St. George's College
Subject: BIOLOGY Teacher's notes
The Cell Membrane
Date: April 1st
Link and Learn
8th Milton ‐ The Cell Theory Name
Marcelo Antonella Paulo Sergio María Fernanda Alejandro Alejandra Brenda Almendra Diego Anna Paula Gabriel Sandra E‐C Maia Valeria María Belén Cristina Alfredo Giuliana Joshua Kinley Arianne María Gracia Sandra M. Fiorella Gonzalo N. Rodrigo Giulia Paolo Gonzalo R. Giorgio Jaime Stefano Bruno Nicolás María Claudia
CELL: SIZE AND SHAPE
• All substances that pass in or out of the cells have to go through the surface of the cell. • The larger the cell, the more nutrients it can take up and more wastes it has to release. • Cell size is limited by a cell's surface area : volume ratio. • A cell's ability to exchange materials can be assessed by calculating the cell's surface area : volume ratio.
m 4 c
Cube A Surface Area of one face Surface Area of Cube Volume of Cube Ratio: Surface Area/Volume
1 cm x 1 cm = 1 cm2 6 x 1 cm = 6 cm2 1 cm x 1 cm x 1 cm = 1 cm3 6 cm2 / 1 cm3 = 6:1
What happens to the surface area/volume ratio as the cube increases in size?
SURFACE AREA/VOLUME Cell grows
• Which means that the cell volume increases a lot faster than its surface area. • As the cell gets bigger, more food and oxygen needs to be absorbed through its surface, eventually becoming too small. • The cell must now divide or die.
What does it do?
• Every cell is surrounded by a cell membrane. • The cell membrane protects the cell and helps move substances and messages in and out of the cell. • By regulating transport, the membrane helps the cell maintain constancy and order. • Membranes are also found in the majority of organelles present in eukaryotic cells.
HOMEOSTASIS • All living things respond to their environments in order to maintain the constancy and order, the HOMEOSTASIS. • It is the maintenance of stable internal conditions in a changing environment. • One way that a cell controls homeostasis is by controlling the movement of substances across the cell membrane.
Membrane Composition • The Cell Membrane is made out of a sea of phospholipids. • A Phospholipid is a specialized lipid (biomolecule) made of a phosphate "head", and two fatty acid "tails". • The phosphate head is polar and is attracted to water. • The fatty acid tails, instead, are non‐polar and repelled by water.
Phospholipids in Action • Depending on their components and the environment that surrounds them, lipids react differently forming enclosed environments, separating an inner and outer space.
Principles of Biochemistry ‐ Lehninger
LIPID BILAYER STRUCTURE • As there's water inside and outside of the cell, the phospholipids form a double layer called the lipid bilayer. • The non‐polar tails, hydrophobic, make up the interior of the lipid bilayer; and the polar heads, hydrophilic, point toward the surfaces of the lipid bilayer.
FLUID MOSAIC MODEL • Singer and Nicholson proposed this theory in 1972, suggesting the cell membrane as a lipid bilayer. • Further analysis found diverse proteins were located in the cell membrane "floating". • Some of these are intrinsic proteins, completely spanning the cell membrane. • Other proteins are extrinsic proteins, found either on the inner or the outer surface.
How fluid is the Membrane? • Depending on the type of fatty acid, saturated • or unsaturated, the membrane will be more or less fluid. • The membrane is more fluid when it is composed by more unsaturated fatty acids. • The shorter the fatty acid tails the more fluid the membrane. • The membrane is less fluid when it contains more cholesterol (steroid).
The Role of Proteins in the Membrane • Each membrane contains a diverse amount of proteins, this presence determines the function of the membrane. • These are the main types of proteins:
Channel proteins Active transport proteins Receptor proteins Enzymes
E‐Portfolio • Start the reading: Atherosclerosis, The New view • Correlate that information with the cell membrane topic. • Is our lifestyle affecting our health, and cell membranes, specifically? • Publish it in a wiki (select one of the members). • Just remember: CITE your SOURCES of INFORMATION, and USE YOUR OWN WORDS. Click below for the easy way
Click below for the right way
Debate Groups Alpha Group 1 Antonella Cristina Marcelo Joshua Gonzalo N. Gonzalo R.
Group 2 Diego Brenda Paulo Paolo Gabriel Ma. Gracia Group 3 Ma.Clau Giuliana Valeria Nicolas Alex Giorgio 21
Resources Used Slide (Group)
G1 ‐ 2 Image
G1 ‐ 3 Image
G1 ‐ 4 Image
G1 ‐ 6 Image
G1 ‐ 8 Image
G1 ‐ 10 Image
Principles of Biochemistry ‐ Lehninger
G1 ‐ 11 Image Phospholipid Animation Phospholipid
G1 ‐ 12 Image
Phospholipid structure http://bit.ly/CvjG
G1 ‐ 13 Image
Mosaic Fluid Model
G1 ‐ 14 Image
G1 ‐ 15 Images Fatty Acids, Cholesterol Principles of Biochemistry ‐ Lehninger Animations Cholesterol Unknown Unknown Fluid Membrane G1 ‐ 16 Animation Cell Membrane
G1 ‐ 18 Images E‐Portfolio Animation Puzzle pieces Copy and Paste Idea
http://bit.ly/W7ccA http://bit.ly/Dbbtf http://bit.ly/2ZxTj Notebook Gallery
Teacher's Notes This class has been designed to cover the topics of The Cell Membrane from Monday March 23rd till Friday March 27th. For further knowledge about this topic: 1. Conduct a thorough search under the topic: The Cell Membrane on the Web, books and magazines. 2. If findings are not specific, ask your teacher for suggestions.
Objectives • Identify and describe the components, properties and functions of the Cell Membrane. • Analyze The Fluid Mosaic Model of the Cell Membrane. • Describe the additional molecules that act on the cell membrane.
Note: All, or most, of the objectives will be covered during class time, however the student must be responsible for those objectives not covered or concluded.
Vocabulary • • • • • • • • •
Membrane: Lipids: Cholesterol: Mosaic: Proteins: Pumps: Ions: Phospholipids: Homeostasis:
Note: Most of the vocabulary words will be covered during class time, however the student must be responsible for those words not covered or concluded.
Link and Learn You can visit the following websites to improve your understanding on the present topic: • • • • • •
http://library.thinkquest.org/C004535/cell_membranes.html http://www.johnkyrk.com/cellmembrane.swf www.cellsalive.com http://learningandscience.blogspot.com http://bit.ly/hCg8Z http://bit.ly/15vd0q
Gerardo LAZARO Science Lead Teacher Email: firstname.lastname@example.org Wiki: http://science‐learning2009.wikispaces.com Blog: http://learningandscience.blogspot.com Twitter: http://twitter.com/glazaro