CH 8: Cellular Transport

Diffusion and Osmosis What is diffusion? - the movement of molecules from regions of high concentration to regions of low concentration, “down” a concentration gradient. What is osmosis? The diffusion of water across a selectively permeable membrane Why do we need to regulate osmosis? To maintain homeostasis because the plasma membrane is naturally permeable to water

Osmosis How long does water diffuse in a solution? - Until it has reached equilibrium (even distribution) What controls osmosis? The concentration gradient What is a concentration gradient? The unequal distribution of particles

Types of Solutions: Isotonic Remember: Salt Sucks!!! "ISO" means the same Definition: When the concentration of water is the same inside and outside the cell so a cell remains the same. Both animal and plant cells retain normal shape and pressure

Types of Solutions: Hypotonic The prefix "HYPO" means less -Less water inside the cell than outside so water will move into the cell. Definition: When the concentration of water is lower inside the cell than outside the cell so the cell swells What happens: The cell swells up Animal Cell- swell until they burst Plant Cell- swell beyond their normal size as pressure increases; this pressure is called turgor pressure. The plasma membrane presses against the cell wall and makes the cell more firm (why grocers mist fruits at the market)

Types of Solution: Hypotonic

Types of Solution: Hypertonic The prefix "HYPER" means more -More water inside the cell than outside so the water leaves the cell. Definition: When the concentration of water is higher inside the cell than outside the cell so the cell shrivels What happens: Cell shrivels up Animal cell- shrivels up Plant cell – loses pressure as the plasma membrane shrinks away from the cell wall; the plant wilts = plasmolysis

Types of Solution http://www. tvdsb. on

Red Blood Cells in Solution Burst---------------Swollen----------Normal-----------------Plasmolysis---------

http://www.wiley.com/college/boyer/0470003790/animations/membrane_transport/membrane_transport.htm http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html

Passive Transport: No Energy Required Passive Transport -the movement of particles across a membrane that goes with the concentration gradient…high concentration low concentration…and energy is not required What do materials need to cross the plasma membrane? Transport proteins What is this process called? Facilitated diffusion

Types of Transport Proteins Channel Proteins- form channels that allow specific molecules to flow through. Carrier Proteins - change shape to allow a substance to pass through the plasma membrane.

Active Transport: Requires Energy Active Transport – Movement of particles through a membrane against a concentration gradient…low concentration high concentration…Energy is required How does active transport occur? A carrier protein binds with the substance to be transported. The protein changes shape so that the particle can be released into the cell--like the opening of a door.

Type of Transport Protein Used? Direction of Movement Requires energy from the cell? Classification of transport Simple Diffusion No With Concentration Gradient Passive Facilitated Yes- channel protein or carrier protein Active Yes- carrier protein Against Yes

Passive Transport vs. Active Transport

Transport of Large Particles Endocytosis- The process by which a cell surrounds and takes in material from its environment Explain the process of endocytosis- the material is engulfed and enclosed by a portion of the cells plasma membrane.

Exocytosis Exocytosis- the expels or secretes materials from a cell.

Transport of Large Particles Phagocytosis- the engulfing and ingesting of solid particles- “cell eating” Pinocytosis- the ingestion of fluid into a cell- “cell drinking”

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