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Transport Across Membranes. Can you remember the role of the cell membrane?. The Cell Membrane. Controls what enters and leaves the cell. Watch the following video clip and see if you can name 2 new parts of the membrane at the end. The Cell Membrane. - PowerPoint PPT Presentation
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Transport Across Membranes
Can you remember the role of the cell membrane?
The Cell Membrane• Controls what enters and leaves the
cell.
• Watch the following video clip and see if you can name 2 new parts of the membrane at the end.
The Cell Membrane• The cell membrane is made of
proteins and phospholipids.
• Label these on your diagram.
• Proteins can either pass through the membrane or float on the surface.
• Phospholipids have a phosphate head and lipid tails.
The Cell Membrane
Fluid Mosaic Model• Phospholipids provide the
membrane with fluidity.
• The combination of large proteins and small phospholipids make the membrane look like a mosaic.
Model Cell Membrane• Now try building a model cell
membrane with your partner.
• You should be prepared to present your model to your table in 10mins.
• Remember to use the terminology we have learned in describing your model.
Question Time!1. What is the role of the cell
membrane?2. Name the two structures which
make up the cell membrane?3. Why is the cell membrane shown
using a “fluid mosaic model”?
Transport Across the Membrane - Diffusion
What is diffusion?
Diffusion ExperimentEquipment:
Petri Dish20ml waterFood colouringLaminated circleTimer
Diffusion Experiment• Place the laminated circle under the Petri
dish.
• Add 20ml of water to the Petri dish.
• Add one drop of food colouring to the Petri dish.
• Immediately, start the timer.
• At 1 minute, 3 minutes, 5 minutes and 8 minutes colour in the Petri dish to show how far the colour had spread.
Diffusion Experiment
Diffusion• Watch the video clip.
• http://www.bbc.co.uk/learningzone/clips/the-cell-membrane/10644.html
• Can you pick out a definition of diffusion which matches the result of your experiment?
• the movement of a substance from an area of high concentration to an area of low concentration.
• Diffusion is a form of passive transport.
It does not require energy.
Diffusion
• During diffusion substances move down a concentration gradient.
Diffusion
High
Low
Why is it important?• Diffusion is important in animals to allow the
raw materials needed for respiration to enter, e.g. Oxygen and Glucose.
• It also allows the products of respiration to leave the cell, e.g. Carbon dioxide and Water.
Why is it important?• Diffusion is important in plants to allow the
raw materials needed for photosynthesis to enter, e.g. Water and Carbon Dioxide.
• It also allows the products of photosynthesis to leave the cell, e.g. Oxygen and Glucose.
Question Time!1. What is the definition of diffusion?2. Why is diffusion an example of passive transport?3. During diffusion substances move down a concentration
gradient, what does this mean?4. Which substances will move in and out of an animal cell
by diffusion?5. Which substances will move in and out of an plant cell by
diffusion?6. What effect will a uniform concentration have on
diffusion?7. Glucose is constantly used up in the cell. Why does this
help diffusion to continue?8. Why is diffusion important in animal cells?
Visking Tubing 1Equipment:
BeakerWaterVisking Tubing15ml Starch Solution15ml Glucose SolutionClips
• Test the liquid inside and outside the visking tubing for starch.
• Test the liquid inside and outside the visking tubing for glucose.
• Draw a diagram and make a note of your results.
Visking Tubing 1
• Test the liquid inside and outside the visking tubing for starch.
• Test the liquid inside and outside the visking tubing for glucose.
• Draw a diagram and make a note of your results.
• What does this show about the cell membrane?
Visking Tubing 2
The membrane is selectively permeable to small molecules (e.g. oxygen, carbon dioxide and water).
Larger molecules such as dissolved food pass through more slowly.
Even larger molecules cannot pass through at all. All this is due to the tiny pores (holes) in the membrane.
Diffusion in Multicellular Organisms
• Diffusion is very important in the lungs.
• When you breath in, the concentration of oxygen is higher in the lungs than in the blood.
• Therefore oxygen diffuses from the
to the and CO2 diffuses from the to the .
Questions1. What is the definition of diffusion?2. Why is diffusion an example of passive
transport?3. Why is the cell membrane called selectively
permeable?4. What effect will a uniform concentration have
on diffusion?5. Glucose is constantly used up in the cell. Why
does this help diffusion to continue?6. Why is diffusion important in multicellular
organisms?
What molecules move by diffusion?
Oxygen
Carbon Dioxide
Glucose
Water
Odd one out?
Osmosis
• The movement of water from an area of high concentration to an area of low concentration through a selectively permeable membrane.
Drowning Gummies
The drowning gummies exptYou will be adding gummy sweets to different solutions and observing what happens to the sweets.
Before starting we need the vital statistics of your new gummy friends
The measurementsYou will have 3 gummy friends to ‘play’ with.
You need measurements for each one (so 3 tables)
The MethodSet up the experiment as shown below using your chosen
gummies
Tap water 40% salt water
The ResultsWhen instructed remove your gummies on to a paper towel and complete the ‘After’ measurements.
Use the ‘mass’ measurements to calculate and % change in mass
% change in mass = change in mass x 100 initial mass
Use the information about change in mass to graph your results
• Analysis: In your own words explain the difference between the three gummies and what you think was happening.
• Evaluation: Is there anything could be done to improve the experiment?