2.9 MEMBRANE LIPIDS: CHOLESTEROL

Question 1

● the third of the three major types of membrane lipids, is a specific compound rather than a family of compounds like the phospholipids. structure differs markedly from that of other membrane lipids in that (1) there are no fatty acid residues present and (2) neither glycerol nor sphingosine is present as the platform molecule. it is also considered as a steroid

Answer 1

(Cholesterol)

Question 2

● lipid whose structure is based on a fused ring system that involves three 6-membered rings and one 5-membered ring

Answer 2

Steroid

Question 2

● Steroid fused ring is als called?

Answer 2

steroid nucleus

Question 2

● What distinguishes steroids from one another?

Answer 2

( Location of double bonds within the fused-ring system and the nature and location of substituents)

Question 3

● Most steroids have an oxygen functional group (=O or –OH) at _______and some kind of side chain at_____

Answer 3

carbon 3; carbon 17

Question 4

● is a C27 steroid molecule that is a component of cell membranes and a precursor for other steroid-based lipids.
It is the most abundant steroid in the human body. The -ol ending in the name cholesterol conveys the information that an alcohol functional group is present in this molecule; it is located on carbon 3 of the steroid nucleus

Answer 4

(CHOLESTEROL)

Question 5

● Location of the alcohol molecule in cholesterol

Answer 5

CARBON 3)

Question 6

● Location of the methyl attachments in cholesterol

Answer 6

carbons 10 and 13

Question 6

● The lack of a large polar head group causes cholesterol to have limited water solubility. The ______ on carbon 3 is considered the head of the molecule.

Answer 6

(-OH GROUP ON C3)

Question 6

● Where is cholesterol found in the human body?

Answer 6

cell membranes (up to 25% by mass), in nerve tissue, in brain tissue (about 10% by dry mass), and in virtually all fluids.)

Question 6

● Location of the carbon–carbon double bond in cholesterol

Answer 6

carbons 5 and 6)

Question 7

● Location of the eight-carbon branched chain in a cholesterol

Answer 7

carbon 17)

Question 8

● Every 100 mL of human blood plasma contains about _____of free cholesterol and about _______of cholesterol esterified with various fatty acids.

Answer 8

(50 mg; 170 mg)

Question 9

● Although a portion of the body’s cholesterol is obtained from dietary intake, most of it is biosynthesized by the ________and (to a lesser extent) the_______. Typically, 800–1000 mg are biosynthesized each day.

Answer 9

liver, intestine

Question 9

● The lipoproteins that carry cholesterol from the liver to various tissues are called _________and those that carry excess cholesterol from tissues back to the liver are called _________

Answer 9

[LDLs (low-density lipoproteins); HDLs (high-density lipoproteins).]

Question 9

● Because cholesterol is only sparingly soluble in water (blood), a protein carrier system is used for its distribution. These cholesterol protein combinations are called

Answer 9

lipoproteins.)

Question 10

● High blood cholesterol levels contribute to _________, a form of cardiovascular disease characterized by the buildup of plaque along the inner walls of arteries

Answer 10

atherosclerosis

Question 11

● The cholesterol associated with LDLs is often called “_________” because it contributes to increased blood cholesterol levels, and the cholesterol associated with HDLs is often called “________” because it contributes to reduced blood cholesterol levels

Answer 11

BAD CHOLESTEROL; good cholesterol)

Question 12

● a mound of lipid material mixed with smooth muscle cells and calcium. It deposits in the arteries that serve the heart reduce blood flow to the heart muscle and can lead to a heart attack

Answer 12

(Plaque)

Question 13

1. The “ steroid nucleus” common to all steroid structure involves a fused-ring system that contains

Answer 13

• 3 6-membered rings and one 5-membered rings

Question 14

2. Which of the following types of membrane lipids has a steroid structure?

Answer 14

• CHOLESTEROL

Question 15

3. Which of the following statements concerning cholesterol is correct?

Answer 15

• an alcohol functional group is present in its structure