Chapter 6: Lipids and membranes

A food company hydrogenated a barrel of fat. The treatment ... (a) made the fat less fluid. (b) made the fat less saturated. (c) lengthened the fat tails. (d) put more bends (kinks) in the fat tails. Both (a) and (d).

(a) made the fat less fluid. **Hydrogenation removes double bonds, so the tails can straighten. Do you know why that makes the fats less fluid?

What do fats, steroids, and waxes have in common? (a) Moderate polarity. (b) Low solubility in water. (c) They occur in membranes. Both (a) and (c). Both (b) and (c).

(b) Low solubility in water. Low water solubility is the trait that defines lipids

Phospholipids

- Amphipathic (both hydrophilic and hydrophobic regions)

Dr. Haxton told one of his students, "To move in the bloodstream, fats need the help of phospholipids." What would a good student say? 1) Sorry, Dr. Haxton! Help comes from cholesterol, not phospholipids. 2) Not so. Fats are small enough to travel easily without help. 3) Yes. Nonpolar molecules aren't compatible with water. 4) Right. Fats are too polar to travel alone in water. 5) You have it backwards. Fats help phospholipids to travel.

3) Yes. Nonpolar molecules aren't compatible with water. ***Water rejects nonpolar molecules such as fats, so fats travel inside particles that are coated with polar parts of phospholipids and proteins

Hemolysis

A red blood cell in a hypotonic solution will swell and potentially burst in a process called

Crenation

A red blood cell placed in a hypertonic solution will shrink in a process called

The presence of many C-C and C-H bonds causes fats to be ... (a) rich in energy. (b) insoluble in water. (c) low in energy. Both (a) and (b). Both (b) and (c).

Both (a) and (b). The many C-C and C-H bonds make fats nonpolar and insoluble in water. They can also be oxidized, releasing much energy.

Triglycerides vary with respect to the number of ... (a) hydrocarbon tails. (b) C atoms in the tails. (c) double bonds in the tails. Both (b) and (c). All of the above.

Both b and c. Tail lengths of 16 to 22 are common. There may be from 0 to 6 double bonds.

Lipids are insoluble in water because_____. A. they are very large with many carbon atoms B. they contain multiple hydroxyl groups C. they contain nonpolar C-C and C-H bonds D. The statement is not true. Lipids are soluble in water.

C. they contain nonpolar C-C and C-H bonds

Glycerol

Fats form when dehydration reactions connect glycerol to three fatty acids and produce easter linkages.

In the reaction that builds a fat,________ groups react with ________ groups. hydroxyl; carboxyl carboxyl; amino sulfhydryl; carboxyl phosphate; amino hydroxyl; phosphate

Hydroxyl; carboxyl. Fatty acids supply the carboxyl groups; the hydroxyls come from glycerol.

Which statement accurately summarizes a feature of passive transport? It makes the cell interior and exterior more different from one another. No membrane proteins are involved. It is a spontaneous process. It involves no change in entropy

It is a spontaneous process.

The most unsaturated fats have ... a. the highest ratio of H to C. b. the most double bonds. c. the fewest double bonds. d. the shortest hydrocarbon tails. e. the longest hydrocarbon tails.

The most double bonds. Every double bond is a place where hydrogen could be added

Which statement best explains the effect on membrane permeability of cholesterol and/or temperature? a. Adding cholesterol reduces permeability because its steroid rings fill gaps in the hydrophobic membrane interior. b. Increasing temperature increases permeability because it increases the strength of hydrophobic interactions in the membrane interior. c. Adding cholesterol increases permeability because its steroid rings increase the density of the hydrophobic membrane interior. d. Adding cholesterol increases permeability because its steroid rings decrease the density of the hydrophobic membrane interior.

a. Cholesterol's bulky steroid rings result in a denser membrane interior, making it more difficult for materials to pass through.

One of the roles of plasma membrane proteins is to____. See Section 6.4 dissolve the lipids in the membrane allow passage of select molecules that could not otherwise cross the lipid bilayer form one side of the membrane bilayer provide a structure on which the membrane lipids can assemble a bilayer

allow passage of select molecules that could not otherwise cross the lipid bilayer

Amphipathic

both hydrophilic and hydrophobic regions

Structure of saturated hydrocarbon chains?

consist of only single bond between the carbons - max number of hydrogen atoms

The movement of molecules through a plasma membrane channel protein is always _____. See Section 6.4 against the molecule's electrochemical gradient "paid for" by an expenditure of cellular energy toward the inside of the cell down the molecule's electrochemical gradient

down the molecule's electrochemical gradient

In fat synthesis, ________ and fatty acids combine to make fats plus________. phosphate; glycerol glycerol; water esters; phosphate glucose; phosphate esters; water

glycerol; water. Water is a by-product of the reaction that makes ester links between glycerol and fatty acids.

Structure of unsaturated hydrocarbon chains?

have one or more double bonds in the hydrocarbon chains - hydrogen atoms are removed to make double bonds - forms a "kink" in the chain - Polyunsaturated chains have many double bonds

Lipid vesicles are formed containing pure water. If these vesicles are transferred to a solution that contains a rather high concentration of solutes, the solution outside the vesicle is said to be_____.

hypertonic

The three different ways a solution can be described in relation to a cell placed in the solution:

isotonic, hypotonic, and hypertonic.

Decreasing the saturation of the fatty acid chains on a particular type of phospholipid would result in the formation of _____. glycerol more fluid bilayers cholesterol a bilayer with decreased permeability to CO2

more fluid bilayers

Osmosis

net movement of water across a semipermeable membrane from an area of lower solute concentration to an area of higher solute concentration. The water will continue to move across the semipermeable membrane as the system attempts to reach equilibrium, where both solutions have the same concentration.

isotonic solution

water flows into the cell to the same extent that it flows out of the cell

hypotonic solution

water flows into the cell, which causes it to swell and potentially burst

hypertonic solution

water flows out of the cell, which causes it to shrink