Download The Cell Theory and Membrane Transport

Cell Membrane Review
Functions
– Provides boundary for cell
– Selectively Permeable: only allows
certain things to pass through. “Picky”
Ex: Window screen
– Maintains homeostasis: balance
within the cells
Cell Membrane
Structure vs. Function
– Membrane is a phospholipid bilayer
– Phospholipids: two sided molecule with a
head that loves (hydrophilic) and a tail
that repels (hydrophobic) water
– Embedded Proteins: “club bouncers”
Decide who goes in & out
Markers for recognition
TYPES OF TRANSPORT
Passive Transport:
-Uses No Energy
-Movement from high concentration to low
concentration
Active Transport:
–
–
Uses Energy (ATP)
Movement against the concentration gradient
(from low concentration to high concentration)
Passive Transport
Diffusion = movement of molecules from
high concentration to low concentration
Passive Transport
Osmosis =
movement (or
diffusion) of
water from
area of high
concentration
to low
concentration
Higher Concentration
of Water
Lower Concentration
of Water
(Water molecules)
(Sugar molecules)
HYPO/HYPER/ISO
HYPOTONIC:
•Concentration of solute is lower outside cell than
inside cell, meaning more water outside cell
•Water will move INTO cell causing it to SWELL
•Animal cells could rupture if the cell takes in too much
water
•Causes TURGOR PRESSURE in plant cells (more
support)
HYPERTONIC:
•Concentration of solute is higher outside the cell
and lower inside cell, meaning less water outside
•HYPERTONIC means “above strength”
•H2O rushes OUT of cell causing it to shrivel
•Results in PLASMOLYSIS in plants (wilting)
ISOTONIC:
Concentration outside the cell is the
same as the inside of the cell for both
water and solute
ISO- means “equal to” or “same”
Movement into cell = movement out
of cell; cell does not change.
Special Types of Passive Transport
Facilitated Diffusion = diffusion through
protein tunnels to help larger molecules (like
sugar) cross the membrane. Facilitated
means “assisted”. Still passive. No energy.
Active Transport
Movement against the concentration gradient.
Molecules will move from an area of low
concentration to an area of high
concentration.
Requires cell energy in the form of ATP
(Adenosine Triphosphate) and protein pumps
Example - Sodium-Potassium Pump: Protein
that actively transports sodium and potassium
ions into or out of the cell. Necessary for
your nervous system.
More Active Transport
Endocytosis = the active process by which cells
take in particles using vessicles; into the cell
– Pinocytosis = drinking action, used for small
particles or water
– Phagocytosis = devouring action, used for large
particles like food
Exocytosis = the active process by which
cells remove wastes and large particles
through vessicles; exit the cell