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::: {.wrap} ::: {.header} Image of Globe ::: {.courseTitle} SBI4U: Biology, Grade 12, University Preparation ::: Unit 1: Biochemistry ==================== Activity 2: Molecules of Life Working Together ---------------------------------------------- ::: ::: {.subNav} [Overview](overview.html) \|...

::: {.wrap} ::: {.header} Image of Globe ::: {.courseTitle} SBI4U: Biology, Grade 12, University Preparation ::: Unit 1: Biochemistry ==================== Activity 2: Molecules of Life Working Together ---------------------------------------------- ::: ::: {.subNav} [Overview](overview.html) \| [Expectations](expectations.html) \| **Content** \| [Assignment](assignment.html) ::: ### Content ------------------------------------------------------------------------ **Cell Processes** The molecules you have studied work together in various parts of the cell to help the cell carry out its life functions. Let's look at how cells allow materials to enter and exit the cell. **Diffusion** Small molecules, such as water and oxygen move in and out of the cell through diffusion.  Diffusion is the movement of molecules from an area of high concentration to an area of low concentration.  In the top diagram, the gas molecules diffuse from a highly concentrated area and spread to a low concentrated area to fill the space. When you smell a person wearing perfume, this is an example of diffusion. The perfume particles spread by diffusion from the person wearing the perfume to your nose.  Diffusion is a natural process and does not require energy to be expended by the cell. [{.border width="156" height="100"}](images/difuse_lrg.png) [Diffusion]{.caption} [This is a diagram of molecules moving across the bilayer of a cell membrane.](images/simple_diffusion_lrg.png) +-----------------------------------+-----------------------------------+ | ::: {data-align="center"} | **Osmosis** | | [{.b | concentration through a | | order | semi-permeable membrane. | | width="300" | | | height="157"}](images/osmosis_lrg | In the first diagram, water moves | |.png) | from the inside of the cell to | | [Osmosis ]{.caption} | the outside.  As a result the red | | ::: | blood cells appear to shrink. | | | Molecules always move from an | | | area of high concentration to an | | | area of low concentration. | +-----------------------------------+-----------------------------------+ The solution on the outside is said to be hypertonic because it has a lower water concentration than the solution inside the cell. When the water concentration is the same inside and outside the cell, the solution is said to be isotonic. There is no net movement because the concentration of water is the same. (Water molecules do move in and out of the cell, but they move at the same rate.)  In a hypotonic solution, there is more water outside the cell than inside. Therefore the water moves into the cell where the concentration of water is lower and the red blood cell expands. +-----------------------------------------------------------------------+ | ::: {data-align="center"} | | [This is a diagram of molecules moving across the plasma membrane | | using a protein to carry it across.](images/facilitated_lrg.png) | | [Faciliated Diffusion]{.caption} | | ::: | +-----------------------------------------------------------------------+ **Facilitated Diffusion** This is another form of diffusion that does not require energy.  In facilitated diffusion, a transmembrane carrier protein is used to transport large molecules across the cell membrane. When the molecule lands on the protein, the protein changes shape and flips inside out releasing the molecule inside the cell membrane. This protein is a transmembrane protein that spans the plasma membrane and is also referred to as a carrier channel.  Protein channels are open pores that allow only certain molecules or ions to pass through. Passage is usually dependent on the charge and size of the particle.  In the diagram, the particles still move passively (without expending energy), from an area of high concentration in the extracellular space to an area of low concentration in the intracellular space. Diffusion, osmosis and facilitated diffusion are all examples of passive transport meaning that they do not require energy from the cell to cross the cell membrane. **Active Transport** +:---------------------------------:+-----------------------------------+ | [{.border | the opposite direction of | | width="400" | naturally occurring diffusion and | | height="180"}](images/sodium-pota | therefore requires energy.  This | | ssium_lrg.png) | energy is supplied by the cell in | | [Na+- K+ Pump]{.caption} | the form of ATP -- adenosine | | | triphosphate.  The diagram shows | | | a transmembrane protein called | | | the Na+- K+ pump.   Na+ is pumped | | | out of the cell and K+ is pumped | | | into the cell. This process uses | | | up a molecule of ATP.  | +-----------------------------------+-----------------------------------+ +-----------------------------------+:---------------------------------:+ | **ATP** | This is a diagram of ATP -- a | | | nucleotide with three phosphate | | ATP or adenosine triphosphate is | groups. [ATP]{.caption} | | the molecule that carries energy | | | in the cell.  When the cell needs | | | energy, ATP is broken down by | | | removing a phosphate group and | | | releasing the energy to where it | | | is needed in the cell.  This is | | | done through a hydrolysis | | | reaction. Although molecules like | | | glucose carry energy, that energy | | | is not available for immediate | | | use in the cell. This is the role | | | of ATP. As you will learn in | | | later activities, the energy | | | stored in molecules like glucose | | | must first be transferred to | | | energy carrier molecules like ATP | | | before it is of use in the | | | cell.    | | +-----------------------------------+-----------------------------------+ #### []{#return}Did you know? +-----------------------------------+-----------------------------------+ | {.i | important role in transmission | | con} | within the nerve cell. Without it | | | you would not be able to react, | | | move, think, or feel. | +-----------------------------------+-----------------------------------+ \ +-----------------------------------+-----------------------------------+ | external link icon | Learn more about movement across | | | the cell membrane. | | | | | | \ | | | [ Osmosis & | | | Diffusion](http://www.diffen.com/ | | | difference/Diffusion_vs_Osmosis)\ | | | [Active | | | Transport](http://www.biology-onl | | | ine.org/dictionary/Active_transpo | | | rt)\ | | | [Co-Transport](http://physioweb.m | | | ed.uvm.edu/bodyfluids/membrane.ht | | | m)\ | | | [Secondary | | | Transport](http://www.bio-medicin | | | e.org/biology-definition/Active_t | | | ransport/) | +-----------------------------------+-----------------------------------+ \ \ ::: {.dropbox} {.icon} **Portfolio:** *Notes help prepare you for tests. Keep all of your notes in your portfolio.* *Be prepared to submit your portfolio notes and organizers to your teacher for assessment at various times during the course.* Use your portfolio to research the following:  transport in cells, osmosis, diffusion, active transport -- primary and secondary and co-transport. ::: [Back](content_02.html) \| [Next](content_04.html) This is a disclaimer. External Resources will open in a new window. Not responsible for external content.\ Unless otherwise indicated, all images in this Activity are from the public domain or are © clipart.com or Microsoft clipart and are used with permission. ------------------------------------------------------------------------ ::: {.subNav} [Overview](overview.html) \| [Expectations](expectations.html) \| **Content** \| [Assignment](assignment.html) ::: :::