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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 ------------------------------------------------------------------------ For cells to live, they must exchange materials with their external environment.  In order to do that, material must pass in and out of the cell membrane.  The cell membrane is also called the plasma membrane.  Let's take a closer look at the components of the membrane. +-----------------------------------+:---------------------------------:+ | **Fluid Mosaic Model ** | [{.border | | cell membrane is a mosaic of | width="365" | | various macromolecules that are | height="150"}](images/Cell_membra | | fluid (capable of motion) within | ne2_lrg.png) | | the membrane.  Although the | [Fluid Mosaic Model]{.caption} | | membrane is not rigid, it does | | | protect the cell structurally. | | | | | | **Bilayer** | | +-----------------------------------+-----------------------------------+ +:---------------------------------:+-----------------------------------+ | [This is a diagram of four | The main component of the cell | | phospholipid | membrane is the phospholipid | | molecules.](images/Phospholipid_l | bilayer.  The bilayer is composed | | rg.png)[Phospholipid\ | of many phospholipd molecules.  | | \ | Recall the structure of a | | 1. hydrophilic head 2. | phospholipid.  It is made of two | | hydrophobic tails A. | fatty acids which are hydrophobic | | phosphatidylcholine B. | (called the tail) and a phosphate | | phosphatidylethanolamine C. | group which is hydrophilic | | phosphatidylserine ]{.caption} | (called the head).  Another | | | component of the head is a short | | | carbon chain which is also polar | | | and hydrophilic.  These carbon | | | chains distinguish between the | | | various types of phospholipids | | | shown as A, B, and C in the | | | diagram. | | | | | | The hydrophobic tails orient | | | themselves away from water and | | | face towards the inside of the | | | bilayer.  The heads face | | | outwards, towards the | | | intercellular and extracellular | | | fluid which consists mainly of | | | water. | +-----------------------------------+-----------------------------------+ **Proteins** Proteins are found in the plasma membrane.  They have various functions such as acting as channels, receptor sites, connectors, identification markers, and more. Some of the proteins rest on one side or the other of the membrane.  These are called peripheral proteins or monotopic proteins.  Other proteins span both sides of the membrane. These proteins  are called transmembrane or integral proteins.  Many proteins have a quaternary structure and are made of several polypeptide chains.  The insulin receptor found on the surface of the cell membrane has a quaternary structure and is made of an alpha and beta subunit.  The alpha subunit binds to the hormone insulin.  The beta subunit breaks ATP for energy. Some proteins have sugars/ carbohydrates attached to the surface.  These proteins are referred to as glycoproteins. ::: {data-align="center"} [{.border width="202" height="150"}](images/Cell_membrane_protein_lrg.png)[Cell Membrane]{.caption} ::: 1. phospholipid 2. cholesterol 3. glycolipid 4. sugar 5. polytopic protein (transmembrane protein) 6. monotopic protein (here, a glycoprotein) 7. monotopic protein anhcored by a phospholipid 8. peripheral membrane protein (here, a glycoprotein) +:---------------------------------:+-----------------------------------+ | [A diagram of various types of | Other parts of the membrane | | proteins found in the membrane as | include molecules of cholesterol | | well as showing the bilayer and | with adds to the structural | | phospholipid up | integrity of the membrane.  | | close.](images/Cell_membrane_lrg. | Glycolipids form when a | | png)[Components | carbohydrate attaches to a lipid | | of Fluid Mosaic Model]{.caption} | (fat) molecule.  | | | | | | The cell membrane is very small | | | and appears as a line through a | | | light microscope.  The bilayer | | | and all its components can be | | | seen in detail through an | | | electron microscope. | | | | | |   | | | | | |   | | | | | |   | +-----------------------------------+-----------------------------------+ \ +-----------------------------------+-----------------------------------+ | { | membrane. | |.icon} | | | | \ | | | [Cell | | | Membrane](http://www.infoplease.c | | | om/cig/biology/fluid-mosaic-model | | | -membrane-structure-function.html | | | ) | +-----------------------------------+-----------------------------------+ \ \ ::: {.dropbox} Portfolio 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:  Fluid Mosaic Model, membrane proteins and functions of the cell membrane. ::: [Back](content.html) \| [Next](content_03.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) ::: :::