BIOQUI - 29/06/2023
Understanding Omega-3 Fatty Acids and Their Importance
Introduction to Omega-3 Fatty Acids
- The speaker greets students and addresses technical difficulties, indicating a focus on the topic of omega-3 fatty acids.
Properties and Sources of Omega-3 Fatty Acids
- Discussion includes specific properties attributed to omega-3 fatty acids, their sources in both plant and animal forms, and the concept of isomerism (cis vs. trans).
Synthesis of Fatty Acids in the Body
- The body can produce fatty acids through lipogenesis, primarily up to 16 carbon atoms, occurring mainly in organs like the liver, lungs, and kidneys.
Role of Mitochondria in Fatty Acid Synthesis
- Emphasizes that fatty acid synthesis involves not only cytosol and endoplasmic reticulum but also mitochondria via citrate from the Krebs cycle.
Enzymatic Processes in Fatty Acid Synthesis
- The synthesis process is reductive using NADPH as a reducing agent formed during the pentose phosphate pathway; six enzymes known as fatty acid synthases are involved.
Essential vs. Non-Essential Fatty Acids
Classification of Essential Fatty Acids
- Historically three essential fatty acids were identified: arachidonic, linoleic, and linolenic; currently recognized are only linoleic and linolenic.
Arachidonic Acid's Significance
- Arachidonic acid is crucial for producing important molecules; its absence leads to decreased prostaglandin production which has various physiological roles.
Physiological Functions of Prostaglandins
Impact on Health
- Essential fatty acids contribute to prostaglandin production; lack thereof affects numerous physiological functions including pain transmission and inflammation.
Therapeutic Implications
- Prostaglandins have protective roles in various organs; anti-prostaglandin medications target these pathways for therapeutic benefits against pain/inflammation.
Dietary Sources of Essential Fatty Acids
Dietary Recommendations
- Emphasizes dietary inclusion of essential fatty acids such as arachidonic acid found abundantly in meat products which supports prostaglandin synthesis.
Fat Storage and Metabolism
Esterification Process
- Discusses how fatty acids esterify with alcohol (glycerol or sphingosine), forming triglycerides stored in adipose tissue until mobilized through lipolysis into free fatty acids for energy use.
Understanding Lipids and Their Role in Diet
The Composition of Dietary Lipids
- Lipids, including triglycerides, are essential components of our diet, constituting about 30% of total caloric intake.
- The recommended macronutrient distribution is approximately 50% carbohydrates, 30% lipids, and 20% proteins.
- Lipids serve as the primary energy source for the body and provide essential fatty acids and fat-soluble vitamins.
Functions of Different Types of Lipids
- Cholesterol is a well-known lipid that acts as a precursor for bile acids and steroid hormones; it plays a structural role in cell membranes.
- Unsaturated fatty acids from plant sources are primarily omega-6, while fish oils like salmon contain beneficial omega-3 fatty acids.
Impact on Cholesterol Levels
- Saturated fats can raise LDL (bad cholesterol), whereas monounsaturated fats increase HDL (good cholesterol).
- Trans fats negatively affect cholesterol levels by lowering HDL and raising LDL; their consumption should be minimized.
Complex Lipid Structures: Phospholipids
- Phospholipids are complex lipids composed of glycerol or sphingosine, fatty acids, and additional compounds such as amino alcohols or sugars.
- An example is phosphatidylcholine, which consists of choline (an amino alcohol), phosphate groups, glycerol, and two fatty acid chains.
Functional Importance of Phospholipids
- Phospholipids have polar heads that interact with water (hydrophilic), while their tails are hydrophobic due to the presence of fatty acids.
- Loss of one fatty acid chain from a phospholipid results in lysophospholipid formation; these play various roles in cellular functions.
Surfactants and Their Role in Physiology
- Surfactants containing phosphatidylcholine help newborn infants breathe by preventing respiratory distress syndrome at birth.
- Lecithin (a type of phosphatidylcholine) contains palmitic acid chains crucial for its function in surfactant properties.
Additional Important Phospholipids
- Other significant phospholipids include cephalins (phosphatidylethanolamine), which participate in coagulation processes within the body.
Overview of Lipids and Their Functions
Cardiolipin and Its Role
- Cardiolipin is a lipid found exclusively in mitochondrial membranes, playing a crucial role in cellular energy production.
- It serves as a reagent for syphilis testing, highlighting its medical significance beyond cellular functions.
Types of Phospholipids
- Lysophospholipids are monoacyl lipids formed when one fatty acid is lost; they play roles in cell signaling.
- Plasmalogens are another type of phospholipid located primarily in the central nervous system (CNS), particularly in the brain and muscle tissues.
Sphingolipids and Their Importance
- Sphingolipids contain sphingosine alcohol and are integral to myelin composition, enhancing nerve impulse transmission.
- They produce important compounds like ceramides, cerebrosides, and gangliosides, which have sugar components that contribute to their function as glycolipids.
Glycolipid Functionality
- Cerebrosides and gangliosides serve as receptors or transmitters for cellular communication, especially within the intestines.
- Gangliosides consist of ceramide with added sugars; they play critical roles in signal transduction across cell membranes.
Cholesterol: Structure and Health Implications
- Cholesterol is a complex lipid known for its role as a steroid component of cell membranes; it can lead to health issues like atherosclerosis when present in excess.
- Structurally, cholesterol has 27 carbon atoms with specific functional groups that classify it as an alcohol and steroid.
Dietary Sources of Cholesterol
- Foods high in cholesterol include organ meats (like brains), egg yolks, seafood (like caviar), aged cheeses, and processed meats.
Cholesterol and Its Derivatives
Cholesterol as a Precursor
- Cholesterol serves as a precursor for various steroids, including bile acids, adrenal hormones, sex hormones, vitamin D, and cardiac glycosides.
- In plants, cholesterol is absent; instead, they contain ergosterol. Other compounds like polyisoprenoids and terpenes also share the same biosynthetic pathway as cholesterol.
Biosynthesis of Isoprenoids
- The synthesis of these compounds begins with acetyl-CoA. The isoprenoid structure is the first to emerge in this process.
- Isoprenoids lead not only to cholesterol but also to other important compounds such as beta-carotenes, menthol, and lycopene (the pigment in tomatoes).
Vitamins Related to Terpenes
- Several vitamins are classified as terpenes:
- Vitamin A (retinol)
- Vitamin E (alpha-tocopherol)
- Vitamin K (phylloquinone)
Hormones Derived from Cholesterol
- Sex hormones like progesterone and testosterone are derived from cholesterol. Their structural differences define male and female characteristics.
Conclusion of Lecture