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Cellular Transport
Objectives:-Summarize the structure & function of the plasma membrane -Summarize passive transport and the four main types-Summarize active transport and the three main types-Relate cell transport to homeostasis
Selectively Permeable Membrane
Passive TransportFour types:
diffusionosmosisfacilitated transportion channels
Common characteristics: -No addition of energy (ATP) required.-molecules move from high concentrations to low
concentrations.
1. Diffusion-Simplest type of passive transport.
-No energy required
-Movement of molecules from a high concentration to a low concentration.
-Substances being diffused: lipids, gases, fat-soluble molecules
Diffusion
2. Osmosis
-Passive transport…no ATP needed
-Function: diffusion of water across a selectively permeable membrane, high concentration to low concentration.
-Substance being diffused: water
Osmosis
Cells are subject to Osmosis because they are surrounded by water solutions.
1. Isotonic Solutions-outside concentration = inside concentration.
2. Hypotonic Solutions-Concentration (of sugar) is lower outside than inside
the cell.
This means water wants to move into the cell. Cells begin to swell and may burst. (cytolysis)
3. Hypertonic Solution-Concentration (of sugar) is higher outside of the cell
than inside.
Water tends to flow out of the cell causing animal cells to shrivel and plant cells to wilt.
*Remember…it’s just water moving!
Some cells have developed ways to rid themselves of water.
Contractile vacuoles (unicellular orgs.)
Turgor Pressure, Plasmolysis, Cytolysis
Turgor Pressure Plasmolysis
Contractile Vacuole
3. Facilitated Diffusion
-Passive transport…no ATP needed
-Function: transports sugars and amino acids using membrane transport proteins that are specific to the molecules that need to pass.
-Common molecules…sugars & amino acids
4. Ion Channels
-Passive transport…no ATP needed.
-Function: transports ions using membrane transport proteins that are specific to the ions that need to pass.
Examples of Ions: Cl- Na+ Ca2+ K+
Active Transport
Active Transport- movement against a concentration gradient from “low to high”.
-requires input of energy (ATP) and membrane transport proteins.
1. Cell Membrane Pumps: Sodium-Potassium Pump (move K inside the cell, move Na outside the cell.) -Used in the human muscular and nervous systems.
Active Transport
Active Transport
Types of Active Transport:
2. Endocytosis: cell membrane surrounds and takes in material from its environment.
-pinocytosis-fluids -phagocytosis-large particles or cells
Pinocytosis Phagocytosis Endo & Exo
3. Exocytosis: the expulsion or secretion of materials out of a cell.-works with the golgi apparatus in forming vesicles to remove large molecules such as proteins, waste products, and toxins out of the cell.
Endocytosis Exocytosis
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