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 Transport
Four types:
diffusion
osmosis
facilitated transport
ion 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 Solutionsoutside concentration = inside concentration.
2. Hypotonic SolutionsConcentration (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 SolutionConcentration (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