Unit 1 (Chapter 3 Part 3) Lipids

Question 1

What is a molecule composed of predominately of hydrogen and carbon atoms?

Answer 1

Lipids.

Lipids are nonpolar and therefore very insoluble in water. They include fats (triglycerides), phospholipids, waxes, and steroids. 40% of matter in the human body.

Question 2

What is a molecule composed of three fatty acids linked by ester bonds to a molecule of glycerol?

Answer 2

Triglyceride

Question 3

What is another name for a triglyceride?

Answer 3

Triacylglycerol

Question 4

Describe the chemical structure of a glycerol molecule.

Answer 4

A three-carbon molecule with one hydroxyl group (-OH) bonded to each carbon. 5 hydrogen atoms with one on the center carbon atom.

Question 5

Describe the chemical structure of a fatty acid?

Answer 5

A chain of carbon and hydrogen atoms with a carboxyl group (-COOH)

A carbon atom with a double bond to oxygen and a covalent bond to -OH.

Question 6

What happens for a triglyceride (fat) to form?

Answer 6

The hydroxyl groups in glycerol link to the carboxyl groups in fatty acids by the removal of water molecules using the dehydration reaction. This reaction happens three times.

Question 7

What type of bond is formed in the new molecule?

Answer 7

Ester bond.

They are characterized by a carbon bound to three other atoms: a single bond to a carbon, a double bond to an oxygen, and a single bond to an oxygen

Question 8

What is the shorthand notation for depicting fatty acid chains?

Answer 8

(CH2)n, where n is greater than 2.

So CH2-CH2… etc… -CH3

Question 9

Even though both saturated and unsaturated fatty acids have carboxyl functional group on one end, what makes them different throughout their chain?

Answer 9

Unsaturated fatty acids have two double bonds between carbon atoms that kink it and give it a 3-dimensional structure.

Question 10

What is a fatty acid in which all the carbons are linked by single covalent bonds?

Answer 10

Saturated fatty acid. The carbons are “saturated” with covalently bonded hydrogens.

Question 11

What is a fatty acid that contains one or more C=C double bonds?

Answer 11

Unsaturated fatty acid. One double bond is monosaturated fatty acid while two or more double bonds is a polyunsaturated fatty acid.

Question 12

What is another name for saturated and unsaturated fatty acids?

Answer 12

Stearic acid (saturated) and Linoleic acid (unsaturated)

Unsaturated fatty acids are essential to health since they cannot be created by humans.

Question 13

What fats tend to have a high melting point and tend to be solid at room temperature? And where are these fats generally located?

Answer 13

Saturated fats and they are typically located in animals.

This is why liquid greese forms in the pain and turns white (solid) when removed from heat.

Question 14

What is a modern way today where vegetable (not animal) fats are changed in their double bonds to carbon atoms?

Answer 14

Hydrogenation.

In products for baking called shortenings, the double-bonds to carbon become single bonds because of the addition of hydrogen atoms. This makes a vegetable fat “saturated” with hydrogen bonds and forces the fat to become a solid at room temperature.

Question 15

What configuration are most saturated fats existing as?

Answer 15

The cis configuration.

For trans configuration, like in trans fats, they are artificially configured this way to increase shelf life and to improve in baking.

However, research as revealed these are extremely unhealthy and linked to coronary artery disease.

Question 16

What are the benefits of fat?

Answer 16

• Large energy storage in the form of fat which can be metabolized into energy to make ATP.
• A structural role by forming cushion for organs.
• Also provides insulation under the skin during cold weather for mammals and marine animals in cold water.
• Fat is an efficient means of energy storage for mobile organisms for which excess body mass may be a disadvantage.

Question 17

How is energy determined in fats and carbohydrates?

Answer 17

The number of C-H bonds.

Question 18

Why does fat yield more energy than carbohydrates?

Answer 18

Fats have many C-H bonds while carbohydrates have many C-OH bonds.

1g of fat stores more energy than 1g of starch or glycogen.

Since fats have less oxygen, they are more prone to yielding more energy in the oxidative process than carbohydrates and protein.

Question 19

What is a type of lipid that is similar in structure to a triglyceride, but with the third hydroxyl group of glycerol linked to a phosphate group instead of a fatty acid; a key component of biological membranes?

Answer 19

Phospholipid.

These are amphipathic molecules because of polar and non polar (fatty acid) regions.

Question 20

What is an important function of this amphipathic phospholipids?

Answer 20

They create a biological membrane in cells. The bilayer (area between two rows of phospholipids interact with each other.

Question 21

What is a lipid containing four interconnected rings of carbon atoms and it functions as a hormone in animals and plants?

Answer 21

Steroids.

Question 22

What is attached to the ring structure of a steroid but not numerous enough to make it highly water-soluble?

Answer 22

Polar hydroxyl groups.

These are known as sterols, most well known as being cholesterol.

Question 23

What is the difference between the chemical structure of testosterone and estrogen?

Answer 23

Estrogen differs from testosterone by having one less methyl group, a hydroxyl group instead of a ketone group and additional double bonds in one of its rings.

Question 24

What is a methyl group?

Answer 24

-CH3

Question 25

What is a carbonyl group?

Answer 25

An oxygen atom double bonded to a carbon atom.

Question 26

Note: These small differences between testosterone and estrogen molecules are enough for whether an animal exhibits male or female characteristics.

Answer 26

(No Answer)

Question 27

What are the lipids called waxes used for in plants and animals?

Answer 27

They are secreted on the surface such as leaves of plants and the cuticles of insects.

All waxes contain hydrocarbons and long structures that resemble a fatty acid attached by its carboxyl group to another long hydrocarbon.

They are very nonpolar and therefore exclude water, providing a barrier to water loss. They are also used as structural elements such as beeswax that forms honeycombs produced by bees.