BIOL 101: MasteringBiology: CH. 6a – Flashcards

They contain nonpolar C-C and C-H bonds Since lipids contain nonpolar bonds, there are no partial charges on the atoms and nothing for water to be attracted to. Thus, lipids are hydrophobic.

transport protein The protein is allowing solute molecules to enter the cell.

B, C, and D Ions, such as H ions and hydrophilic molecules, such as water and glucose, cannot rapidly pass directly through phospholipids of a plasma membrane. To move rapidly thru membrane, they must pass thru membrane transport proteins.

E- NONE

preventing leakage from cells. Every cell depends on phospholipid bilayers to limit leakage of molecules thru *membranes* (phospholipid bilayers are found in cell membranes).

membranes Great majority of cell's phospholipids occur in membranes.

Ester Linkages. Like fats, phosphoglycerides are made by coupling fatty acids to glycerol by means of ester linkages.

All of the above

Water molecules make H bonds. H bonds in water exclude the nonpolar tails of phospholipids, forcing the molecules into a bilayer.

(c) tails; tails water on both sides of the memrane excludes the tails, forcing them into interior where they face one another, as shown.

Polar molecules attract one another. Polar molecules have trouble escaping from water to enter a membrane, and nonpolar molecules have trouble moving from membrane into water. Thus, neither kind of molecule moves easily thru membranes.

Phospholipid *amphipathic = molecule that possesses both hydrophobic and hydrophilic elements. * A Phospholipid has a strongly polar (charged) head and two nonpolar tails.

Both B and C. They are phospholipids. Water orients them because they are amphipathic.

All of the above. Phospholipids are close relatives of fats, but the difference makes them amphipathic and allows them to form the basis of membranes.

A-there is no change in the concentration of the molecule on either side of the membrane. Equilibrium is a dynamic state where molecules can still move, but there is no net change in concentrations.

diffusion diffusion is the movement of *particles down* their concentration gradient.

E- a greater proportion of unsaturated phospholipids The fluidity - ease with which lipids move in the plane of the bilayer. The fluidity of cell membranes depends on their *chemical composition and temperature:* At low temperatures the lipids within the bilayer are *not very mobile* and there are many stabilizing interactions. *Higher temperature, higher fluidity.* Lipids with *longer fatty acid chains* have more interactions between the hydrophobic fatty acid tails (predominantly van der Waals interactions), making the membrane *less fluid.* Saturated fatty acids are straight, contain no double bonds, and can pack more tightly than those that have double bonds. The kinks in the unsaturated chains simply make it more difficult to pack them in an orderly manner. So, the fluidity of bilayers containing *lipids rich in unsaturated fatty acids is greater* than the fluidity of bilayers containing lipids rich in saturated fatty acids. . By decreasing the mobility of a few methylene groups (CH2) in the fatty acids tails, cholesterol makes lipid bilayers less deformable and lessens their permeability to small water-soluble molecules. Therefore, *cholesterol makes membranes less fluid.* -http://sites.fas.harvard.edu/~lsci1a/10-19notes.pdf

more fluid bilayers From above: less saturated (more unsaturated) means higher fluidity because unsaturated fats have kinks. See figure.

lipids are largely hydrophobic. Process of Elimination: Lipids = hydrophobic -> no bond with water. Carbs, proteins, and nucleic acids also contain carbon and are also so large that they don't readily diffuse thru the plasma membrane a

B- Adding cholesterol reduces permeability because its steroid rings fill gaps in the hydrophobic membrane interior. *Increase cholesterol-> decrease permeability and vice-versa Increase temperature-> increase permeability and vice-versa* Cholesterol's bulky steroid rings result in a denser membrane interior, making it more difficult for materials to pass through.

C- The polarity of membrane phospholipids Phospholipids contain both a polar head and a nonpolar hydrocarbon tail, both of which are necessary for their ability to form membrane bilayers. Factors that affect permeability: -cholesterol -temperature -saturation of tails

Lipids are mostly nonpolar. Lipids are nonpolar molecules, whereas sugars are polar. Process of Elimination: a-Lipid=hydrophobic. b-"only" - too extreme answer d-there are unsaturated lipids.

True. Osmosis is the diffusion of water across a selectively permeable membrane.

amphipathic nature Detergents form micelles around the grease, which are then washed away because polar head groups facing outward on micelle are water-soluble. See figure.

Oxygen Small, nonpolar molecules such as oxygen can diffuse across cell membranes.

True. The hydrophilic, or water-loving, portion of a phospholipid is the polar head, whereas the hydrophobic portion is the nonpolar tail.

Hypotonic salt concentration in solution is lower than it is in cell, so water enters the cell, causing it to burst. See figure.

Hypertonic A hypertonic solution has more solutes than a second solution to which it is being compared.

osmosis it is the passive transport of water.

hypertonic There is greater concentration of solute outside the cell.

hypotonic...swelled a cell will gain water when placed in a hypotonic solution

in a hypotonic solution in a hypotonic solution plant cells experience a net gain of water and become turgid.

hypertonic solution...lost water a cell will lose water when placed in a hypertonic solution.

RNA it is a nucleic acid.

saturated fat fatty acids tails lack double bonds and therefore no kinks.

phospholipids are composed of a phosphate group, a glycerol, and fatty acids.

olive oil it is a plat oil, and most plant oils are rich in unsaturated fats.

as a component of animal cell membranes Cholesterol is an important component of animal cell membranes.

Both hyphilic and hydrophobic regions Amphipathic (dual-sympathy) molecules contain both hydrophilic and hydrophobic regions.