Ch 5 - Lipids: Not Just Fat

2. How does chain length and saturation of fatty acids affect a fat's structure at room temperature?

-Chain length: Shorter fatty acids remain liquid at room temperature even with refrigeration and are more water soluble -Saturation: Saturated fatty acids have all single bonds between the carbons making them more solid at room temperature. Unsaturated fatty acids have a double bond, making them more liquid at room temperature.

8. How can you tell if a fat is essential or non-essential? Give an example of an essential fatty acid and non-essential fatty acid.

-Fatty acids with no double bonds before the 9th carbon are nonessential. -Essential fatty acid: alpha-linolenic acid, linoleic acid -Nonessential fatty acid: arachidonic acid

17. Why do some people use Olestra? How does it work?

-Olestra is a fat replacer that is indigestible so it provides no calories. -reduces absorption of fat-soluble vitamins -Digestive enzymes do not recognize the fatty acid arrangement so the fat replacement is not broken down and absorbed and thus provides half the calories of fat.

7. What is the difference between non-essential and essential fatty acids?

-non-essential fatty acids: can be made in body, non "essential" to have in your diet -essential fatty acids: must come from food, cannot be made by the body; two families: Omega-3 (alpha-linolenic acid) Omega-6 (linoleic acid)

13. What are functions of sterols? Give examples.

1. structural (stabilize cell membrane structure, cell communication) component of cell membranes 2. precursor to other substances examples: vitamin D, sterol hormones (estrogen, testosterone), bile salts

15. How is fat absorbed? Which vehicles does it use? How are lipids transported in our body?

If fat-soluble (TG, Pl, Ch), travel in chylomicron using lacteals to exit the small intestine and go to the veins which then goes to the heart, the arteries. The chylomicron then reach the capillary beds, where O2 and nutrient absorption into the tissue occurs. The chylomicron enters the capillary vessels and interact with lipoprotein lipase (fat breakdown in lipoprotein carrier). The fatty acids and glycerol that results, are absorbed in nearby cells. If it's an adipose cell, it's stored. If it's another type, it can be broken down for energy. The leftover, the chylomicron remnant, still contains some TGs, PLs, and Ch that weren't absorbed. These are sent to the LIVER. If the nutrients are water-soluble, they are absorbed directly into the capillaries through the portal vein to the liver. Excess glucose is converted into fatty acids (acid). These fatty acids and the chylomicron remnant are repackaged into another lipoprotein carrier known as VLDL (very-low density lipoprotein, the density is how dense the protein is relative to the fat). Like chylomicron, VLDL is TG rich, travels through bloodstream, delivering TGs to our body cells. Lipoprotein lipase in capillary walls will breakdown TGs in the VLDL into MGs and FFAs, which diffuse into nearby adipose cells or peripheral cells. As VLDL loses TGs, it becomes smaller and denser, becoming an iDL (intermediate-density lipoprotein carrier). iDL returns to the liver, converted to LDL (low-density lipoprotein), "bad" cholesterol. Technically not a cholesterol, it is more than half Ch and cholesterol esters, it delivers cholesterol to the bodies which use it to synthesize membrane hormones and other vital compounds. Unique receptors on the cell walls, known as LDL receptors, bind LDL and engulf it. High-density lipoprotein (HDL), "good" cholesterol, can go around your body and pick up cholesterol from arial plaques. HDL brings it back to the liver, where Ch is converted into bile salts, which is released into the small intestine for fat digestion.

6. What are pros/cons of having trans fat in your food?

PROS: longer shelf life (b/c it protects against oxidation); improved texture and taste CONS: Trans fat is known to raise LDL ("bad") cholesterol, and lower HDL ("good" cholesterol), promote systemic inflammation, and increase triglycerides in your blood.

5. How is trans fat produced?

Trans fat is produced by hydrogenation (adding hydrogen to oil to remove some of the double bonds)

12. What are functions of phospholipids? What about phospholipids ideal for emulsifiers and cell membranes? How does the food industry use phospholipids?

-Functions: 1. ideal emulsifiers (keep fat suspended in water, keep oil and water mixed): in human body, bile salts form micelles used to emulsify fats during digestions 2. perfect structural element for cell membranes (able to communicate with watery environments of blood and cell fluids; allows other lipids to enter and exit cells) 3. lipid digestion and transport: mouth and stomach (fat breakdown for digestion); intestine (continue emulsifying fat); blood (coat surface of lipoproteins that carry lipid particles to their destinations in the body) - They are ideal for emulsifiers because their hydrophilic heads and hydrophobic tails make them compatible with both fat and water. It keeps fat suspended in water and keeps oil and water mixed. - For cell membranes, they selectively allow both fatty and water-soluble substances into the cell; store fatty acids temporarily, and play and important role in nerve cells. -In the food industry, lecithin, an emulsifier, is a blend of phospholipids with different nitrogen-containing compounds. 1. It functions as an emulsifier to combine two ingredients that don't ordinarily mix, like oil and water (e.g. salad dressing) 2. It can be used in high-fat powdered products (e.g. dry milk, coffee creamers, milk replacers) helps mix fatty compounds with water

11. What are good sources of saturated fat and polyunsaturated fats?

-Saturated fat: animals foods, tropical oils (coconut/palm oil) -Polyunsaturated fats: animal and plant foods; Omega-3 (soybeans, flaxseed oils, salmon, tuna; Omega-6 (seeds, nuts, corn oil, meats, poultry, eggs)

3. What is the difference between saturated and unsaturated fatty acids?

-Saturated fatty acids have all single bonds between the carbons, so they easily stack on top of each other, making them solid at room temperature. -Unsaturated fatty acids have a double bond that creates a kink between the fatty acids, allowing the fatty acids to move and rotate, making them more liquid at room temperature.One double bond? Monounsaturated fatty acid (MUFA) Two or more than one double bond? Polyunsaturated fatty acid (PUFA)

16. Explain fat transport using chylomicron, VLDL, LDL, IDL, and HDL. What are the differenced between each of the lipoprotein carrier - not just their composition but what they carry/deliver/pick up?

-The chylomicron (made in small intestine, a lipoprotein carrier) delivers triglycerides to our tissues. -VLDL (very-low-density lipoproteins, made in liver, a lipoprotein carrier) -LDL (low-density lipoproteins): "bad" cholesterol, delivers Ch -iDL (intermediate-density lipoproteins) delivers triglycerides -HDL (high-density lipoproteins): "good" cholesterol (actually not cholesterol, but a lipoprotein carrier), picks up Ch

10. What is the difference between visceral and subcutaneous fat? How can we use that info to apply to someone with apple or pear shaped body?

-Visceral fat surrounds and protects organs. -Subcutaneous fat is under the skin and insulates the body. -Pear shaped bodies carry more weight below the waist. That weight is mostly subcutaneous fat. -Apple shaped bodies carry more weight in the abdominal area. That weight is largely visceral. -Apple shaped individuals are more likely to have health risks for heart diseases, diabetes, and other metabolic syndrome related complications.

1. What are the different types of fats in our body? Which of the fat types are most and least prevalent? Which type of fat are found in our food?

-triglycerides (most abundant): found in food (fats, oils), stored as adipose tissue in body -phospholipids (2% of dietary lipids): plant/animal origin, body can make them, fat/water soluble -sterols (very, very small % of lipids): well known-cholesterol

14. Explain how fat is physically and chemically digested. Name enzymes, organs (from mouth to small intestine).

1. Physical and chemical digestion of fats start in MOUTH: salivary amylase secretes lingual lipase (digestive enzyme for fats) 2. The bolus travels down the esophagus and enters the STOMACH: Gastric lipase joins in and the stomach's contractions and churning keep the fat dispersed. After 2 to 4 hours in the stomach, digestion has broken down 30% of the triglycerides (TG) to diglycerides (DG) (two fatty acids) and free fatty acids (FFA) 3. In the SMALL INTESTINE, the fat tends to clump together into a lipid droplet containing TG, DG, MG (monoglycerides), FFA, and Ch (cholesterol). To aid digestion, it must be emulsified into smaller droplets so that fat digesting enzymes can access the fatty acids more easily. The gallbladder contracts bile into the small intestine. Bile is made of bile salts and a phospholipid called lecithin. The fat droplets are suspended in water and dispersed into smaller droplets as they are surrounded by bile acids. Water-soluble pancreatic lipases are able to break off one fatty acid at a time, digesting all available TGs and DGs into monoglycerides and FFAs. Digestive lipids are packaged into micelles, made of lecithin and bile acids for delivery through the digestive fluids to the brush border. Hydrophilic head of lecithin allows micelles to easily traverse in the watery environment while the hydrophobic tails keeps the digestive fats inside. Digestive lipids leave the micelle as they are near the brush borders and they absorbed by transporters on the surface of the cell and absorbed into the brush border. Most of the bile salts and lecithin make their way to the liver to be used again, they don't get absorbed (recycling process called enterohepatic circulation). Not all bile acids go back, they can be eliminated in the feces. The digested fat parts are now in the intestinal cells. We must repackage the fatty acids and MGs into TGs. Phospholipids and cholesterol also follow the TGs. All three are packaged and put into a carrier molecule called a lipoprotein. Lipoprotein is made of a shell of phospholipids embedded with protein and cholesterol. Because it's made of phospholipids, the fats are carried on the inside, while the hydrophilic can move within the aqueous environment. This carrier molecule is a type of lipoprotein carriers known as chylomicron. The intestinal cells are surrounded by two circulatory pathways: capillaries and lymphatic capillaries (lacteals). Carbs (glu, gal, fru) and protein (A.A.) are small enough to be absorbed by the capillaries. Chylomicrons are too big to enter the capillaries so they enter the lymphatic system to deliver them and make way to the bloodstream.

19. What are some AHA recommendations from your textbook? Don't need to memorize them, but be able to recognize them.

1. Use up as many calories as you take in. -know how many calories you should be eating and drinking to maintain your weight -don't eat more calories than you know you can burn up every day -increase the amount and intensity of your physical activity to match the number of calories you take in -aim for at least 30 min of moderate physical activity on most days of the week or 30 min every day 2. eat a variety of nutritious foods from all the food groups -eating a variety of fruits and vegetables may help you control your weight, cholesterol, and blood pressure -to get the nutrients you need, eat a dietary pattern that emphasizes: fruits and veggies, whole grains, low-fat dairy products, poultry, fish, and nuts while limiting red meat and sugary foods and beverages 3. eat less of nutrient-poor foods -you could use your daily allotment of calories on a few high-calorie foods and beverages, but you probably wouldn't get the nutrients your body needs to be healthy -limit foods and beverages high in calories but low in nutrients, limit amount of saturated fat, trans fat, and sodium you eat 4. as you make daily food choices, base your eating pattern on these recommendations: -choose lean meats and poultry without skin and prepare them without added saturated and trans fat -eat fish at least twice a week -select fat-free, 1% fat, and low-fat dairy products -cut back on foods containing partially hydrogenated vegetable oils to reduce trans fat in your diet -to lower cholesterol, reduce saturated fat to no more than 5 to 6% of total calories -cut back on beverages and foods with added sugars -choose and prepare foods with little to no salt -drink alcohol in moderation -keep your portion sizes in check

4. What is the difference between cis and trans fatty acids? How is trans fat produced?

1. cis fatty acids: bent chain (hydrogens on same side), occur naturally, more common 2. trans fatty acids: straighter chain (hydrogens on opposite sides), produced by hydrogenation

9. What are the main functions of triglycerides?

1. energy source: 9kcal/g 2. carrier of fat-soluble nutrients 3. sensory qualities (flavor, odor, texture) in food 4. energy reserve: form of stored energy in adipose tissue 5. insulation and protection: visceral fat (protect organs), subcutaneous fat (insulate)

18. Name some diseases/health risks associated with a high fat diet.

1. heart disease risk factors: high blood cholesterol (high LDL, low HDL), smoking, high blood pressure 2. obesity: high fat diets promote weight gain, significant within the U.S. population (34.9% of American adults, 17% of American children and adolescents) 3. metabolic syndrome: affects 1/4 of American adults, cluster of at least three symptoms -excess abdominal fat -high blood glucose -high serum triglycerides -low HDL cholesterol -high blood pressure 4. cancer: results from complex mix of lifestyle, hereditary, and environmental factors; role of nutrition and diet complex -evidence suggests 30-40% due to poor food choices and physical inactivity -some dietary factors act as promoters, while others serve a protective role