Human Nutrition

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73 Terms

1

Carbohydrates

Protein sparing, meaning if there aren’t enough carbs in the diet, the body will convert protein into protein into glucose to meet energy needs.

  • Definition: Carbohydrates are "hydrated carbons" – for every carbon atom, there is one molecule of water.

  • Primary Fuel Source: Carbohydrates are the body's main source of energy, especially for the CNS, brain, and red blood cells.

  • Energy Content: Carbs provide 4 calories per gram.

  • Glucose: The carbohydrate we consume is converted into glucose, which is transported through the blood as "blood sugar." It is stored as glycogen in muscles and the liver.

  • Excess Carbohydrates: When carbs are consumed in excess, they are converted and stored as fat.

  • Blood Glucose Regulation:

    • Insulin: Lowers blood glucose levels.

  • Glucagon: Increases blood glucose levels.

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Blood Glucose Levels

  • Normal: 70–99 mg/dL

  • Pre-Diabetes: 100–125 mg/dL

  • Diabetes: 126+ mg/dL

  • Hypoglycemia: Low blood glucose levels (<70 mg/dL)

  • Hyperglycemia: High blood glucose levels (>100 mg/dL)

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Types of Carbohydrates

  • Monosaccharides

  • Disaccharides

  • Oligosaccharides

  • Polysaccharides

  • Glycogen

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Monosaccharides

  • Single sugar molecules.

    • Fructose: Known as "fruit sugar," found in fruits, vegetables, honey, and high-fructose corn syrup.

    • Galactose: Most commonly consumed as part of lactose in dairy.

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Disaccharides

  • Two monosaccharides linked together.

    • Maltose: Glucose + Glucose (alpha bond), found in sprouting seeds and malted beverages.

    • Sucrose: Glucose + Fructose (alpha bond), known as "table sugar," found in sugarcane, sugar beets, and maple syrup.

    • Lactose: Glucose + Galactose (beta bond), found in dairy products.

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Oligosaccharides

  1. Complex carbohydrates made up of 3 to 10 monosaccharides.

    • Fructans/Fructo-oligosaccharides – Chains of fructose with glucose at the end.

    • Galactans/Galacto-oligosaccharides – Chains of galactose with glucose at the end.

    • Raffinose – A trisaccharide composed of galactose, glucose, and fructose.

    • Stachyose – A tetrasaccharide composed of two galactose, one glucose, and one fructose.

    • Oligosaccharides act as fiber and prebiotics since we cannot digest them

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Fructans/Fructo-oligosaccharides

Chains of fructose with glucose at the end

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Galactans/Galacto-oligosaccharides

Chains of galactose with glucose at the end

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Raffinose

A trisaccharide composed of galactose, glucose , and fructose

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Stachyose

A tetrasaccharide composed of two galactose, one glucose, and one fructose

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Lactose Intolerance

  • Cause: Insufficient lactase enzyme production, which decreases after childhood (around 3-5 years old).

  • Symptoms: Undigested lactose attracts water into the GI tract and is fermented by bacteria, causing gas, bloating, cramping, and diarrhea.

  • Primary Lactose Intolerance: Natural decline in lactase production with age.

  • Secondary Lactose Intolerance: Caused by diseases (e.g., Crohn's or Celiac disease) that damage lactase-producing cells.

  • Management: Some people can tolerate low-sugar dairy (e.g., hard cheeses, yogurt), as the lactose is broken down during fermentation.

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Polysaccharides

  1. Complex carbohydrates composed of multiple sugar units.

    • Digestible Polysaccharides (Starch)

      • Amylose – Linear and unbranched; glucose linked by alpha 1-4 bonds.

      • Amylopectin – Highly branched; glucose linked by alpha 1-4 and alpha 1-6 bonds.

    • Indigestible Polysaccharides (Fiber)

      • Soluble Fiber – Dissolves in water, becomes gel-like, and is fermented by probiotics.

        • Aids in blood sugar control.

        • Lowers blood cholesterol levels.

        • Acts as a prebiotic, promoting gut health and diversity.

        • Promotes satiety and aids in weight control.

      • Insoluble Fiber – Does not dissolve in water and is not fermented by probiotics.

        • Promotes bowel regularity.

        • Adds bulk to stool and prevents constipation.

        • Promotes satiety and aids in weight control.

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Amylose

Linear and unbranched; glucose linked by alpha 1-4 bonds. (Digestible polysaccharide: aka Starch)

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Amylopection

Highly branched; glucose linked by alpha 1-4 and alpha 1-6 bonds. (Digestible Polysaccharides: Aka Starch)

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Soluble FIber

Dissolves in water, becomes gel-like, and is fermented by probiotics

  • Aids in blood sugar control.

  • Lowers blood cholesterol levels.

  • Acts as a prebiotic, promoting gut health and diversity.

  • Promotes satiety and aids in weight control.

  • Indigestible Polysaccharides (Fiber)

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Insoluble FIber

Does not dissolve in water and is not fermented by probiotics.

  • Promotes bowel regularity.

  • Adds bulk to stool and prevents constipation.

  • Promotes satiety and aids in weight control.

  • Indigestible Polysaccharide (fiber)

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Glycogen

Storage Form of Glucose in Humans

  • Structure is similar to amylopectin, with glucose linked by alpha bonds.

  • Liver glycogen – Maintains blood sugar levels.

  • Muscle glycogen – Used by muscles for energy.

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Sugar Alcohols

Also known as Polyols or Polyhyrdric Alcohols

  • Contain an -OH (hydroxyl) group.

  • Common sugar alcohols: Sorbitol, Mannitol, Xylitol, Erythritol, Maltitol.

  • Often end in "-ol."

  • FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols).

    • FODMAPs produce gas.

    • Consuming sugar alcohols in large amounts may cause gas, bloating, and GI distress.

    • Foods containing sorbitol or mannitol must include a warning on their label:
      “Excess consumption may have a laxative effect.”

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FODMAPS

Fermentable Oligosaccharides, Disaccharides, Monosaccharides, And Polyols.

  • FODMAPS Produce gas

  • May cause bloating, gas, and GI distress

  • ***Foods containing sorbitol or mannitol must include a warning on their label: “Excess consumption may have a laxative effect.”

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Sweeteners

  • Nutritive Sweeteners – Provide calories.

  • Non-Nutritive Sweeteners – Do not provide calories (e.g., artificial sweeteners).

    • Extremely sweet and calorie-free.

    • FDA-approved artificial sweeteners recognized as safe:

      • Saccharin

      • Aspartame

      • Sucralose

      • Neotame

      • Acesulfame-Potassium

      • Advantame

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Nutritive Sweeteners

Provide calories

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Non-Nutritive Sweeteners

Do not provide calories (artificial sweeteners)

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FDA approved artificial Sweeteners

  • Saccharin

  • Aspartame

  • Sucralose

  • Neotame

  • Acesulfame-Potassium

  • Advantame

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Orthorexia

An unhealthy obsession with healthy eating

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Functions of Carbohydrates

  • Primary source of energy for the body

  • Brain/CNS prefers glucose as an energy source

  • Carbohydrates spare protein, preserving body protein/muscle

  • Prevents ketosis (excessive ketone production from fat breakdown)

  • Ketones: Alternative energy source formed from fatty acids (acidic)

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Ketones

Alternative energy source formed from fatty acids (acidic)

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Carbohydrate Digestion and Absorption

  1. Mouth – Salivary amylase begins breaking starch into polysaccharides and disaccharides

  2. Stomach – No carbohydrate digestion (amylase inactivated by stomach acid)

  3. Pancreas – Releases pancreatic amylase and dextrinase to break starch into disaccharides

  4. Small Intestine – Enzymes break disaccharides into monosaccharides, which are absorbed

  5. Liver – Monosaccharides travel via the portal vein to the liver

  6. Large Intestine – Some soluble fiber is fermented into acids and gases

  7. Rectum/AnusInsoluble fiber is excreted in feces

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Mouth

Salivary amylase begins breaking starch into polysaccharides and disaccharides

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Stomach

No carbohydrate digestion (amylase inactivated by stomach acid)

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Pancreas

Releases pancreatic amylase and dextrinase to break starch into disaccharides

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Small Intestine

Enzymes break disaccharides into monosaccharides, which are absorbed

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Liver

Monosaccharides travel via the portal vein to the liver

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Large Intestine

Some soluble fiber is fermented into acids and gases

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Rectum/Anus

Insoluble fiber is excreted in feces

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Glucose & Galactose

Actively absorbed (requires ATP)

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Fructose

Slowly diffuses across the GI Tract

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Non-glucose monosaccharides

In the Liver non-glucose monosaccharides are converted to glucose and glucose can be released into the bloodstream, stored as glycogen, and converted to fat.

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Fiber

Binds minerals in the digestive tract

  • Recommended Intake:

    • Before age 50: 25g/day (women), 38g/day (men)

    • After age 50: 21g/day (women), 30g/day (men)

    • Adequate Intake: 14g per 1000 kcal

  • High Fiber Risks:

    • Low liquid intake → Constipation

    • Insufficient calorie intake → Micronutrient deficiencies

    • Early satiety → Can limit overall nutrient intake

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Blood Glucose Regulation

Organs Involved:

  • Liver: Determines glucose release into bloodstream, stores excess as glycogen

  • Pancreas: Releases hormones for blood glucose regulation

Key Hormones:

  • Insulin (Anabolic Hormone):

    • Lowers blood glucose levels (facilitates glucose uptake into cells)

    • Acts as a "key" for glucose entry into cells

  • Glucagon:

    • Increases blood glucose by breaking down glycogen

    • Stimulates glucose production from non-carbohydrate sources

  • Other Hormones That Raise Blood Glucose:

    • Cortisol, Epinephrine, Norepinephrine, Growth Hormone

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Insulin (Anabolic Hormone)

  • Lowers blood glucose levels (Facilitates glucose uptake into cells

  • Acts as a key for glucose entry into cells

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Glucagon

  • Increases blood glucose by breaking down glycogen

  • Stimulates glucose production from non-carbohydrate sources

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Other Hormones that Raise Blood Glucose

  • Cortisol

  • Epinephrine

  • Norepinephrine

  • Growth Hormone

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Dietary Carbohydrate Recommendations

  • RDA: 130g/day

    • Supplies adequate glucose for the brain/CNS

    • Prevents excessive ketone production

  • AMDR: 45-65% of total energy intake

  • Athletes/Active Individuals: Should consume a higher proportion of carbs

  • Added Sugar:

Limit to ≤10% of total daily energy intake

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Type 1 Diabetes (5% of cases)

  • Cause: Autoimmune destruction of pancreatic cells

  • Symptomes

    • Ketosis: Ketones are formed from fatty acids and are an alternative energy source for the body (Ketones are acidic)

    • Weight loss

    • Increased thirst, hunger, urination

    • Fruity/acetone breath

  • Treatment:

    • Insulin therapy

    • Diet & exercise

    • Monitor: Blood glucose, urine ketones, HbA1c

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Type 2 Diabetes (90% of cases)

  • Cause: Insulin resistance

  • Symptoms:

    • Fatigue

    • Nighttime urination

    • Ketosis usually absent

  • Treatment:

    • Exercise & Diet

    • Oral medication to lower blood glucose

    • Monitor: Blood glucose, HbA1c

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Glycemic Index (GI)

Ranks carbs (0-100) based on their impact on blood sugar

  • High Gi foods—>Rapid blood sugar spike

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Glycemic Load (GL)

Takes into account both carbohydrate quantity and quality

  • Low GL meals —> Better blood sugar control

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Functions of Lipids

  • Energy source (9 kcal/g)

  • Insulation & protection (preserve body heat, protect organs)

  • Aid in absorption & transport of fat-soluble vitamins (A, D, E, K)

  • Structural component of cells & hormones

  • Enhance food flavor and texture

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Types of Lipids

  1. Triglycerides (most common in food & body)

    • Composed of glycerol + 3 fatty acids

  2. Phospholipids (major component of cell membranes)

  3. Sterols (e.g., cholesterol)

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Fatty Acid Types

  • Saturated Fatty Acids (SFA) – No double bonds (solid at room temp)

    • Found in meat, dairy, coconut oil, palm oil

  • Monounsaturated Fatty Acids (MUFA) – One double bond

    • Found in olive oil, avocado, nuts

  • Polyunsaturated Fatty Acids (PUFA) – Two or more double bonds

    • Includes Omega-3 (EPA, DHA) and Omega-6

Found in fish, flaxseeds, walnuts

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Fatty Acid Length

  • Long-Chain FA (>12 C): Beef, pork, lamb, fish, plant oils (slow digestion)

  • Medium-Chain FA (6-10 C): Coconut oil, dairy (rapid digestion)

  • Short-Chain FA (<6 C): Butter, gut-fermented fiber (quick digestion)

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Lipid Metabolism Processes

  • Esterification: Formation of triglycerides

  • De-esterification: Release of fatty acids (hydrolysis)

  • Re-esterification: Reattachment of fatty acids

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Recommended Fat Intake

  • No RDA (Recommended Dietary Allowance) for adults

  • AI (Adequate Intake) established for infants

  • AMDR (Acceptable Macronutrient Distribution Range): 20-35% of total kcal

  • Omega-3 Adequate Intake (as ALA)

    • Males (19-50 years old): 1.6 g

    • Females (19-50 years old): 1.1 g

  • Dietary Guidelines for Americans (DGAs):

    • Consume more unsaturated fats

    • Limit saturated fat to <10% of total calories

    • Avoid artificial trans fats

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Saturated Fat

  • Sources

    • Animal Products (butter, ghee, lard, red meat, dairy)

    • Tropical oils (coconut oil, palm oil, palm kernel oil)

    • Baked goods & Ultra processed foods

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Monounsaturated Fat (MUFA)

  • Sources

    • Plant-based oils (olive oil, canola oil, peanut oil, avocado oil)

    • Whole foods (olives, avocados, nuts, seeds, nut butters)

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Polyunsaturated Fat (PUFA)

  • Sources

    • Plant oils (safflower, sunflower, corn, soybean)

    • Nuts & seeds (walnuts, flaxseeds, chia seeds)

    • Fish & seafood (salmon, mackerel, sardines)

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Trans Fat

  • Naturally found in dairy

  • Artificial sources: Partially hyrogenated oils, fast food, fried food

  • PHOs (Partially Hydrogenated Oils) banned in 2020

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Essential Fatty Acids (EFAs)

  • Body cannot synthesize EFAs—> Must come from food

  • Alpha-Linolenic Acid (ALA) (18:3) w3)- Omega 3 PUFA

  • Linoleic Acid (LA) (18:2 w6)- Omega-6 PUFA

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Alpha-Linolenic Acid (ALA) (18:3 ω3) – Omega-3 PUFA

  • Used to make: EPA & DHA + certain eicosanoids

  • Sources: Nuts, seeds, flaxseed oil, chia seeds, walnuts, canola oil, soy-based foods

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Linoleic Acid (LA) (18:2 ω6) – Omega-6 PUFA

  • Used to make: Arachidonic Acid (ARA) + certain eicosanoids

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Omega-3 Fatty Acids

Eicosapentaenoic Acid (EPA) (20:5 ω3)

  • Synthesized from ALA or obtained from diet

  • Needed for:

    • Fetal development

    • Healthy aging

Docosahexaenoic Acid (DHA) (22:6 ω3)

  • Synthesized from EPA or obtained from diet

  • Supports:

    • Brain & eye development/function

    • Nervous system function

    • Memory & cognition

  • Deficiency linked to: Depression, suicidal behavior, anger, hostility

  • Sources of EPA & DHA:

    • Fatty fish (herring, salmon, mackerel, sardines, trout, tuna)

    • Seafood (oysters, crab)

    • Omega-3 supplements (fish oil, krill oil, cod liver oil, algal oil)

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Eicosapentaenoic Acid (EPA) (20:5 ω3)

  • Synthesized from ALA or obtained from diet

  • Needed for:

    • Fetal development

    • Healthy aging

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Docosahexaenoic Acid (DHA) (22:6 ω3)

  • Synthesized from EPA or obtained from diet

  • Supports:

    • Brain & eye development/function

    • Nervous system function

    • Memory & cognition

  • Deficiency linked to: Depression, suicidal behavior, anger, hostility

  • Sources of EPA & DHA:

    • Fatty fish (herring, salmon, mackerel, sardines, trout, tuna)

    • Seafood (oysters, crab)

    • Omega-3 supplements (fish oil, krill oil, cod liver oil, algal oil)

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Functions of Triglycerides

  • Energy source: 9 kcal/g

  • Main fuel source when resting or doing light activity

  • Body stores excess calories as fat

  • Protects vital organs & maintains body temperature

  • Aids in absorption of fat-soluble vitamins (A, D, E, K)

  • Transports essential nutrients in the bloodstream

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Fat Cell Growth

  • Hypertrophy: Increase in cell size

  • Hyperplasia: Increase in cell number

  • Weight gain → Fat droplets enlarge

  • Weight loss → Fat droplets shrink

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Phospholipids

  • Two major roles:

    • Cell membrane component

    • Functions as an emulsifier

  • Sources:

    • Dietary: Lecithin (egg yolks, wheat germ, peanuts)

    • Synthesized by the body

    • Unrefined plant oils (vegetable, nut, olive oil)

  • Structure:

    • Phosphate "head" – Hydrophilic

    • Fatty acid "tails" – Hydrophobic

  • In water, phospholipids form micelles

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Sterols & Cholesterol

  • Sterols: Type of steroid (multi-ringed structure)

  • Best known sterol: Cholesterol

  • Functions of cholesterol:

    • Used to make steroid hormones (testosterone, estrogen)

    • Adrenal hormones (aldosterone, cortisol)

    • Cell membranes

    • Vitamin D

    • Bile acids

Sources: Found in animal-based foods or synthesized by the body

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Eicosanoids: Hormone-like compounds

  • Regulate:

    • Blood pressure & clotting

    • Sleep/wake cycles

    • Body temperature

    • Inflammation & immune response

    • Kidney function & fluid balance

  • Omega-3-derived eicosanoids: Anti-inflammatory

  • Omega-6-derived eicosanoids: Pro-inflammatory

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Phytosterols

  • Plant stanols & sterols (cholesterol-like compounds)

  • Function:

    • Lower LDL cholesterol by interfering with dietary cholesterol absorption

    • 2 g/day can reduce LDL by 8-10%

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Fatty Acid Nomenclature

Two Naming Systems:

  1. Omega (ω) System

    • Methyl end (CH₃) = Omega end

    • Number indicates first double bond closest to methyl end

    • Example: Linoleic Acid (18:2 ω6)

  2. Delta (Δ) System

    • Describes fatty acids from carboxyl end (COOH)

    • Indicates all double bond locations

    • Example: Linoleic Acid (18:2 Δ9,12)

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Hydrogenation & Trans Fats

  • Hydrogenation: Process of adding hydrogen to unsaturated fats

  • Fully Hydrogenated Oils:

    • All double bonds → single bonds

    • Converts liquid oil → solid fat

  • Partially Hydrogenated Oils (PHOs):

    • Some double bonds → single bonds

    • Forms trans fats

  • PHOs banned in 2020 (no longer GRAS by FDA)

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Lipoproteins

Lipoproteins: Transporters of Lipids in the Blood

  • Chylomicrons

    • Primary Component: Triglyceride

    • Key Role: Transports dietary fat from the small intestine (SI) to the cells

  • Very-Low-Density Lipoprotein (VLDL)

    • Primary Component: Triglyceride

    • Key Role: Produced by the liver – Carries lipids from the liver to the cells

  • Intermediate-Density Lipoprotein (IDL)

  • Low-Density Lipoprotein (LDL) – "Bad" Cholesterol

    • Arises from VLDL

    • Primary Component: Cholesterol

    • Key Role: Carries cholesterol made by the liver and from other sources to the cells

  • High-Density Lipoprotein (HDL) – "Good" Cholesterol

    • Primary Component: Protein

    • Key Role: Reverse Cholesterol Transport

      • Helps remove cholesterol from the cells and excretes it from the body

      • Can prevent LDL from being oxidized

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Lipoprotein Lipase (LPL)

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