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?

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 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

12Bio 2007 Transport processes Active transportPassive transport Movement of materials down a concentration gradient No energy needed Movement of materials against a concentration gradient Requires energy 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 BIG PROCESSES! 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 Facilitated diffusion Osmosis - Water only Ion pumps Exocytosis Endocytosis

DIFFUSION