Transcript Cell Transport - St. Mary Catholic Secondary School

Cell Transport
The Need For Security
• The cell membrane controls what
may enter or exit the cell.
• It is semi-permeable – only certain
substances may pass into, or out
of, the cell.
• Not just anyone
gets to hang with
us McLovin!
Passive vs. Active Transport
• Passive transport does not require the
use of ATP.
• Active transport does require the
energy of ATP.
• What factors decide which method of
cell transport will be employed?
– Size of molecules – big or little?
– The concentration gradient – with or
against it?
– Charge on molecules?
Passive Transport - DIFFUSION
• Diffusion is the movement of molecules
from an area of higher concentration to an
area of lower concentration.
• The movement continues in this high to low
manner until the concentration in both areas
is the same – this is equilibrium.
• Temperature and pressure can also affect
the rate of diffsuion.
Passive – SIMPLE DIFFUSION
PASSIVE - OSMOSIS
• Osmosis is the movement of water from an area of
higher concentration to an area of lower
concentration across a semi-permeable membrane.
• Water moves because a solute within the cell is
imbalanced with what is in the etracellular fluid.
• The water moves in order to push out or bring
together the internal solute particles in an effort
to match the concentration of the external solute
particles.
OSMOSIS – Isotonic Conditions
• If the solute concentration in the cell and
its external solution is the same – the
conditions are said to be isotonic.
• Water still moves into and out of the cell
but does so in a way that there is no net
change in the concentration
• One water molecule moves in while another
water molecule exits the cell.
OSMOSIS – Isotonic Conditions
OSMOSIS – Hypertonic Conditions
OSMOSIS – Hypotonic Conditions
PASSIVE – Facilitated Diffusion
• Facilitated diffusion uses transmembrane proteins
as channels to transport ions or polar molecules
across the membrane from high to low.
• The proteins used here are called transport
proteins and there are two types:
• Channel Proteins – A hydrophilic pathway that allows
water and ions to pass through it.
• Carrier Proteins – A protein that binds to a molecule
and transports it across the phospholipid bilayer.
PASSIVE – FACILITATED DIFFUSION
http://www.youtube.com/watch?v=W52PYXXPknU
PASSIVE TRANSPORT
ACTIVE TRANSPORT
• Active transport invovles the use of ATP.
There are several methods of active transport
including:
• Protein Pumps
• Primary & Secondary Transport
•
•
•
•
Phagocytosis
Pinocytosis
Receptor-Mediated Endocytosis
Exocytosis with Vesicles
ACTIVE – PROTEIN PUMPS
• Primary Transport – The protein pumps
substances against the concentration
gradient with the use of ATP. Energy (ATP)
is consumed in the process.
• Secondary Transport – The protein pumps
substances against the concentration
gradient using the energy of an electrostatic
gradient created by a method of primary
transport.
PRIMARY TRANSPORT
SECONDARY TRANSPORT
ACTIVE – PROTEIN PUMPS
http://www.youtube.com/watch?v=JGF6ry0SWPs
ACTIVE - PHAGOCYTOSIS
• Phagocytosis means “process of cell
eating”.
• The cell recignizes the vital molecule
or foreign invader. Then, extensions of
the cell memebrane called pseudopods
reach out and engulf the nutrient or
neighbouring cell and place it in a
(phagocytic) vesicle.
• We see this in unicellular protists and
white blood cells.
ACTIVE – PHAGOCYTOSIS
http://www.youtube.com/watch?v=6-N1cFQ0yJI
ACTIVE - PINOCYTOSIS
• Pinocytosis means “process of
cell drinking”. This process used
to take in smaller dissolved
nutrients.
• The cell invaginates (indents) and
takes in a small portion of the
extracellular fluid and the
dissolved molecules within it.
• This fluid and solute is placed in a
(pinocytic) vesicle.
ACTIVE - PINOCYTOSIS
ACTIVE - RECEPTOR-MEDIATED
ENDOCYTOSIS
• The cell membrane has proteins on its outer
surface that can be used to identify cell
surface proteins on a nearby cell or protien
based hormones.
• The shape of receptor protein and target
protein are like a key and lock.
• When several receptor proteins have their
target proteins attached, they move along the
fluid membrane of the cell to a common point.
• Now the cell will carry out a process much
like pinocytosis and encapsulate the target
protein molecules and receptors in a vesicle.
ACTIVE - RECEPTOR-MEDIATED
ENDOCYTOSIS
ENDOCYTOSIS METHODS
ACTIVE - EXOCYTOSIS
• Exocytosis is the process of materials being
moved from the cytoplasm, inside the cell, to
the extracellular fluid, outside of the cell.
• We often see this process undertaken with
proteins made by the Rough ER. They are
sent to the Golgi, packaged in a secretory
vesicle and sent to the cell membrane where
they are released into the extracellular fluid or
blood.
ACTIVE - EXOCYTOSIS & VESICLES
http://www.youtube.com/watch?v=Ptzp_xZSYlM
ENDOCYTOSIS & EXOCYTOSIS
http://www.youtube.com/watch?v=qpw2p1x9Cic
FIN