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Transcript
Lesson #3.2Cell Membrane About the Cell (Plasma) Membrane… • Purpose is to separate the cell’s contents (inside of cell) from the external environment • It is present in ALL living things o animals, plants, fungi, protists and bacteria • Controls what enters and exits the cell • It is used by the cell to take in nutrients from the outside environment and get rid of wastes Structure of Membrane… • The membrane is made of lipids and proteins • It is a double layer of phospholipids, called a phospholipid bilayer Structure of Membrane… • The phospholipid is made up of a phosphate group and a lipid • The phosphate group is hydrophilic (or polar), meaning it mixes in water (water soluble) • The lipid tails are hydrophobic (or non-polar), they do not mix in water (not water soluble Water-loving Water-hating Structure of Membrane… • The phosphate groups are on the outside of the membrane, that means they face the inside of the cell and the outside of the cell • The lipids are buried in the inner part of the membrane and face each other Structure of Membrane… • Many different protein molecules are found embedded in the cell membrane • Phospholipids make up most of the structure; proteins carry most of the functions Structure of Membrane… • Many different protein molecules are found embedded in the cell membrane • Integral proteins go right through the cell membrane-from one side all the way to the other side, peripheral proteins are found on only one side of the membrane Function of Membrane… 1. Transport • • • Some of the proteins embedded in the membrane make it selectively permeable = this means the proteins (transport proteins) control which materials can enter and leave the cell Nutrients enter the cell and wastes are removed Ex. Na+/K+ pump proteins in nerve cells cause electrical signals to flow along nerves Function of Membrane… 2. Receptor Sites • • Other membrane proteins bind specific substances that control how the cell functions these are receptor proteins Ex. Insulin is a hormone that attaches itself to specific receptor proteins embedded in the cell membrane, this causes the protein to open and let sugar molecules inside the cell Function of Membrane… 3. Identity • Certain membrane proteins are used to give cells their identity to the immune system Ex. ABO blood types immune system recognizes our own blood type, but attacks foreign blood types • • This is why transplants are sometimes rejected Activity and Homework 1.Read pages 47-49 – Skip Liposomes and Aquaculture 2.Answer questions on page 49 #1,2,5 (Homework check) 3.Start Cell Membrane and Transport PACKAGE, only do questions 1-6