Module 4

How are fatty acids similar to one another?

All fatty acids are strings of carbon w/ hydrogens attached All fatty acids have carboxyl group on one end All fatty acids have a methyl group on the opposite end

What are the chemical elements (atoms) that make up triglycerides?

Carbon and hydrogen with a small amount of oxygen

19. What are some compounds made from cholesterol in the body?

Cholesterol; interconnecting rings of carbon atoms w/ side chains of carbon, hydrogen and oxygen attached.

What type of chemical reaction is needed to make a triglyceride from its component parts?

Dehydration (synthesis) reactions

14. What is meant by "essential" fatty acid? Name the two essential fatty acids. For each of the two fatty acids, indicate how many total carbons are in the chain, how many double bonds are present and whether they are omega-3 or omega-6 fatty acids.

Do not eat them, we develop deficiency symptoms Linoleic acid & linolenic acid Both linoleic & linolenic acid have 18 carbons but differ in number of double bonds present & location of first double bond. Linoleic acid is an omega-6 fatty acid w/ 2 double bonds (18:2 omega-6) Linolenic acid is an omega-3 fatty acid with three double bonds (18:3 omega-3).

8. What do we mean when we say that a fatty acid is saturated? monounsaturated? polyunsaturated?

Each & every carbon in chain has two hydrogens attached, we say it is fully saturated w/ hydrogens or "saturated" fatty acid Number of double bonds it contains determines a fatty acid is monounsaturated (one double bond),or polyunsaturated (two or more double bonds).

18. Does your body need cholesterol in order to thrive? If so, do you need to get it from food? If not, why not?

Essential component of cell membranes. Couldn't live without cholesterol but we don't have to get it from the diet. Liver can make all the cholesterol we need.

35. Why can't fatty acids be converted to glucose? (pay attention to arrows in figure 5.14)

Fatty acids are metabolized 2 carbons at a time into acetyl units of acetyl-CoA and we have no enzymes to convert acetyl-CoA into pyruvate or any other metabolite in the gluconeogenesis pathway.

31. What is the difference between lipolysis and beta-oxidation?

lipolysis which refers to the breaking apart of a triglyceride into fatty acids and glycerol. The next step is called beta-oxidation and begins when fatty acids are broken into 2-carbon units.

41. What foods contain cholesterol?

only animal sources (eggs, liver, shellfish)

If we say that a fatty acid is a 22:6 fatty acid, what does this mean?

A fatty acid w/ 22 carbons, 6 double bonds & first double bond located three carbons from methyl or free end would be called 22:6 n-3 or 22:6 omega-3

29. What is the fate of triglycerides in the cell (i.e. once the cell receives them, what can they be used for)?

First step is lipolysis which refers to the breaking apart of a triglyceride into fatty acids & glycerol. Next step is called beta-oxidation & begins when fatty acids are broken into 2-carbon units. A coenzyme A (CoA) unit is added to each 2- carbon unit to make Acetyl CoA. A 12 carbon fatty acid can make six acetyl CoA compounds & as well as high energy electrons. These acetyl CoA compounds then enter citric acid cycle (also called TCA or Krebs cycle) where more high energy electrons are produced during their metabolism. High energy electrons will travel to electron transport system where they will be used to produce ATP, our internal energy currency

33. How are fatty acids made? Triglycerides made? What is the name for these processes?

From acetyl-CoA and NADPH through the action of enzymes derived from carbohydrates via the glycolytic pathway. Fatty acid synthesis

28. Mr. X has coronary heart disease (cardiovascular disease affecting the heart vessels). What sort of lipid profile would you expect to see in his medical chart? For example, would his LDL be elevated or depressed? What about his HDL? Total Cholesterol? HDL to total cholesterol ratio?

High LDL Low HDL Cholesterol 240 or over.

30. What are the major steps involved in breaking down fatty acids and glycerol for energy? In other words, how do triglycerides enter the cellular respiration process (figure 5.14).

High energy electrons will travel to electron transport system where they will be used to produce ATP, our internal energy currency. The description in Fig. 5.14 is a good one. It shows the breakdown of triglyceride for energy just as Fig 4.15 did with glucose. I have also provided you with a simpler graphic of triglyceride breakdown for energy below. The glycerol can also be used for energy but since it is first converted to pyruvate, it can also be used to make a little glucose if it is needed

Name 5 foods that are more than 80% kcalories from fat.

Hotdog, Hard Cheeses, Most Nuts, Butter and Oil

Digestion and Absorption Describe the digestion and absorption of triglycerides (fats) in as much detail as possible. Be able to identify any chemical substances secreted from any organs to facilitate triglyceride digestion. Discuss any intermediate compounds formed during digestion (i.e. micelle, chylomicron) and identify the constituents of these compounds. Be sure to be clear about where each step in digestion and absorption is taking place. (see online lecture and figure 5.9 for a summary)

In the Intestinal Lumen: * Food we take in the mouth break down into Triglycerides * Bile from liver emulsifies TG forming lipid droplets called micelles * Lipase from pancreas breaks apart TG to fatty acids, glycerol and monoglycerides In the Intestinal Tract Cell: * TG reforms *TG, cholesterol, phospholipids, proteins and fat soluble vitamins join to form Chylomicron, In the Luymph or Blood: *To lymph and then to blood

If a food states that it has 23% of the DV for saturated fat in one serving of the food, what does this mean?

It is the recommended percentage of fat in the food.

25. What are the steps in plaque formation in an artery? What cells and compounds play a role in this process. What can precipitate a heart attack or stroke? (figure 5.16).

LDLs can deposit cholesterol into artery wall, causing a blockage to build up on interior of blood vessel. This is especially true for the smaller LDL compounds as they can more easily penetrate artery wall. Look at Fig. 5.16 of your text for a depiction of this undesirable buildup. Take time to study this diagram so you know the components of a plaque and the steps involved in its formation. When enough plaque builds up in the blood vessel wall, the blood cannot flow through the vessel and a heart attack or stroke can occur. Heart attacks occur when blood flow to the heart is interrupted whereas strokes occur when blood flow to the brain is interrupted.

How do you know if a fatty acid is an "omega-3" or an "omega-6"?

Linoleicacid is omega-6 fatty acid w/ 2 double bonds (18:2 omega-6) Linolenic acid is omega-3 fatty acid w/ three double bonds (18:3 omega-3)

What is the name of the compound that transports lipids in the blood? Why is a special compound needed to transport lipids in the blood? What are the four major "ingredients" or subunits that make up this lipid transport vehicle? Where in the compound is each ingredient located (i.e. what makes up the "shell"? What specifically is the role of the phospholipid subunit?

Lipoproteins

40. Why is the ratio of omega-6 to omega-3 fatty acids so much higher that it was 100 years ago?

Major reason for imbalance in our omega-6 to omega-3 fatty acids is invention & incorporation of omega-6 rich vegetable oils into our diet. Boosted our omega-6 fatty acids dramatically. Moving from grass fed animals to corn fed animals also lowered our omega-3 fatty acids.

27. Should a vegan be worried about developing a cholesterol deficiency? Why or why not?

No, because the body by itself can produce enough cholesterol.

6. How do fatty acids differ from one another?

Number of carbons in the hydrocarbon Each and every carbon in chain has two hydrogens attached to it, fully saturated w/ hydrogens or saturated" fatty acid Two of hydrogens are absent around two central carbons. Removing hydrogen would break "4 bond" rule, since two carbons only have 3 bonds surrounding them

24. What are the non-dietary risk factors for heart disease?

Obesity, less exercise and genetics.

10. What does the term "omega" refer to in a fatty acid?

Omega symbol or n- & then indicate number of carbon before first double bond occurs

36. What type of fatty acids are eicosanoids made from? How does the behavior of eicosanoids differ based on the type of fatty acid that they are made from? (Fig. 5.13)

Omega-3 and Omega-6 Signaling molecules in the body that regulate blood pressure, inflammation. Blood clotting. .

What are the subunits or compounds that link together to form the triglycerides?

One compound of glycerol (an alcohol) and three fatty acids

17. Give an example of a sterol. How does the structure of a sterol differ from other lipids (in general)?

Part of cell membrane is a fatty bilayer. Cell membrane is made up of two layers of lipid....specifically phospholipid. Phospholipids have fat loving fatty acid chains oriented in center of membrane & glycerol & phosphate group on outside, interacting with the fluids bathing Inside or outside of cell. Fig. 5.7 provides a visual depiction of a) a chemical view of phospholipid, b) it's role as a coating for oil so it stays dispersed in water and c) its configuration in the cell membrane. Part of lipoproteins are fat transport vehicles or compounds which we wlecture. Phospholipid coats large transport compound so it can stay dispersed in watery blood.

39. How does the typical ratio of omega-3 to omega-6 fatty acids in the diet of the average person in the US differ from the recommended ratio? Why is this a concern?

People have a ratio of omega-6 to omega-3 fatty acids that is too high. In other words, they consume too much omega-6 in comparison to omega-3 fatty acids. United States, the typical omega-6 to omega-3 fatty acid ratio is 15:1 (15 omega-6 fatty acids for every one omega-3 fatty acid) whereas the recommended ratio is somewhere closer to 5:1

16. What is the major role of phospholipids? Give two examples of specific instances or substances where phospholipids serve this role. How is a phospholipid configured within the cell membrane?

Phospholipids can thus serve as an interface between droplets of oil & water & keep them emulsified or mixed up

15. Describe the structure of a phospholipid. How does it differ from a triglyceride? Identify the hydrophilic and hydrophobic portions of the phospholipid.

Phospholipids look like triglycerides w/ one exception. One of fatty acids in triglyceride is replaced by phosphorus containing compound. So compound is made up of a glycerol backbone, two fatty acids & a phosphorus containing compound (or phosphate group) Phospholipids, hydrophilic portion includes both glycerol backbone & phosphate group & hydrophobic portion consists of two fatty acid chains

23. What are the other dietary risk factors associated with cardiovascular disease?

Replacing saturated fatty acid rich foods w/ low glycemic index carbohydrates or healthier fats seems protective, replacing w/ high glycemic refined carbohydrates increases risk.

38. What does the hardness or softness of a dietary fat typically indicate?

The fat's saturation, the softer a fat is a room temperature the less saturated it is.

32. Why aren't ketones produced most of the time when fats (triglycerides) are burned for energy? When are ketones produced from fats? (think back to chapter 4)

They are three water-soluble molecules . The liver produces it from fatty acids during periods of low food intake.

26. What is an acceptable blood cholesterol level? What is considered a borderline blood cholesterol level? What level of blood cholesterol is considered high?

Total Cholesterol - Acceptable = less than 200 mg/dL - Borderline = 200 - 239 mg/dL (often stress diet and lifestyle to lower) - High = 240 mg/dL or greater (usually requires medication to lower)

42. What is the maximum amount of fat, saturated fat and cholesterol that a person should consume on average each day (from food)?

Total fat 20-35% of kcalories Saturated fat 10% or less of total kcalories (7% or less if at risk for CVD) Cholesterol 300 mg or less per day (remember that is it not an essential nutrient as our liver can make it. Only found in animal products

Which of the above lipids is the major lipid in foods?

Triglycerides

What are the 3 major categories of lipids found in foods?

Triglycerides (kcalorie containing fat in food), phospholipids and sterols.

9. Compared to a saturated fatty acid, for every double bond in an unsaturated fatty acid, _____ hydrogens are missing.

Two

22. What influence do LDL and HDL have on the risk of cardiovascular disease? Why? What foods or lifestyle factors raise or lower the blood levels of these two lipoproteins?

Unfortunately LDLs can deposit cholesterol into artery wall, causing a blockage to build up on interior of the blood vessel High density lipoprotein's role, bring cholesterol from tissues back to liver to be degraded or incorporated into other substances. Prevents cholesterol from being laid down in artery wall. High levels of HDL are associated w/ reduced risk of CVD. Raise HDL: exercise, possibly small amounts of alcohol, omega-3 polyunsaturated fatty acids lower HDL: omega-6 polyunsaturated Raise LDL: saturated fatty acids, cholesterol lower Lower LDL: polyunsaturated fatty acids, monounsaturated fatty acids

13. Are omega-3 fatty acids saturated or unsaturated? Where do we find them in foods? What is their influence on health?

Unsaturated Olive, canola, and corn oil

34. Would you be likely to find a 15-carbon fatty acid?

Yes