CELL TRANSPORT

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CELL TRANSPORT The ABSORPTION and CIRCULATION of
materials into a cell.   Mrs.
Woytowich Regents Biology
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OBJECTIVES Upon completion of this unit
students will be able to   1. Define the key
terms associated with the processes of the
cell membrane. 2. State the difference
between diffusion and osmosis.   3. Explain
the differences between passive transport and
active transport. 4. List and briefly describe
the various types of active and passive
transport.   5. State the difference between
EXOcytosis and ENDOcytosis.   6. State the
difference between pinocytosis and
phagocytosis.   7. Identify and differentiate
isotonic, hypotonic, and hypertonic solutions.  
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NOT IN GLOSSARY, SO USE INDEX OF TEXTBOOK OR
DICTIONARY.COM
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• INTRODUCTION CELL TRANSPORT
• Vital materials, such as OXYGEN AND DIGESTED
  FOODS that allow a living organism to survive
  must REACH ALL CELLS OF THE ORGANISM. Also, the
  waste materials must be carried away and released
  into the environment.
• The life function of TRANSPORT is responsible for
  this movement and is defined as THE LIFE FUNCTION
  BY WHICH ORGANISMS ABSORB AND DISTRIBUTE
  MATERIALS NECESSARY TO MAINTAIN LIFE
• We will talk about both absorption and
  circulation as separate processes.

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• A. ABSORPTION
• Absorption is THE 1ST STAGE OF TRANSPORT CELLS
  TAKE DISSOLVED MATERIALS THROUGH THE CELL
  MEMBRANE TO THE INTERIOR
• I.   THE CELL MEMBRANE
• The key organelle involved with cell transport is
  the CELL MEMBRANE
• The function of the cell membrane is to CONTROL
  what enters and leaves the cell. Because not all
  substances can easily go into and out of the
  cell, the cell membrane is said to be SELECTIVELY
  PERMEABLE.

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REMEMBER The cell membrane is a LIPID bilayer
with floating PROTEINS (floating icebergs of
protein in a fatty sea)  
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• The model on the previous page is used to
  describe the structure of the cell membrane and
  is called the FLUID-MOSAIC MODEL. Fluid because
  the lipid bilayer continually moves around and is
  never motionless. Mosaic because that is how it
  appears a mosaic is A PIECE OF ART THAT IS MADE
  UP OF LOTS OF LITTLE PIECES PUT TOGETHER
• Factors that affect the movement of materials
  into and out of a cell include
• 1. SIZE OF THE MOLECULES
• 2. ELECTRICAL PROPERTIES OF MOLECULES
• 3. TYPE OF CELL

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•  
• I. PASSIVE TRANSPORT
• 1.   Diffusion
• No cellular energy is expended in this absorption
  process.
• Diffusion is a natural process by which molecules
  move from and area of HIGH CONCENTRATION to an
  area of LOW CONCENTRATION
• Diffusion occurs because THE MOLECULES ARE IN
  CONSTANT RANDOM MOTION and only if THERE IS A
  CONCENTRATION GRADIENT (DIFFERENCE IN
  CONCENTRATION)
• As a result of diffusion, THE MOLECULES
  EVENTUALLY BECOME EVENLY DISTRIBUTED THROUGHOUT
  THE AVAILABLE SPACE

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      EQUILIBRIUM IS WHERE THE MOLECULES ARE
STILL IN MOTION, BUT THERE ARE EQUAL AMOUNTS OF
MOLECULES MOVING OUT OF A GIVEN AREA AS ARE
MOVING INTO THE AREA
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•    2. Osmosis
• Osmosis is the THE DIFFUSION OF WATER MOLECULES
  INTO OR OUT OF A CELL THROUGH THE CELL MEMBRANE
• It is also a form of PASSIVE transport because it
  DOES NOT REQUIRE ENERGY
• Whether there is a net movement if water into or
  out of a cell depends on THE CONCENTRATION
  GRADIENT WHETHER THERE IS A HIGHER CONCN OF
  WATER ON ONE SIDE OF THE CELL MEMBRANE THAN THE
  OTHER

REMEMBER All osmosis is diffusion BUT not all
diffusion is osmosis
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1.ISOTONIC SOLUTION CONCN GRADIENT IS ZERO NO
NET GAIN OR LOSS OF WATER BY THE CELL 2.HYPOTONIC
SOLUTION CONCN OF H20 IS LOWER INSIDE OF THE
CELL NET MOVEMENT OF H20 INTO THE CELL ANIMAL
CELLS WILL SWELL AND BURST WHILE PLANT CELLS WILL
SWELL AND HAVE INCREASED TURGOR PRESSURE 3.
HYPERTONIC SOLUTIONCONCN OF H20 IS HIGHER
INSIDE OF THE CELL NET MOVEMENT OF H20
OUT OF THE CELL ANIMAL CELLS WILL
SHRINK WHILE IN PLANT CELLS THE CYTOPLASM
WILL SHRINK (PLASMOLYSIS)
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• B. OTHER TYPES OF ABSORPTION
• I. Active Transport
• PROBLEM Some needed substances are needed in
  HIGHER concentration inside the cell.
• This means that after equilibrium is reached,
  these substances must move AGAINST their
  CONCENTRATION GRADIENT and move from an area of
  LOW concentration to HIGH concentration
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• SOLUTION Pumps ? Active Transport

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• HOMEOSTASIS makes it possible for a cell to
  maintain a stable internal environment that is
  chemically different from its surroundings.
• The plasma membrane is be involved in active
  transport through the use of PROTEIN RECEPTORS

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Active and Passive Transport have often been
compared to rolling a ball up and down a hill
It requires no energy or ATP to roll a ball down
a hill. It happens naturally just like
diffusion. However, pushing the ball up the
hill, against the gradient, requires the input of
energy/ATP.
Selectively permeable membrane
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• C. GETTING THE BIG STUFF IN AND OUT
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• A. MOVEMENT OUT ? EXOCYTOSIS
• Exocytosis involves THE MOVEMENT OF LARGE
  MATERIALS OUT OF THE CELL
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• B. MOVEMENT IN ? ENDOCYTOSIS
• Endocytosis involves THE MOVEMENT OF LARGE
  MATERIALS INTO A CELL
• There are 2 types of endocytosis, and they both
  require energy so they are also forms of ACTIVE
  TRANSPORT

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• 1. PINOCYTOSIS CELL DRINKING
• This involves the absorption of SMALL molecules
  that still too big to diffuse through the cell
  membrane

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• 2. PHAGOCYTOSIS CELL EATING
• This involves the absorption of molecules much
  TOO BIG to diffuse through the cell membrane and
  structures called PSEUDOPODS
• The term ENGULF is commonly used when
  describing phagocytosis

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 An Ameba engulfing a Paramecium.
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SUMMARY Methods of Transport Across a Cell
Membrane
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CELL TRANSPORT REVIEW 1. T is the life
process that involves the A and C
of materials throughout a cell or organism.   2.
P transport does NOT require E or .   3.
D and O are forms of passive
transport.   4. D is the movement of
molecules from an area of H concentration to
L concentration.   5. O is the diffusion of
W .   6. A transport DOES require E or
.   7. Two types of E include P or
cell drinking and P or cell eating.