Lipids Flashcards

Lipids

Classes of Lipids

• Types of Lipids

  • Triglycerides (fats and oils)

  • Phospholipids (e.g., lecithin)

  • Sterols (e.g., cholesterol)

Triglycerides: Composition and Properties

• Chemical Structure

  • Composed of carbon, hydrogen, and oxygen.

  • Higher proportion of carbon and hydrogen compared to oxygen leads to greater calorie yield per gram compared to carbohydrates.

  • Structure: Three-carbon atom glycerol backbone with three attached fatty acids.

  • Variability in types of fatty acids can occur within a triglyceride molecule.

Fatty Acids: Structure and Classification

• Basic Structure

  • Chains of carbon atoms with hydrogen atoms attached.

  • Structure has a methyl group (CH₃) on one end and a carboxylic acid group (COOH) on the other.

• Chain Length

  • Long-chain fatty acids: > 12 carbon atoms.

  • Medium-chain fatty acids: 8-12 carbon atoms.

  • Short-chain fatty acids: Up to 6 carbon atoms.

• Degree of Saturation

  • Saturated Fatty Acids: All carbon atoms have single bonds, fully saturated with hydrogen. Tend to be solid at room temperature; known as "bad" fats due to their effect on LDL cholesterol levels.

  • Unsaturated Fatty Acids: Contain one or more double bonds (mono- or polyunsaturated). Usually liquid at room temperature; beneficial as they can lower LDL and raise HDL cholesterol levels.

  • Note: The position and type of double bond determines the type of essential fatty acid (Omega-3, Omega-6, Omega-9).

Essential Fatty Acids

• Omega-3 Fatty Acids (n-3): E.g., alpha-linolenic acid (ALA) found in flaxseed, walnuts.

• Omega-6 Fatty Acids (n-6): E.g., linoleic acid (LA), abundant in plant oils.

Trans Fatty Acids

• Definition: Refers to the configuration of hydrogen atoms around double carbon bonds. Can negatively affect cholesterol levels and health.

• Natural and Synthetic Sources: Trans fats are found naturally in small amounts in some food but are mainly from partially hydrogenated oils.

Functions of Fat in the Body

• Primary Function: Provide energy (9 cal/g); important at rest (60% of the body's energy).

• Additional Functions:

  • Insulation and cushioning of organs.

  • Temperature regulation.

  • Facilitate absorption of fat-soluble vitamins (A, D, E, K).

Digestion and Absorption of Fats

• Digestion: Minimal chemical digestion in mouth and stomach; mainly occurs in the small intestine.

• Absorption: 95% of consumed fat is absorbed.

  • Small fat particles absorbed directly; larger fat particles are absorbed via micelles and chylomicrons that distribute lipids throughout the body.

Dietary Reference Intakes (DRI) for Fats

• Recommendations: Total fat intake should be 20% to 35% of total calories. Saturated fat intake should be limited to under 10% of total calories.

• No established requirement exists for trans fats due to lack of health benefits.

Health Aspects of Fats

• Health Recommendations:

  • Focus on replacing saturated fats with unsaturated fats in diet.

  • Reduce intake of processed and animal fats high in saturated fat and trans fats.

  • Maintain balanced dietary patterns emphasizing healthy food types over individual nutrients.

Summary of Key Points

• Lipids include triglycerides, phospholipids, and sterols.

• Understanding different types of triglycerides and fatty acids is essential for nutritional knowledge.

• Fats play critical roles in energy production, nutrient absorption, and overall health, making balanced intake important for maintaining health.

Lipids are classified into triglycerides, phospholipids, and sterols.

Triglycerides:

• Composed of carbon, hydrogen, and oxygen with a higher carbon to oxygen ratio providing greater energy yield.

• Structure: A glycerol backbone attached to three fatty acids with variability in fatty acid types.

Fatty Acids:

• Basic Structure: Chains of carbon with a methyl group (CH₃) and a carboxylic acid group (COOH).

• Chain Length: Long-chain (>12), medium-chain (8-12), and short-chain (up to 6) fatty acids.

• Degree of Saturation:

  • Saturated: Single bonds, solid at room temperature, linked to increased LDL cholesterol.

  • Unsaturated: One or more double bonds, liquid at room temperature, beneficial for cholesterol levels (Omega-3 and Omega-6).

Essential Fatty Acids:

• Omega-3 (e.g., ALA from flaxseed) and Omega-6 (e.g., LA from plant oils).

Trans Fatty Acids:

• Configuration affects health, mainly from partially hydrogenated oils.

Functions of Fats:

• Provide energy (9 cal/g), insulation, cushioning, temperature regulation, and absorption of fat-soluble vitamins.

Digestion and Absorption:

• Minimal digestion in the mouth/stomach; mainly in the small intestine. 95% absorption; smaller particles absorbed directly.

Dietary Recommendations:

• Total fat intake: 20%-35% of calories; limit saturated fat to under 10%.

Health Considerations:

• Replace saturated fats with unsaturated fats and focus on a balanced diet.

Overall, fats play vital roles in energy, nutrient absorption, and health,