Lipids Chapter 06

What Are Lipids? Organic macronutrients Roles of lipids Oil Fat Insoluble in water Hydrophobic Roles of lipids Oil Liquid at room temperature Fat Solid at room temperature Major lipids

What Are Lipids? Fatty acids Most abundant type of lipid in body and diet Structure Carbon chain Alpha end – carboxylic acid group Omega end – methyl group Types Number of carbons Types & locations of chemical bonds

Fatty Acid Structure

Fatty Acids, Triglycerides, and Phospholipids

What Are Lipids? Fatty acids Chain length Most naturally-occurring fatty acids have even number Short-chain, medium-chain, and long-chain fatty acids Chemical properties Physiological functions Solubility in water

Fatty Acids Can Have Different Chain Lengths?

What Are Lipids? Fatty acids Chemical bonds Single bonds Double bonds Saturated fatty acids (SFAs) Double bonds Monounsaturated fatty acids (MUFAs) Polyunsaturated fatty acids (PUFAs) Chemical nature

Saturated & Unsaturated Fatty Acids

What Are Lipids? Fatty acids Cis double bonds Trans double bond Hydrogens on same side of double bond Trans double bond Hydrogens on opposite sides of double bond Trans fatty acids in food Naturally occurring Hydrogenation

Cis versus Trans Fatty Acids Insert figure 6.5 from page 128 here

What Are Lipids? Naming fatty acids Characteristics Alpha naming system Relative to carboxylic acid end Omega naming system Double bond’s distance from the methyl end Omega-3 and omega-6 fatty acids Common names

The Alpha (α) Naming System

What Are Essential, Conditionally Essential, & Nonessential Fatty Acids? Linoleic acid 18 carbons; 2 double bonds; omega-6 fatty acid Arachidonic acid Linolenic acid 18 carbons; 3 double bonds; omega-3 fatty acid EPA DHA

What Are Essential, Conditionally Essential, & Nonessential Fatty Acids? Eicosanoids Roles Omega-6 eicosanoids Cause inflammation and constriction of blood vessels Omega-3 eicosanoids Reduce inflammation and stimulate dilation of blood vessels

Fatty Acid Metabolism & Eicosanoid Formation

What Are Essential, Conditionally Essential, & Nonessential Fatty Acids? Deficiency Primary Rare Secondary Diseases that disrupt lipid absorption Cystic fibrosis

What Are Essential, Conditionally Essential, & Nonessential Fatty Acids? Conditionally essential fatty acids Infancy Arachidonic acid DHA Dietary sources of fatty acids Linoleic acid Linolenic acid EPA and DHA

What Are Essential, Conditionally Essential, & Nonessential Fatty Acids? Dietary sources SFAs PUFAs MUFAs Roles

Distribution of Fatty Acid Types in Commonly Consumed Lipids

What Is the Difference between Mono-, Di- & Triglycerides? Number of fatty acids in chemical structure Saturation of fatty acids Lipogenesis Fatty acids combine with glycerol

Triglyceride Structure

What Is the Difference between Mono-, Di- & Triglycerides? Richest source of energy 9 kcal per gram Lipolysis β-oxidation Ketones Ketogenesis

What Is the Difference between Mono-, Di- & Triglycerides? Storage in adipose tissue Adipocytes Stored as triglycerides Advantages Location of adipose tissue Subcutaneous vs. visceral adipose tissue Role of insulin Insulation

What Are Phospholipids and Sterols? Roles Cell membranes Transport of lipids in bloodstream No dietary requirements for either of them

What Are Phospholipids and Sterols? Has two fatty acids Phosphate-containing hydrophilic head Amphipathic Roles Cell membranes Digestion, absorption, and transport of lipids Other functions

Phospholipid Structure

Cell Membrane Made from Phospholipid Bilayer

What Are Phospholipids and Sterols? Multi-ring structure Cholesterol Synthesis of bile acid Component of cell membranes Reproductive hormones Other roles Sources Phytosterols

Structure of Cholesterol

Cholesterol Content of Selected Foods

How Are Triglycerides Digested, Absorbed, & Circulated? Basic goal of digestion Mouth Lingual lipase Stomach Gastrin Gastric lipase

Overview of Triglyceride Digestion

How Are Triglycerides Digested, Absorbed, & Circulated? Small intestine Phase 1: Micelle formation Bile disperses large globules into smaller droplets Emulsification Gallbladder disease Removal of gallbladder

Emulsification of Lipids to Form Micelles in the SI

How Are Triglycerides Digested, Absorbed, & Circulated? Small intestine Phase 2: Pancreatic lipase Secretin Release of pancreatic lipase Final products of lipid digestion Fatty acids Glycerol Monoglycerides

How Are Triglycerides Digested, Absorbed, & Circulated? Absorption Two ways Unassisted transport into intestinal cells Short- and medium-chain fatty acids Repackaging into micelles in lumen Contents released into intestinal cell’s interior

How Are Triglycerides Digested, Absorbed, & Circulated? Circulation Depends on hydrophilic nature of lipid More hydrophilic Circulation in blood attached to albumin Circulates to liver Less hydrophilic Circulated in lymph Lipoproteins Liporotein lipase

Absorption & Circulation of Lipids

The Lipoproteins

What Are the Types & Functions of Various Lipoproteins? Produced in the liver Transport lipids in the blood Complex globular structures Apoprotein Chylomicron Largest and least dense Produced in small intestine Transport dietary lipids exclusively

Origins and Major Functions of Lipoproteins

What Are the Types & Functions of Various Lipoproteins? Very low-density lipoprotein (VLDL) Lower lipid-to-protein ratio than chylomicrons Primary function Low-density lipoproteins (LDL) LDL receptors “Bad” cholesterol Plaque Intermediate-density lipoprotein (IDL)

What Are the Types & Functions of Various Lipoproteins? High-density lipoproteins (HDL) Lowest lipid-to-protein ratio Collect excess cholesterol Transport it back to the liver “Good” cholesterol Different types Not equally effective in removing cholesterol

How Are Dietary Lipids Related to Health? High-fat foods and obesity Major public health concern Associated health risks Fat substitutes Examples Typically made from carbohydrates or proteins Products may be fat free, but not calorie free

How Are Dietary Lipids Related to Health? Cardiovascular disease Common types Heart disease Stroke Atherosclerosis Blood clot Aneurysm Lipids of concern Genetics

Causes of Cardiovascular Disease

How Are Dietary Lipids Related to Health? Cardiovascular disease Nutritional guidelines Moderate overall energy intake Balance your macronutrients Whole grains Dietary fiber Cancer Recommendations

What Are Some Overall Dietary Recommendations for Lipids? Essential fatty acids Consume adequate amounts DRIs AIs Omega-3 fatty acid intake Limit cholesterol, SFAs, and Trans fat Dietary guidelines Total lipid consumption AMDRs

Reading Nutrition Facts Panels