Download CELL MEMBRANE: Structure and Function

CELL MEMBRANE:
Structure and Function
Membrane Function:
Supports cell contents by holding
the cell together.
Maintains cellular homeostasis by
regulating what enters (food and
nutrients) and leaves (waste).
The fluid mosiac
Membrane Structure:
A phospholipid bilayer seperates
the cell contents from the
environment. Phophate is
hydrophilic (water soluble) while
lipids are hydrophobic (water
insoluble).
Embedded Carbohydrates act as
chemical messengers attracting
molecules like hormones to the
cell.
Embedded Proteins regulate the
entry and exit of certain
substances. Examples: nutrients,
wastes, food.
Membrane Permeablility
Cell membranes will allow
the passage of some
molecules but not others. It
is selectively permeable.
Passive Transport
Requires no energy because
molecules move with the concentration
gradient. High to low.
Diffusion- solute molecules move from
an area of high concentration to an
area of low concentration.
Diffusion
Facilitated Diffusion- protein
passageways allow the movement of
larger molecules through the cell
membrane in accordance with the
concentration gradient.
Facilitated diffusion
Osmosis- the movement of water from
an area of higher to lower
concentration… or the movement of
water from an area of low solute
concentration to an area of high solute
concentration.
Hypertonic vs. Hypotonic vs. Isotonic
Osmosis
Osmosis
Active Transport- requires energy
Requires energy because it moves
against the concentration gradient from
lower to higher concentration.
Transport proteins- use energy to
pump molecules into and out of the
cell. Example: Sodium/Potassium
pump
Transport proteins/Molecular pumps
Active vs. Passive transport
Endo and Exocytosis- energy is used
to engulf molecules, surrounding them
with storage vesicles for later use or
expelling them from the cell through
the membrane.
Endo/exocytosis
CELL WALL
Found around bacteria, fungi
and plant cells.
Rigid structure made of
complex carbohydrates.
Protects and supports the
cell.