2.6 Lipids

Question 1

What is a lipid?

Answer 1

molecules that contain more energy per gram than other biological molecules

Question 2

What is a fat?

Answer 2

an energy storage lipid molecule that tends to be of animal origin and are solid at room temperature

Question 3

What is an oil?

Answer 3

an energy storage lipid molecule that tends to be of plant origin and are liquid at room temperature

Question 4

What are the functions of fat in our bodies?

Answer 4

• long-term energy storage
• insulates against heat loss
• forms a protective cushion around major organs

Question 5

How do fats and oils form?

Answer 5

when one glycerol molecules reacts with 3 fatty acid molecules

Question 6

Why is a triglyceride?

Answer 6

another name for a fat molecule because of its 3-part structure

Question 7

Why is the term “neutral fat” sometimes used?

Answer 7

because the molecule is nonpolar

Question 8

How can fats and oils mix with water?

Answer 8

although they’re hydrophobic, the addition of emulsifiers can allow them to mix with water

Question 9

What is an emulsifier?

Answer 9

contains molecules with a nonpolar end and a polar end

Question 10

What is emulsification?

Answer 10

process in which molecules position themselves about an oil droplet so that their nonpolar ends project inwards and their polar ends project outwards, resulting in the fat or oil to disperse in water

Question 11

Give some examples of emulsification.

Answer 11

• dirty clothes are washed with soap or detergents

- some salads are uniform consistency (emulsified!) while others separate into two layers

Question 12

Give an example of emulsification in the human body?

Answer 12

fats are emulsified by bile in the intestines before they are digested

the liver produces bile, which is then stored in the gall bladder (people who have had their bladder removed may have trouble digesting fatty foods

Question 13

What is a fatty acid?

Answer 13

a hydrocarbon chain that ends with the acidic group

–COOH

Question 14

How many carbon atoms do most fatty acids in cells contain?

Answer 14

16 or 18 carbon atoms per molecule, although smaller ones with fewer carbons are also known

Question 15

What is a saturated fatty acid?

Answer 15

fatty acid that has no double covalent bonds between carbon atoms

the carbon chain is ‘saturated’ with all the hydrogens it can hold

Question 16

What do saturated fatty acids account for?

Answer 16

the solid nature at room temperature of fats

Question 17

What is an unsaturated fatty acid?

Answer 17

fatty acid that has double bonds between carbon atoms wherever the number of hydrogens is less than 2 per carbon atom

Question 18

What do unsaturated fatty acids account for?

Answer 18

the liquid nature of vegetable oils at room temperature

Question 19

What is an unsaturated cis fat?

Answer 19

the hydrogen atoms are both on the same side of the double bond

Question 20

What is an unsaturated trans-fat?

Answer 20

the hydrogen atoms are on opposite sides of the double bond (one hydrogen on each side)

Question 21

How are trans-fats often produced?

Answer 21

by hydrogenation, or the chemical addition of hydrogen to vegetable oils

*this is done to convert the fat into a solid and is often found in processed foods

Question 22

What is a phospholipid?

Answer 22

fatty acid constructed like fats except that in place of the third fatty acid is a polar phosphate group, or a grouping that contains both phosphate and nitrogen

Question 23

Why are phospholipids and fats not electrically neutral?

Answer 23

because the phosphate and nitrogen-containing groups are ionized

• they form the polar (hydrophilic) head of the molecule while the rest of the molecule becomes the nonpolar (hydrophobic) tails

Question 24

What do phospholipids illustrate?

Answer 24

that the chemistry of a molecule helps determine its function

Question 25

What are the primary components of cellular membranes?

Answer 25

phospholipids

Question 26

What do phospholipids do in an aqueous environment?

Answer 26

they spontaneously form a bilayer in which the hydrophilic heads face outward toward watery solutions and the tails form the hydrophobic interior

Question 27

What do plasma membranes do?

Answer 27

separate extracellular from intracellular environments and are absolutely vital to the form and function of a cell

Question 28

What are steroids?

Answer 28

type of lipid with a backbone of 4 fused carbon rings

Question 29

How does each fused carbon ring in the backbone of a steroid differ?

Answer 29

primarily by the arrangement of the atoms in the rings and the type of functional groups attached to them

Question 30

What is cholesterol?

Answer 30

a steroid formed by the body that also enters the body as part of our diet

Question 31

What are the important functions of cholesterol?

Answer 31

• component of animal cells’ plasma membranes

- precursor of several other steroids such as bile salts, and the sex hormones testosterone and estrogen

Question 32

What can a diet high in saturated fats, trans-fats, and cholesterol cause?

Answer 32

can cause fatty material to accumulate inside the lining of blood vessels thereby reducing blood flow