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Lipids -lecture 5
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- 1Lipids• Lipids are class of naturally-occurring organic compounds that you may know by their common names: fats and oils
• Examples of common lipids include butter, vegetable oil, cholesterol, waxes, phospholipids, and fat-soluble vitamins.
• The common characteristic of all of these compounds is that they are essentially insoluble in water
Fatty acids-
• long chains of carbon atoms
• fatty acids have carboxylic acid
(COOH) functional group- most
often even number of C atoms
(as shown to the right) - 2O1- Saturated and Unsaturated fatsSaturated fats-
• contain only single covalent bonds
Unsaturated fats-
• contain one or more (mono or poly)
double covalent bonds (as shown to the
right)
• monounsaturated fats have one double
covalent bond - 3O1- lipids...• Unsaturated fatty acids that have more than one double bond are ‘polyunsaturated’
• Those whose double bond is next to the third carbon are known as omega-3 fatty acids, or next to the sixth carbon is omega-6
• The first 18-carbon fatty acids that fit these descriptions are alpha-linolenic acid (omega-3) and linoleic acid (omega-6) - 4O1- TriglyceridesThe most common fat in our diet, contain one molecule of glycerol and three fatty acids
- 5O1- Functions of Triglycerides• Storage of energy, are also the storage form of excess carbohydrates and proteins you eat
• Cushioning and protection of organs
• Consuming high levels of triglycerides, particularly saturated fats are a risk factor for coronary artery disease - 6O1- Trans fatty acids• Cis and Trans fatty acids differ in the way atoms are arranged around the double bonds
• Trans configuration more closely resembles saturated fats
• Trans are not typically found in nature; Cis fatty acids arenaturally occurring form - 7O1- Trans fatty acids function• Trans fatty acids are produced during industrial saturation (hydrogenation) of vegetable oils to stop fats becoming spoiled during exposure to oxygen
• Eating Trans fats lead to adverse effects on blood lipids, leading to increased blood clots and cardiovascular disease
Found in “baked goods” and fried foods where hard margarines and vegetable shortening is used - 8O1- Cis and Trans fatty acids compared
- 9O1- PhospholipidsAre derivatives of triglycerides that consist of a glycerol molecule with two fatty acids, a phosphate group on the third carbon, and commonly an additional polar molecule.
The diglyceride portion of a phospholipid is hydrophobic (water hating), while the phosphate is hydrophilic (water loving) - 10O1- PhospholipidsLocation: Cell membrane
Function: Form basis of cellular membranes
Examples:
Phospholipid bilayer of the cellular membrane
Lecithins are one family of phospholipids that are emulsifiers- they suspend fat in water by forming a shell of water and other molecules around the fat to break fat globules into smaller bits and prevent fat from coalescing - 11O1- SterolsLocation: Cellular membrane, digestive system, endocrine system
Function:
Hormones, which enter cells and initiate specific chemical reactions
Part of cellular structure, adding fluidity to cellular membranes - 12O1- Transport of lipids in the Blood
- 13O1- HDL and LDL
- 14O1- Eicosanoids• Eicosanoids are hormone-like compounds
synthesized from polyunsaturated fatty acids
• can make prostaglandins, thromboxanes,
leukotrienes, lipoxins, prostacyclins
Functions-
• Prostaglandin- hormone-like compound that has various actions (uterine contraction, sleep cycles, body temp, blood vessel dilation and constriction)
• Prostacyclin- made by blood vessel walls, potent anticoagulant
• Thromboxane- stimulates blood clotting
• Leukotriene- involved in inflammation, hypersensitivity reactions, and asthma
• Lipoxin- made by WBCs, involved in immune and allergic responses - 15O2- Role of Lipids• energy source and form of energy storage
• insulation and protection; cushions organs
• part of cell structure
• transport of fat soluble vitamins
• provide flavour, palatability and texture and contribute to satiety (feeling of fullness)
• are essential for completion of development of central nervous system
• act as emulsifiers (thickeners for foods and suspend fats)
• building blocks for several hormones, hormone-like compounds (involved in inflammation control & immunity) and bile acids - 16O3- Omega 6• Linoleic Acid (LA)
• Is derived from plants
• Sources include vegetable oils, nuts, seeds
• Precursor of arachidonic acid via Gamma linolenic Acid
• Needed for integrity of cell membranes and for eicosanoid production
• Yields prostaglandins that are pro-inflammatory, immunostimulant and which favour clotting
• lowers LDL cholesterol
• Deficiency results in severe eczematous skin rash & increased infections - 17O3- Omega 3s...Alpha Linolenic Acid (ALA)-
• Can convert to EPA (shown in diagram)
• plant derived
• Sources include flaxseed, mustard seed, canola, walnuts, wild green leafy vegetables (found in chloroplasts!)
Eicosapentanoic Acid (EPA)-
• Need >0.22g/d, animal derived; can also be made from ALA
• Involved in eicosanoid production
• Yields prostaglandins that diminish inflammation, immune activation & platelet aggregation
• Sources include: cold-water oily fish (such as blue-eye trevally, atlantic salmon, blue mackerel, salmon, gemfish, sardines, tuna, herring and pilchards) & seafood, eggs & lean meats
Docosahexanoic Acid (DHA)-
• Animal derived
• Human synthesis from EPA is inefficient
• Vital for cell signalling and membrane function especially in brain, retina, heart
• Essential for brain development
• Sources include fish & seafood (especially oily cold water fish), eggs, lean meats, golden marine algae - 18O3- Essential fatty acids• Both LA & ALA compete for same enzyme (Delta 6 desaturase), therefore, ratio of these two fatty acids is important. Ideally 1-5:1, but in Western Diets ratio is morelike 20-30:1
• Also concerns that essential fatty acids levels are lower in formula milk than breast milk - 19O3- Monounsaturated fats• plant derived
• sources are avocados, almonds, cashews, peanuts and sunflower, canola, soybean, olive, sesame and peanut oils
• protective for heart disease - 20Role of Fats in Animals• Fat is an essential ingredient in the diet of all species and maintaining sufficient quality fat is an important consideration in the lower fat normal diets of dogs and cats.
• Provide an important source of essential fatty acids and fat soluble vitamins (A, D, E, and K).
• Young animals need dietary fat and cholesterol for growth and to maintain proper health. Adult dogs and cats require
essential fatty acids in the diet to sustain metabolic and physiologic functions.
• Dietary linoleic and alpha-linolenic acid are two essential fatty acids for dogs and cats. - 21O4- Human Fat Intake• Currently no RDI for fat
• Upper limit of 10% energy intake from
polyunsaturated fatty acids is recommended
• requirements about 7-10g day total
• No more than 30% of kilojoules from fat in most food pyramid diets
• Recommendation: 20-30% from fats, and less than 10% from saturated fats
• Sources of saturated fats are: animal fats, butter, palm and coconut oils.
• Eat mostly monounsaturated and polyunsaturated fat - 22O4- omega 6 and 3 intakeFrom omega 6-
• need 4.4-6.7g/day, from vegetable oils, nuts, seeds
From omega 3-
• ALA need >2.2g/day, from flaxseed, mustardseed, canola, walnuts, wild green leafy vegetables
• EPA need >0.22g/day, from fish & seafood
(especially oily cold water fish), eggs & lean
meats
• DHA need >0.22g /day, from fish & seafood (especially oily cold water fish), eggs, lean meats, golden marine algae - 23O5- Excessive Fat Intake• High polyunsaturated fat (higher than 10% of total caloric intake) increases blood LDL and cholesterol deposits in plaques, and impair immune system function
• Moderate omega-3 fatty acid intake (8 ounces of fish/week) can reduce blood clotting abilities and regulate heart rate, reducing heart attack risk
• 4-8 ounces of fish/day can reduce blood triglycerides
Colon cancer risk might be due to excess bile salt (for fat breakdown) secretion irritating intestinal cells and damaging them, leading to increased rate of mitosis and possible tumour development
Higher risk of breast and prostate cancer - 24O5- Essential fatty acid deficiency in AnimalsIf the deficiency persists, exudation from a localized area of the skin may lead to a moist
dermatitis.
These lesions are common in the external ear
canal and between the toesal though they may develop other places on the body resulting in "hot spots"
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- Degree (Semester 1 lectures) Introduction to Nutrition Fichas sobre Lipids -lecture 5, creado por chloe.toto198 el 07/06/2016.
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- chloe.toto198
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