Groups
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Nell, Gaui, Jak
Graeden, Jordan, Thomas
Lewis, Bradley F, Bradley P
Robbie, John, Luke
Shannon, Garrion, Denis
Rory, Eugene, Mitch P
Josh M, Isaac, Martyn
Scott, Josh, Bruce
 ONCE FINISHED – CARRY ON WITH DIFFUSION
PRACTICAL FROM YESTERDAY
DO NOW!
 What does active transport mean?
 What is a fair test?
 What is an independent variable?
 What is a dependent variable?
DO NOW!!
 Write everything you know about the cell
membrane
 Think back to Year 10 science – what is
diffusion and what is osmosis?
 What is the function of flagella?
DO NOW!!
 What was the purpose of yesterdays
experiment?
 What is osmosis?
DO NOW!
 What does hypotonic mean?
 What does isotonic mean?
CELL TRANSPORT - OSMOSIS
What is it??
Osmosis is...
 The movement of water molecules from an
area of lower to higher solute
concentrations through a semi-permeable
membrane
Also described as...
 The movement of water molecules from an
area of high water concentration (low
solute conc.) to an area of low water
concentration (high solute conc.)through a
semi-permeable membrane
Osmosis cont...
• Osmosis is a type of passive transport.
• Water moves freely through pores in the
semi-permeable membrane.
Dialysis tubing expt.
 In groups of three conduct an experiment
with dialysis tubing and golden syrup to
observe osmosis in action
 Look at the example from Mrs H and create
your own
Cells in solutions or
external environments
 Words you NEED to know
 Isotonic
 Hypertonic
 Hypotonic
HYPOTONIC
 Hypotonic Solutions: contain a low
concentration of solute relative to another
solution (e.g. the cell's cytoplasm). When a
cell is placed in a hypotonic solution, the
water diffuses into the cell, causing the cell to
swell and possibly explode
HYPERTONIC
 Hypertonic Solutions: contain a high
concentration of solute relative to another
solution (e.g. the cell's cytoplasm). When a
cell is placed in a hypertonic solution, the
water diffuses out of the cell, causing the cell
to shrivel.
Isotonic
 The concentration of solute in the solution
can be equal to the concentration of solute in
the cells. The cell is in an isotonic solution.
(iso = same as normal)
Explanations!!
 Explain to your neighbour the concept of osmosis and
isotonic, hypertonic, and hypotonic then write your
own paragraph in your books
 Use Bayley pg. 121 -122 to answer the following
questions
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What does plasmolysed mean?
What happens if plants loose too much water?
How do single celled organisms cope with water regulation?
How do freshwater fish cope?
How do fish keep osmoregulation?
DO NOW!!
 What is diffusion?
 What things would need to diffuse in and out
of cells?
 Is this passive or active transport?
DIFFUSION
 Refers to the movement of particles in liquids
and gases where the particles move randomly
from an areas where they are in HIGH
concentration to an area where they are in
LOWER concentration
 INTO CELLS: FOOD AND OXYGEN
 OUT OF CELLS: CARBON DIOXIDE AND
WASTE PRODUCTS
Concentration Gradients
 These occur from a region of high
concentration to a region of low
concentration. The greater the difference in
concentration the FASTER the rate of
diffusion.
 Small particles diffuse FASTER than larger
particles
DIFFUSION IN CELLS
Transport processes
Passive transport
Movement of materials
down a concentration
gradient
No energy needed
membrane
Active transport
Movement of materials
against a concentration gradient
Requires energy
membrane
12Bio 2007
FACILITATED DIFFUSION?
 Evidence suggests that plasma membrane
contains proteins which help (facilitate) the
diffusion of substances
 Increases speed of certain substances
General rule
Copy Rule
Cells are limited to a
certain size.
 Generally cells are so small we need a
microscope to see them.
 We don’t see cells the size of whole plants.
WHY??
Complete the experiment to find the
answer!
ALL DOING THIS FOR THE FIRST TIME SO
READ ALL INSTRUCTIONS CAREFULLY!!!
Surface Area to Volume Ratio
 This ration SA/V gives a comparison of surface
area to volume
 Greater rate of activity with an increase in SA/V
ratio
 Cell organelles: folding of cristae in mitochondria
allows respiration to occur more quickly
 Organ level: Villi - small projections from intestine
increase SA
 Organism level: native Africans are generally tall and
thin, allowing rapid heat loss to stop overheating
Cell Size and Shape
 Size and shape are limited by
 The distance materials must travel inside the cell
 The number of places at which materials can enter
the cell
 The distance materials must travel can be
reduced by
 Cells having centres which do not require an
exchange of materials
 Cells dividing to form two news cells
ACTIVE TRANSPORT
 This is the movement of substances
(molecules and ions) from an area of LOW
concentration to an area of HIGH
concentration.
 MOVEMENT AGAINST THE CONCENTRATION
GRADIENT
 REQUIRES ENERGY
Examples – active transport
 Ion pumps
 Active pumping of ions against a concentration
gradient
(e.g. Na+, K+)
Small process
 Endocytosis:
 Phagocytosis: ingestion of solids
 Pinocytosis: ingestion of liquids
BIG
PROCESSES!
 Exocytosis
 Expelling of substances from the cell
12Bio 2007
Examples of transport
12Bio 2007
Summary – transport processes
Transport
Passive transport
- No energy required
- Driven by diffusion
- Movement down a conc. gradient
Diffusion
Facilitated
diffusion
Active transport
- Energy required
- Movement against a
conc. gradient
Ion pumps
Osmosis
- Water only
Endocytosis
Exocytosis
12Bio 2007
DIFFUSION