Question 1

The density of lipoproteins is determined by the relative amounts of

Accepted Answer

The density of lipoproteins is determined by the relative amounts of lipids and proteins, with higher protein content resulting in higher density.

Question 2

Functions of cholesterol include all of the following except:

Accepted Answer

Cholesterol is not used for energy production when fatty acids are in short supply. Instead, the body relies on other sources such as glucose or amino acids.

Question 3

In an omega-3 fatty acid of any chain length the first double bond is

Accepted Answer

The first double bond in an omega-3 fatty acid is between the third and fourth carbons counting from the omega (methyl) end of the molecule. This is why omega-3 fatty acids are classified as such, as the first double bond is located 3 carbons away from the omega end. Choice B is not correct as it refers to the alpha (carboxylic acid) end of the molecule, which is not relevant to determining the location of the double bond. Choice C is also not correct as it refers to the sixth and seventh carbons, which is not where the first double bond is typically located in omega-3 fatty acids. Choice D is also not correct as the configuration of the double bond is not specified in the question.

Question 4

Lipids in micelles are taken up by intestinal cells, where

Accepted Answer

After lipids are taken up by intestinal cells, fatty acids and monoglycerides are reassembled into triglycerides and incorporated into chylomicrons for transport. This is facilitated by the endoplasmic reticulum and Golgi apparatus of the intestinal cells. Chylomicrons are then released into the lymphatic system before entering the bloodstream.

Question 5

In addition to promoting glucose uptake into cells, insulin

Accepted Answer

Insulin promotes triglyceride storage during times of energy excess by increasing the uptake and storage of glucose in adipose tissue, which is then converted into triglycerides for storage. Insulin inhibits lipolysis, the breakdown of stored triglycerides into free fatty acids, and promotes fat storage instead. Insulin also inhibits both β-oxidation, the process by which fatty acids are broken down for energy, and ketogenesis, the process by which ketone bodies are produced from fatty acids.

Question 6

High intakes of saturated fatty acids, trans fatty acids, and _____ are associated with increased risk of cardiovascular disease in certain people.

Accepted Answer

High intakes of saturated fatty acids, trans fatty acids, and cholesterol are associated with increased risk of cardiovascular disease in certain people. Monounsaturated fatty acids, phytosterols, and lecithin are generally considered to have health benefits and are not associated with increased cardiovascular risk.

Question 7

One advantage of storing excess energy as triglycerides as compared to storing it as glycogen is that

Accepted Answer

Triglycerides contain over twice the amount of energy as carbohydrates, making them a more efficient way to store excess energy. Additionally, triglycerides are stored without water, which makes them lighter and more space-efficient than glycogen.

Question 8

Rather than cholesterol, plants produce cholesterol-like compounds called phytosterols. Phytosterols have been shown to

Accepted Answer

Phytosterols have been shown to lower blood cholesterol levels through unknown mechanisms. They compete with cholesterol for absorption in the intestine, preventing the absorption of cholesterol and leading to a decrease in total cholesterol levels in the body. This is why phytosterols are often added to foods such as margarine, yogurt, and orange juice, as a functional food ingredient to help reduce cholesterol levels.

Question 9

Short- and medium-chain fatty acids

Accepted Answer

Short- and medium-chain fatty acids can be absorbed directly by intestinal cells without the need for micelles or chylomicrons. This is because they are relatively small molecules that can diffuse through the cell membrane. Once inside the cell, they can be used as an immediate source of energy or transported to other tissues for use.

Question 10

Monoglycerides, diglycerides, and triglycerides are distinguished from one another by

Accepted Answer

Monoglycerides have one fatty acid attached to the glycerol backbone, diglycerides have two, and triglycerides have three. The types, length, and saturation of the fatty acids can vary within each group.

Question 11

Excess dietary fatty acids that are not required for energy production or other functions are

Accepted Answer

Excess dietary fatty acids are stored as triglycerides in adipose tissue. This is a process called lipogenesis, which is the conversion of excess dietary carbohydrates and fats into triglycerides for storage in adipose tissue. The triglycerides can then be used for energy when needed.

Question 12

Adipose tissue plays an important insulating role in the body. People with minimal adipose tissue

Accepted Answer

Adipose tissue helps to regulate body temperature by providing insulation, so people with minimal adipose tissue would have difficulty staying warm as they cannot benefit from this insulation.

Question 13

Under certain conditions, such as starvation, fatty acids can be used to form

Accepted Answer

During starvation or low-carbohydrate diets, the body can convert fatty acids into ketones, which can serve as an alternative energy source for some tissues, such as the brain. Therefore, choice A is the best choice. Choice B is incorrect because fatty acids cannot be used to form amino acids, as amino acids are the building blocks of proteins. Choice C is also incorrect because fatty acids cannot be directly converted into glucose, which is the primary fuel for the brain.

Question 14

During infancy, the ability to process the essential fatty acids to other fatty acids such as arachidonic acid and DHA may be impaired due to immature production of the required enzymes. In this situation, arachidonic acid and DHA are considered

Accepted Answer

Arachidonic acid and DHA are conditionally essential fatty acids during infancy because the production of required enzymes is immature, and the ability to process these fatty acids is impaired. Although they are non-essential fatty acids for adults, they are essential for infants for proper growth and development.

Question 15

The products of pancreatic lipase acting on a triglyceride molecule are

Accepted Answer

Pancreatic lipase breaks down triglycerides into a monoglyceride and two free fatty acids by hydrolyzing ester bonds.

Quiz 6: Lipids