Surface Area and Transport Flashcards
Explain why cells are often limited in size by the SA:V ratio.
As a cell grows, eventually the surface area can no longer serve the requirements of the cell (nutrients in and waste out through the cell membrane).
A decreasing surface area to volume ratio will stimulate cell division through mitosis (1.6.U1) or binary fission (1.2.U3).
By dividing, the size of the cell is reduced and kept within SA:V limits.
What is diffusion?
The net movement of molecules from areas of higher concentration to areas of lower concentration.
Is diffusion active or passive?
“Passive” - meaning that the cell does not have to use energy to have diffusion happen
What is facilitated diffusion?
Molecules move through a channel protein in the membrane
Used for small charged molecules (ions)
PHOSPHOLIPID BILAYER MUST BE…
studded with channel proteins to allow facilitated diffusion to occur.
OSMOSIS IS…
The movement of water by diffusion across a membrane
Is osmosis active or passive?
It is passive.
How does water move?
Water moves from a
HYPOTONIC to a HYPERTONIC
solution
What is hypotonic?
The cell has a higher solute concentration than the solution.
What is isotonic?
The cell has the same solute concentration as the solution.
What is hypertonic?
The cell has a lower solute
concentration than the solution.
What is active transport?
The movement of substances from areas low concentration to areas of high concentration through protein pumps.
What are protein pumps?
Molecule to be transported enters the pump
Energy from ATP is used to change the shape of the protein
Molecule can now pass to the opposite side of the membrane
What is endocytosis?
Process by which cells take in molecules (such as proteins) or smaller cells by engulfing them.
What is phagocytosis?
Eating; Cell engulfs food particles or particulate material
