Lipids Chapter 06 What Are Lipids Organic macronutrients

Lipids Chapter 06

What Are Lipids? • Organic macronutrients • 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 • 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 • 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? • Essential 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? • Essential 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? • Essential 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? • 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? • Triglycerides • Richest source of energy • 9 kcal per gram • Lipolysis • β-oxidation • Ketones • Ketogenesis

What Is the Difference between Mono-, Di- & Triglycerides? • 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? • Phospholipids • 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? • 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

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