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Study Guide for Exam 2 - Nutrition and Health | 709 255, Study notes of Nutrition

Rutgers University - CamdenNutrition
Prof. J. Dixon

Nutr&Health Exam II Review Material Type: Notes; Professor: Dixon; Class: 709 - NUTRITION AND HEALTH; Subject: NUTRITIONAL SCIENCES; University: Rutgers University;

Typology: Study notes

2011/2012

Uploaded on 03/08/2012

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Exam II Study Guide
Lipids
Why don’t we have free fatty acids (FA) in our blood?
oActually, there is a low concentration of FA in the blood. However, this must be
constantly regulated. If there is more than what is allowed in the blood, that becomes
toxic b/c the free FA will dissolve your membranes. This is because free FAs act as
detergents
A Mass spectrometer allows scientists to see more lipids in biological samples
What are lipids?
oAny compound that has a fatty acid-like component or a sterol component.
oInsoluble in water, but soluble in organic solvents
Example: cholesterol is considered a FA b/c it has a sterol group
In the body lipids function as:
oA compact form of energy
oInsulation and protection for the body’s organs
oCompounds that make skin and hair shiny/soft
oComponents of body tissue and compounds
In food, lipids function as
oFlavor, mouthfeel????? ASK HIM!!
oNutrients (EFA—essential fatty acids, fat soluble vitamins)
What is fat?
oFat is made up of fatty acids attached to a glycerol backbone
Fatty acids are the most abundant type of lipid
Made entirely of C, H, & O
One end has a carboxylic acid group –COOH (ALPHA end)
The other end has a methyl group –CH3 (OMEGA end)
oSaturated Fat
No double bonds!
Found in meats and dairy
SOLID at room temperature
oUnsaturated fat
A FA that contains at least one C-C double bond
oMonounsaturated fatty acid (MUFA)
A FA that contains one C-C double bond
oPolyunsaturated fatty acids (PUFA)
A FA that contains more than one C-C double bond in its backbone
Types of lipids
oTriglycerides
o3 fatty acids attached to a glycerol backbone via ester bonds
oFunction:
Provide the essential FAs needed for the body to function
Also provide FAs used for energy (ATP) production and storage
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Exam II Study Guide Lipids  Why don’t we have free fatty acids (FA) in our blood? o Actually, there is a low concentration of FA in the blood. However, this must be constantly regulated. If there is more than what is allowed in the blood, that becomes toxic b/c the free FA will dissolve your membranes. This is because free FAs act as detergents  A Mass spectrometer allows scientists to see more lipids in biological samples  What are lipids? o Any compound that has a fatty acid-like component or a sterol component. o Insoluble in water, but soluble in organic solvents  Example: cholesterol is considered a FA b/c it has a sterol group  In the body lipids function as: o A compact form of energy o Insulation and protection for the body’s organs o Compounds that make skin and hair shiny/soft o Components of body tissue and compounds  In food , lipids function as o Flavor, mouthfeel ????? ASK HIM!! o Nutrients (EFA—essential fatty acids, fat soluble vitamins)  What is fat? o Fat is made up of fatty acids attached to a glycerol backbone  Fatty acids are the most abundant type of lipid  Made entirely of C, H, & O  One end has a carboxylic acid group –COOH ( ALPHA end)  The other end has a methyl group –CH3 ( OMEGA end) o Saturated Fat  No double bonds!  Found in meats and dairy  SOLID at room temperature o Unsaturated fat  A FA that contains at least one C-C double bond o Monounsaturated fatty acid (MUFA)  A FA that contains one C-C double bond o Polyunsaturated fatty acids (PUFA)  A FA that contains more than one C-C double bond in its backbone  Types of lipids o Triglycerides o 3 fatty acids attached to a glycerol backbone via ester bonds o Function:  Provide the essential FAs needed for the body to function  Also provide FAs used for energy (ATP) production and storage

 Also important for insulation and protection  Hydrogenation of FAs o Process used to solidify an oil by adding H to C=C bonds o Forms a trans fatty acid o Trans fatty acids are found naturally in dairy and meat, but most are made from the partial hydrogenation process o Trans fats are UNHEALTHY AND BAD o Cis-FA: the hydrogen are on the same side of the double bond o Trans-FA : the hydrogen are on opposite sides of the double bonds o The process  They take regular cis-FA’s and add additional H’s by pumping in H2 gas  Once it is saturated it becomes a different FA a trans FA that is saturated o Trans FA are desirable b/c they impart desirable food texture and reduce spoilage. o However, they are very bad for your health o Sometimes the process can reverse, but now you get the monounsaturated FA but with a trans-double bond! BAD  They’re bad because they act like saturated FAs in membranes and can be oxidized  They raise blood cholesterol levels higher than do saturated fatty acids  Essential Fatty Acids o Are needed for immune function, vision, cell membranes and production of hormone-like compounds o The body cannot synthesize double bonds in positions before the omega-9 position, that’s why we have 2 essential FAs o Omega-6 Fatty Acids  Also called linoleic acid  This FA’s first double bond is at the 6th^ carbon from the omega end, which is why this is a fatty acid that the body cannot make  Found in vegetable oils, beef, poultry  We only need about 1 tablespoon per dayArachidonic acid can be made from Omega-6 fatty acidsMetabolized to form eicosanoids  Linoleic Acid (omega-6)dihomo-gamma-linolenic acidarachidonic acid o Omega-3 fatty acids  Also called alpha-linolenic acid  The first double bond is located on the 3rd^ carbon from the omega end  Found primarily in fish oil  Also found in flax  Recommended intake of about 2 servings of fish per week  Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are related  Omega-3 metabolized to form eicosanoids o Signs and Symptoms of Essential Fatty Acids Deficiency  Flaky, itchy skin

o Canola, safflower, sunflower and corn oils have the most PUFA content in their oils o Tropical oils such as coconut oils have a HUGE amount of SFAs in them  SOLID at room temp  Used in chocolate o Our food triglycerides come mainly from plant oils—canola oil o Canola oil is 100% triglycerides  High amount of PUFA  High amount arachadoionic acid???unsure  Other type of lipid phospholipids o No dietary requirement b/c the body can synthesize all that it needs o Built on a glycerol backbone but with only two fatty acid chains o The third one is replaced with a phosphorous containing compound P-CHOLINE o Makes a BIG difference in the functionality of the molecule o Phospholipids are found in the body and are synthesized as needed by the body o Functions  They are integral in the cell membranes of animal cells  Phospholipid bilayer  cell membranes of animal cells  Donates FAs for eicosanoid synthesis  Emulsifierbreaks down large lipid globules and stabilizes them into smaller lipid droplets  Bile acids  Lecithins o Phospholipids have a hydrophillic head and a hydrophobic tail o The hydrophillic head is where the choline group is and is positively charged o The hydrophobic tails are where the fatty acids are o In the bilayer, the heads are all pointing outwards b/c they’re attracted to the water while all the hydrophobic tails end up pointing inward to get away from the water  Other type of lipid Sterols o May contain one fatty acid o Multi-ringed structure o DO NOT HAVE A GLYCEROL BACKBONE o Do not readily dissolve in water because it is a waxy substance o Example: CHOLESTEROL, VitD made from cholesterol—synthesized in the skin o Extremely hydro phobic o Cholesterol  Essential for cellsmade in every cell…so it must be “good” for you  Even coral and algae have cholesterol  Functions  Essential component of cell membrane o Makes stronger membranes. o Very important in animal cells b/c we do not have cell walls o Allows for flexibility of the cell  Found only in animal products

o Like shellfish, meat, butter, eggs and liver  Precursor to important steroid hormones o Estrogen, testosterone, vitD  Precursor to bile acids  Dietary Guidelines recommend that we consume less than 300mg of cholesterol daily Other important information about lipids:  Make up about 30-35% of kcal in current American diet (700 kcal out of 2000)  Provide 9 kcal/gram of energy  95% of dietary lipids will be triglycerides (TAGs)  Lipids resemble gasoline in structure (medium to long hydrocarbons) and have similar energy o Gasoline provides 11 kcal/gram o Fatty acids provide 9 kcal/gram  Palmitic Acid - 16 carbons—saturated—no double bonds  Stearic Acid - 18 carbon—saturated –no double bonds  Oleic Acid - 18 carbon—monounsaturated—one double bond—found in olive oil  Saturated FAs are usually solid at room temperatureMonounsaturated are usually liquid at room temp (ex. Oils)  Polyunsaturated—more than one double bond in the hydrocarbon chain  Saturated FAs, especially the medium chain found in dairy raise blood LDL cholesterol levels TRIGLYCERIDE DIGESTION (DIETARY LIPID TRANSPORT) Steps:

  1. Dietary lipids (mostly TAGs) are broken down in the lumen of the intestine into free FAs and monoglycerides and are taken up by the enterocyte
  2. In the enterocyte, the free FAs are synthesized back into TAGs and are packaged into a large lipoprotein called chylomicron
  3. The chylos enter the lymph and travel to the thoracic duct and then throughout the peripheral circulation a. In circulation, travels to various organs. BONE first b. Some deposited in organs