Groups
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 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
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Transport processesActive transportPassive transport
Movement of materialsdown a concentration gradient
No energy needed
Movement of materialsagainst a concentration gradient
Requires energy
membrane membrane
FACILITATED DIFFUSION?
Evidence suggests that plasma membrane contains proteins which help (facilitate) the diffusion of substances
Increases speed of certain substances
General 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.
Copy Rule
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
12Bio 2007
Examples – active transport Ion pumps
Active pumping of ions against a concentration gradient(e.g. Na+, K+)
Endocytosis: Phagocytosis: ingestion of solids Pinocytosis: ingestion of liquids
Exocytosis Expelling of substances from the cell
BIGPROCESSES!
Small process
12Bio 2007
Examples of transport
12Bio 2007
Summary – transport processes Transport
Passive transport- No energy required- Driven by diffusion- Movement down a conc. gradient
Active transport- Energy required- Movement against a conc. gradient
Diffusion
Facilitateddiffusion
Osmosis- Water only
Ion pumps
Exocytosis
Endocytosis
DIFFUSION
