Cell membrane and selective permeability

Amber Vang

Cell membranes

Cell membranes are barriers around the cell. The job of the cell membrane is to protect and support cells, which lets them interact with their surroundings. Cell membranes contain phospholipid molecules, embedded proteins, lipid bilayers, and cholesterol.

Phospholipids

Phospholipids are molecules composed of hydrophobic and hydrophilic properties. The hydrophobic lipid tails are made of fatty acids connected to the glycerol. The hydrophilic phosphate groups are placed toward the aqueous cytosol.

Embedded proteins

Embedded proteins also contain hydrophobic and hydrophilic properties as well. The hydrophobic proteins are nonpolar side groups. Nonpolar molecules can simply move across the membrane. The hydrophilic proteins are polar side groups. Polar molecules move across the membrane through transport proteins.

Cell membranes and cell walls

Animals, plants, fungi, and protists mainly have cell membranes and walls. However, an animal cell does not contain a cell wall. Overall, the cell membrane’s purpose is to protect the cells and interact with their surroundings.

Selective permeability

Selective permeability is when a cell membrane lets molecules or ions go through it by the process of active or passive transport. Active transport requires the cell to waste energy to move materials. Passive transport does not require cellular energy.

Selective permeability

Facilitated diffusion is a passive transport. Facilitated diffusion allows compounds like sugars and amino acids in. The K+/NA+ pump is active transport. The pump moves K and NA against gradients. The process requires energy. When the energy is being used, ATP falls off and is converted into ADP.

Citations"Biology Ch.7 PDF." Cells. N.p., n.d. Web. 03 Dec. 2015. <https://docs.google.com/a/muhsdstudents.org/viewer?a=v&pid=sites&srcid=bXVoc2Qub3JnfGV0ZXh0c3xneDo1ZmNjNDA2ODhkMGMxYjQx>.

"Selectively Permeable Membranes: Definition & Examples." Study.com. Study.com, n.d. Web. 03 Dec. 2015. <

http://study.com/academy/lesson/selectively-permeable-membranes-definition-examples-quiz.html>.

"Membranes." IB Guides. IB Guides, 2012. Web. 3 Dec. 2015. <http://ibguides.com/biology/notes/membranes>.

"How a Phospholipid Bilayer Is Both Hydrophobic and Hydrophilic."Study.com. Study.com, n.d. Web. 03 Dec. 2015. <

http://study.com/academy/lesson/how-a-phospholipid-bilayer-is-both-hydrophobic-and-hydrophilic.html>.

"Plasma Membrane." Molecular Expressions. Cell Biology, 1 Oct. 2000. Web. 3 Dec. 2015. <

http://micro.magnet.fsu.edu/cells/plasmamembrane/plasmamembrane.html>.

"Cell Wall." UCSB Science Line. UCSB Science Line, 2015. Web. 3 Dec. 2015. <http://scienceline.ucsb.edu/getkey.php?key=4753>.

"Na+/K+ (Sodium/Potassium) Pump." ZeroBio. ZeroBio, n.d. Web. 3 Dec. 2015. <http://www.zerobio.com/central/na_k.htm>.