permeability - connected to the other population of...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
To work properly with active enzymes and appropriate permeability, membranes must be fluid, about as fluid as salad oil. Cells can alter the lipid composition of membranes to compensate for changes in fluidity caused by changing temperatures. For example, cold-adapted organisms, such as winter wheat, increase the percentage of unsaturated phospholipids in the autumn. This allows these organisms to prevent their membranes from solidifying during winter. 2. Membranes are mosaics of structure and function A membrane is a collage of different proteins embedded in the fluid matrix of the lipid bilayer. Proteins determine most of the membrane’s specific functions. The plasma membrane and the membranes of the various organelles each have unique collections of proteins. There are two populations of membrane proteins. Peripheral proteins are not embedded in the lipid bilayer at all. Instead, they are loosely bounded to the surface of the protein, often
Image of page 1

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

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: connected to the other population of membrane proteins. • Integral proteins penetrate the hydrophobic core of the lipid bilayer, often completely spanning the membrane (a transmembrane protein). • Where they contact the core, they have hydrophobic regions with nonpolar amino acids, often coiled into alpha helices. • Where they are in contact with the aqueous environment, they have hydrophilic regions of amino acids. • One role of membrane proteins is to reinforce the shape of a cell and provide a strong framework. • On the cytoplasmic side, some membrane proteins connect to the cytoskeleton. • On the exterior side, some membrane proteins attach to the fibers of the extracellular matrix. • Membranes have distinctive inside and outside faces. • The two layers may differ in lipid composition, and proteins in the membrane have a clear direction....
View Full 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