A&P plasma membrane

functions of membrane proteins

Transport proteins regulate the movement of substances across the membrane, some act as identity markers to communicate with other cells, some are enzymes taking part in chemical reactions, some act as anchoring sites, securing the cytoskeleton to the membrane and some are part of cell to cell attachments

Provide the protein type for each function described. These proteins provide a site on the internal surface of the membrane where microtubules, microfilaments, and intermediate filaments can attach: [a] These proteins allow cells to stick together: [b]

[a] anchoring site [b] cell-adhesion protein

This molecule is responsible for providing strength to the membrane and stabilizing it against temperature changes: [a] To which of the four macromolecules does this molecule belong? [b] Is this a polar or nonpolar molecule? [c] Would it be found among the heads of the phospholipid or the fatty acid tails of the phospholipid? [d]

[a] cholesterol [b] lipids [c] nonpolar [d] heads

Provide the protein type for each function described. These proteins catalyze reactions at the external or internal membrane surface: [a] These proteins are used by the cells in the immune system to distinguish between self and non-self: [b]

[a] enzymes [b] identity markers

What is the term used to refer to the coating of sugar that is important for cell-to-cell recognition? [a] What two molecules make up this structure? [b] [c] What does the prefix "glyco-" refer to? [d] Consider the name and using Fig 4.5 to help you, which part of the molecule would be integral in the membrane? [e]

[a] glycocalyx [b] & [c] glycolipids & glycoprotein [d] sugar [e] protein

In the plasma membrane, the proteins that are dispersed within the lipids make up about half of the plasma membrane by weight (p109). The functions of these proteins are critical for cell function. What is the general term for proteins that are embedded within and extend all the way across the plasma membrane? [a] What is the general term for proteins that are not embedded, but are found on the external or internal surface of the plasma membrane? [b]

[a] integral [b] peripheral

These molecules form the framework of the plasma membrane; they associate to form two sheets. [a] To which of the four macromolecules does this molecule belong? [b] What term is used to communicate that the structure is two sheets? [c] Is the portion of the molecule facing the interstitial fluid or the cytosol polar or nonpolar? [d] What is the name of the portion of the molecule that forms the inner structure of the plasma membrane? [e]

[a] phospholipid [b] lipids [c] phospholipid bilayer [d] polar [e] fatty acid tails

proteins

are also dispersed throughout the membrane and they have several key roles. There are two structural types of membrane proteins, integral proteins and peripheral proteins. Integral proteins are embedded in the membrane and extend across the membrane with many being glycoproteins, which are proteins with carbohydrates attached.

peripheral proteins

are attached to the internal or external surface of the membrane and many times they are attached to an integral protein

glycolipids

are lipids with carbohydrates attached to them, and they are found on the outer portion of the membrane, so they are exposed to the outside of a cell, or the interstitial fluid that surrounds cells. They help maintain the stability of the membrane and aide in cell recognition

cholesterol

is another molecule that is embedded in the plasma membrane. It helps strengthen and stabilize the membrane.

plasma membrane

is the outer boundary of a cell. It is composed mainly of a double layer of phospholipid molecules that are held together by chemical attractions. These phospholipid molecules have a polar hydrophilic water loving head and two non polar hydrophobic water fearing tails. The membrane is formed as the heads face out and the tails face in forming a bilayer that acts like a fence, as you can see here. The inner part of the cell called the cytosol is here, and the outside of the cell is here.

what macromolecules are found in the plasma membrane?

lipids, proteins, & carbs

carbohydrate portions...

of glycoproteins and glycolipids help to form what is called the glycocalyx, which is a sugar like coating on the outside of a cell's surface.