Chapter 5 Flashcards
Lipids
A group of organic molecules, most of which do not dissolve in water. They include fatty acids, triglycerides, phospholipids and sterols
- contain 9 calories per gram
- contribute texture, taste, flavour and aroma
- little in whole grains, lots in meat, lots in oils
What is the AMDR for fat
20-35% kcalories
Unsaturated fat examples
Fish, nuts, soybean, canola, flaxseed, and olive oils
Triglycerides (TG)
The major form of lipid in food and in the body. They consist of 3 fatty acids attached to a glycerol molecule
- utilized for immediate energy
- stored for later use
Fatty acids
Organic molecules made up of a chain of carbons linked to hydrogen atoms with an acidic group at one end and a methyl or omega end on the other.
- classified as: short chain (<6 carbons), medium chain (6-10 carbons), long chain (>12 carbons)
- chain length determines absorption and function
Phospholipids
Types of lipids containing phosphorous. The most common are the phosphoglycerides, which are composed of a glycerol backbone with two fatty acids and a phosphate group attached
- allow for transport in the blood (water based environment)
- EMULSIFIERS
- important to cellular membrane lipid bilayer. Controls what comes in and out of the cell
- phosphates head towards water and fatty acid end towards other lipids
Sterols
Types of lipids with a structure composed of multiple chemical rings.
Types: phytosterol and cholesterol
-cholesterol is made in liver
- do not dissolve well in water
- found in plants and animals
Saturated fatty acids
A fatty acid in which the carbon atoms are bound to as many hydrogens as possible, which, therefore, contains no carbon-carbon double bonds. Found in both plants and animals.
- solid at room temperature!!
- long chains
- butter, lard, animal fats, coconut oil
Tropical oils
A term in the popular media to refer to the saturated oils-coconut, palm and kernel oil-that are derived from plants grown in tropical regions
(Saturated fatty acids)
Unsaturated fatty acids
Contain some carbons that are no saturated with hydrogens. The carbons within the chain that are bound to only 1 hydrogen form carbon-carbon double bonds. If it contains 1 double bond it is a monounsaturated fatty acid. More than one double bond is a polyunsaturated fatty acid.
(One or more double binds in carbon chain)
- Liquid at room temperature
- squiggly looking at carb bonds
- plant oils and seafood
Monounsaturated fatty acid
Polyunsaturated fatty acid
A fatty acid that contains 1 carbon-carbon double bond. (Olive oils and beef)
A fatty acid that contains 2 or more carbon-carbon double bonds. (Corn, soybean oil)
Omega-3 (w-3) fatty acid
A fatty acid containing a carbon-carbon double bond between the third and fourth carbons from the same mega end.
(Unsaturated fatty acid and polyunsaturated fatty acid)
-fish oils
Alpha linolenic acid can become EPA (eicosanoids suppressing inflammation and blood clotting) or DHA (normal brain development)
Omega-6 (w-6) fatty acid
A fatty acid containing a carbon-carbon double bond between the 6th and 7th carbons from the omega end.
-corn and safflower oils, and oils in meat and fish.
Unsaturated fatty acids
Polyunsaturated fatty acids
Linoleic acid can become arachidonic acid for brain development or eicosanoids (promote inflammation and blood clotting)
Trans fatty acid
An unsaturated fatty acid in which the hydrogen atoms are on opposite sides of the double bonds
- has a higher melting point than fatty acids in the cis configuration
- come from a hydrogenation process
- used by the food industry
- turns unsaturated fatty acid into the behaviour of a saturated fatty acid (stiff at room temp-liquid to solid)
- BAD FOR YOU-increase risk of heart disease
Hydrogenation
The process whereby hydrogen atoms are added to the carbon-carbon double bonds of unsaturated fatty acids, making them more saturated.
- most of the trans fat in food supply before prohibited in Canada came from the partial hydrogenation of vegetable oils
- increasing melting point to secure shelf life
Phosphoglycerides
A class of phospholipid consisting of a glycerol molecule, two fatty acids and a phosphate group
- fatty acid end is soluble in fat
- phosphate end is water soluble
Can mix in both water and fat and makes them emulsifiers
Emulsifiers
Substances that allow water and fat to mix by breaking large fat globules into smaller ones
Lipid bilayer
Two layers of phosphoglyceride molecules oriented so that the fat-soluble fatty acid tails are sandwiched between the water-soluble phosphate-containing heads
Lecithin
A phsophoglyeride composed of a glyercol backbone, two fatty acids, a phosphate group and a molecule of choline
- major component of cell membranes
- made in liver
Cholesterol
A lipid that consists of multiple chemical rings and is made only by animal cells
- liver manufactures it so not needed in diet
- found in cell membranes
- found in myelin (coating of nerve cells)
- testosterone and estrogen component
- when it circulates in blood at higher levels it may increase the risk of heart disease
- cell membrane integrity
- precursor for other compounds: vitamin D, Bile acids, sex hormones
Most digestion of dietary fat takes place in …..
Small intestine-lipases
Bile from gallbladder helps break down fat into smaller globules and then lipases from pancreas digest them into fatty acids and monoglycerides. These form micelles which allow for absorption. Inside mucosal cells, fatty acids are reassembled into triglycerides and incorporated into lipid transport particles which enter the lymph
Micelles
Particles formed in the small intestine when the products of fat digestion are surrounded by bile acids. They facilitate the absorption of fat into mucosal cells of small intestine
Lipoproteins
Particles containing a core of triglycerides and cholesterol surrounded by a shell of protein, phospholipids, and cholesterol that transport lipids in blood and lymph
- classified based on density:
- Chylomicron, VLDL, LDL, HDL
Post-prandial state
The time following a meal when nutrients from the meal are being absorbed
Chylomicrons
- LARGEST Lipoprotein
- least dense
- mostly TG
- intestinal cells to liver
- made in small intestine
- carry large dietary lipids such as long-chain fatty acid, cholesterol and fat soluble vitamins through the lymphatic system and eventually enter blood stream then deliver the lipids to various cells of the body. -heart, muscle, mammary and adipose tissue
Lipoprotein lipase
An enzyme that breaks down triglycerides into fatty acids and glycerol; starched to the cell membranes of cells that like the blood vessels.
What is the major lipid producing organ in the body
Liver
Very-low density lipoproteins
Lipoproteins assembled by the liver that carry lipids from the liver and deliver triglycerides to body cells
- as they circulate in the blood stream, they shrink
- some left-over particles circulate back to the liver;others become LDL
- 2nd largest
- less TG
- less dense
- liver to tissues
Low-density lipoproteins
- derivatives of VLDL
- 3rd largest
- mostly cholesterol
- less dense
- transfer from liver to tissues
- deliver cholesterol to tissues via the blood
Referred to as bad cholesterol
-they deliver cholesterol to the tissues and having high levels of LDL in the blood is associated with an increase risk of heart disease.
LDL receptor
A protein on the surface of cells that binds to LDL particles and allows their contents to be taken up for use by the cell
-when cholesterol enters a cell this way, it suppresses the synthesis of new cholesterol in the cell-keeps LDL levels healthy in blood
High-Density lipoproteins
“Good cholesterol”
- smallest
- mostly protein
- more dense
- contains mostly cholesterol
- helps return cholesterol to liver for reuse or elimination
- high levels of HDL in the blood is associated with a reduction in the risk of heart disease
Adipose tissue
Tissue found under the skin and around body organs that is composed of fat-storing cells
-contain large droplets of triglyceride
Functions:
- energy storage (TG in adipocytes)
- protect vital organs (4% of total body fat)
- insulation (subcutaneous fat)
- transport and storage of fat soluble vitamins (A, D, E, K)
Essential fatty acids
Fatty acids that must be consumed in the diet because they cannot be made im by the body. Important in formation of phospholipids for cell membranes
- polyunsaturated fatty acids
- used by the body to make eicosanoids (biologically active compounds that regulate body functions)
- omega-6: linoleic acid (w-3)
- omega-3: alpha-Linolenic acid (w-6)
Eicosanoids
Regulatory molecules, including prostaglandins and related compounds, that can be synthesized from omega-3 and omega-6 fatty acids
-help regulate blood clotting, blood pressure, immune function and other bodily processes
Omega-3 index
The sum of EPA and DHA in red blood cell membranes, expressed as a percent of total fatty acids in membranes
- less than 4% at risk of cardiovascular disease
- more than 8% are considered low risk
EPA
DHA
Eicosapentaenoic acid and docosahexaeonic acid
Long chin omega-3 polyunsaturated fatty acids that are abundant in fish
Beta-oxidation
The first step in the production of ATP from fatty acids. This pathway breaks the carbon chain of fatty acids into 2-carbon units that form acetyl-CoA and release high energy electrons that are passed to the electron transport chain
Hormone-sensitive lipase
An enzyme present in adipose cells that respond to chemical signals by breaking down triglycerides into free fatty acids and glycerol for release into the bloodstream where they can be taken up by cells to produce ATP
Glucose/fatty acid cycle
The relationship between blood glucose and free fatty acids. When blood-glucose levels are high, as in the post-prandial state, free-fatty-acid levels are low. In dating state, when blood-glucose levels decline, free-fatty-acid levels increase
Need normal blood glucose levels
Cardiovascular disease
A disease that results from damage to blood vessels, such as coronary arteries of the heart, which can cause heart attack, or the blood vessels of the brain, which can cause a stroke
Essential fatty acid deficiency
A condition characterized by dry, scaly skin, liver abnormalities, poor wound healing and poor growth in infants that results when the diet does not supply sufficient amounts of the essential fatty acids
Atherosclerosis
A type of cardiovascular disease that involves the buildup of fatty material in the artery walls
Atherosclerotic plaque
The cholesterol-rich material that is deposited in the arteries of individuals with atherosclerosis. It consists of cholesterol, smooth-muscle cells, fibrous tissue and eventually calcium
Oxidized LDL cholesterol
A substance formed when the cholesterol in LDL particles is oxidized by reactive oxygen molecules. It is key in the development of atherosclerosis because it contributes to the inflammatory process
Scavenger receptors
Proteins on the surface of macrophages that bind to oxidized LDL-cholesterol and allow it to be taken up by the cell
Trans fats and saturated fats increase levels of ________. However, trans fat are worse because they also decrease levels of _____
LDL cholesterol
HDL cholesterol
Antioxidants decrease the ________ and therefore, prevent development of ______
Oxidation of LDL cholesterol
Plaque in artery walls
How to calculate % energy from fat
%energy from fat=kcal from fat/total kcal x 100
-energy from fat: grams fat X 9kCal
Fat free
Low fat
Less than 0.5g/ serving
3g or less/ serving
Reduced or less fat
25% less per serving than normal
Hidden dietary fat
Cheese, ice cream, whole milk, crackers, doughnuts, cookies, muffins, fancy drinks
Lipid classes and where they are found
Triglycerides
Phospholipids
Sterols
(In food and body)
Lipoproteins
(In body)
Digestion of triglycerides
- lipoprotein lipase (promotes uptake of lipids into cells)
- hormone sensitive lipase (promotes break down of TG for energy
Cis fatty acids
Both H atoms on the same side of the double bonds
- unsaturated fatty acid
- bent
Why use trans fat
- cheaper
- easier to use than liquid oils in food production
- melt in your mouth feeling
- more stable and less susceptible to rancidity
- increase shelf life
Trans fat free on food labels
Required to be labelled on food
<0.2 grams of trans fat/serving
<2 grams saturated fat/ serving
-look for partially hydrogenated vegetable oil!!!!!! It has trans fat
Trans fat in Canada!!!
Banned in 2017…..but was it really…
Cholesterol has _____ and _____ roles required for health
Precursor and structural
______% of cholesterol is synthesized where
75-80%
In the body
Dietary cholesterol plays a lesser role than _________ in cardiovascular disease
Saturated and trans
Cholesterol and saturated fats create each other’s ____
Synthesis
______% exhibit little increase in blood cholesterol with high cholesterol diet
~60%
Lipid digestion process
-different from carbs and proteins
- Mouth-lingual lipase
- Stomach-gastric lipase
- Small Intestine-presence of chyme signals CCK, bile released from gall bladder, pancreatic enzyme secretin, bicarbonate from pancreas
Lipid metabolism-using fat
- when the body starts to run low on fuel, it turns to body stores
- fatty acids: used for energy by many organs
- typical fuel mix: 50/50 carb/lipid for liver and muscle (at rest)
- any time fat broken down for energy, CHO must be available otherwise ketones develop (products of incomplete fat breakdown) and build up in blood and urine.
Triglyceride metabolism process
- Glycerol molecules which contain three carbon atoms, can be used to produce ATP or small amounts of glucose
- Fatty acids are transported inside the mitochondria, where beta-oxidation splits the carbon chains into two-carbon units that form acetyl CoA and produces high-energy electrons
- If oxygen and enough carbon hydrate are available, acetyl co-A combines with oxaloacetate to enter the citric acid cycle to produce two molecules of carbon dioxide and releasing high energy electrons that are shuffled to the electron transport chain. When there is not enough oxaloacetate, ketone bodies form.
- In final step of aerobic metabolism, the energy in the high energy electrons released from beta-oxidation and the citric acid cycle is trapped and used to produce ATP
Triglyceride metabolism in post-prandial storing excess energy and fasting: using energy from stores
Post-prandial: chylomicron, VLDL—->lipoprotein lipase—> fatty acids and turn into….
Fasting: triglycerides in adipose and use hormone sensitive lipase to pull out fatty acids to use for energy
Risk factors of heart disease
- high LDL cholesterol
- low levels of HDL cholesterol
- high total cholesterol
- high levels of triglycerides
- diabetes
- high blood pressure
- overweight
- family history
- increasing age
- smoking
- sedentary
- diet high in saturated fat and low in fibre, while grains, unsaturated fat, fruits and veggies
- high sodium
- unbalanced ratio of omega 3 and omega 6
- trans fat
- high sugar intake (converts to fat)
How to Reduce risk of heart disease
- consume omega-3 and omega-6 polyunsaturated fats
- consume monounsaturated fats
- replace saturated fats with polyunsaturated fat (except trans) which decrease blood levels of LDL Cholesterol
Dietary fat and cancer
- breast cancer: type of fat
- colon cancer: type of meat (protein)
- diets high in omega-3 fatty acids from fish—> lower incidence of colon cancer
Recommendations for lipids
Linoleic acid: AI 12g/day for women and 17g/day for men
DRI: 20-35% of total kcalories for adults are lipids
Limited saturated and trans fat
Cholesterol free
And low cholesterol
on labels
Contains less than 2 mg of cholesterol and 2g or less of saturated and trans fat per serving
Contains 20mg of less of cholesterol and 2g or less of saturated and trans fat per serving
Lean and extra lean fat label
Meat that contains less than 10g of fat per 100g
Contains less than 7.5g for fat per 100g
Source of omega-3 and omega-6 polyunsaturated fatty acids on labels
Contains 0.3g or more pre serving
Contains 2g or more per serving
Reduced fat-foods
Fat removed, replaced or contain fats that cannot be digested or absorbed (olestra-illegal in Canada)
Fat substitutes can be carbohydrates, protein or fat based.
Mimic the taste and texture of fat
