Lipids: Composition and Functions
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Questions and Answers

What is the general structure of fatty acids represented by?

  • R—CO—OH (correct)
  • R—CO—O
  • R—CO—NH2
  • R—C=O

Which of the following fatty acids has an even number of carbon atoms?

  • Butyric acid (correct)
  • Capric acid (correct)
  • Palmitoleic acid
  • Propionic acid

What differentiates saturated fatty acids from unsaturated fatty acids?

  • Hydroxyl group content
  • Length of hydrocarbon chain
  • Presence of a double bond (correct)
  • Number of carbon atoms

What type of fatty acid has a carbon chain length of 8 to 14 carbon atoms?

<p>Medium chain fatty acids (B)</p> Signup and view all the answers

Which of the following is an example of an odd chain fatty acid?

<p>Gallonic acid (C)</p> Signup and view all the answers

What is the primary component that makes lipids insoluble in water?

<p>Hydrophobic nature (A)</p> Signup and view all the answers

Which fatty acids are defined by having two or more double bonds?

<p>Polyunsaturated fatty acids (A)</p> Signup and view all the answers

What is the role of glycerol in lipids?

<p>To serve as a backbone for fatty acids (D)</p> Signup and view all the answers

What term describes fatty acids that contain two or more double bonds?

<p>Polyunsaturated fatty acids (D)</p> Signup and view all the answers

In the cis configuration of fatty acids, how are the radicals oriented around the double bond?

<p>On the same side of the bond (C)</p> Signup and view all the answers

Which of the following fatty acids is an example of a trans fat?

<p>Elaidic acid (B)</p> Signup and view all the answers

What does the notation '18:1; 9' indicate about oleic acid?

<p>18 carbon atoms with 1 double bond at position 9 (D)</p> Signup and view all the answers

What is the suffix used for saturated fatty acids in nomenclature?

<p>anoic (C)</p> Signup and view all the answers

Which system numbers carbon atoms from the methyl end of the fatty acid molecule?

<p>Omega (ω) nomenclature (B)</p> Signup and view all the answers

How many positional isomers can oleic acid have?

<p>15 (C)</p> Signup and view all the answers

What characteristic distinguishes trans fatty acids from their cis counterparts?

<p>Trans fats have radicals on opposite sides of the double bond (D)</p> Signup and view all the answers

What type of fatty acids predominantly found in coconut oil are classified as medium chain TAG?

<p>Lauric and Myristic acids (B)</p> Signup and view all the answers

Which of the following components are found in phospholipids?

<p>Fatty acids, an alcohol, and phosphoric acid residue (C)</p> Signup and view all the answers

Which of these lipids is classified as a derived lipid?

<p>Steroids (D)</p> Signup and view all the answers

What is the primary function of triglycerides in the body?

<p>Store energy (A)</p> Signup and view all the answers

Which of the following describes the structure of cholesterol?

<p>Amphipathic with a polar head and hydrophobic tail (C)</p> Signup and view all the answers

Which of the following is NOT a function of lipids?

<p>Act as enzymes (C)</p> Signup and view all the answers

Which type of lipids are characterized by containing both sugars and fatty acids?

<p>Glycolipids (D)</p> Signup and view all the answers

What characteristic do neutral lipids such as cholesterol and cholesteryl esters possess?

<p>They have nonpolar characteristics (D)</p> Signup and view all the answers

What type of fatty acid is linoleic acid classified as?

<p>Omega-6 fatty acid (A)</p> Signup and view all the answers

How do the melting points of fatty acids change with respect to chain length and unsaturation?

<p>Increase with chain length and decrease with unsaturation (C)</p> Signup and view all the answers

What are essential fatty acids?

<p>Fatty acids that must be consumed in the diet (A)</p> Signup and view all the answers

Which of the following best describes fats at room temperature?

<p>They are solid and primarily saturated (A)</p> Signup and view all the answers

What is the primary characteristic that differentiates oils from fats?

<p>Oils are liquids at room temperature (A)</p> Signup and view all the answers

What type of lipids contains esters of fatty acids with higher molecular weight monohydric alcohols?

<p>Simple lipids (D)</p> Signup and view all the answers

What happens to lipids in regions of the body subjected to cooling, such as extremities?

<p>They contain more unsaturated fatty acids (B)</p> Signup and view all the answers

What is primarily true about triacylglycerols that contain short-chain triglycerides?

<p>They are insoluble in water (A)</p> Signup and view all the answers

What is the primary function of triacylglycerols in the body?

<p>Store energy as fat (D)</p> Signup and view all the answers

Which type of lipid is primarily responsible for lowering surface tension in the alveoli of the lungs?

<p>Phospholipids (B)</p> Signup and view all the answers

Which phospholipid is the most abundant in cell membranes and plays a key role in nervous transmission?

<p>Phosphatidylcholine (A)</p> Signup and view all the answers

What distinguishes sphingomyelins from other phospholipids?

<p>They yield sphingosine upon hydrolysis (D)</p> Signup and view all the answers

Which of the following lipids is involved in apoptosis?

<p>Phosphatidylserine (C)</p> Signup and view all the answers

Why do triacylglycerols require minimal space compared to hydrated glycogen?

<p>They are non-polar and repel water (C)</p> Signup and view all the answers

What characteristic do phospholipids share that makes them suitable for forming cell membranes?

<p>They have both hydrophobic and hydrophilic regions (C)</p> Signup and view all the answers

In which layer of the cell membrane are sphingomyelins primarily found?

<p>Outer layer (C)</p> Signup and view all the answers

What effect does lower temperature have on the fluidity of the cell membrane?

<p>Decreases membrane fluidity (B)</p> Signup and view all the answers

How do lipid soluble substances travel across the cell membrane?

<p>Via simple diffusion (B)</p> Signup and view all the answers

What is the significance of the asymmetry in membrane phospholipids?

<p>It aids in cell signaling and maintaining membrane shape (A)</p> Signup and view all the answers

Which type of proteins are primarily responsible for the movement of ions and small molecules across the membrane?

<p>Integral protein channels (B)</p> Signup and view all the answers

What role do sphingomyelins play in cell membranes?

<p>They are involved in cell signaling and apoptosis (D)</p> Signup and view all the answers

What happens to phospholipids at high temperatures?

<p>They have higher kinetic energy, increasing membrane fluidity (B)</p> Signup and view all the answers

What can excessive fat deposits lead to in terms of health?

<p>Obesity and increased risk of heart attack (D)</p> Signup and view all the answers

Which of the following best describes the role of integral proteins in the cell membrane?

<p>They facilitate the movement of non-lipid soluble substances (B)</p> Signup and view all the answers

Flashcards

Lipids

A diverse group of organic compounds found in plants and animals that are largely insoluble in water but soluble in organic solvents.

Fatty Acids

Aliphatic carboxylic acids with a hydrocarbon chain and a carboxyl group (-COOH).

Saturated Fatty Acids

Fatty acids with only single bonds between carbon atoms.

Unsaturated Fatty Acids

Fatty acids with one or more double bonds between carbon atoms.

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Even Chain Fatty Acids

Fatty acids with an even number of carbon atoms. Common in nature.

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Odd Chain Fatty Acids

Fatty acids with an odd number of carbon atoms. Found in microbes and milk.

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Glycerol

A three-carbon alcohol with three hydroxyl groups.

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Classification of Fatty Acids

Categorization of fatty acids based on the number of carbon atoms, length of the hydrocarbon chain, and the presence of double bonds (saturated/unsaturated).

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Polyunsaturated fatty acids (PUFAs)

Fatty acids with two or more double bonds.

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Geometric Isomerism in Fatty Acids

Different arrangements of groups around a double bond in unsaturated fatty acids.

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Cis isomer

Fatty acid where groups are on the same side of the double bond.

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Trans isomer

Fatty acid where groups are on opposite sides of the double bond.

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Positional Isomers (Fatty Acids)

Fatty acids with different locations of double bonds along the chain.

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Omega (ω) system nomenclature

Fatty acid numbering system starting from the methyl end.

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Fatty acid nomenclature (general)

Describing fatty acids using number of carbons, double bonds, and position.

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Fatty Acid Naming with Double Bonds

Fatty acids with double bonds have a "enoic" ending.

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TRIACYLGLYCEROLS

A type of lipid formed by three fatty acids esterified to a glycerol molecule.

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Phospholipids

Lipids containing phosphate, fatty acids, an alcohol (usually glycerol or sphingosine), and often a nitrogen-containing base.

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Glycolipids

Lipids containing a fatty acid, sphingosine, and a carbohydrate, like a sugar.

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Derived lipids

Lipids produced by the hydrolysis of simple and compound lipids.

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What makes acylglycerols, cholesterol, and cholesteryl esters 'neutral lipids'?

They are uncharged.

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Sterols

A type of lipid with a steroid alcohol structure.

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Cholesterol

A sterol with a rigid, planar structure and an amphipathic nature.

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Functions of Lipids

Lipids play diverse roles in biological systems, including energy storage, structural components, metabolic regulation, insulation, and body shaping.

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Omega Fatty Acids

Fatty acids are classified using the 'omega' system, which counts carbons from the methyl end, not the carboxyl end, to the first double bond.

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6 Fatty Acid

Linoleic acid is an 6 fatty acid, meaning its first double bond is six carbons away from the methyl (CH3) end.

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Essential Fatty Acids

Certain fatty acids, like linoleic acid, cannot be made by the body and must be obtained through diet.

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Melting Point vs. Unsaturation

The melting point of fatty acids increases with chain length and decreases with unsaturation. More double bonds lead to lower melting points.

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Triacylglycerols: Structure

Triacylglycerols are composed of glycerol (a 3-carbon alcohol) linked to three fatty acid chains.

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Storage vs. Membrane Lipids

Lipids for energy storage tend to be more saturated, while membrane lipids are more unsaturated for fluidity.

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Fats vs. Oils

Fats are solid triacylglycerols at room temperature, usually containing saturated fatty acids, while oils are liquid and contain unsaturated fatty acids.

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Hard vs. Soft Fats

Fats with longer chains and higher saturation tend to be 'hard', while fats with shorter chains and more unsaturation are 'soft'.

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Fat-soluble vitamins

Vitamins A, D, E, and K, which are absorbed into the bloodstream with the help of fats.

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Storage of energy

Triacylglycerols (TAGs) are the main form of energy storage in adipose tissue. They store excess calories in a compact form.

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Phospholipid bilayer

The structural basis of cell membranes. It is composed of two layers of phospholipids with their hydrophobic tails facing inward and hydrophilic heads facing outward.

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Amphipathic

A molecule with both hydrophilic (water-loving) and hydrophobic (water-repelling) regions.

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Lecithin

A type of phospholipid, phosphatidylcholine, found abundantly in cell membranes. It plays a role in nervous transmission.

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Sphingomyelins

Phospholipids found in the outer layer of the cell membrane and myelin sheath. They are involved in cell signaling and apoptosis.

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Phosphatidylethanolamine

A phospholipid found in cell membranes, also known as 'cephalin'.

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Phosphatidylserine

A phospholipid found in most tissues. It plays a role in apoptosis.

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Membrane Fluidity

The ability of the cell membrane to move and change shape, influenced by factors like temperature and lipid composition.

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Temperature's effect on membrane fluidity

Lower temperatures decrease fluidity by making phospholipids pack closer, while higher temperatures increase fluidity by providing more kinetic energy to overcome intermolecular forces.

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Membrane Permeability

The ability of molecules to pass through the cell membrane, which varies depending on their size, charge, and lipid solubility.

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Lipid-soluble transport

The movement of substances that dissolve in lipids through the cell membrane by simple diffusion.

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Non-lipid-soluble transport

The movement of substances that don't dissolve in lipids through the cell membrane by using protein channels or transporters.

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Cell Membrane Asymmetry

The difference in lipid composition between the inner and outer leaflets of the cell membrane, contributing to its structural integrity and function.

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Roles of Lipids in Health

Lipids play vital roles in health, but abnormalities in their metabolism can lead to serious conditions like obesity, atherosclerosis, and cardiovascular diseases.

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Study Notes

Lipids: Composition, Structure, and Functions

  • Lipids are a heterogeneous group of organic substances found in plant and animal tissues.
  • They are relatively insoluble in water but soluble in nonpolar organic solvents (e.g., benzene, chloroform, ether).
  • Lipids consist of carbon, hydrogen, and oxygen.
  • Lipids are made up of fatty acids and glycerol.

Lesson Learning Outcomes

  • Students should be able to describe the general structure of lipids.
  • Students should be able to classify lipids and fatty acids.
  • Students should be able to describe the physiochemical properties of lipids.
  • Students should be able to describe the functions of lipids.
  • Students should be able to outline the clinical significance of lipids.

Glycerol

  • Glycerol is an alcohol with three carbons, five hydrogens, and three hydroxyl (OH) groups.

Fatty Acids

  • Fatty acids are aliphatic carboxylic acids.
  • The general formula is R-CO-OH.
  • The COOH group represents the functional group.
  • Physical properties vary depending on the R group (hydrocarbon chain).

Classification of Fatty Acids

  • Based on the number of carbon atoms:
    • Even-chain fatty acids are prevalent in naturally occurring lipids (e.g., 2, 4, 6, etc.).
    • Odd-chain fatty acids are found in microbial cell walls and milk (e.g., 3, 5, 7, etc.).
  • Based on the length of the hydrocarbon chain:
    • Short-chain (2-6 carbon atoms).
    • Medium-chain (8-14 carbon atoms).
    • Long-chain (16 or more, often up to 24 carbon atoms).
    • Very long-chain (more than 24 carbon atoms).
  • Based on the nature of the hydrocarbon chain:
    • Saturated fatty acids: contain only single bonds.
    • Unsaturated fatty acids:
      • Monoenoic (monounsaturated): one double bond.
      • Polyenoic (polyunsaturated): two or more double bonds.
    • Branched-chain fatty acids.
    • Hydroxy fatty acids.

Isomerism

  • Geometric Isomers:
    • Cis isomers have substituents on the same side of the double bond (often more reactive).
    • Trans isomers have substituents on opposite sides of the double bond.
  • Positional Isomers: Variations in the location of double bonds create different isomers.

Nomenclature of Fatty Acids

  • Fatty acids are often expressed using a formula system indicating the number of carbon atoms, double bonds, and positions of the double bonds (e.g., 18:1;9).
  • Another naming system uses the Greek letter omega (ω) to indicate the position of the last double bond starting from the methyl end of the fatty acid molecule.

Saturated Fatty Acids

  • General formula: CH3-(CH2)n-COOH
  • Examples include acetic acid, butyric acid, palmitic acid, and stearic acid.

Unsaturated Fatty Acids

  • The presence of at least one double bond makes a fatty acid unsaturated.
  • Polyunsaturated fatty acids have two or more double bonds.
  • Unsaturated fatty acids exhibit geometrical isomerism at the double bonds.

Essential Fatty Acids

  • Essential fatty acids cannot be synthesized in the body and must be obtained from the diet.
  • Lack of essential fatty acids can cause growth retardation and other deficiency symptoms.
  • Examples include linoleic acid (ω-6) and linolenic acid (ω-3).
  • Arachidonic acid (ω-6) is not essential but important for various functions.

Physical and Physiologic Properties of Fatty Acids

  • Melting points increase with chain length and decrease with unsaturation.
  • A triacylglycerol with 12+ carbons or more saturated fatty acids at body temperature is solid.
  • A triacylglycerol containing polyunsaturated fatty acids is liquid below 0°C.

Classification of Lipids

  • Simple lipids: Esters of fatty acids with glycerol or other higher alcohols.
    • Fats (solid)
    • Oils (liquid)
    • Waxes (esters of fatty acids with higher molecular weight alcohols)
  • Compound lipids: Fatty acids esterified with an alcohol and other groups.
    • Phospholipids (contain phosphoric acid)
      • Glycerophospholipids (glycerol as alcohol).
      • Sphingophospholipids (sphingosine as alcohol).
    • Glycolipids (contain a carbohydrate).
    • Other complex lipids (e.g., sulfolipids, amino lipids, lipoproteins).
  • Derived lipids: Products of the hydrolysis of simple and compound lipids.
    • Fatty acids, glycerol, steroids, other alcohols, fatty aldehydes, ketone bodies, hydrocarbons, lipid-soluble vitamins and micronutrients.
    • Neutral lipids (uncharged acylglycerols, cholesterol, and cholesteryl esters).
    • Sterols (e.g., cholesterol).

Functions of Lipids

  • Storage form of energy (triglycerides).
  • Structural components of biomembranes (phospholipids and cholesterol).
  • Metabolic regulators (steroid hormones and prostaglandins).
  • Insulation against temperature changes (fat).
  • Protection of internal organs.
  • Aid in absorption of fat-soluble vitamins (A, D, E, K).
  • Improve taste and palatability of food.
  • Act as surfactants, detergents, and emulsifying agents.

Clinical Applications

  • Excessive fat deposits cause obesity.
  • Abnormalities in cholesterol and lipoprotein metabolism lead to atherosclerosis and cardiovascular diseases.
  • Diabetes mellitus can lead to ketosis, affecting fatty acid and lipoprotein metabolisms.

Saponification

  • Hydrolysis of triacylglycerols by alkali produces glycerol and soaps.

Lipid Peroxidation

  • Peroxidation of lipids exposed to oxygen can cause food spoilage (rancidity), and damage to living tissues.
  • It is a chain reaction involving reactive oxygen species.
  • Antioxidants can control and reduce lipid peroxidation.

Membrane Functions

  • Fluidity: influenced by cholesterol, chain length, and saturation of fatty acid tails.
  • Permeability: cell membranes have selective permeability barrier function.
  • Shape: cell membrane asymmetry of phospholipids (e.g., outer leaflet: choline-containing phospholipids; inner leaflet: amino phospholipids).

Phospholipids

  • The main lipid components of membranes.
  • Amphipathic, with both hydrophobic and hydrophilic portions.
  • Examples include phosphatidylcholines (lecithins), sphingomyelins, phosphatidylethanolamine (cephalin), phosphatidylserine, and phosphatidylinositol.

Cardiolipin

  • Found only in mitochondria.
  • Essential for mitochondrial function.
  • Decreased levels or alterations affect mitochondrial function and can contribute to various diseases.

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Description

Explore the fascinating world of lipids, including their structure, classification, and functions in biological systems. This quiz will cover the key properties of lipids and their clinical significance, helping students deepen their understanding of this essential topic in biochemistry.

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