Download - Movement through Cells
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All organisms are made of cellsCells are mostly liquid. Surrounding the cells is also liquid.
Movement through Cells
Inside Cell
Cell membrane
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The cell membrane separates the cell from the liquid it is bathed in.
a) It allows only certain particles to enters and leave the cell. Therefore the cell membrane is considered
____________________
Role of the Cell Membrane
Selectively Permeable
lipid bilayerprotein channels
b) The cell membrane is made up of two parts:
___________________________
____________________________
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Large particles can only enter and exit the cell through the protein channels BUT
Small particles can enter and exit straight through the lipid bilayer!!
Role of the Cell Membrane
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All particles of matter--atoms or molecules are constantly in motion. In liquids, the molecules randomly move.*A solution is made when particles of sugar,
salt, or oxygen, etc. are dissolved in liquids
Particles of liquids
= solution+
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What is a solution? Liquid mixture of 2 or
more substances. Water - solventThe substance dissolved
in the water - soluteConcentration =
mass of solute/volume of solvent
Concentration is similar to density.
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Imagine you have a beaker filled with sugar water.
Problem: Imagine you add double the amount of sugar to the water.
Which beaker
contains a more
concentrated sugar
solution?
Sugar
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Concentration of SolutionsMolarity (M) = unit of concentration used in
biochemistryThe greater the molarity of a solution the
greater the concentration. 0.25M sucrose solution (read as 0.25 molar)
has half of the concentration of a 0.50M sucrose solution.
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Particles within an organism must continuously enter and exit the cell through the cell membrane using one of four processes:• Diffusion• Osmosis• Facilitated diffusion• Active transport
Particles in solution cross the cell membrane
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The movement of a substance (liquid or gas) from areas of high concentration to areas of low concentration.
The motion is random --eventually all particles spread out evenly throughout the solution = equilibrium.
Diffusion
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Food coloring (solute)+ water (solvent). What do you think will happen over time in
the solution? Discuss at table and draw on white board.
Diffusion Demonstration
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Once equilibrium is reached, the movement of particles continues, but it is equal in all directions.
Solution remains in equilibrium. Particles remain equally spaced out.*See molecular workbench and answer
questions. (p1-6)
Diffusion
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The cell membrane allows many types of particles (ions, atoms, molecules) to move in and out of the cell by diffusion.
But some types of molecules are not able to cross the membrane.
What determines whether a particle can cross the cell membrane?
Diffusion Across a Cell Membrane
Complete Worksheet to find out!
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Design an experiment to test the effect of the size of a particle on its ability to diffuse. Your materials:
Diffusion Across a Cell Membrane
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Small particles diffuse __________ than large particles across a cell membrane
• Only substances that can permeate the cell membrane can diffuse across it.
• Diffusion occurs from areas of ________concentration of solute particles to areas of ________ concentration.
• The movement of particles is always taking place.
Conclusions for Diffusion: faster
The cell expends NO ENERGY on the process of diffusion
high low
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Particles dissolved in water cross the cell membrane
•Diffusion•Osmosis
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Diffusion of water through a selectively permeable membrane. Water diffuses from where there is less solute (sugar, salt, etc.) to where there is more solute.
Osmotic pressure is the force that is placed on a selectively permeable membrane due to the flow of water into one side more than the other.
See molecular workbench and answer questions
Osmosis: A special type of diffusion
OSMOTIC PRESSURE-placed on semipermeable membrane
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Osmosis:Osmosis results in equilibrium when the
concentration of the solutions is equal on both sides of the membrane. A solution in equilibrium is also referred to as isotonic.
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When solutions on both sides of the cell membrane do not have equal concentration they are described as hypotonic or hypertonic.
Hypotonic = lower concentration of soluteHypertonic = higher concentration of solute
Osmosis
Overall Direction of Water flow
Inside cell
Outside cell
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Osmosis in AnimalsAt your table: Draw a picture illustrating #1 and
#2 below and answer the questions! Use arrows to show the movement of water.
1. What happens if blood cells are placed in a hypertonic (more concentrated) solution? (saltwater)*
2. What happens if blood cells are placed in a hypotonic (less concentrated) solution?(distilled water)*
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Osmosis in Animals
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Osmosis in AnimalsUnder normal bodily conditions, blood is the
liquid that surround the cells. Blood has the same concentration of solutes as
those inside the cell. This means that blood and cytoplasm are ______________________ to each other.
isotonic
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Osmosis in Plants
1) What happens if plant cells are placed in a hypertonic solution (example: salt water)?
2) What happens if plant cells are placed in a hypotonic solution (example: distilled water)?
3) What happens if plant cells are placed in an isotonic solution (example: water with minerals)?
Healthy Plant
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A plant cell is filled with proteins, sugars, salts.
The cytoplasm of plant cells is more concentrated than fresh water
The plant cell is hypertonic relative to freshwater
Since freshwater is used to water plants (not blood), the plant cells fill up with water.
Osmotic Pressure = Pressure created by water moving into a hypertonic cell.
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With your table answer the following question:
Why doesn’t a plant cell burst (like a blood cell) when placed in freshwater? (Hint: What is a MAJOR difference between plant and animal cells?)
Osmotic Pressure = Pressure created by water moving into a hypertonic cell.
Cell Wall is RIGID
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In one-celled organisms the cell does not burst when in a hypotonic solution (for example pond water).
One-celled organisms have mini-pumps called contractile vacuoles. As water enters the cell, it is pumped out by this organelle.
Osmosis in one-celled organisms
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Because osmosis is a special type of diffusion
Osmosis:
The cell expends NO ENERGY on osmosis
Now: Complete Worksheet on OSMOSIS
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Particles cross the cell membrane
•Diffusion•Osmosis•Facilitated diffusion•Active transport
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Movement of specific molecules through protein channels in the cell membrane
The protein channels are specific to a type of particle. Example: glucose moves through a protein channel that is specific to glucose.
Facilitated Diffusion
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The movement of particles is two ways but always from areas of high concentration (hypertonic) to areas of low concentration (hypotonic).
Cells use facilitated diffusion for substances such as salt, sugars and starches*.
Facilitated Diffusion
The cell expends no energy on facilitated diffusion.
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Particles cross the cell membrane
•Diffusion•Osmosis•Facilitated diffusion•Active transport
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Active Transport: Movement of material across the cell membrane in the OPPOSITE direction of diffusion.
During diffusion particles always moves in the direction of high concentration to low concentration (=concentration gradient).
During active transport particles move against the concentration gradient from low concentration to high concentration.
Active Transport
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Because the flow of solute is from an area of LESS concentration to an area of MORE concentration the solute must be pumped by the cell*.
See molecular workbench.
Complete Packet on Transport through a Cell Membrane
Active Transport
The cell EXPENDS ENERGY (found in molecules of ATP) on Active Transport
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You will be assigned an article on a topic with a group of students. Read and discuss the article with your group and present the information to the class…as a poster, as a play, as a song, etc.
Topics Facilitated diffusion, insulin and diabetesDiffusion of oxygen into our lungs and emphysema Diffusion and alcoholPregnancy and diffusion of nutrients between
mother and fetus.
Connections to Daily Life