Chapter 5 - Chapter 5 What Is the Structure of a Biological...

Info icon This preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Chapter 5 What Is the Structure of a Biological Membrane? Cell membranes are bilayered, dynamic structures that: Perform vital physiological roles Form boundaries between cells and their environments Regulate movement of molecules into and out of cells Lipids, proteins, and carbohydrates in various combinations make these tasks possible. The lipid portion of a cell membrane is a barrier for water-soluble molecules. The general design is called the fluid mosaic model The phospholipid bilayer is like a “lake” in which a variety of proteins “float.” Membrane proteins embedded in phospholipid bilayer Carbohydrates attach to lipid or protein molecules on the membrane. Membrane core is hydrophobic region Exterior and interior are hydrophilic regions Membranes vary in lipid composition Phospholipids vary – fatty acid chain length, degree of saturation, phosphate groups Membranes may be up to 25% cholesterol Cholesterol concentration varies to increase or decrease fluidity Fluidity also depends on temperature and the degree of saturation of fatty acids Membranes of cells that live at low temperatures tend to be high in unsaturated (kinked) and short-chain fatty acids to maintain optimal fluidity. All biological membranes contain proteins Protein to phospholipid ratio varies depending on membrane function Many membrane proteins have hydrophilic and hydrophobic regions (or domains) Membrane proteins and lipids are independent – only interact non covalently Both lipids and proteins are free to move around laterally , but do not “flip-flop” Integral membrane proteins have hydrophobic regions that penetrate or entirely cross phospholipid bilayer Transmembrane proteins have a specific orientation, showing different “faces” on either side of membrane, each with different properties Peripheral membrane proteins lack hydrophobic regions and are not embedded in bilayer Some membrane proteins can move freely within bilayer Others are anchored to a specific region Some can be anchored by cytoskeleton elements, or… lipid rafts lipids in semisolid state Membranes are dynamic and are constantly forming, transforming, fusing, and breaking down
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
How Is the Plasma Membrane Involved In Cell Adhesion and Recognition? Some cells have carbohydrates on the external surface Glycolipid – carbohydrate bound to lipid Glycoprotein – c arbo-hydrates bound to protein Plasma membrane glycoproteins enable cells to be recognized by other cells and proteins.
Image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern