CELL BOUNDARIES
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Transcript CELL BOUNDARIES
CELL BOUNDARIES
The Cell Membrane and Transport
Processes
I. The Structure and Function of the
Cell Membrane
Components of the cell membrane:
Phospholipid bilayer – nonpolar fatty
acid tails turn inside, polar phosphate
heads turn outside – forms a flexible
structure as a boundary
Proteins – can be integral proteins or
peripheral proteins. They can act as
enzymes, receptors, transport and binding
molecules
Carbohydrates – Identification tags
outside of the cell membrane (glycolipids
and glycoproteins)
Cholesterol – helps stabilizing the
membrane by making it more solid –
animal cells
The Function of the Cell Membrane
Surrounds the cell.
Regulate the transport of molecules
in and out of the cell -semipermeable
Immune response
Attaches the cells to other cells or
surfaces.
The model that describes cell
membrane, the Fluid Mosaic Model
http://www.youtube.com/watch?v=GW0lqf4Fqpg
http://www.youtube.com/watch?v=Qqsf_UJcfBc
Selective Permeability
Cell membranes control what goes
in and out of the cell
It allows some substances to cross
more easily than others
II. Passive Transport Processes
Transport means the movement of
molecules from one side of the cell
membrane to the other
Transport is influenced by:
The
The
The
The
size of substances
polarity of substances
concentration of substances
permeability of the cell membrane
Passive transport: requires no
energy from the cell, the energy
comes from the difference in
concentration not ATP (energy from
the cell).
Moves smaller substances from the
higher to the lower concentration
area.
Important in transporting O2, CO2,
water, small molecules.
http://bcs.whfreeman.com/thelifewire/content/chp05/0502001.html
Types of Passive Transport
Diffusion – moving substances
within the cell and small nonpolar
molecules across the phospholipid
bilayer.
http://www.stolaf.edu/people/giannini/flashani
mat/transport/osmosis.swf
Osmosis: the movement of water
across the cell membrane by using
the phospholipid bilayer or transport
proteins.
Tonicity:
Describes the tendency of a cell in a given
solution to lose or gain water.
Isotonic, hypertonic, and hypotonic
Osmosis in action
Isotonic solutions – when cells are put into
solutions that have equivalent salt
concentration, visible osmosis does not take
place.
Hypotonic solutions – Cells in very dilute
solutions will take in water and eventually can
burst (animal cells).
Hypertonic solutions – Cells in very
concentrated solutions will lose water and
shrink.
http://www.linkpublishing.com/video-transport.htm#Elodea_-_Osmosis
https://www.youtube.com/watch?v
=mzo_B5F7pk4
Facilitated Diffusion – a special
type of diffusion in which the
transported molecules are moved
by the help of a transport protein.
Determine the type and direction of transport in the cases
below (glucose, ions and water are able to pass through
the membrane)
A cell has 15 % starch while its outside has
5% starch. What is moving across the
membrane? By what transport? In what
direction?
A cell has 5% glucose, the outside has 8 %
glucose. What is moving across the
membrane? By what transport? In what
direction?
The outside has 15 % O2, inside the cell has
7 %. What is moving across the membrane?
By what transport? In what direction?
III. Active Transport
http://bcs.whfreeman.com/thelifewire/content/chp05/0502002.html
Transport processes that can move
substances from the lower concentration
area to the higher by using energy.
Transport proteins are always required
A type of active transport is the NaK ion pump
3 sodium ions move out of the cell
with the help of a transport protein,
while 2 potassium ions move into
the cell.
H + ion pump – this active
transport moves hydrogen ions
(protons) from low to high
concentration area by using energy
from the cell (ATP).
IV. Bulk Transport
Bulk transport – transport of large substances
through the cell membrane by using vesicles.
Endocytosis – a process by which large particles can
move into the cell
Types of endocytosis:
Phagocytosis – engulfing solid particles
Pinocytosis – engulfing liquids, solutions
Receptor-mediated endocytosis – moving
into the cell by first binding with receptor
molecules on the cell’s surface.
http://www.youtube.com/watch?v=4gLtk8Yc1Zc
http://www.youtube.com/watch?v=pvOz4V699gk – amoeba eating
two paramecia
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/rectpr.htm
https://www.youtube.com/watch?v=prfMUwjobo8
Exocytosis – the process by which
the cell releases large molecules
through its cell membrane