through the cell membrane Two types: Channel protein Carrier protein

9 Channel Proteins Ions, sugars, and amino acids can diffuse with help of channel proteins Proteins, sometimes called pores, serve as tunnels through the lipid bilayer Each channel allows the diffusion of a specific substance Ex only sodium ions can pass through sodium ion channels

10 Carrier Protein Transport substances that fit within their binding site (1)Carrier protein binds to specific substances on one side of cell membrane (2)Binding causes protein to change shape (3)As shape changes, the substance is moved across the cell membrane and released on other side

11 Facilitated Diffusion

12 Osmosis Definition diffusion of water across selectively permeable membrane Type of facilitated diffusion (passive transport) From high to low concentration Allows cells to maintain water balance as environment changes Pass through water channels Protein channels specific to water..

13 Osmosis

14 Osmosis There are three possibilities for the direction of water movement: Water moves out (hypertonic solution) Causes cell to shrink Water moves in (hypotonic solution) Causes cell to swell Cell could burst if it swells too much Plant cells have rigid cell wall to prevent this No net water movement (isotonic solution) No change in cell volume

15 Hypertonic, Hypotonic, and Isotonic Solutions

16 Effects of Osmosis **Plants and fungi have cell walls to help regulate Most plants are healthiest in a hypotonic environment Some unicellular eukaryotes have contractile vacuoles Force excess water in cell out Animals cells do not have cell walls or contractile vacuoles They actively remove solutes from cytoplasm

17 Active Transport Transports of substance against concentration gradient Low to high concentration Active Transport requires energy Most energy supplied directly or indirectly in the form of ATP (adenosine triphosphate)

18 Pumps Substances bind to carrier proteins in low concentrations, released in higher concentration Carrier proteins function as pumps move substances against their concentration gradient called membrane pumps

19 Sodium-Potassium Pump One of the most important membrane pumps in animal cells In a complete cycle, the sodium-potassium pump transports three sodium ions, Na +, out of a cell and two potassium ions, K +, into the cell. Pump actively transports against their concentration gradients Energy supplied by ATP

20 Sodium-Potassium Pump **The sodium-potassium pump has four steps: 1. Three sodium ions inside the cell bind to the sodiumpotassium pump. 2. The pump changes shape, transporting the three sodium ions across the cell membrane and releasing them outside the cell. 3. Two potassium ions outside the cell bind to the pump. 4. The two potassium ions are transported across the cell membrane and are released inside the cell.

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22 Sodium-Potassium Pump Important: Pump prevents sodium from accumulating in the cell Pump helps maintain the concentration gradient of sodium ions and potassium ions across cell membrane Many cells use this pump to help transport other substances (glucose) across the cell membrane

23 Movement in Vesicles Many substances, like proteins and polysaccharides, are too large to be transported by carrier proteins So, they are moved across the cell membrane by vesicles The movement of a substance into a cell by a vesicle is called endocytosis The movement of a substance by a vesicle to the outside of a cell is called exocytosis

24 ENDOCYTOSIS

25 EXOCYTOSIS