Chapter 17

Question 1

Explain Lipids and their functions.

Answer 1

• Lipids are hydrocarbon like molecules
• They are insoluble in water

Functions:
- To store energy
- Components of membranes
- Chemical Messengers

Question 2

What are the types of Lipids?

Answer 2

• Fatty Acids
• Glycerides
• Non Glyceride lipids
• Complex Lipids

Question 3

Explain how plants store energy.

Answer 3

Plants store energy as starch
- Starch is a carbohydrate polymer

Question 4

Explain how animals store energy.

Answer 4

Animals store energy as fats
- Stored in adipose tissue
- Lipids reserves can maintain the human body for 30 days with water.

Question 5

Explain Membrane Components.

Answer 5

Lipid membrane separates cellular components
- The hydrocarbon end of the lipid is hydrophobic.
- The opposite end is hydrophilic.

Question 6

Explain Chemical Messengers.

Answer 6

Primary Messengers:
- Delivers chemical signals from one part of the body to another.

Secondary Messengers:
- Mediate the hormonal responces.

Question 7

Explain Triacylglycerols (Triglycerides)

Answer 7

Triglycerides are the major form of energy storage for animals.
- In the body fatty acid are stored as Triglycerides.

Question 8

How is a Triglycerides made?

Answer 8

Esters of glycerol and 3 long fatty acid chains.

Question 9

Explain the Structure of Lipids.

Answer 9

• Fatty acid lipids are all unbranched carboxylic acids
• The carboxylic acid chains contain an even number of carbon atoms
• Some acids contain double bonds, in those that have double bonds the cis isomer predominates.

Question 9

Explain the Properties of Lipids.

Answer 9

• They are insoluble in water
• Fats from animals are solid and are saturated.
• Oils from plants are liquid and unsaturated.

Question 10

Explain Animal Fats.

Answer 10

Straight chain fatty acids allow the molecules to be closely packed together increasing the attractive forces between molecules.

Question 11

Explain Plant Fats.

Answer 11

The cis double bond interrupt the close packing of the fatty acid chain and disrupts the attraction between acid molecules.

Question 12

Can humans synthesize fatty acids?

Answer 12

Humans are capable of synthesizing some fatty acids from carbohydrates or other fatty acids, but we cannot synthesize sufficient amounts of polyunsaturated fatty acids.
- Because of this, polyunsaturated fatty acids must be obtained from diet as they are known as essential.

Question 13

What is Saponification?

Answer 13

The reaction of a fat with a strong base in the presence of heat to create soap.
- It splits triglycerides into glycerol and the salts of fatty acids.

Question 14

Explain the structure and solubility of carboxylic acid salts.

Answer 14

The solubility of carboxylic acid salts having 12-18 carbons is governed by two different structural units.
- Long nonpolar hydrocarbon chain: Hydrophobic
- Polar carboxylate group: Hydrophilic

Question 15

Explain the structure of Soaps.

Answer 15

In aqueous solutions molecules orient themselves into micelles.
- The hydrocarbon tail is pointed inward and the carboxylate group is pointed outward toward the surrounding water.

Question 16

Explain Synthetic Detergents.

Answer 16

Most cleaning substances are detergents, it cleans like soap but dosent form soap scum

Question 17

What are phospholipids?

Answer 17

Phospholipids are a family of lipids similar in structure to triglycerides. They include glycerophospholipids and sphingomyelin.

Question 18

What are Glycerophospholipids made of?

Answer 18

• Two fatty acids that form esters bonds with the first and second hydroxyl groups of glycerol.
• A hydroxyl group that forms an ester with phosphonic acid, which form another phosphodiester bond with an animo acid.

Question 19

What is Lecithin and Cephalin?

Answer 19

Two types of glycerophospholipids that are abundant in brain and nerve tissue and found in yolk, whear, and yeast.

Question 20

Explain the Structure and Polarity of Glycerophospholipids.

Answer 20

• They contain polar and nonpolar regions that allow them to interact with polar and nonpolar substances.
• They have a polar head containing ionized amino alcohol and phosphate portions, which is strongly attracted to water.
• They have a nonpolar hydrocarbon tail portion soluble only in nonpolar substances such as lipids.

Question 21

Explain Sphingomyelin.

Answer 21

It contains:
- Sphingosine instead of glycerol
- A fatty acid, phosphate, and amino acid

Question 22

Explain Cell Membranes.

Answer 22

• They are semipermeable so that nutrients can enter the cell and waste products can leave.
• They seperate cellular contents from the external environments.
• Consist of a lipid bilayer made of two rows of phospholipids.
• Hava an inner portion made of the nonpolar tails and phospholipids, with the polar heads at the outer and inner surfaces.

Question 23

Explain Fluid Mosaic Membrane.

Answer 23

Called a Mosaic because of imbedded proteins and other substances that float in the lipid bilayer.

Question 24

What is the general structure of a Setroid.

Answer 24

A collection of 4 fused carbon rings

Question 25

Explain Cholesterol.

Answer 25

- The most abundant steroid in the body. - Used as a component of plasma membranes regulate fluidity - Used as starting material for other steroids - Hydrophobic, need transport mechanism, lipoproteins

Question 26

Explain Bile Salts.

Answer 26

- Oxidation products of cholesterol - Have polar and nonpolar ends

Question 27

Explain Prostaglandins.

Answer 27

- Hormone like substances produced in small amounts in most cells - The differ by the substituents attached to the 5 carbon ring - Have many functions such as raising blood pressure and stimulating contractions and relaxation of the smooth muscle of the uterus.

Question 28

T/F: When tissues are injured, arachidonic acid is converted to prostaglandins that produce i flammation and pain.

Answer 28

True

Question 29

What are Lipoproteins? Explain the structure.

Answer 29

Lipoproteins act as a transporter for lipids since lipids are hydrophobic (not water soluble) and our bodies are primarily water. - Lipoproteins have a hydrophobic interior and a hydrophilic exterior.

Question 30

What are the 4 groups of Lipoproteins?

Answer 30

- Chylomicrons - Very Low Density Lipoproteins (VLDL) - Low Density Lipoproteins (LDL) - High Density Lipoproteins (HDL)

Question 31

Explain Chylomicrons

Answer 31

A type of Lipoprotein that delivers dietary lipids to cells in the liver

Question 32

Explain Very Low Density Lipoproteins (VLDL)

Answer 32

A type of Lipoprotein that delivers triglycerides to cells

Question 33

Explain Low Density Lipoproteins (LDL)

Answer 33

A type of Lipoprotein that delivers cholesterol to cells

Question 34

Explain High Density Lipoproteins (HDL)

Answer 34

A type of Lipoprotein that picks up cholesterol for removal or recycling

Question 35

Explain the effects of LDL and HDL.

Answer 35

- In general, high LDL levels mean high cholesterol in plasma because LDL cannot enter cells to be metabolized - High LDL combined with low HDL levels are a warning sign for atherosclerosis - Desirable to have low levels of LDL combined with high levels of HDL (low LDL/HDL ratio)