Lipids Flashcards

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Questions and Answers

What are the characteristics of lipids?

Generally hydrophobic, amphipathic, water-insoluble organic compounds, do not form large covalent polymers, associate through noncovalent forces, have a polar (hydrophilic) head and a nonpolar (hydrophobic) hydrocarbon tail.

Why are lipids hydrophobic?

A large portion of their structure is hydrocarbon.

What are the functions of lipids?

Energy storage, signaling, formation of membrane structures.

What are the types of lipids?

Triacylglycerols, glycerophospholipids, waxes, prostaglandins, and steroids. Signup and view all the answers

What are membranes?

Partitions that divide compartments from one another and separate the cell from its surroundings. Signup and view all the answers

What are the features of cellular membranes?

Selective membrane permeability, establish order by compartmentation, allow free energy to be stored in concentration gradients. Signup and view all the answers

Where can you find lipids in living organisms?

Rarely found free in solution; they are in complex with soluble protein transporters or part of higher-order assemblies like micelles, vesicles, and bilayers. Signup and view all the answers

What are the interactions that hold lipid molecules in water together?

Noncovalent interactions including the hydrophobic effect and van der Waals interactions. Signup and view all the answers

How do lipids form membranes in aqueous solutions?

The polar hydrophilic head groups of membrane lipids associate with water, allowing the formation of surface monolayers, bilayers, micelles, and vesicles. Signup and view all the answers

What is the structure of fatty acid?

A hydrophilic carboxylate group at one end of the hydrocarbon chain, typically containing 12-24 carbons. Signup and view all the answers

What are the two types of fatty acids?

Saturated fatty acid and unsaturated fatty acid. Signup and view all the answers

What is saturated fatty acid?

The carbons of the tail are all saturated with hydrogen atoms with no double bonds. Signup and view all the answers

What are the features of saturated fatty acids?

Single C-C bonds, fit closely together in a regular pattern, strong attractions between fatty acid chains, high melting points. Signup and view all the answers

What is unsaturated fatty acid?

Contain one or more double bonds and are typically liquid at room temperature. Signup and view all the answers

Why are saturated fats solid at room temperature?

Long saturated chains can pack closely together, increasing van der Waals contacts and forming regular bonds. Signup and view all the answers

Why are unsaturated fats liquid at room temperature?

The bends caused by cis double bonds prevent tight packing, making them more dynamic. Signup and view all the answers

What are the two orientations of double bonds in unsaturated fatty acids?

Cis and trans. Signup and view all the answers

What does the cis double bond do to the hydrocarbon chain?

Inserts a bend into the hydrocarbon chain. Signup and view all the answers

Can the bonds in the hydrocarbon chain rotate?

True Signup and view all the answers

Why do most naturally occurring fatty acids have an even number of carbon atoms?

They are synthesized by sequential additions of a two-carbon precursor. Signup and view all the answers

What are the possible structures of the hydrocarbon chains?

Hydrocarbon chains are linear in most fatty acids, with some containing branches or cyclic structures. Signup and view all the answers

What does the nomenclature of the fatty acid 20:4c^5,8,11,14 tell you?

20 carbons, 4 cis double bonds, double bonds at C5, C8, C11, C14. Signup and view all the answers

How do nutritionists name fatty acids?

By the location of C=C bonds using terms like omega carbon. Signup and view all the answers

What is w-3 fatty acid?

A fatty acid with a double bond at the third C atom from the w carbon. Signup and view all the answers

What is the average pKa of fatty acids?

4.5. Fatty acids are weak acids defined as RCOOH ⇌ RCOO- + H+. Signup and view all the answers

Study Notes

Characteristics of Lipids

Generally hydrophobic or amphipathic; consist of water-insoluble organic compounds.
Do not form large covalent polymers; associate through noncovalent forces.
Composed of a polar (hydrophilic) head and a nonpolar (hydrophobic) hydrocarbon tail.

Hydrophobic Nature of Lipids

The large hydrocarbon portion of lipids contributes to their hydrophobic properties.

Functions of Lipids

Serve key roles in energy storage, cell signaling, and forming membrane structures.

Types of Lipids

Lipids with fatty acids include: triacylglycerols, glycerophospholipids, waxes, and prostaglandins.
Steroids are lipids that do not contain fatty acids.

Membranes

Membranes partition cells into compartments and separate them from their surroundings.

Features of Cellular Membranes

Exhibits selective permeability, creating compartmentalization.
Allows for the storage of free energy in concentration gradients.

Location of Lipids in Organisms

Typically not found free in solution; exist as complexes with protein transporters or in higher-order structures like micelles, vesicles, and bilayers.

Interactions in Lipid Aggregation

Lipid molecules are held together in water primarily by noncovalent interactions.
Hydrophobic effects help nonpolar tails interact, while van der Waals forces stabilize hydrocarbon regions.

Membrane Formation in Aqueous Solutions

Polar, hydrophilic head groups of membrane lipids interact with water, leading to the formation of monolayers, bilayers, micelles, and vesicles.

Structure of Fatty Acids

Composed of a hydrophilic carboxylate group and a hydrocarbon chain typically containing 12-24 carbons.

Types of Fatty Acids

Saturated fatty acids: contain no double bonds.
Unsaturated fatty acids: contain one or more double bonds.

Characteristics of Saturated Fatty Acids

Composed entirely of single C-C bonds; fit closely together in a regular pattern.
Exhibit strong intermolecular forces and high melting points (solid at room temperature).

Characteristics of Unsaturated Fatty Acids

Contain one or more double bonds; typically liquid at room temperature.
Example: Oleic acid.

Solid Nature of Saturated Fats

Long, saturated chains pack closely due to strong van der Waals interactions, resulting in higher melting points.

Liquid Nature of Unsaturated Fats

Presence of bends from cis double bonds prevents tight packing, contributing to a more dynamic structure.

Orientations of Double Bonds in Fatty Acids

Unsaturated fatty acids may have cis or trans double bonds.

Impact of Cis Double Bonds

Cis double bonds introduce a bend in the hydrocarbon chain.

Flexibility of Hydrocarbon Chains

Single bonds within the hydrocarbon chain rotate freely.

Carbon Chain Evenness in Fatty Acids

Most naturally occurring fatty acids have an even number of carbon atoms due to synthesis from two-carbon precursors.

Hydrocarbon Chain Structures

Fatty acids usually have linear hydrocarbon chains, although some may exhibit branches or cyclic structures.

Fatty Acid Nomenclature Example

20:4c^5,8,11,14 specifies 20 carbons, 4 cis-double bonds at carbons 5, 8, 11, and 14.

Naming of Fatty Acids by Nutritionists

Naming convention involves identifying the location of C=C bonds, referencing the 'omega' carbon (last C) and 'alpha' carbon (COO- carbon).

Omega-3 Fatty Acid

Defined as having a double bond at the third carbon from the omega carbon.

Average pKa of Fatty Acids

The average pKa is 4.5, indicating that fatty acids are weak acids, existing in an equilibrium between their protonated and deprotonated forms.

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Description

Test your knowledge about lipids with these flashcards. Dive into the key characteristics, structure, and functions of lipids to enhance your understanding. Perfect for students looking to grasp the fundamentals of lipid biology.