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Nutrition Midterm#2 Review.docx

Course Code
NUTR 1010
Andrea Buchholz
Study Guide

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Nutrition Midterm #2 Review
The “Skinny” on Fat
What is dietary fat?
-Part of a larger group of substances called lipids (Insoluble in water)
-Fat comes in different forms (Triglycerides, Phospholipids, Sterols)
-95% of dietary fat and body fat is made up of Triglycerides
(A triglyceride is a molecule made up of three fatty acids attached to a three-carbon
glycerol backbone)
Fatty acids are classified by their length, saturation, and shape.
-Length refers to number of C (carbon atoms) in fatty acids (Short, medium, long)
Why are fatty acids “Acids”?
-They contain an acid group (COOH) at the end of their chain (harmless!)
-Most triglycerides contain fatty acids of varying lengths (short, medium, and long)
Fatty acids are classified by their length, saturation, and shape.
-Saturated fatty acid (SFA): No double bonds; all C atoms saturated with hydrogen (H)
-Monounsaturated fatty acid (MUFA): One double bond
-Polyunsaturated fatty acid (PUFA): 2 or more double bonds
Most triglycerides are mixed (they contain a mix of SFA, MUFA, and PUFA)
Fatty acids are classified by their length, saturation, and shape.
-Hydrogen atoms on the same side of carbon atoms
What foods have saturated fats?
-Animal foods, tropical oils
What foods have monounsaturated fats?
-Olive oil, canola oil
What foods have polyunsaturated fats?
-Canola, safflower and corn oils; fish; nuts and seeds.
There are different kinds of polyunsaturated fats
-Linoleic acid (an omega-6 fat) is an essential fatty acid found in vegetable oils
Metabolized in the body into compounds in which regulate functions like blood pressure,
blood clotting
-The word “essential” in nutrition (an essential nutrient must be obtained through diet)

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-Alpha-linoleic acid (an omega-3 fat) is also an essential fatty acid (found in leafy greens,
flaxseed and flaxseed oil, soy-based products, canola oil, fish and fish oils.
Metabolized in body to compounds, which decrease inflammation, blood clotting and
triglycerides and therefore decreases risk of heart disease.
Most fatty acids have cis bonds; come fatty acids have trans bonds
-Also called trans fats
-Industrial trans fats look and act like saturated fats in our bodies (can increase risk of
heart disease)
Where do industrial trans fats come from?
-The food manufacturing industry
-Fat is prone to oxidation (males a product rancid) Therefore manufacturers package food
airtight or add preservatives and antioxidants. Add hydrogen atoms to polyunsaturated
fats to increase saturation and make product resistant to oxidation (result in trans fat)
Adding hydrogen atoms to a polyunsaturated fat is called hydrogenation
-Does more than prevent oxidation
-Hydrogenation also: makes the fat more stable when heated to high temperatures, turns
liquid fat into a solid fat.
The other 5% of fat is made up of:
-Phospholipids (compounds found in cell membranes, help keep our cell membranes
-Sterols (a group of hydrophobic compounds, the most common is cholesterol)
Cholesterol is a precursor to vitamin D, testosterone, and estrogen
How does our body digest, absorb, and metabolize fat?
1. Mouth: Salivary glands in the mouth produce an enzyme, lingual lipase that
digests small amounts of triglycerides
2. Stomach: Fat arrives intact at the stomach, where it is mixed and broken into
droplets. Gastric lipase digests some triglycerides
3. Gall-Bladder: Releases bile into the small intestine
4. Small intestine: Bile from the gallbladder breaks fat into smaller droplets. Lipid
digesting enzymes from the pancreas break triglycerides into monoglycerides and
fatty acids. Micelles transport free fatty acids to the mucosal cells of the small
intestine for absorption

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Absorption of fat occurs mostly in the small intestine
-With the help of micelles (Transport fatty acids and monoglycerides to intestinal cells)
-Once inside intestinal cell (Long-chain fatty acids and monoglycerides are repackaged
back into triglycerides, triglycerides are then packaged with protein and phospholipids
into chylomicrons)
A chylomicron is packed like a suitcase (the suitcase is made up of protein, the clothes
are triglycerides. Chylomicrons transport fat out of intestinal cells to the rest of the body.
Nutrients travel through the body in the blood, but fat wont mix. The solution is
lipoproteins (these are proteins, which help carry fat in blood throughout the body.)
Chylomicrons are lipoproteins (made in the cells of the small intestine, carry dietary fat
to the body for burning or storage, then they go to the liver)
As chylomicrons circulate around the body, the fat inside has one of three fates:
1. Source of energy for cells
2. Make lipid-containing compounds in the body
3. Become stored as body fat
Source of energy for cells
-9 Kcal/gram
-Major source of fuel at rest
-Also fuels activity
Make lipid-containing compounds in the body
-We‟ve already covered some examples (Cholesterol: a precursor to vitamin D,
testosterone, and estrogen. Essential fatty acids: make compounds that regulate many
body functions)
Become stored as body fat
-Provide protection to body (insulation and padding)
-Help maintain integrity of cell membranes
-Energy store
Fat is carried around the body as part of lipoproteins
-Chylomicrons made in cells of small intestine carry fat throughout the body
Other lipoproteins are made in the liver:
-Very low-density lipoprotein (VLDL) transports triglycerides in blood to the body
-Low-density lipoprotein (LDL) transports mostly cholesterol in blood to the body
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