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Cellular Transport
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
How long does water diffuse in a solution? Until it has reached equilibrium evenly distributed)
What controls osmosis? The concentration gradient
What is a concentration Gradient? The unequal distribution of particles
Type of Solutions ------Remember: Salt Sucks
"ISO" means the same
Definition: concentration of water is the same inside and outside
the cell
Both the animal and plant cells retain normal shape and
pressure
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The word "HYPO" means less, in this case there are
less solute (salt) molecules outside the cell, since salt
sucks, water will move into the cell.
cell swells up
Plant Cell- swell beyond their normal size as pressure
increases; the plasma membrane presses against the cell
wall and makes the cell more firm. (why grocers
keeping misting vegetables at the market)
Animal Cell- swell until they burst
The word "HYPER" means more, in this case there
are more solute (salt) molecules outside the cell,
which causes the water to be sucked in that direction.
Cell shrivels up
Plant cell – loses pressure as the plasma membrane
shrinks away from the cell wall.
Animal cell- Shrivels up
Passive and Active Transport
Passive Transport -the movement of particles across a membrane.
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. (fig. 8.5B)
Carrier Proteins - change shape to allow a substance to pass through the plasma membrane.
Active Transport
Active Transport – Movement of materials through a membrane against a concentration gradient
How does active transport occur? (2 sentences)
A carrier protein binds with the substance to be transported. The cell changes to the shape of the carrier
protein so that the particle can be released into the cell-like the opening of a door.
Type of
Transport
Transport
Protein Used?
Direction of
Movement
Requires energy Classification of
from the cell?
transport
Simple Diffusion
No
No
Passive
Facilitated
Diffusion
Yes- Channel
Protein or carrier
protein
Yes- Carrier Protein
With Concentration
Gradient
With Concentration
gradient
No
Passive
Against
Concentration
Gradient
Yes
Active
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 Endocytosisthe material is engulfed and enclosed by a portion of the cells plasma membrane.
Exocytosis- the expulsion or secretion of materials from a cell.
Phagocytosis- the engulfing and ingesting of particles- “cell eating”
Pinocytosis- the ingestion of fluid into a cell- “cell drinking”