Harper's Biochemistry Chapter 21 - Lipids of Physiologic Significance

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Questions and Answers

Which type of lipid structures can form lipid bilayers?

Glycerophospholipids (correct)

Steroids

Triacylglycerols

Fatty acids

What structural feature distinguishes sphingolipids from glycerophospholipids?

Presence of a glycerol backbone

Saturation of fatty acids

Formation of lipid rafts

Presence of a sphingosine backbone (correct)

What role do lipid rafts play in cell membrane structure?

Promote apoptosis signaling

Concentrate specific proteins and lipids (correct)

Facilitate lipid hydrolysis

Prevent membrane fluidity

Which of the following is NOT a characteristic of apoptotic signaling regulated by lipids?

Formation of lipid micelles Signup and view all the answers

Lipid bilayers primarily function to:

Facilitate selective permeability Signup and view all the answers

What structure is characteristic of glycerophospholipids?

Glycerol linked to a phosphocholine group Signup and view all the answers

Which of the following components is NOT typically found in sphingolipids?

Glycerol backbone Signup and view all the answers

What role do lipid rafts play in cell membranes?

They act as platforms for cell signaling Signup and view all the answers

Which lipids are most associated with apoptosis signaling?

Phosphatidylserine Signup and view all the answers

In the structure of sphingomyelin, which component is linked to the sphingosine?

Phosphate Signup and view all the answers

What is a key structural difference between glycerophospholipids and sphingolipids?

Sphingolipids have more structural variety Signup and view all the answers

What is the primary function of choline in phosphatidylcholine?

To stabilize the membrane structure Signup and view all the answers

Which of the following is a function of the fatty acid components in sphingolipids?

Provides structural integrity to the membrane Signup and view all the answers

What is the primary structural component of biologic membranes formed by amphipathic lipids?

Lipid bilayers Signup and view all the answers

Which type of lipid is primarily involved in the formation of micelles in an aqueous medium?

Bile salts Signup and view all the answers

Which statement accurately describes the orientation of amphipathic lipids at oil-water interfaces?

Polar groups are in the water phase and nonpolar groups in the oil phase. Signup and view all the answers

Which of the following lipids can potentially be used as drug carriers in targeted cancer therapy?

Phospholipids Signup and view all the answers

What forms when there is a critical concentration of amphipathic lipids in an aqueous medium?

Micelles Signup and view all the answers

Which statement about emulsions, formed in an aqueous medium, is correct?

They are larger particles formed by nonpolar lipids. Signup and view all the answers

Which type of lipid is least likely to be involved in the formation of lipid bilayers?

Triacylglycerols Signup and view all the answers

In biological membranes, lipid rafts are primarily composed of which types of lipids?

Cholesterol and sphingolipids Signup and view all the answers

Which amphipathic lipid is specifically mentioned as a potential carrier for gene transfer into vascular cells?

Phospholipids Signup and view all the answers

Which function is least associated with liposomes formed from amphipathic lipids?

Formation of energy reserves Signup and view all the answers

Which statement accurately describes the role of choline in the cell membrane?

Choline serves as a precursor for the neurotransmitter acetylcholine. Signup and view all the answers

What is the significance of dipalmitoyl lecithin in lung function?

It is crucial for the surfactant that reduces surface tension in the lungs. Signup and view all the answers

Which of the following correctly identifies the major constituents of the cell membrane?

Glycerophospholipids and cholesterol. Signup and view all the answers

In what way does the absence of dipalmitoyl lecithin in premature infants affect respiratory health?

It results in respiratory distress syndrome due to increased surface tension. Signup and view all the answers

Which of these lipids is not a major type of glycerophospholipid derived from choline?

Phosphatidylserine. Signup and view all the answers

Which process can be affected by lipid rafts in the cell membrane?

Cell signaling and membrane fluidity. Signup and view all the answers

What cellular function do sphingolipids significantly contribute to?

Signaling pathways implicated in apoptosis. Signup and view all the answers

Which lipid type is characterized primarily by containing a sphingosine backbone?

Sphingomyelins. Signup and view all the answers

What is the primary role of glycolipids in the cell membrane?

Cell recognition and signaling. Signup and view all the answers

How do Glycerophospholipids behave in relation to aqueous environments?

They can form micelles by orienting their hydrophilic heads outward. Signup and view all the answers

Which statement accurately describes the structure of glycerophospholipids?

They consist of a glycerol backbone, two fatty acid tails, and a phosphate group attached to a polar head. Signup and view all the answers

What role do sphingolipids play in cell membranes?

They contribute to the formation of lipid rafts, enhancing cell signaling. Signup and view all the answers

Which characteristic is essential for the formation and function of lipid rafts?

The presence of cholesterol and specific proteins. Signup and view all the answers

How does lipid peroxidation influence apoptosis signaling?

It generates free radicals that can initiate apoptosis. Signup and view all the answers

What is a defining feature of membranes formed by phospholipids and sphingolipids?

They create a bilayer structure with hydrophobic and hydrophilic regions. Signup and view all the answers

Which of the following correctly describes the role of cholesterol in cell membranes?

It maintains membrane fluidity and stability under varying temperatures. Signup and view all the answers

What is the primary function of glycosphingolipids in membranes?

Cell recognition and signaling. Signup and view all the answers

How does the degree of unsaturation in fatty acids affect membrane properties?

It increases membrane permeability and fluidity. Signup and view all the answers

Which of the following statements accurately differentiates between cis and trans carbon–carbon double bonds?

Trans bonds promote a more linear structure, while cis bonds create kinks. Signup and view all the answers

What is a fundamental reason why antioxidants are important in lipid metabolism?

They prevent the initiation of lipid peroxidation and protect cell membranes. Signup and view all the answers

Which lipid class is most directly involved in the formation of eicosanoids?

Unsaturated fatty acids Signup and view all the answers

What structural feature differentiates cholesterol from most other lipids?

Presence of a cyclic nucleus Signup and view all the answers

In relation to lipid peroxidation, which statement is accurate regarding free radicals?

They can cause damage to tissues. Signup and view all the answers

How does the chain length of fatty acids affect their melting point?

Longer chains increase melting point. Signup and view all the answers

Which functional property of amphipathic lipids is crucial for membrane formation?

Balancing hydrophobic and hydrophilic properties Signup and view all the answers

What is the primary function of antioxidants in lipid metabolism?

Protecting lipids from peroxidation Signup and view all the answers

Which factor influences the behavior of lipids in an aqueous environment?

Degree of saturation Signup and view all the answers

What is the primary conformation of the rings in naturally occurring steroids?

Chair form Signup and view all the answers

Which junction between the rings in naturally occurring steroids is trans?

B and C rings Signup and view all the answers

What occurs to ergosterol when it is irradiated with ultraviolet light in the skin?

It opens ring B to form vitamin D2 Signup and view all the answers

Which type of configuration is usually present at the junctions between the rings in natural steroids?

Mixed configurations Signup and view all the answers

What aspect of the steroid nucleus contributes to the formation of numerous stereoisomers?

Asymmetry within the steroid structure Signup and view all the answers

Which fatty acid is found in nearly all fats and has one double bond?

Palmitoleic acid Signup and view all the answers

Which fatty acid is identified as possibly the most common in natural fats?

Oleic acid Signup and view all the answers

Which of the following fatty acids has three double bonds?

α-Linolenic acid Signup and view all the answers

What is the systematic name of the fatty acid commonly known as Arachidonic acid?

all-cis-5,8,11,14-Eicosatetraenoic acid Signup and view all the answers

Which aquatic oil is particularly high in Eicosapentaenoic acid (EPA)?

Salmon oil Signup and view all the answers

Which unsaturated fatty acid is characterized by having four double bonds?

Arachidonic acid Signup and view all the answers

What is the significance of Elaidic acid in dietary fats?

A primary component in ruminant milk Signup and view all the answers

Which fatty acid is abundant in oil from evening primrose and borage?

γ-Linolenic acid Signup and view all the answers

Which of the following fatty acids is characterized by having six double bonds?

Cervonic acid Signup and view all the answers

What characterizes the leukotrienes and lipoxins derived from the lipoxygenase pathway?

They possess three or four conjugated double bonds. Signup and view all the answers

What is the typical configuration of double bonds in naturally occurring unsaturated fatty acids?

Cis configuration. Signup and view all the answers

In unsaturated fatty acids, what phenomenon occurs due to the presence of carbon-carbon double bonds?

Geometric isomerism. Signup and view all the answers

What structural change occurs in the carbon chains of saturated fatty acids at higher temperatures?

They undergo shortening. Signup and view all the answers

Which type of prostaglandin is characterized by the presence of a keto group at position 9?

PGE2. Signup and view all the answers

What effect do leukotrienes have on the respiratory system?

They induce bronchoconstriction. Signup and view all the answers

Which of the following statements regarding trans-fatty acids is correct?

They originate from ruminant fat. Signup and view all the answers

What is the primary effect of increasing temperatures on biomembranes composed of saturated fatty acids?

They become thinner. Signup and view all the answers

What is the primary difference between the 'E' and 'F' types of prostaglandins in terms of functional groups?

E type has a keto group, F type has a hydroxyl group. Signup and view all the answers

What outcome is primarily associated with the presence of double bonds in fatty acids?

Increased membrane fluidity. Signup and view all the answers

What role does cardiolipin play in mitochondrial membranes?

It is essential for proper mitochondrial function. Signup and view all the answers

Which statement best describes the structural difference between glycerophospholipids and sphingolipids?

Glycerophospholipids have a glycerol backbone, while sphingolipids have a sphingosine backbone. Signup and view all the answers

How does phosphatidylinositol 4,5-bisphosphate (PIP2) function in cellular signaling?

It gets cleaved to produce internal signaling molecules. Signup and view all the answers

What is a primary function of the hydrocarbon tails in phospholipids?

To create hydrophobic interactions in the membrane. Signup and view all the answers

How do plasmalogens differ from typical phosphatidylethanolamine?

They feature an ether link instead of an ester link. Signup and view all the answers

What can alterations in cardiolipin levels indicate?

Mitochondrial dysfunction related to various diseases. Signup and view all the answers

Which phospholipid is implicated in promoting atherosclerosis?

Phosphatidylinositol. Signup and view all the answers

What key characteristic is shared by mitochondrial phospholipids such as cardiolipin and plasmalogens?

Both contribute to membrane fluidity and integrity. Signup and view all the answers

What type of substances are diacylglycerol and inositol trisphosphate upon PIP2 cleavage?

Second messengers. Signup and view all the answers

Which of the following best describes the impact of aging on cardiolipin levels?

Decreased levels are associated with mitochondrial dysfunction. Signup and view all the answers

Match the following fatty acids with their characteristics:

Oleic acid = Cis configuration, V shape Elaidic acid = Trans configuration, straight shape Arachidonic acid = Four cis double bonds, U shape Thromboxanes = Cyclopentane ring interrupted with an oxygen atom Signup and view all the answers

Match the following eicosanoids with their categories:

Prostaglandins (PGs) = Derived from eicosa polyenoic fatty acids Leukotrienes (LTs) = Derived from arachidonic acid Lipoxins (LXs) = Forms from lipoxygenase pathway Thromboxanes (TXs) = Involved in blood clotting Signup and view all the answers

Match the compounds with their related structures:

Cyclopentane ring = Prostaglandins Oxane ring = Thromboxanes Double bond in cis configuration = Bent shape Double bond in trans configuration = Straight shape Signup and view all the answers

Match the following statements with their corresponding eicosanoids:

Prostaglandins = Exist in virtually every mammalian tissue Leukotrienes = Act as inflammatory mediators Lipoxins = Counteract inflammation Thromboxanes = Promote platelet aggregation Signup and view all the answers

Match the following descriptions with the corresponding terms:

Cis double bonds = Increase molecular bending Trans double bonds = Alter spatial relationships in lipids Eicosa fatty acids = Comprise 20-carbon length Polyunsaturated fatty acids = Contain two or more double bonds Signup and view all the answers

Match the following types of unsaturated fatty acids with their configuration:

Cis fatty acids = Double bonds in the same plane Trans fatty acids = Double bonds in opposite planes Oleic acid = Cis configuration Elaidic acid = Trans configuration Signup and view all the answers

Match the following eicosanoid derivatives with their formation pathway:

Prostaglandins = Cyclooxygenase pathway Leukotrienes = Lipoxygenase pathway Thromboxanes = Cyclooxygenase pathway Lipoxins = Lipoxygenase pathway Signup and view all the answers

Match the following unsaturated fatty acids with their characteristics:

Cis double bonds = Bend the carbon chain Trans double bonds = Straighten the carbon chain Naturally occurring unsaturated fatty acids = Always in cis configuration Partially hydrogenated oils = Contain trans fatty acids Signup and view all the answers

Match the following groups of compounds with their unique features:

Leukotrienes = Cause bronchoconstriction Prostaglandins = Contain a keto group Lipoxins = Involved in inflammation Eicosanoids = Derived from fatty acids Signup and view all the answers

Match the following terms related to fatty acid behavior with their descriptions:

Cis-trans isomerism = Orientation around double bonds Conjugated double bonds = Shared electrons between alternating bonds Saturated fatty acids = No double bonds Unsaturated fatty acids = Contain one or more double bonds Signup and view all the answers

Study Notes

Lipids of Physiologic Significance

Lipids are a diverse group of compounds including fats, oils, steroids, waxes, and related molecules.
They are relatively insoluble in water but soluble in nonpolar solvents.
They are important in the diet, providing energy, essential fatty acids, fat-soluble vitamins, and other lipophilic nutrients.

Objectives

Define simple and complex lipids, and identify lipid classes.
Describe the structure of saturated and unsaturated fatty acids, explaining how their length and saturation affect their melting point.
Differentiate between cis and trans carbon-carbon double bonds.
Describe the formation of eicosanoids from unsaturated fatty acids, naming classes and functions.
Explain the general structure of triacylglycerols and their function.
Explain the general structure of phospholipids and glycosphingolipids and their functions.
Explain the role of cholesterol as a precursor for important biological molecules such as hormones, bile acids, and vitamin D, and describe the shared cyclic structure of steroids
Explain why free radicals damage tissues and the three stages of lipid peroxidation.
Describe how antioxidants protect lipids from peroxidation.
Explain how amphipathic lipid molecules influence their behavior in aqueous environments and form biological membranes.

Fatty Acids

Fatty acids are commonly found as esters in fats and oils.
They typically contain an even number of carbon atoms.
They can be saturated (no double bonds) or unsaturated (one or more double bonds).

Saturated Fatty Acids

Consist of no double bonds.
Examples include acetic acid, butyric acid, valeric acid, caproic acid, palmitic acid, and stearic acid.
Their properties depend upon chain length and degree of saturation.

Unsaturated Fatty Acids

Contain one or more double bonds.
Include monounsaturated and polyunsaturated types.
Examples include oleic acid and linoleic acid.
Cis and trans isomers influence properties.

Polyunsaturated Fatty Acids (PUFAs)

Contain more than one carbon-carbon double bond in their structure.
Important for various biological roles.
Classified as omega-3, omega-6, and others, depending on the location of the first double bond from the methyl (omega) end.

Triacylglycerols (Triglycerides)

Major storage form of fatty acids.
Formed by the esterification of glycerol with three fatty acids.
Important for energy storage.

Phospholipids

Key constituents of biological membranes.
Derived from phosphatidic acid.
Contain a glycerol backbone, two fatty acid chains, a phosphate group, and a polar head group (like choline, ethanolamine, serine, or inositol).
Amphipathic nature is crucial for membrane formation.

Sphingolipids

Important membrane components.
Contain a sphingosine backbone instead of glycerol.
Examples include sphingomyelin.

Glycosphingolipids

Contain sugar moieties attached to their sphingosine backbone.
Examples include cerebrosides and gangliosides, crucial for cell signaling and recognition.

Cholesterol

Important structural component of cell membranes.
Precursor for steroid hormones, bile acids, and vitamin D.
Cholesterol structure is characterized by a specific four-ringed structure.

Lipid Peroxidation

Lipid damage through oxidation.
Initiated by free radicals.
Antioxidants defend against peroxidation.

Amphipathic Lipids

Contain both hydrophobic and hydrophilic moieties.
Crucial for membrane formation and function.
Examples include phospholipids and sphingolipids.

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Description

This quiz covers key concepts related to lipids, including their classification as simple and complex lipids, and their roles in biological functions. You will explore the structure and properties of fatty acids, the formation of eicosanoids, triacylglycerols, phospholipids, and the importance of cholesterol. Test your understanding of how these compounds contribute to health and nutrition.