Passive Transport
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There are two main types of cellular transport - passive and active. Passive transport does not require energy and includes diffusion, facilitated diffusion, and osmosis. Active transport moves molecules against their concentration gradient and requires energy from ATP. The sodium-potassium pump is an example of active transport, moving sodium and potassium ions across the cell membrane against their gradients. Large molecules are transported across membranes via endocytosis and exocytosis using vesicles.
Passive Transport
- 1. Cellular Transport ‘ 07 Biology
- 2. 2 Types: Passive No energy! Active Energy!
- 3. Passive Transport Substances are allowed to cross the cell membrane without any input of energy Remember: The cell membrane is “selectively permeable”
- 4. Types of Passive Transport Diffusion Facilitated Diffusion Osmosis
- 5. Diffusion Movement of molecules from areas of high concentration to low How does it work? “ Kinetic energy” (energy in motion) Concentration gradient- caused by a difference in concentration Diffusion results in equilibrium (all molecules occupy the same amount of space)
- 6. Facilitated Diffusion Some molecules are helped across the cell membrane by carrier proteins No energy is required in this process
- 7. Osmosis The diffusion of water across the cell membrane The direction of osmosis depends on the concentration of solutes inside and outside the cell
- 8. Osmosis (continued) Hypotonic- concentration of solutes outside the cell is lower than the concentration inside Hypertonic- concentration outside is higher than inside Isotonic- concentrations inside and out are equal
- 10. Active Transport Sometimes cells must move molecules against the concentration gradient This process requires energy (ATP) and special protein “pumps”
- 11. Sodium-Potassium Pump Special proteins within the membrane that transport Na+ and K- ions Some cells must have a higher concentration of Na+ ions outside of the cell and a higher concentration of K- ions inside the cell 2 Potassiums are brought in for every 3 Sodiums removed
- 13. Movement In Vesicles Some molecules are too big to be transported across the cell membrane by passive and active transport Endocytosis- “cell eating” Exocytosis- “cell pooping”
- 14. Endocytosis Process by which cells ingest macromolecules, fluids, large particles and even other cells These molecules are enclose in a bubble of membrane ( vesicle ) that pinches away from the cell membrane
- 15. Endocytosis (continued) Pinocytosis- ingestion of small particles and fluid Phagocytosis- ingestion of large molecules or other cells
- 16. Exocytosis Process by which waste and large particles are released from the cell A vesicle will fuse with the membrane, releasing its contents into the extra cellular environment
Editor's Notes
- #2: What is meant by the word transport? Moving substances across the cell membrane
- #4: What is the cell membrane made of? Lipids make it polar--> oxygen and co2 can readily pass through Small molecules can pass through protein pores
- #6: Spray aerosol into the corner of the classroom Kinetic energy --> Particles are constantly moving and bumping into each other Start a mosh pit in the corner of the classroom In the absence of outside influence diffusion will continue until equilibrium is reached
- #7: Molecules may be too large or not soluble in lipids --> glucose
- #10: Hypotonic solutions are good Cells adapt by pumping water or solutes out of the cytosol (contractile vacuoles or solute pumps) Plants love hypotonic environments --> turgor pressure Hypertonic solutions are bad…emkay Results in the loss of water --> plasmolysis Some cells cannot adjust to changes in environment (rbc’s) --> cytolysis or “cell bursting “ may result
- #14: Macromolecules, nutrients, large quantities of small molecules
- #15: The vesicles then fuse with other membrane bound organelles within the cell
- #16: Phagocytosis can be used to ingest bacteria or viruses that invade the body! Pic --> white blood cell ingestng bacteria