Biology-Lipids

Which of these classes of biological molecules does NOT include polymers?

Lipids; fats are NOT polymers but they are large molecules assembled from small ones- glycerol and fatty acids

The characteristic that all lipids have in common is that _____.

none of them dissolves in water

Which of these is NOT a lipid?

RNA; Are lipids: wax, steroids, cholesterol, phospholipids

What do unsaturated fatty acid tails lack?

Double bonds

Which of these is rich in unsaturated fats?

olive oil; one or more bonds with one fewer hydrogen; liquid at room temperature

A function of cholesterol that does not harm health is its role _____.

Cholesterol is an important component of animal cell membranes.

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

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

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

glycerol;water

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

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

Fats 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.

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

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

The most unsaturated fats have …

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

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

They contain carbonyl groups.

Which of the following statements concerning unsaturated fats is true?

They have double bonds in the carbon chains of their fatty acids.

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

Low solubility in water.

Dr. Haxton told one of his students, "To move in the bloodstream, fats need the help of phospholipids." What would a good student say?

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.

Phospholipids are most important for …

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

To find the best source of phospholipids, look at …

membranes; The great majority of a cell’s phospholipids occur in membranes.

What do phosphoglycerides and fats have in common?

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

Which statement is true of phospholipids?

Their synthesis uses fatty acids, Some of their tails have double bonds and They all ioniz

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

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

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

tails; tails Water on both sides of the membrane excludes the tails, forcing them into the interior where they face one another.

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.

Which lipid is most amphipathic?

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

The molecule shown here probably … (phospolipid)

is structurally related to a fat, is highly amphipathic and is made partly from fatty acids. Phospholipids are close relatives of fats, but the difference makes them amphipathic and allows them to form the basis of membranes. Important stuff!

How do phospholipids interact with water molecules?

The polar heads interact with water; the nonpolar tails do not.

Steroids are considered to be lipids because they _____.

are NOT soluble in water

What does cholesterol have in common with sex hormones?

Four linked rings

For good health, you don’t want your body to run the LDL part of this diagram faster than the HDL part because …

LDL cholesterol is stored; HDL cholesterol is destroyed If LDL exceeds HDL, your body is probably storing excess cholesterol, which may clog the arteries and cause heart disease.

What is the function of Structure E? (Cholesterol)

stabilization of the phospholipids

Identify Structure A. (glycoprotein) How can you tell?

It is composed of both a carbohydrate and a protein.

Which of the following is least likely to be important in holding the components of a biological membrane together?

covalent interactions between the phospholipid and protein components of the membrane This is not an important interaction because there are rarely covalent bonds between the phospholipids and integral membrane proteins.

Things important in holding the components of a biological membrane together?

-polar interactions among the phospholipid head groups on the same surface of the membrane -hydrophobic interactions among the fatty acid tails of phospholipids on opposite sides of the membrane -hydrophobic interactions between the phospholipid tails and the surface of integral membrane proteins buried in the membrane -hydrophobic interactions among the fatty acid tails of phospholipids on the same side of the membrane

Which of the following is a reasonable explanation for why unsaturated fatty acids help keep a membrane more fluid at lower temperatures?

The double bonds form kinks in the fatty acid tails, preventing adjacent lipids from packing tightly.

In what way do the membranes of a eukaryotic cell vary?

Certain proteins are unique to each membrane.