LIPIDS

Lipids Essential macronutrients Provide energy Provide energy Building blocks for cell membranes Building blocks for cell membranes Form many important hormones Form many important hormones Help transport fat-soluble nutrients Help transport fat-soluble nutrients Contribute to flavor and texture of food Contribute to flavor and texture of food Often used in cooking Often used in cooking

Two unrelated types: Only thing they have in common: Hydrophobic Lipids

Two unrelated types: Only thing they have in common: Hydrophobic 1. Fats and Oils: Fatty acids DiglyceridesTriglyceridesPhospholipids Lipids

Two unrelated types: Only thing they have in common: Hydrophobic 1. Fats and Oils: Fatty acids DiglyceridesTriglyceridesPhospholipids 2. Sterols:Cholesterol and its derivatives its derivatives Lipids

Two unrelated types: Only thing they have in common: Hydrophobic 1. Fats and Oils: Fatty acids DiglyceridesTriglyceridesPhospholipids 2. Sterols:Cholesterol and its derivatives its derivatives Lipids Fuel molecules to provide and store energy. Major part of cell membranes. Form steroid hormones, bile salts, vitamin D.

Lipids: Fats and Oils Basic unit = Fatty Acid: Long chains of carbons (always even number) bonded to hydrogens with carboxyl group at one end.

Lipids: Fats and Oils Basic unit = Fatty Acid: Long chains of carbons (always even number) bonded to hydrogens with carboxyl group at one end. When metabolized, fatty acids are excellent sources of energy, but Many fatty acids are also important structural molecules and play important roles in regulating body processes.

Lipids: Fats and Oils Basic unit = Fatty Acid: Long chains of carbons (always even number) bonded to hydrogens with carboxyl group at one end. Not all fatty acids are the same: carbons = “short chain” fatty acid 6-10 carbons = “medium chain” fatty acid 12 or more carbons = “long chain” fatty acid

Lipids: Fats and Oils Basic unit = Fatty Acid: Long chains of carbons (always even number) bonded to hydrogens with carboxyl group at one end. If all carbons single-bonded to each other: Saturated If two or more carbons double-bonded: Unsaturated

Lipids: Fats and Oils Basic unit = Fatty Acid: Long chains of carbons (always even number) bonded to hydrogens with carboxyl group at one end. If all carbons single-bonded to each other: Saturated If two or more carbons double-bonded: Unsaturated Let’s take a closer look at unsaturated fatty acids

Lipids: Fats and Oils Basic unit = Fatty Acid: If two or more carbons double-bonded: Unsaturated One pair of carbons Two or more pairs of One pair of carbons Two or more pairs of double-bonded: carbons double-bonded: double-bonded: carbons double-bonded: Monounsaturated Polyunsaturated Monounsaturated Polyunsaturated

Lipids: Fats and Oils Basic unit = Fatty Acid: If two or more carbons double-bonded: Unsaturated Depending on the arrangement of the double bonds in either monounsaturated or polyunsaturated fatty acids, they are classified as either they are classified as either cis-unsaturated trans-unsaturated cis-unsaturated trans-unsaturated fatty acids fatty acids fatty acids fatty acids

Lipids: Fats and Oils

Why should we care if fatty acids in our diet are Saturated or unsaturated? Saturated or unsaturated? Monounsaturated or polyunsaturated? Monounsaturated or polyunsaturated? Cis-unsaturated or trans-unsaturated? Cis-unsaturated or trans-unsaturated? ?

Lipids: Fats and Oils Why should we care if fatty acids in our diet are Saturated or unsaturated? Saturated or unsaturated? Monounsaturated or polyunsaturated? Monounsaturated or polyunsaturated? Cis-unsaturated or trans-unsaturated? Cis-unsaturated or trans-unsaturated? Unsaturated fatty acids decrease the risk of heart disease, cancer, and other diseases. Polyunsaturated fatty acids are best ?

Lipids: Fats and Oils Why should we care if fatty acids in our diet are Saturated or unsaturated? Saturated or unsaturated? Monounsaturated or polyunsaturated? Monounsaturated or polyunsaturated? Cis-unsaturated or trans-unsaturated? Cis-unsaturated or trans-unsaturated? Trans fatty acids increase the risk of heart disease, diabetes, Alzheimer’s disease, and other diseases “Hydrogenation” is used to stabilize & preserve food but increases the trans fatty acids ?

Lipids: Fats and Oils Thus: USDA and DHHS recommend: Minimizing the amounts of Minimizing the amounts of - saturated fatty acids - saturated fatty acids - trans saturated fatty acids - trans saturated fatty acids and and Increasing the percentage of fats Increasing the percentage of fats containing polyunsaturated fatty acids containing polyunsaturated fatty acids

Lipids: Fats and Oils Fatty acids are obtained from many foods, and the human body is able to synthesize most of them. However, certain fatty acids must be obtained in the diet. We define Nonessential fatty acids as those not needed in the diet Essential fatty acids as those needed in the diet

Lipids: Fats and Oils Fatty acids are obtained from many foods, and the human body is able to synthesize most of them. However, certain fatty acids must be obtained in the diet. We define Nonessential fatty acids as those not needed in the diet Essential fatty acids as those needed in the diet Be careful! Don’t confuse “nonessential” with “nonimportant” “nonimportant” Many nonessential fatty acids are very important

Lipids: Fats and Oils There are two essential fatty acids for humans: Neither can be synthesized by human cells

Lipids: Fats and Oils There are two essential fatty acids for humans: These are examples of “omega-6” and “omega-3” fatty acids, and they are used as precursors to synthesize other beneficial fatty acids Neither can be synthesized by human cells

Other important omega-3 fatty acids (which can be in the diet or synthesized from linolenic acid) are eicosapentanoic acid (EPA) and docosohexanoic acid (DHA) Lipids: Fats and Oils

Other important omega-3 fatty acids (which can be in the diet or synthesized from linolenic acid) are eicosapentanoic acid (EPA) and docosohexanoic acid (DHA) Lipids: Fats and Oils From the Mayo Clinic: “There is evidence from multiple studies (that) recommended amounts of DHA and EPA in the form of dietary fish or fish oil supplements lowers triglycerides, reduces the risk of death, heart attack, abnormal heart rhythms, and strokes in people with known cardiovascular disease, slows the buildup of atherosclerotic plaques ("hardening of the arteries"), and lowers blood pressure slightly. However, high doses may have harmful effects, such as an increased risk of bleeding.”

Health benefits of omega-6 fatty acids are less defined: - Known to be necessary for normal skin and hair growth - Known to be necessary for normal brain function - Linked to healthy bone growth Lipids: Fats and Oils

Health benefits of omega-6 fatty acids are less defined: - Known to be necessary for normal skin and hair growth - Known to be necessary for normal brain function - Linked to healthy bone growth Lipids: Fats and Oils From the University of Maryland: “Omega-6 fatty acids may be useful for the following health conditions: Diabetic neuropathy, Rheumatoid arthritis, Allergies, Breast cancer, High blood pressure (Hypertension), & Menopausal symptoms, (However), some omega-6 fatty acids tend to promote inflammation. In fact, some studies suggest that elevated intakes of omega-6 fatty acids may play a role in Complex Regional Pain Syndrome.”

Sources of omega-3 fatty acids Soybean, canola, walnut, flaxseed oils Salmon, tuna, mackerel, fish-oil supplements Sources of omega-6 fatty acids Seeds, nuts, vegetable oils Meat, poultry, eggs Diglycerides and Triglycerides

Lipids: Fats and Oils

Fatty acids, however, are very rarely found alone in either the diet or the human body. Instead, they are linked together with a molecule called glycerol to form diglycerides and triglycerides, and they can be further modified to form phospholipids

Lipids: Fats and Oils All those carbons, however, take a lot of time to draw, so we will begin using the abbreviatons used in your book: Diglycerides Triglycerides Phospholipids ======

Structure: Glycerol + two fatty acids Glycerol + two fatty acids Glycerol + three fatty acids Glycerol + three fatty acids Hydrophobic = does not dissolve in water Functions: Energy reserve – primarily in adipose tissue 15% - 30% of body mass = fat; 95% = triglycerides 15% - 30% of body mass = fat; 95% = triglycerides Fatty acids detached & metabolized: 9kcal/g Fatty acids detached & metabolized: 9kcal/g Insulation under skin Protection (visceral fat surrounding organs) Carrier of fat-soluble vitamins Diglycerides and Triglycerides

Structure: Glycerol + two fatty acids + phosphate group + phosphate groupAmphipathic: Phospate (“head”) group hydrophilic Phospate (“head”) group hydrophilic Fatty acids (‘tails”) hydrophobic Fatty acids (‘tails”) hydrophobicFunctions Primary component of cell membranes cell membranes Lipid transport as part of lipoproteins of lipoproteinsEmulsifiers Phospholipids

Food sources: Meat, egg yolks, liver, soybeans, peanuts Moderate amounts in all foods Phospholipids

Recall: Two unrelated types: Only thing they have in common: Hydrophobic 1. Fats and Oils: Fatty acids DiglyceridesTriglyceridesPhospholipids 2. Sterols:Cholesterol and its derivatives Lipids

Sterols: Cholesterol Functions: Component of cell membranes Precursor to other substances Vitamin D Steroid hormones Bile salts Synthesized in the liver Sterols in food: Found only in animal foods

Lipids in the Diet Recommended intakes: Total fat: 65 g/day (~20-35% of calories) Total fat: 65 g/day (~20-35% of calories) Essential fatty acids: Essential fatty acids: Linoleic acid – 12 g/day Linoleic acid – 12 g/day Linolenic acid – 2 g/day Linolenic acid – 2 g/day Saturated fats: <20 g/day Saturated fats: <20 g/day Cholesterol: <300 mg/day Cholesterol: <300 mg/day

Lipids in the Diet The Facts Panel of all foods must include the total grams of fat and percentage of daily value based on a 2,000 kcal/day diet.

Lipids in the Diet The Facts Panel of all foods must include the total grams of fat and percentage of daily value based on a 2,000 kcal/day diet. If that “total fat” number is not “0”, it must also include the amounts of saturated fat, trans fat, & cholesterol. (It may, but is not required to, also list amounts of monounsaturated and polyunsaturated fats.)

Lipids in the Diet If that “total fat” number is not “0”, it must also include the amounts of saturated fat, trans fat, & cholesterol. (It may, but is not required to, also list amounts of monounsaturated and polyunsaturated fats.) If that “total fat” number is not “0”, it must also list the recommended daily intake for total fat, saturated fat, and cholesterol The Facts Panel of all foods must include the total grams of fat and percentage of daily value based on a 2,000 kcal/day diet.

Lipid Digestion Digestion of diglycerides and triglycerides

Lipid Absorption

Summary: - Short-chain and medium-chain fatty acids are absorbed into the blood and carried to the liver bound to proteins.

Lipid Absorption Summary: - Short-chain and medium-chain fatty acids are absorbed into the blood and carried to the liver bound to proteins. - Cholesterol, long-chain fatty acids, monoglycerides, diglycerides, and triglycerides (re-formed by intestinal cells) are absorbed into lymphatic fluid and carried to cells all around the as part of chylomicrons.

Lipid Absorption These chylomicrons “hide” the hydrophobic lipids in the center, surrounded by amphipathic phospholipids and proteins. Thus, they are a form of lipoprotein.

Lipid Absorption These chylomicrons “hide” the hydrophobic lipids in the center, surrounded by amphipathic phospholipids and proteins. Thus, they are a form of lipoprotein. There are three other types of lipoproteins which carry hydrophobic lipids from one place to another in the body

Lipids in the Body Very-low-density lipoproteins (VLDL) Deliver triglycerides to cells Low-density lipoproteins (LDL) Deliver cholesterol to cells High-density lipoproteins (HDL) Pick up cholesterol for removal or recycling

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