Biochemistry Chapter 11: Lipids Quiz

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Questions and Answers

What is the definition of lipids?

Water-insoluble molecules that are highly soluble in organic solvents.

List some of the biochemical roles of lipids.

Energy storage, components of membranes, play a variety of roles in signal transduction pathways.

Do lipids form polymers?

False

List the five major classes of lipids.

Free fatty acids, triacylglycerols, phospholipids, glycolipids, steroids. Signup and view all the answers

What are free fatty acids used for?

Fuel. Signup and view all the answers

What are triacylglycerols used for?

It is the storage form of fatty acids. Signup and view all the answers

What are phospholipids used for?

To construct membranes. Signup and view all the answers

What do phospholipids consist of?

Fatty acids attached to a scaffold that bears a charged phosphoryl group. Signup and view all the answers

This creates a macromolecule with a _ head and a _ tail.

polar; nonpolar. Signup and view all the answers

What are glycolipids bound to?

Carbohydrates. Signup and view all the answers

They are important __________ constituents.

membrane. Signup and view all the answers

How do steroids differ from other classes?

They are polycyclic hydrocarbons. Signup and view all the answers

What is the most common steroid?

Cholesterol. Signup and view all the answers

Fatty acids always terminate in...?

Carboxylic acid groups. Signup and view all the answers

What are two key roles for fatty acids?

Fuels and building blocks for membrane lipids. Signup and view all the answers

Why are fats good fuels?

Because they are more reduced than carbohydrates. Signup and view all the answers

What does this mean?

The carbon atoms are bonded to hydrogen atoms and other carbon atoms rather than to oxygen atoms. Signup and view all the answers

Because of this greater reduction, fats yield more _______ than carbohydrates.

energy. Signup and view all the answers

When do fats yield energy?

Undergoing combustion to carbon dioxide and water. Signup and view all the answers

What is a fatty acid's systematic name derived from?

The name of its parent hydrocarbon with the substitution of 'oic' for the final e. Signup and view all the answers

What are saturated fatty acids?

Fatty acids composed of single bonds. Signup and view all the answers

Why are these acids considered to be saturated?

Because every carbon atom is attached to four other atoms. Signup and view all the answers

What are unsaturated fatty acids?

Acids with one or more double or triple bonds. Signup and view all the answers

How are fatty acid carbons usually numbered?

Starting at the carboxyl terminus. Signup and view all the answers

What are carbon atoms 2 and 3 often referred to as?

Alpha and beta, respectively. Signup and view all the answers

What is the last carbon atom in the chain called?

The ω-carbon atom. Signup and view all the answers

What is the position of a double bond represented by?

The symbol Δ followed by a superscript number. Signup and view all the answers

Are fatty acids ionized at physiological pH?

True Signup and view all the answers

What does this mean in terms of their carboxylic acid groups?

The carboxylic acid groups are deprotonated. Signup and view all the answers

Fatty acids in biological systems are usually how long?

Between 14 and 24 carbon atoms. Signup and view all the answers

What is the most common chain length?

16 and 18 carbons long. Signup and view all the answers

Is the configuration of most double bonds in fatty acids cis or trans?

False Signup and view all the answers

The double bonds in polyunsaturated fatty acids are always separated by...?

At least one methylene group. Signup and view all the answers

The properties of fatty acids and lipids are markedly dependent upon what two factors?

Chain length and degree of saturation. Signup and view all the answers

Compare the melting points of unsaturated vs. saturated fatty acids.

Unsaturated fatty acids have lower melting points than those of saturated fatty acids of the same length. Signup and view all the answers

What is the reason for this trend?

The presence of a double bond introduces a kink in the fatty acids and makes tight packing between chains impossible. Signup and view all the answers

Study Notes

Definition of Lipids

Lipids are water-insoluble molecules, soluble in organic solvents.

Biochemical Roles of Lipids

Functions include energy storage, membrane components, and roles in signal transduction pathways.

Lipid Structure

Lipids do not form polymers.

Major Classes of Lipids

Five main classes are:
- Free fatty acids
- Triacylglycerols
- Phospholipids
- Glycolipids
- Steroids

Uses of Lipids

Free fatty acids serve as fuel.
Triacylglycerols act as storage forms of fatty acids.
Phospholipids construct cellular membranes.

Phospholipid Composition

Composed of fatty acids attached to a scaffold with a charged phosphoryl group.
Forms a macromolecule with a polar head and a nonpolar tail.

Glycolipids

Glycolipids are bound to carbohydrates and are important constituents of membranes.

Steroids

Steroids differ from other lipids as they are polycyclic hydrocarbons.
Cholesterol is the most common steroid.

Fatty Acid Structure

Fatty acids terminate in carboxylic acid groups.
Act as fuels and building blocks for membrane lipids.

Energy Content of Fats

Fats are good fuel sources due to being more reduced than carbohydrates.
Fats yield more energy upon combustion to carbon dioxide and water.

Nomenclature of Fatty Acids

Systematic names derive from parent hydrocarbons, substituting “oic” for the final ‘e’.

Types of Fatty Acids

Saturated fatty acids contain only single bonds, resulting in each carbon being attached to four other atoms.
Unsaturated fatty acids include one or more double or triple bonds.

Fatty Acid Numbering

Carbons are numbered starting at the carboxyl terminus.
Carbon atoms 2 and 3 are known as alpha and beta, respectively.
The last carbon in the chain is referred to as the ω-carbon.

Double Bonds in Fatty Acids

The position of double bonds is represented by the symbol Δ followed by a superscript number.
Fatty acids are typically ionized at physiological pH, resulting in deprotonated carboxylic acid groups.

Common Chain Lengths

Biological fatty acids usually range from 14 to 24 carbon atoms, typically with even numbers.
The most common lengths are 16 and 18 carbons.

Configuration of Double Bonds

Most double bonds in fatty acids are in the cis configuration, which introduces kinks in the structure.

Properties Influenced by Structure

The properties of fatty acids and lipids depend on chain length and degree of saturation.
Unsaturated fatty acids generally have lower melting points than saturated ones due to the presence of double bonds, preventing tight chain packing.

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Description

Test your knowledge on lipids with this quiz based on Chapter 11 of Biochemistry. Explore definitions, roles, and classifications of lipids as you go through the flashcards. Perfect for reinforcing your understanding of this essential biomolecule.