Chapter 4 - Structure and Function of the Plasma Membrane | BIO 214 - Principles of Cell Biology, Quizzes of Cell Biology

Download Chapter 4 - Structure and Function of the Plasma Membrane | BIO 214 - Principles of Cell Biology and more Quizzes Cell Biology in PDF only on Docsity! TERM 1 Why do phospholipids associate into bilayer structures? DEFINITION 1 Energetically favored orientation for the polar head groups -- facing the aqueous compartments outside of the bilayer TERM 2 peripheral proteins DEFINITION 2 Location: entirely outside the lipid bilayer associated with the surface of the membrane by noncovalent (weak electrostatic) bonds (attached to the membrane by weak bonds/easily solubilized) TERM 3 integral proteins DEFINITION 3 Location: penetrate/pass entirely through lipid bilayer have domains that protrude from both the extracellular & cytoplasmic sides of the membrane TERM 4 transmembrane domains DEFINITION 4 segments of integral proteinsembedded in the membrane- consist of a string of about 20 predominantly nonpolar amino acids that span the core of the lipid bilayer as an alpha helix TERM 5 lipid-anchored proteins DEFINITION 5 Location: outside of the lipid bilayer covalently linked to a lipid molecule situated within the bilayer. TERM 6 What are the three types of membrane proteins? DEFINITION 6 integral proteins peripheral proteins [noncovalent] lipid-anchored proteins [covalent] TERM 7 freeze-fracture replication DEFINITION 7 technique from which was derived the concept that proteins penetrate through membranes.- tissue is frozen and struck with a knife blade.- fracture plane goes between the two lipid bilayers- marked with metals to form metallic replica TERM 8 Carbohydrates DEFINITION 8 covalently linked to lipids and proteins on the extracellular surface of the bilayer. TERM 9 glycoproteins DEFINITION 9 proteins that have short, branched carbohydrates for interactions with other cells and structures outside the cell TERM 10 glycolipids DEFINITION 10 lipids with larger carbohydrate chains that may be cell-to-cell recognition sites TERM 21 What are the three main classes of lipids? DEFINITION 21 phospholipids [includes phosphoglycerides] sphingolipids [includes glycolipids, ceramides, cholesterol TERM 22 What is the benefit of membrane fluidity? DEFINITION 22 It provides a compromise between structural rigidity and complete fluidity. Allows for interactions to take place within the membrane.- in a rigid ordered structure, mobility would be absent.- in a completely fluid nonviscous liquid, components of the membrane could not be oriented; structural organization and mechanical support would be lacking. TERM 23 membrane assembly DEFINITION 23 Membranes arise only from preexisting membranes. Growth is accomplished by insertion of lipids and proteins into the fluid matrix. TERM 24 maintaining membrane fluidity DEFINITION 24 Organisms remodel their membranes by changing the lipid makeup to account for temperature fluctuations. This is an example of homeostasis.Remodeling the lipid bilayers involves saturation or desaturation of acyl chains, and replacement of acyl chains by phospholipases or acyltransferases. TERM 25 lipid rafts DEFINITION 25 Cholesterol and sphingolipids pack together to form highly-ordered microdomains. (These provide a favorable environment for cell- surface receptors and GPI-anchored proteins.)These are only observed in artificial bilayers and biologists are unsure whether or not they exist in living cells.The notion of inserting order into chaos is an attractive one; lipid rafts organize the membrane into functional compartments. TERM 26 What is the primary method of substance transport across cell membranes? DEFINITION 26 DIFFUSION. TERM 27 diffusion DEFINITION 27 The spontaneous process in which a substance moves from a region of high concentration to a region of low concentration, eventually eliminating the concentration difference between the two regions.Exergonic process, driven by an increase in entropy. TERM 28 net flux DEFINITION 28 Indicates that the movement of a substance into the cell (influx) and out of the cell (efflux) is not balanced, but that one actually exceeds the other. TERM 29 What does the free energy change depend on, during diffusion of nonelectrolytes? DEFINITION 29 The concentration gradient. TERM 30 What does the free energy change depend on, during diffusion of electrolytes? DEFINITION 30 The electrochemical gradient.-- chemical gradient - determined by concentration difference-- electric potential gradient - determined by the difference in charge TERM 31 facilitated diffusion DEFINITION 31 Passive, specific, saturable, and regulated -- for getting substances across membranes that can't fit otherwise - usually large or hydrophilic substances. Transmembrane proteins are usually the facilitative transporters.They don't transport as much as ion channels. TERM 32 ion channels DEFINITION 32 Openings in the membrane that are permeable only to specific ions.Always from a state of higher to lower energy. TERM 33 What's the difference between 'hypertonic,' 'hypotonic,' and 'isotonic'? DEFINITION 33 Hypotonic describes the compartment of lower solute concentration Hypertonic describes the compartment of higher solute concentration Isotonic refers to the state at which the internal solute concentration equals the external solute concentration TERM 34 active transport DEFINITION 34 Active transport is the movement of a substance against its concentration gradient.Coupled to ATP hydrolysis. TERM 35 plasmolysis DEFINITION 35 When a plant cell is placed into a hypertonic medium, its volume shrinks as the plasma membrane pulls away from the surrounding cell wall.Plasmolysis is the process in plant cells where the cytoplasm pulls away from the cell wall due to the loss of water through osmosis. plant cells are usually hypertonic compared to their fluid environment.