FNH 250 M.6 - Lipids

what are lipids and their major types?

lipids are water-insoluble organic compounds that contain C, H, and O

Major types include: fatty acids, triglycerols, phospholipids and sterols

what is a fatty acid and how are they classified?

fatty acids are chains of carbon and hydrogen with a methyl and acid group

they are classified by chain length (short, medium, long), saturation and double bond position

compare saturated, monounsaturated and polyunsaturated fatty acids

saturated: solid at room temp, found in animal fats and tropical oils

monounsaturated: liquid, in olive oil and avocado

polyunsaturated: liquid, omega-6 (sunflower oil), omega-3 (flaxseed, fish oil)

what is the difference between cis and trans fatty acid?

cis: hydrogens on the same side, common in nature

trans: hydrogens on opposite sides, mostly from hydrogenation; increase CDK risk - banned in Canada if industrially produced

what are essential fatty acids?

omega-6 and omega-3 are essential (body cannot make them; must be obtained from food)

roles of omega-3 and omega-6 fatty acids?

omega-6: (ARA) pro-inflammatory, cell membranes, eiosanoids

omega-3: (EPA/DHA) anti-inflammatory, brain/eye health, reduce CDK risk

what is a triglyceride?

glycerol + 3 fatty acids. Major dietary and body fat. Provides energy, insulation and essential fatty acids

structure and function of phospholipids?

glycerol + 2 fatty acids + phosphate. Amphipathic. Key for cell membranes, emulsification and lipid transport

what are sterols and examples?

lipids with a ring structure. Cholesterol (animal products) used in membranes, hormones, bile acids. Plant sterols lower cholesterol absorption

what are the steps for lipid digestion and absorption

1. mouth: salivary glands release lingual lipase, which begins to digest some fat. Lingual lipase plays only a small role in lipid digestion in adults, but is more important for infants

2. stomach: churning of the stomach mixes the lipid. A small amount of lipid is digested by residual lingual lipase and an acid-stable gastric lipase

3. small intestine: most digestion and absorption of lipids

   digestion:

   • lipids in digestive tract tend to separate from the watery portions of the GI fluid much like oil and water - limits the ability of enzymes to come into contact with and digest lipids - to overcome this lipids are emulsified with bile in the small intestine (process described in diff flashcard)

   • triglycerides are digested by pancreatic lipsase into monoglycerides (glycerol + 1 fatty acid) and 2 free fatty acids

   • fatty acids removed from phospholipids by phospholipase

   • sterols do not need to be digested

4. absorption

• Short & medium-chain fatty acids and glycerol:

  • Absorbed directly into intestinal cells.

  • Enter the bloodstream and travel to the liver via the portal vein, bound to albumin.

• Long-chain fatty acids and monoglycerides:

  • Form micelles with bile for absorption into intestinal cells.

  • Inside cells, they’re reassembled into triglycerides.

  • Packaged with other lipids and proteins into chylomicrons (lipoproteins).

• Chylomicrons:

  • Enter the lymphatic system first (not bloodstream).

  • Eventually enter bloodstream via the thoracic duct.

  • Deliver triglycerides to body cells, where lipoprotein lipase breaks them down.

  • Remnants return to the liver for processing.

what are lipoproteins and their types?

lipid transport clusters

• Chylomicrons: carry dietary fat.

• VLDL: liver fat to tissues.

• LDL: “bad” cholesterol to cells.

• HDL: “good” cholesterol back to liver.

why is LDL “bad” and HDL “good”?

LDL deposits cholesterol (increases CDK risk); HDL removes it. Diets high in sat/trans fat increases LDL; omega-3 and fibre decrease LDL and TG

functions of adipose tissue?

stores triglycerides, provides energy, insulation, hormone secretion (adipokines). Links to metabolism and chronic disease

lipid intake recommendations

• Fat: 20–35% of energy.

• Omega-6: 12g (W), 17g (M)

• Omega-3: 1.1g (W), 1.6g (M)

• WHO EPA/DHA: 250 mg–2 g/day; ≤3 g/day.