lipids unit 5 nutrition class

Following is a list of the various lipoproteins and their functions:

VLDLs . Very low-density lipoproteins are made in the liver from remnants of chylomicrons and transport [triglycerides] from the liver to various tissues in the body. As the VLDLs travel through the circulatory system, the lipoprotein lipase strips the VLDL of [triglycerides]. As triacylglycerol removal persists, the VLDLs become intermediate-density lipoproteins. IDLs . Intermediate-density lipoproteins transport a variety of fats and cholesterol in the bloodstream and are a little under half triacylglycerol in composition. While travelling in the bloodstream, cholesterol is gained from other lipoproteins while circulating enzymes strip its phospholipid component. When IDLs return to the liver, they are transformed into low-density lipoprotein.

Excessive consumption of Omega-6 fatty acids, especially in the context of inadequate consumption of Omega-3 fatty acids, can be

pro-inflammatory and increase risk of heart disease. The first double bond appears on the 6th carbon from the methyl end in an Omega-6 fatty acid. So just the location of the first double bond from the methyl end of a fatty acid can have profound effects on health

A common misconception is that fat is simply fattening. However, fat is

probably the reason we are all here. Throughout history, there have been many instances when food was scarce. Our ability to store excess caloric energy as fat for future usage allowed us to continue as a species during these times of famine.

Cholesterol is found both in animal products that we eat and in our bodies—plants make some sterols, but they do not make cholesterol]. It is the best-known sterol because of its role in

role in heart disease. Cholesterol forms a large part of the plaque that narrows the arteries in atherosclerosis. [The problem with cholesterol is that if it gets stuck in the blood vessels (usually from damage caused by hypertension, smoking, and/or diabetes), it forms plaque which becomes atherosclerosis which causes vessel blockage.]

saturated fatty acids

saturated fatty acids a fatty acid carrying the maximum possible number of hydrogen atoms. a saturated fat is composed of triglycerides in which most of the fatty acids are saturated

the chylomicrons are responsible for

shuttling the [triglycerides] to various locations such as the muscles, breasts, external layers under the skin, and internal fat layers of the abdomen, thighs, and buttocks where they are stored by the body in adipose tissue for future use.

Lipids perform three primary biological functions within the body:

they serve as structural components of cell membranes, function as energy storehouses, and function as important signaling molecules.

monounsaturated

Any fatty acid that has only one double bond is a monounsaturated fatty acid, an example of which is olive oil (75 percent of its fat is monounsaturated). Monounsaturated fats help regulate blood cholesterol levels, thereby reducing the risk for heart disease and stroke.

We have two categories of fat:

"essential" or "storage". We generally have much less essential fat than storage fat. Essential fat is found in our bone marrow, heart, liver, lungs, spleen, muscles, kidneys, and in the nervous system. Essential fat is, well, essential because it is necessary for health and life. Around 3% of total body fat in males is considered essential while around 12% of total body fat is considered essential due to sex-specific fat needs in the pelvis, thighs, and breasts.

Good/bad cholesterol refers to its action in our bodies, not in the form that it comes in foods. So there are two different "versions" of cholesterol:\

(1) dietary cholesterol is the cholesterol present in animal products that we eat and (2) blood cholesterol is the cholesterol that our body makes (or re-uses from dietary cholesterol) and is in our bodies.

The location of the first double-bond also effects the function of mono and poly-unsaturated fatty acids. If you start counting carbons from the methyl (CH3) end of a fatty acid chain, the first carbon you come to with a double bond is that fatty acid's "omega" designation

. Omega-3 fatty acids appear to have anti-inflammatory properties and have an important role in the prevention of heart disease. The first double bond is found on the 3rd carbon from the methyl end.

Phospholipids make up only about _____ percent of dietary lipids.

2% They are water-soluble and are found in both plants and animals. Phospholipids are crucial for building the protective barrier, or membrane, around your bodys cells. In fact, phospholipids are synthesized in the body to form cell and organelle membranes. In blood and body fluids, phospholipids form structures in which fat is enclosed and transported throughout the bloodstream.

For healthy total blood cholesterol, the desired range you would want to maintain is under

200 mg/dL. More specifically, when looking at individual lipid profiles, a low amount of LDL and a high amount of HDL prevents excess buildup of cholesterol in the arteries and wards off potential health hazards.

Triglycerides make up _____ of the fats that we eat in foods, but the other _____consists of sterols and phospholipids.]

95% 5%

Yet again, another hurdle presents itself. How will the fats pass through the watery layer of mucous that coats the absorptive lining of the digestive tract?

As before, the answer is bile. Bile salts envelop the fatty acids and monoglycerides to form micelles. Micelles have a fatty acid core with a water-soluble exterior. This allows efficient transportation to the intestinal microvillus. Here, the fat components are released and disseminated into the cells of the digestive tract lining.

Cholesterols absorption

Cholesterols are poorly absorbed when compared to phospholipids and [triglycerides]. Cholesterol absorption is aided by an increase in dietary fat components and is hindered by high fiber content. This is the reason that a high intake of fiber is recommended to decrease blood cholesterol. Foods high in fiber such as fresh fruits, vegetables, and oats can bind bile salts and cholesterol, preventing their absorption and carrying them out of the colon.

according to the National Institutes of Health (NIH), the following total cholesterol values are used to target treatment (2).

Desirable . Under 200 milligrams per deciliter Borderline high . 200-239 milligrams per deciliter High risk. 240 milligrams per deciliter and up

Fatty acids have different chain lengths and different compositions.

Foods have fatty acids with chain lengths between four and twenty-four carbons and most of them contain an even number of carbon atoms. When the carbon chain length is shorter, the melting point of the fatty acid becomes lower—and the fatty acid becomes more liquid.

Foods that have a high percentage of saturated fatty acids tend to be solid at room temperature. Examples of these are fats found in chocolate (stearic acid, an eighteen-carbon saturated fatty acid is a primary component) and meat. Foods rich in unsaturated fatty acids, such as olive oil (oleic acid, an eighteen-carbon unsaturated fatty acid, is a major component) tend to be liquid at room temperature. Flaxseed oil is rich in alpha-linolenic acid, which is an unsaturated fatty acid and becomes a thin liquid at room temperature.

Foods that have a high percentage of saturated fatty acids tend to be solid at room temperature. Examples of these are fats found in chocolate (stearic acid, an eighteen-carbon saturated fatty acid is a primary component) and meat. Foods rich in unsaturated fatty acids, such as olive oil (oleic acid, an eighteen-carbon unsaturated fatty acid, is a major component) tend to be liquid at room temperature. Flaxseed oil is rich in alpha-linolenic acid, which is an unsaturated fatty acid and becomes a thin liquid at room temperature.

LDL/HDL warnings.

High LDL values warn of increased health risks for heart disease, while high HDL values indicate a reduced risk for heart disease.

lipoproteins

Inside the intestinal cells, the monoglycerides and fatty acids reassemble themselves into [triglycerides]. [triglycerides], cholesterol, and phospholipids form lipoproteins when joined with a protein carrier. Lipoproteins have an inner core that is primarily made up of [triglycerides] and cholesterol esters (a cholesterol ester is a cholesterol linked to a fatty acid). The outer envelope is made of phospholipids interspersed with proteins and cholesterol.

LDL/HDL composition.

LDL is approximately 25 percent protein and 75 percent cholesterol and other fats. LDL is bigger (yet lighter) and richer in cholesterol than HDL. HDL is 50 percent protein and 50 percent cholesterol and other fats. HDL is smaller, more dense, and richer in protein.

According to the NIH, the following desired values are used to measure an overall lipid profile:

LDL. Less than 160 milligrams per deciliter (if you have heart disease or diabetes, less than 100 milligrams per deciliter) HDL. Greater than 40-60 milligrams per deciliter [Triglycerides]. 10-150 milligrams per deciliter VLDL. 2-38 milligrams per deciliter

Oxidized LDL.

LDLs become more dangerous when oxidized.Oxidation is defined as the loss of electrons between two substances via a chemical reaction. If an LDL oxidation occurs, the oxidized LDL is left unstable. Oxidized LDL can speed up the process of plaque formation in the arteries. It is believed to hasten the deposition of cholesterol into the arterial walls and to induce a chronic inflammatory effect throughout the bodys vast network of vessels. This activity promotes atherosclerosis and significantly increases risks for heart attack or stroke.

LDL/HDL function.

LDLs carry cholesterol into cells for normal usage, but LDLs can also deposit cholesterol into the walls of blood vessels, which can lead to harmful disease. HDLs scavenge excess cholesterol from the cells, tissues, and blood vessels and deliver these back to the liver, where these are either reused or excreted.

LDL/HDL and inflammation.

LDLs carry lipids that are proinflammatory and may contribute to heart disease. HDLs transport lipids that are anti-inflammatory and may reduce the occurrence of heart disease.

Lecithin's

Lecithin's crucial role within the body is clear, because it is present in every cell throughout the body; 28 percent of brain matter is composed of lecithin and 66 percent of the fat in the liver is lecithin. Many people attribute health-promoting properties to lecithin, such as its ability to lower blood cholesterol and aid with weight loss. no need to take supplements for this bc the body makes most of it

Fatty acids can differ from one another in [three important ways:

Length of the carbon chain Degree of saturation Location of any double bonds

emulsifiers

Phospholipids are ideal emulsifiers that can keep oil and water mixed. Emulsions are mixtures of two liquids that do not mix. Without emulsifiers, the fat and water content would be somewhat separate within food. Lecithin (phosphatidylcholine), found in egg yolk, honey, and mustard, is a popular food emulsifier. Mayonnaise demonstrates lecithin's ability to blend vinegar and oil to create the stable, spreadable condiment that so many enjoy. Food emulsifiers play an important role in making the appearance of food appetizing. Adding emulsifiers to sauces and creams not only enhances their appearance but also increases their freshne

How is this accomplished? lipoprotein-lipase

Recall that chylomicrons are large lipoproteins that contain a [triglyceride] and fatty-acid core. Capillary walls contain an enzyme called lipoprotein-lipase that dismantles the [triglycerides] in the lipoproteins into fatty acids and glycerol, thus enabling these to enter into the adipose cells. Once inside the adipose cells, the fatty acids and glycerol are reassembled into [triglycerides] and stored for later use.

In the body phospholipids bind together to form cell membranes.

The amphiphilic nature of phospholipids governs their function as components of cell membranes. [Because the phosphorus-containing head is polar, it attracts charged particles such as water, located both outside and inside your cells. Its fatty-acid containing tail is nonpolar, so it mingles and lines up with other non-polar molecules such as the fatty acid-containing ends of other phospholipids. This forms] a double layer in [your] cell membranes, thus effectively protecting the inside of the cell from the outside environment while at the same time allowing for transport of fat and water through the membrane.

You may have heard of the abbreviations LDL and HDL with respect to heart health.

These abbreviations refer to low-density lipoprotein (LDL) and high-density lipoprotein (HDL), respectively. Lipoproteins are characterized by size, density, and composition. As the size of the lipoprotein increases, the density decreases. This means that HDL is smaller than LDL.

Adipose tissue releases various adipokines.

These are hormones made from proteins that regulate energy balance and impact the body's functions. When we have too much adipose tissue, we release more of the adipokine called resistin which actually promotes inflammatory responses and insulin resistance (one of the reasons why obesity is linked to Type 2 Diabetes). At the same time, having more adipose tissue than is necessary reduces the release of the adipokine adiponectin which is actually protective against inflammation, heart disease, and Type 2 Diabetes. Adiponectin helps regulate glucose and fatty acid breakdown

Phospholipids solubility amphiphilic

This unique structure makes phospholipids water soluble. Phospholipids are what we call amphiphilic —the fatty-acid sides are hydrophobic (dislike water) and the phosphate group is hydrophilic (likes water).

Cholesterol is perhaps the best well-known sterol.

Though cholesterol has a notorious reputation, the body gets only a small amount of its cholesterol through food—the body produces most of it. Cholesterol is an important component of the cell membrane and is required for the synthesis of sex hormones, vitamin D, and bile salts.

Chylomicrons

Together they form a chylomicron, which is a large lipoprotein that now enters the lymphatic system and will soon be released into the bloodstream via the jugular vein in the neck. Chylomicrons transport food fats perfectly through the body's water-based environment to specific destinations such as the liver and other body tissues.

in contrast, a low value of HDL is a telltale sign that a person is living with major risks for disease.

Values of less than 40 milligrams per deciliter for men and 50 milligrams per deciliter for women mark a risk factor for developing heart disease. In short, elevated LDL blood lipid profiles indicate an increased risk of heart attack, while elevated HDL blood lipid profiles indicate a reduced risk.

unsaturation.

When one or more bonds between carbon atoms are a double bond (C=C), that fatty acid is called an unsaturated fatty acid, as it has one or more points of unsaturation.

Naturally occurring fatty acids usually have a _____configuration.

When the hydrogen atoms are bonded to the same side of the carbon chain, it is called a cis fatty acid. Because the hydrogen atoms are on the same side, the carbon chain has a bent structure. Naturally occurring fatty acids usually have a cis configuration.

As the body calls for additional energy, the adipose tissue responds by dismantling its

[triglycerides] and dispensing glycerol and fatty acids directly into the blood. Upon receipt of these substances the energy-hungry cells break them down further into tiny fragments. These fragments go through a series of chemical reactions that yield energy, carbon dioxide, and water. Fat is able to provide more energy per gram than glucose or protein, but it is unable to be converted into either protein or glucose.

The three main types of lipids are

[triglycerides], phospholipids, and sterols. [triglycerides] also known as triaglycerols)] make up more than 95 percent of lipids in the diet and are commonly found in fried foods, vegetable oil, butter, whole milk, cheese, cream cheese, and some meats. Naturally occurring [triglycerides] are found in many foods, including avocados, olives, corn, and nuts. We commonly call the [triglycerides] in our food fats and oils.

Which organ in the body produces cholesterol? a. liver b. pancreas c. gallbladder d. pituitary gland

a correct Right! Good job! The liver is responsible for creating both very low density lipoprotein (which then becomes low density lipoprotein) and high density lipoprotein. The liver also regulates the amount of all lipoproteins in the blood

In comparison to a low-density lipoprotein, a high-density lipoprotein contains a. less lipid. b. less protein. c. more cholesterol. d. more triglycerides.

a correct Right! Good job! HDLs have a very large protein composition coupled with low cholesterol content (20 to 30 percent) compared to the other lipoproteins.

polyunsaturated fatty acids

a fatty acid that lacks four or more hydrogen atoms and has two or more double bonds between carbons. A polyunsaturated fat is composed of triglycerides in which most of the fatty acids are polyunsaturated

monounsaturated fatty acids

a fatty acid that lacks two hydrogen atoms and has one double bond between carbons. a monounsaturated fat is composed of trigycerides in which most of the fatty acids are monounsaturated

Our bodies store energy in the form of ___________ and _______________. [mark all correct answers] a. adipose tissue (fat) b. glycogen (carbohydrate) c. muscles (protein) d. vitamins e. minerals

ab correct Right! Good job! Our body stores energy as fat in our adipose tissue or as glycogen in our muscles and liver. Protein is always being used for something else so we don't actually have "stores" of protein for use by the body. Vitamins do not provide energy. Review from Unit 1 & Unit 4.

What health risk has been associated with trans fats? [mark all correct answers] a. Increased blood cholesterol levels b. Increased risk of heart disease c. Increased risk of stroke d. Increased risk of obesity

abc correct Right! Good job! Consumption of trans-fatty acids from hydrogenated oils increases your risk of cardiovascular disease (including stroke). However, trans-fatty acids contain 9 caloriers per gram just like any other fatty acid so they're no more likely to contribute directly to obesity than consuming too much of any other type of fat.

A high risk of heart attack correlates with high blood levels of [mark all correct answers] a. triglycerides. b. high-density lipoproteins. c. low-density lipoproteins. d. very low-density lipoproteins.

ac correct Right! Good job! High LDL values warn of increased health risks for heart disease, while high HDL values indicate a reduced risk for heart disease. Elevated triglycerides are also associated with an increased risk of cardiovascular disease and may also indicate the presence of metabolic syndrome which is correlated with Type 2 Diabetes as well.

Heart attack and atherosclerosis are conditions often caused by cholesterol that has

accumulated and thickened in the walls of arteries. HDLs and LDLs are directly connected to these life-threatening ailments. By comparing and contrasting the roles each of these lipoproteins serves in the health of heart and blood vessels, you will be able to construct and evaluate a plan of action for your personal health.

Storage fat is where triglycerides are stored in depots made from

adipose tissue. We do not just use storage fat for energy, however. Storage fat helps cushion under our skin and around our organs, but it is considered 'expendable', meaning that we could survive without it.

Eicosanoids .

affect the synthesis of all other body hormones and control all body systems, such as the central nervous system and the immune system. Among the many functions eicosanoids serve in the body, their primary function is to regulate inflammation. Without these hormones the body would not be able to heal wounds, fight infections, or fight off illness each time a foreign germ presented itself

LDLs . As low-density lipoproteins

are commonly known as the bad cholesterol it is imperative that we understand their function in the body so as to make healthy dietary and lifestyle choices. LDLs carry cholesterol and other lipids from the liver to tissue throughout the body. LDLs are comprised of very small amounts of [triglycerides], and house over 50 percent cholesterol and cholesterol esters. How does the body receive the lipids contained therein? As the LDLs deliver cholesterol and other lipids to the cells, each cells surface has receptor systems specifically designed to bind with LDLs. Circulating LDLs in the bloodstream bind to these LDL receptors and are consumed. Once inside the cell, the LDL is taken apart and its cholesterol is released. In liver cells these receptor systems aid in controlling blood cholesterol levels as they bind the LDLs. A deficiency of these LDL binding mechanisms will leave a high quantity of cholesterol traveling in the bloodstream, which can lead to heart disease or atherosclerosis. Diets rich in saturated fats will prohibit the LDL receptors. Thus, LDL receptors are critical for regulating cholesterol levels.

HDLs . High-density lipoproteins

are responsible for carrying cholesterol out of the bloodstream and into the liver, where it is either reused or removed from the body with bile. HDLs have a very large protein composition coupled with low cholesterol content (20 to 30 percent) compared to the other lipoproteins. Hence, these high-density lipoproteins are commonly called good cholesterol.

Which of the following is a function of sterols in the body? a. Forms cell walls due to its hydrophillic head and hydrophobic tails. b. Precursor of bile, vitamin D, and some sex hormones. c. Forms long-term energy storage in the body. d. None of these apply

b correct Right! Good job! Hormones are be made from sterols including testosterone, cortisol. Sterols form bile acids and vitamin D. We can make vitamin D when cholesterol under our skin is exposed to UV rays from the sun. In fact, there is some debate at to whether or not Vitamin D should be considered a vitamin since its something we can make ourselves. The liver takes cholesterol and converts it to bile acids. One of the reasons fiber intake is so important for heart health is that fiber traps bile acids during digestion. This removes them from the body rather than allowing the body to recycle them again as bile acids. This forces the liver to either make new cholesterol or use already existing cholesterol to make more bile acids--reducing the amount of circulating lipids in the blood.

What is the immediate precursor for the eicosanoids? a. Glucose b. Fatty acids c. Hormones d. Cholesterol

b correct Right! Good job! Polyunsaturated, Omega-6 & Omega-3 fatty acids are responsible for the eicosanoids.

Which of the following is a feature of phospholipids? a. Resistant to digestion b. Soluble in both water and fat c. Highly susceptible to oxidation d. Found naturally only in animal foods

b correct Right! Good job! The reason phospholipids are so critical to our body processes is because they are able to navigate both watery and fatty environments. Without their ability to do this, it would be virtually impossible to access fats for energy, fat-soluble vitamins, and even to digest fat!

Unlike cis fatty acids, most trans fatty acids are not found naturally in foods,

but are a result of a process called hydrogenation. Hydrogenation is the process of adding hydrogen to the carbon double bonds, thus making the fatty acid saturated (or less unsaturated, in the case of partial hydrogenation). This is how vegetable oils are converted into semisolid fats for use in the manufacturing process. [This process came about as both an effort to use cheaper fats in food production but also to allay consumer concerns about the saturated fat content of their food. Since saturated fats such as butter and lard give important structural and texture qualities to foods such as baked goods, food manufacturers needed a way to use cheaper (and supposedly healthier) vegetable oils while at the same time having the same properties as saturated fats on foods. Thus lard and butter were replaced with vegetable shortening and margarine. However, this only appear to make things worse for our health (see the optional recommended article below)].

Which of the following substances cannot be absorbed directly into the bloodstream after digestion and absorption? a. glycerol b. short-chain fatty acids c. long-chain fatty acids d. none of these can be absorbed into the bloodstream

c correct Right! Good job! Glycerol, once detached from a triglyceride, can fit into the capillaries of the digestive system. Short-chain fatty acids are small enough to fit as well. It is long-chain fatty acids that must be bound up into chylomicrons for transport through the lymphatic system.

A low risk of cardiovascular disease correlates with high blood levels of a. triglycerides. b. free fatty acids. c. high-density lipoproteins. d. very-low-density lipoproteins.

c correct Right! Good job! High LDL values warn of increased health risks for heart disease, while high HDL values indicate a reduced risk for heart disease.

An important function of fat in the body is to a. build muscle tissue. b. regulate blood glucose levels. c. protect vital organs against shocks. d. provide precursors for glucose synthesis.

c correct Right! Good job! Part of the job of fat storage is to provide a protective cushion around our organs.

During which process are trans fats created? a. saponification b. emulsification c. hydrogenation d. oxygenation

c correct Right! Good job! Hydrogenation is the process of adding hydrogen to the carbon double bonds, thus making the fatty acid saturated (or less unsaturated, in the case of partial hydrogenation). This is how vegetable oils are converted into semisolid fats for use in the manufacturing process.

A triglyceride always contains 3... a. carbons. b. glycerols. c. fatty acids. d. double bonds.

c correct Right! Good job! Its called a triglyceride because of the three (tri-) fatty acids one each attached to one each of the three carbon atoms in a glycerol molecule.

Fatty acid chains are held together by _____ atoms that attach to each other and to _____ atoms. The term saturation refers to whether or not a

carbon hydrogen fatty acid chain is filled (or "saturated") to capacity with hydrogen atoms. If each available carbon bond holds a hydrogen atom we call this a saturated fatty acid chain. All carbon atoms in such a fatty acid chain are bonded with single bonds.

Fatty acids consist of a ______on one end of a carbon chain and a ______ on the other end.

carboxylic acid (−OOH) group methyl group (−CH3)

Eating too much Omega-6 fatty acids will The eicosanoids are important because they act similar to hormones in that they

cause not enough Omega-3 fatty acids to be processed. relay messages. They only travel to nearby cells, however, rather than going throughout the body as many hormones will. Plus, depending on the cell, an ecosanoid can have a different affect whereas a hormone always has the same effect.

Plant sterols in foods can be good for us because they interfere with

cholesterol absorption. They are similar in structure so they compete for the same absorption pathways in the intestines] which can contribute to lower cholesterol levels. Although cholesterol is preceded by its infamous reputation, it is clearly a vital substance in the body that poses a concern only when there is excess accumulation of it in the blood.

trans fatty acids have been associated with increased risk for

coronary heart disease because of the way they negatively impact blood cholesterol levels (1). [Trans-fatty acids cause problems in the body because the body treats them as saturated fats. Worse, while at least saturated fat intake can positively affect good cholesterol levels, trans-fatty acids both raise bad cholesterol and lower good cholesterol.

A single gram of fat provides calories.

correct 9 Right! Good job! The longer carbon chains of fatty acids provide a lot more energy than either carbohydrate or protein. The fact that fats provide 9 calories per gram is why we store our excess energy as fat rather than another nutrient. It's much more efficient.

The lipid bilayer of cell membranes is primarily made up of ________.

correct Right! Good job! Because the Phosphorus-containing head is polar, it attracts charged particles such as water, located both outside & inside your cells. Its fatty-acid containing tail is nonpolar, so it mingles & lines up with other non-polar molecules such as the fatty acid-containing ends of other phospholipids. This creates a 2-layer membrane that surrounds the cell & acts as a barrier, allowing certain substances to enter the cell but keeping others from leaving.

The human body is able to store much more energy as than as .

correct fat correct carbohdyrate Right! Good job! Fat is a more efficient way to store fuel and we have an unlimited capacity to store fat energy unlike glycogen which we can only store so much.

The most prominent form of fat in food and in the human body is/are .

correct triglycerides Right! Good job! Our essential and storage fat are composed of triglycerides. We have a much smaller component of body lipids in phospholipids and cholesterol.

Which of the following describes a feature of cis-fatty acids and trans-fatty acids? a. In nature, most double bonds are trans b. Hydrogenation converts trans-fatty acids to cis-fatty acids c. The conversion of cis-fatty acids to trans-fatty acids is inhibited by the presence of antioxidants d. In the body, trans-fatty acids are metabolized more like saturated fats than like unsaturated fats

d correct Right! Good job! he body considers trans fatty acids (artificial ones, produced by hydrogenation) to be saturated fatty acids.

Unsaturated fats: a. may be monounsaturated or polyunsaturated. b. cannot be cooked at very high temperatures. c. are found mostly in plant foods. d. all of these are correct

d correct Right! Good job! The double bonds in unsaturated fatty acids make them somewhat unstable which is why they have a low "smoke point"--when the fatty acids degrade due to heat. Frying at high temperatures is safer with saturated fatty acids because they have a much higher smoke point--a more stable fatty acid. Saturated fatty acids come from animal products and tropical oils (coconut, palm, and palm kernel) while monounsaturated and polyunsaturated fats primarily come from plants (with the exception of the Omega-3 fatty acids which are more prevalent in fatty fish).

Once the stomach contents have been emulsified, fat-breaking

enzymes work on the [triglycerides] and diglycerides to sever fatty acids from their glycerol foundations. As pancreatic lipase enters the small intestine, it breaks down the fats into free fatty acids and monoglycerides.

Any fat that you consume in a meal that isn't needed for body processes or energy simply isn't absorbed and is excreted by the body in the feces. True False

f correct Right! Good job! Our bodies are VERY efficient at absorbing the macronutrients (carbohydrates, proteins, fats) and will absorb nearly 100% of all consumed calories

Our regular cells can only store so much An adipocyte

fat, so we have specialized cells called adipose cells whose job is to store fat. (fat cell) consists are a large center droplet of fat surrounding by a thin layer of cytoplasm which holds the nucleus and mitochondria of the adipocyte. The fat droplet at the center of an adipocyte accounts for up to 95% of the total volume of that cell. A single fat cell can expand as many as 1,000 times before it cannot hold any more energy (which is when the body will start make more adipose tissue).

Recall that chylomicrons are transporters of

fats throughout the watery environment within the body. After about ten hours of circulating throughout the body, chylomicrons gradually release their [triglycerides] until all that is left of their composition is cholesterol-rich remnants. These remnants are used as raw materials by the liver to formulate specific lipoproteins.

A polyunsaturated fatty acid is a

fatty acid with two or more double bonds or two or more points of unsaturation. Soybean oil contains high amounts of polyunsaturated fatty acids. Both monounsaturated fats and polyunsaturated fats provide nutrition that is essential for normal cell development and healthy skin.

Sterols have a very different structure

from [triglycerides] and phospholipids. Most sterols do not contain any fatty acids but rather multi-ring structures. They are complex molecules that contain interlinking rings of carbon atoms, with side chains of carbon, hydrogen, and oxygen attached.

In the stomach,

gastric lipase starts to break down [triglycerides] into diglycerides and fatty acids. Within two to four hours after eating a meal, roughly 30 percent of the [triglycerides] are converted to diglycerides and fatty acids. The stomach's churning and contractions help to disperse the fat molecules, while the diglycerides derived in this process act as further emulsifiers. However, even amid all of this activity, very little fat digestion occurs in the stomach

Like [triglycerides], phospholipids have a _______backbone.

glycerol But unlike [triglycerides], phospholipids are diglycerides (two fatty-acid molecules attached to the glycerol backbone) while their third fatty-acid chain has a phosphate group coupled with a nitrogen-containing group.

Composed of fats and oils, lipids are molecules that yield ____ energy and have a chemical composition mainly of ___,____,___.

high carbon, hydrogen, and oxygen

if fats are not absorbed properly as is seen in some medical conditions, a person's stool will contain

high amounts of fat. If fat malabsorption persists the condition is known as steatorrhea. Steatorrhea can result from diseases that affect absorption, such as Crohn's disease and cystic fibrosis

other important jobs of lipids

hormones , some vitamins , and other critical compounds. The presence of lipids in the body is critical for fat-soluble vitamin metabolism. [Lipids provide structure in cell membranes (as the phospholipids) and are part of a structure that cushions and protects nerve cells.

Like phospholipids, cholesterol is present in all body cells as it is an

important substance in cell membrane structure. Approximately 25 percent of cholesterol in the body is localized in brain tissue. Cholesterol is used in the body to make a number of important things, including vitamin D, glucocorticoids, and the sex hormones, progesterone, testosterone, and estrogens.

Triglycerides] are the main form of lipid found

in the body and in the diet. Fatty acids and glycerol are the building blocks of [triglycerides]. Glycerol is a thick, smooth, syrupy compound that is often used in the food industry. To form a triacylglycerol, a glycerol molecule is joined by three fatty acid chains. [Triglycerides] contain varying mixtures of fatty acids. [For example, saturated fats have mostly saturated fatty acids while unsaturated fats have mostly unsaturated fatty acids; but a single triglyceride could have one fatty acid that is saturated, one that is monounsaturated, and one that is polyunsaturated, too.]

The terms fats, oils, and [triglycerides] are discretionary and can be used

interchangeably

Sterols are the ______common type of lipid.

least

The _______________ is the organ in the body which produces cholesterol from saturated fatty acids.

liver correct Right! Good job! Cholesterol is made naturally in our bodies—in fact more than what we get from foods. We do not even need to eat cholesterol (its a non-essential nutrient) because we can make it perfectly well on our own.

The first step in the digestion of [triglycerides] and phospholipids begins in the

mouth as lipids encounter saliva. Next, the physical action of chewing coupled with the action of emulsifiers enables the digestive enzymes to do their tasks. The enzyme lingual lipase, along with a small amount of phospholipid as an emulsifier, initiates the process of digestion. These actions cause the fats to become more accessible to the digestive enzymes. As a result, the fats become tiny droplets and separate from the watery components.

The body transforms carbohydrates into glycogen that is in turn stored in the

muscles for energy. When the muscles reach their capacity for glycogen storage, the excess is returned to the liver, where it is converted into [triglycerides] and then stored as fat. [ Remember that fat is a more efficient way to store energy because it contains nine calories per gram rather than the four per gram of glucose].

Muscle cells may also take up the fatty acids and use them for

muscular work and generating energy. When a person's energy requirements exceed the amount of available fuel presented from a recent meal or extended physical activity has exhausted glycogen energy reserves, fat reserves are retrieved for energy utilization.

a classic example of trans fat is vegetable shortening

through formulation are improving now since vegetable oils are liquid at room temperature, they were processed using hydrogenation to make them solid at room temperture people frequently turn to veg shortening as a healthy alternative to using lard from pigs, it was not until the lsat couple of decades that we realize trans fat containing foods like shortening were worse for health than lard.

If you decide to limit or redirect your intake of fat products, then choosing

unsaturated fat is more beneficial than choosing a saturated fat. This choice is easy enough to make because unsaturated fats tend to be liquid at room temperature (for example, olive oil) whereas saturated fats tend to be solid at room temperature (for example, butter). Avocados are rich in unsaturated fats. Most vegetable and fish oils contain high quantities of polyunsaturated fats. Olive oil and canola oil are also rich in monounsaturated fats. Conversely, tropical oils are an exception to this rule in that they are liquid at room temperature yet high in saturated fat. Palm oil (often used in food processing) is highly saturated and has been proven to raise blood cholesterol. Shortening, margarine, and commercially prepared products (in general) report to use only vegetable-derived fats in their processing. But even so, much of the fat they use may be in the saturated and trans fat categories

As stomach contents enter the small intestine, the digestive system sets out to manage a small hurdle, namely, to combine the separated fats with its own

watery fluids. The solution to this hurdle is bile. Bile contains bile salts, lecithin, and substances derived from cholesterol so it acts as an emulsifier. It attracts and holds on to fat while it is simultaneously attracted to and held on to by water. Emulsification increases the surface area of lipids over a thousand-fold, making them more accessible to the digestive enzymes

These lipidsare necessary in our diet because

while our body can make most lipids it needs, we are not able to make the 18-carbon fatty acid called linoleic acid and the 18-carbon linolenic acid. Nor can we make linolenic acid into linoleic acid or vis versa. However, our bodies can alter the structure slightly to make three different substances: arachadonic acid (from linoleic acid), eicosapentaenoic acid (EPA, from linolenic acid), and docosahexaenoic acid (DHA, also from linolenic acid). This process is rather slow and both linolenic and linoleic acid use the same enzyme for this process.