About this video

• Video Title: Fats - biochemistry
• Channel: Osmosis from Elsevier
• Speakers: None specified
• Duration: 00:12:20

Overview

This video explains the biochemistry of fats, their role in a healthy diet, and how they are digested and absorbed. It categorizes fatty acids based on chain length, saturation, and the position of double bonds (omega classification), and discusses the health implications of different types of fats, including saturated, unsaturated, omega-3, omega-6, and trans fats. The video also covers the recommended daily intake of fats.

Key takeaways

• Essential Dietary Components: Fats are vital for diet, contributing to food taste and texture, providing energy, forming cell components, absorbing vitamins, and aiding cell communication.
• Fatty Acid Structure: Fats consist of a glycerol backbone and fatty acid chains. These chains can vary in length (short, medium, long) and in the type of bonds between carbon atoms (single bonds in saturated fats, double bonds in unsaturated fats).
• Saturated vs. Unsaturated Fats: Saturated fats have only single bonds, are straight, pack well, and are typically solid at room temperature. Unsaturated fats have one or more double bonds, have kinks, pack less tightly, and are usually liquid at room temperature.
• Omega Classification: Fatty acids are classified by the position of the first double bond from the methyl end (omega end). Omega-3, omega-6, and omega-9 are key examples, with omega-3 and omega-6 being essential fatty acids that cannot be synthesized by the body.
• Trans Fats: Formed through partial hydrogenation, trans fats have a trans configuration at double bonds, making the chain straighter. They are associated with coronary heart disease and have been largely removed from food products.
• Digestion and Absorption: Fats are digested by lipases, with bile salts aiding in emulsification. Digested fats form micelles, are absorbed by enterocytes, reassembled into triglycerides, packaged into chylomicrons, and transported via the lymphatic system to the bloodstream.
• Health Benefits: Polyunsaturated fats can lower cholesterol and blood pressure, while long-chain omega-3s (DHA and EPA) benefit cardiovascular health and infant development. The health impact of saturated fat is complex and depends on what it replaces in the diet.
• Dietary Recommendations: It's recommended that 20-35% of daily calories come from fats, with less than 10% from saturated fats and minimal trans fat consumption. Prioritizing unsaturated fats over saturated and trans fats is beneficial for cardiovascular health.

Review Notes on Fats - Biochemistry

I. Introduction to Fats

• Importance: Essential in diet; contribute to taste/texture, energy source, cell components, vitamin absorption, cell communication (prostaglandins).
• Structure: Glycerol backbone + fatty acid chains.

II. Fatty Acid Chains

• Composition: String of carbon and hydrogen atoms.
• Formation: Glycerol + fatty acid = triglyceride (releasing H2O).
  • Monoglyceride (1 fatty acid)
  • Diglyceride (2 fatty acids)
  • Triglyceride (3 fatty acids)

III. Classification of Fatty Acids

• By Length:
  • Short-chain: 2-5 carbons
  • Medium-chain: 6-12 carbons
  • Long-chain: 13+ carbons
• By Bonds:
  • Saturated: Only single bonds between carbons. Max hydrogen atoms ("saturated"). Straight chains, pack well, usually solid at room temp. Longer chains = more likely solid.
  • Unsaturated: One or more double bonds between carbons. Not fully saturated with H atoms. Double bonds cause kinks, don't pack well, usually liquid at room temp.
    • Monounsaturated: Single double bond.
    • Polyunsaturated: Two or more double bonds.
• By Omega Position (Location of first double bond from methyl end):
  • Omega-3: First double bond at 3rd carbon. (e.g., ALA, EPA, DHA). Often polyunsaturated.
  • Omega-6: First double bond at 6th carbon. (e.g., Linoleic acid, Arachidonic acid). Often polyunsaturated.
  • Omega-9: First double bond at 9th carbon. (e.g., Oleic acid). Typically monounsaturated.
  • Essential Fatty Acids: ALA (Omega-3) and Linoleic acid (Omega-6) must be obtained from diet.

IV. Cis vs. Trans Configuration

• Cis: Functional groups on the same side of the double bond. Causes natural bend/kink. More fluid (e.g., cooking oils).
• Trans: Functional groups on opposite sides of the double bond. Chain remains straighter, packs easier. Results from partial hydrogenation.

V. Partial Hydrogenation

• Process: Adding hydrogens to some (not all) double bonds in cis-fats.
• Result: Can convert some cis double bonds to single, but others may reform, potentially creating trans double bonds. Turns unsaturated fats into semi-solid fats.
• Sources:
  • Natural: Digestive tract of animals (found in meat/dairy).
  • Artificial: Partial hydrogenation of liquid oils (makes them solid).
• Health Concern: Associated with coronary heart disease. Largely removed from North American/European foods.

VI. Digestion and Absorption

1. Emulsification: Fats form hydrophobic globules. Saliva/stomach/pancreatic lipases begin breakdown. Liver produces bile salts that break large globules into smaller droplets (increase surface area).
2. Micelle Formation: Monoglycerides and free fatty acids form mixed micelles with hydrophilic exteriors.
3. Absorption: Micelles travel to enterocytes (intestinal wall) and release contents, which diffuse into cells.
4. Reassembly: Inside enterocytes, fatty acids & monoglycerides reassemble into triglycerides.
5. Chylomicron Formation: Triglycerides are packaged into chylomicrons (lipoprotein: lipids + proteins). Outer membrane has phospholipids/proteins; hydrophobic core has triglycerides, cholesterol, fat-soluble vitamins (A, D, E, K).
6. Transport: Chylomicrons exit enterocytes, enter lymphatic capillaries (lacteals), flow through lymph, enter bloodstream via thoracic duct (bypassing portal vein).
7. Delivery: In blood, chylomicrons release fatty acids/monoglycerides to peripheral tissues (muscle for energy, adipose for storage).
8. Remnant Uptake: After delivering fats, chylomicrons shrink and are engulfed by the liver.

VII. Health Benefits of Fats

• Polyunsaturated Fats:
  • Precursors for prostaglandins (vasodilators -> lower blood pressure).
  • Reduce total and LDL cholesterol -> lower risk of cardiovascular disease (heart attacks, strokes).
• Long-Chain Omega-3s (DHA, EPA):
  • Lower plasma triglyceride levels -> protect against cardiovascular disease.
  • DHA: Important for infant eye and brain development.
• Saturated Fats: Impact is complex. Generally recommended to keep consumption low. Different types may have different effects. Replacing saturated fat with polyunsaturated fat is beneficial; replacing with refined carbs is not.

VIII. Dietary Recommendations

• Total Fat: 20-35% of daily calories (400-700 calories / 44-78g for a 2000 kcal diet).
• Saturated Fat: Less than 10% of daily calories.
• Trans Fat: Keep as low as possible.
• Focus: Emphasize mono- and polyunsaturated fats over saturated and trans fats for better cardiovascular health. The type of fat is more important than just the amount.

Review Notes: Fats (Short Version)

I. What are Fats?

• Essential for diet: energy, cell structure, vitamin absorption, taste/texture.
• Structure: Glycerol + fatty acid chains = Triglycerides.

II. Fatty Acid Types

• Length: Short (2-5 C), Medium (6-12 C), Long (13+ C).
• Saturation:
  • Saturated: All single bonds (C-C). Straight, solid at room temp.
  • Unsaturated: ≥1 double bond (C=C). Kinked, liquid at room temp.
    • Monounsaturated: 1 double bond.
    • Polyunsaturated: 2+ double bonds.
• Omega: Position of first double bond from end (e.g., Omega-3, Omega-6 are essential).
• Cis vs. Trans:
  • Cis: Natural bend, fluid.
  • Trans: Straightened (from partial hydrogenation), packed easier. Bad for heart health.

III. Digestion & Absorption

• Bile salts emulsify fats.
• Lipases break down triglycerides.
• Absorbed into enterocytes, reassembled, packaged into chylomicrons.
• Transported via lymph, then blood.

IV. Health & Diet

• Good Fats: Unsaturated fats (mono & poly) lower cholesterol, blood pressure. Omega-3s good for heart & brain.
• Limit: Saturated fats, especially trans fats (linked to heart disease).
• Recommendation: 20-35% daily calories from fat, <10% from saturated, minimal trans. Focus on type of fat.