Lipids and Essential Fatty Acids

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Questions and Answers

What are triglycerides from plants primarily characterized by?

Being colorless and tasteless

A higher melting point

Being solid at room temperature

A higher proportion of unsaturated fatty acids (correct)

Which type of fat is generally considered bad for heart health?

Trans fats

Polyunsaturated fatty acids (PUFA)

Saturated fatty acids (SFA) (correct)

Monounsaturated fatty acids (MUFA)

What is the dietary source of essential fatty acids?

They can be synthesized in adequate amounts in the body

They are only found in animal fats

They are primarily found in processed foods

They must be obtained from dietary sources (correct)

Which of the following oils is considered to be high in omega-6 fatty acids?

Corn oil Signup and view all the answers

What reaction involves the breaking down of triglycerides?

Hydrolysis Signup and view all the answers

What is the state of most plant triglycerides at room temperature?

Liquid Signup and view all the answers

Which type of fatty acids is abundant in a typical Inuit diet?

Omega-3 fatty acids Signup and view all the answers

What is the effect of hydrogenation on triglycerides?

It increases the melting point Signup and view all the answers

What is an emulsion?

A colloidal suspension of one liquid in another Signup and view all the answers

What differentiates sphingolipids from glycerophospholipids?

Glycerophospholipids contain a glycerol core Signup and view all the answers

What is lecithin also known as?

Phosphatidylcholine Signup and view all the answers

Which of the following best describes cholesterol?

A type of steroid not derived from fatty acids Signup and view all the answers

What is the primary role of triacylglycerols?

Storage molecules for energy Signup and view all the answers

What constitutes the basic structure of steroids?

Four fused cycloalkane rings Signup and view all the answers

What replaces one of the fatty acids in sphingolipids?

Sphingosine Signup and view all the answers

What is formed during complete hydrolysis of triglycerides?

Glycerol and free fatty acids Signup and view all the answers

Which fatty acid is a major starting material for eicosanoids?

Arachidonic acid Signup and view all the answers

Which lipids are crucial components of cell membranes?

Phospholipids and sterols Signup and view all the answers

What is produced during the saponification of triglycerides?

Fatty acid salts and water Signup and view all the answers

What occurs during partial hydrolysis of triglycerides?

One or more fatty acids remain attached to glycerol Signup and view all the answers

Which of the following fatty acids is necessary for normal brain development?

DHA Signup and view all the answers

What is a likely outcome of a diet lacking essential fatty acids?

Red and irritated skin Signup and view all the answers

What are fat substitutes primarily designed to do?

Create sensations of creaminess without fat Signup and view all the answers

Under basic conditions, what is produced from the hydrolysis of triglycerides?

Glycerol and fatty acid salts Signup and view all the answers

What is a characteristic feature of leukotriene A4?

It contains three conjugated double bonds. Signup and view all the answers

What defines saponifiable lipids?

They can be hydrolyzed to yield smaller molecules. Signup and view all the answers

Which substance is an example of a nonsaponifiable lipid?

Lanolin Signup and view all the answers

What is the primary function of waxes in biological systems?

To act as protective, waterproof coatings. Signup and view all the answers

What is the chemical classification of waxes?

Esters Signup and view all the answers

Which of the following statements about lanolin is accurate?

It enhances water retention in skin products. Signup and view all the answers

What process leads to the formation of esters in waxes?

Reacting carboxylic acids with alcohols. Signup and view all the answers

Which characteristic is true for nonsaponifiable lipids?

They possess a four-ring steroid nucleus. Signup and view all the answers

What is the role of polyunsaturated fatty acids in plant phospholipids?

They help form a fluid character in the membrane. Signup and view all the answers

Which type of lipoprotein is primarily responsible for transporting triglycerides from the digestive tract?

Chylomicrons Signup and view all the answers

What is the function of cholesterol in the cell membrane?

To maintain rigidity and stability of the membrane. Signup and view all the answers

Which type of lipoprotein is often referred to as 'good cholesterol'?

HDL Signup and view all the answers

What is the significance of kinks in the fatty acid chains of lipids?

They prevent tight packing and contribute to fluidity. Signup and view all the answers

How can HDL and LDL levels in the blood be used in health assessments?

To evaluate risk for atherosclerosis. Signup and view all the answers

What type of complex is formed by carbohydrates attached to proteins in the cell membrane?

Glycoproteins Signup and view all the answers

What is TRUE about propensities of lipoproteins?

HDL helps remove excess cholesterol from tissues. Signup and view all the answers

Study Notes

### Lipids

Lipids are a diverse group of naturally occurring molecules that are grouped together due to their solubility in nonpolar solvents.
Lipids are typically composed of hydrocarbons.
Lipids can be classified as fats, oils, waxes, steroids, and phospholipids.
Fats and oils are triglycerides.
Triglycerides are esters of glycerol and fatty acids.

Essential Fatty Acids

Essential fatty acids are those that the human body cannot synthesize and must be obtained through the diet.
Two of the most important essential fatty acids are linoleic acid and linolenic acid.
Linoleic acid (18:2) can be converted into arachidonic acid (20:4).
Linolenic acid (18:3) can be converted into EPA (20:5) and DHA (22:6)
Arachidonic acid is a key starting material for eicosanoids, which regulate blood pressure, clotting and other important functions.
EPA and DHA are important constituents of the brain and are necessary for normal brain development.
Essential fatty acid deficiencies can result in red and irritated skin, infections, dehydration, and liver abnormalities.

### Triglycerides

Triglycerides can come from plant and animal sources.
Triglycerides from plants tend to have a higher proportion of unsaturated fatty acids.
Plant-based triglycerides are typically liquids at room temperature and are called oils.
Examples of plant-based oils include corn oil, canola oil, peanut oil, and olive oil.
Triglycerides from animals tend to have a higher melting point.
Examples of animal-based fats include butter, lard, and bacon grease.
Saturated fatty acids (SFAs) are generally considered bad for heart health.
Monounsaturated fatty acids (MUFAs) are generally considered good for heart health.
Polyunsaturated fatty acids (PUFAs) can be either good or bad for heart health depending on the type.
Omega-3 fatty acids, found primarily in fish, are generally considered good for health while Omega-6 fatty acids, found in plant oils, are considered bad for heart health.
Pure fats and oils are colorless, odorless, and tasteless.

Chemical Reactions of Triacylglycerols

Triglycerides can undergo several chemical reactions, including hydrolysis, hydrogenation, oxidation, and base-catalyzed hydrolysis (saponification).

Hydrolysis

Hydrolysis is the breaking down of a molecule by the addition of water.
Hydrolysis of triglycerides can be done under acidic or basic conditions.
Acidic hydrolysis produces glycerol and fatty acids.
Basic hydrolysis produces glycerol and fatty acid salts.
Hydrolysis in the stomach can form diacylglycerols (one outer fatty acid is removed) followed by monoacylglycerols (another outer fatty acid is removed).
Partial hydrolysis refers to any hydrolysis where at least one fatty acid remains attached to the glycerol molecule.
Complete hydrolysis refers to the complete removal of all fatty acids.

Saponfication

Saponfication is a base-catalyzed hydrolysis of the ester bonds in triglycerides.
Products of saponfication are glycerol and fatty acid salts.
Saponification of animal fat is a process that is used to make soap.
To make soap, lard (fat) is heated with lye (an impure form of KOH)

Phospholipids and Glycolipids

Phospholipids are amphipathic molecules that are found in cell membranes.
Phospholipids are similar to triglycerides with the exception that one of the fatty acids is replaced with a phosphate group.
The phosphate group can be attached to a variety of other molecules.
The sphingolipids are similar to the glycerophospholipids but do not contain a glycerol core.
Sphingolipids contain a molecule called sphingosine instead of glycerol.
The fatty acid found in the glycerol molecule is replaced by a phosphate group and an alcohol.

Glycolipids

Glycolipids are similar to phospholipids with the exception that the phosphate group is replaced with a carbohydrate.

Lipoproteins

Lipoproteins are used to transport water-insoluble lipids, such as triglycerides, phospholipids, and cholesterol, in the blood.
Lipoproteins are composed of lipids and proteins.
Chylomicrons transport primarily triglycerides from the digestive tract to the liver.
Low-density lipoproteins (LDLs) transport cholesterol, triglycerides, and phospholipids from the liver to other tissues.
High-density lipoproteins (HDLs) transport cholesterol and phospholipids back to the liver.
The ratio of LDL to HDL in the blood can be used to assess a person’s risk for atherosclerosis.
High levels of HDL are considered good cholesterol and are higher than 40 mg/dL.
High levels of LDL are considered bad cholesterol.

### Membrane Lipids: Cholesterol

Cholesterol is a steroid, a type of lipid that is not derived from fatty acids.
Steroids are based on a system of four cycloalkane rings fused together (3 six-membered rings and 1 five-membered ring).
Cholesterol is a component of cell membranes and regulates rigidity.
Cholesterol molecules orient themselves within the lipid bilayer with the hydroxyl head group to the exterior and the alkyl tail group to the interior.

### Protective-Coating Lipids: Biological Waxes

Waxes are made by combining fatty acids with long-chain alcohols.
Waxes are esters and are very hydrophobic.
Plants and animals use waxes for protective and water-proof coatings.
Lanolin is a mixture of waxes obtained from sheep wool that is used as a base for creams and ointments to enhance water retention.

### Chemical Action Classification of Lipids

Lipids can be classified based on their chemical action.
Saponifiable lipids undergo hydrolysis in a basic solution to yield two or more smaller product molecules.
Nonsaponifiable lipids do not undergo hydrolysis in a basic solution.

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Description

This quiz focuses on the classification and functions of lipids, including fats, oils, waxes, steroids, and phospholipids. It highlights the role of essential fatty acids such as linoleic and linolenic acid, which are vital for human health and brain development. Test your knowledge on these important biological molecules.