Mastering Biology Chapter 6 Homework

What effects membrane permeability

-The saturation of hydrocarbon tails in membrane phospholipids -Temperature -The amount of cholesterol in the membrane

Which statement is true of phospholipids? a) Their synthesis uses fatty acids. (b) Some of their tails have double bonds. (c) They all ionize.

ALL OF THE ABOVE LOL

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

Adding cholesterol reduces permeability because its steroid rings fill gaps in the hydrophobic membrane interior Cholesterol's bulky steroid rings result in a denser membrane interior, making it more difficult for materials to pass through.

Which statement most accurately describes the relationship between the permeability and fluidity properties of phospholipid bilayers and their structure?

Bilayers are most permeable and most fluid when they consist of shorter, unsaturated hydrocarbon tails Hydrophobic interactions are weaker for shorter, unsaturated hydrocarbon tails, resulting in a bilayer whose interior is held together less tightly.

Triglycerides vary with respect to the number of ...

C atoms in the tails and double bonds in the tails. Tail lengths of 16 to 22 are common. There may be from 0 to 6 double bonds.

What do phosphoglycerides and fats have in common?

Ester linkages

What does cholesterol have in common with sex hormones?

Four linked rings

In fat synthesis,________and fatty acids combine to make fats plus________.

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

In the reaction that builds a fat,________ groups react with ________ groups.

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

What do fats, steroids, and waxes have in common?

Low solubility in water

A food company hydrogenated a barrel of fat. The treatment ...

Made the fats less fluid Hydrogenation removes double bonds, so the tails can straighten. Do you know why that makes the fats less fluid?

How do fats differ from proteins, nucleic acids, and polysaccharides?

Only fats do not form from the polymerization of monomers. Lipids interact through hydrophobic interactions. The other macromolecules form via the polymerization of monomers: amino acids for proteins, nucleotides for nucleic acids and monosaccharides for polysaccharides.

True or false? Osmosis is a type of diffusion

Osmosis is the diffusion of water across a selectively permeable membrane

Which lipid os most amphipathic?

Phospholipid A phospholipid has a strongly polar (charged) head and two nonpolar tails

It is difficult for molecules to pass through the phospholipid bilayer because ...

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

Phospholipids are most important for ...

Preventing leakage from cells Every cell depends on phospholipid bilayers to limit leakage of molecules through membranes

The presence of many C-C and C-H bonds causes fats to be ...

Rich in energy and insoluble in water The many C-C and C-H bonds make fats nonpolar and insoluble in water. They can also be oxidized, releasing much energy.

In a membrane, the________of the phospholipids in one monolayer face the________of the phospholipids in the other monolayer.

Talis; tails

To find the best source of phospholipids look at...

The membrane

The most unsaturated fats have ...

The most double bonds

What do DNA, proteins, and fats have in common?

They contain carbonyl groups

Which fact is most important in causing phospholipids to behave as they do in water?

Water molecules make hydrogen bonds

Lipids are insoluble in water because_____.

they contain nonpolar C-C and C-H bonds