Biology
Hamilton Science Department
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Organisms must
maintain a balance of
materials that enter
and leave their cells.
Without this ability,
they will die.
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The property of a
membrane to
allow only certain
particles through
while keeping
others out is
known as
selective
permeability.
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Non-permeable- no materials can get into or
out of the membrane
Semi-permeable- based upon size of the
material, some molecules can get through
while other can’t.
Permeable- Most or all molecules can move
through the membrane
Polar Head
Non polar Tails
Marker Protein
Channel Protein
Lipid Bi-Layer
Receptor Protein
DIFFUSION:

THE NET MOVEMENT
OF PARTICLES FROM
HIGHER
CONCENTRATION TO
AN AREA OF LOWER
CONCENTRATION
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Diffusion is a
CONTINUOUS
MOVEMENT UNTIL
DYNAMIC
EQUILIBRIUM IS
REACHED.
Until EQUAL
AMOUNTS OF
SUBSTANCE ARE ON
BOTH SIDES OF THE
MEMBRANE
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PASSIVE TRANSPORT
continued..
2. OSMOSIS:
DIFFUSION OF WATER
MOLECULES THROUGH A
SELECTIVELY PERMEABLE
MEMBRANE.
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3 TYPES OF SOLUTIONS AROUND A CELL:
1. ISOTONIC: CONCENTRATION OF DISSOLVED
SUBSTANCES AND WATER SAME ON BOTH SIDES OF
MEMBRANE
2. HYPOTONIC: CONCENTRATION OF DISSOLVED
SUBSTANCES IS LOWER THAN IN THE CELL
CONTRACTILE VACUOLES: PROTISTS HAVE THESE
ORGANIELLES - COLLECT EXCESS WATER AND
EXCRETE IT SO CELL DOESN’T BURST
3. HYPERTONIC: SOLUTION. CONCENTRATION OF
DISSOLVED SUBSTANCES IS HIGHER THAN IN THE
CELL.
If a cell is placed in a…….
Water moves
out
of the cell
Water moves
into the cell!!
ISOTONIC SOLUTIONS ARE BALANCED !!
 TURGOR PRESSURE –
 The water pressure inside a plant
cell.
 HIGH TURGIDITY = CRISPNESS
 LOW TURGIDITY = WILTEDNESS
•PLASMOLYSIS:
• LOSS OF WATER FROM A CELL RESULTING
IN A DROP IN TURGOR PRESSURE
•CYTOLYSIS:
• GAINING OF WATER IN THE CELL
CYTOPLASM,,,THUS AN INCREASE IN
TURGOR!
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FACILITATED
DIFFUSION:
TRANSPORT
PROTEINS
PROVIDE OPENINGS
FOR PARTICLES TO
PASS THROUGH –
EX: SUGARS
FROM HIGH TO LOW
CONCENTRATION.
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The “ion channel”
allows sodium,
calcium, and
potassium ions to
enter and leave
the cell.
called Ion Pumps
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ACTIVE
TRANSPORT
REQUIRES ENERGY
MOVEMENT OF SUBSTANCES
FROM LOW
CONCENTRATION. TO
ALREADY HIGH
CONCENTRATION
EXAMPLE:
MINERALS INTO CELL SCARCE
Substances move
AGAINST GRADIENT
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ENDOCYTOSIS:
USE ENERGY TO TAKE IN LARGE
PARTICLES. CELL SURROUNDS THE
PARTICLES - DOESN’T PASS THROUGH
CELL MEMBRANE
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PHAGOCYTOSIS: “CELL
EATING” TAKE IN WHOLE
PIECES BY PINCHING IN
MEMBRANE
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PINOCYTOSIS: “CELL
DRINKING” TAKE IN FLUID
BY PINCHING IN MEMBRANE
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EXOCYTOSIS:
RELEASE OF WASTES FROM CELL
VACUOLE. VACUOLE FUSES WITH
MEMBRANE AND CONTENTS ARE
RELEASED TO OUTSIDE.