Lipids Flashcards
Function of fats
Provide energy at rest and during exercise.
Protect vital organs.
EFAs make important biological compounds.
Transport of fat soluble vitamins (A, D, E, and K).
Maintain cell function.
Contribute to flavour and texture of food.
Helps us feel satiated (higher energy density; slower to digest).
Oils vs Fats (Lipids)
Oils are liquid at room temperature.
Fats are solid at room temperature.
Both are insoluble in water
Types of Lipids
Triglycerides
Phospholipids
Sterols
Triglycerides
3 fatty acids (FA) attached to glycerol backbone
Characteristics include chain length, and saturation and shape
Most triglycerides have a combination of FA chains.
Chain Length of FA
Short-chain = less than 6 carbon atoms
Medium chain = 6-12 carbon atoms
-includes coconut oil, palm kernel oil, and dairy
-digested, absorbed, transported, and metabolized quicker than long-chain FA’s
Long-chain = 14+ carbon atoms
-abundant in nature (ie. meat, fish, vegetable oils)
Saturation and Shape
Different levels of FA saturation includes saturated FA, monosaturated FA, polyunsaturated FA.
-animal fats have higher saturated fat content (industrial meats have ~9x the saturated fat compared to grass fed and game meats because they are fed cheaper products such as grain and corn compared to grass fed meats)
-plants are typically higher in mono- and poly-unsaturated fats
FA shape is dependent on level of saturation.
-straight and stackable saturated FAs have implications for heart disease as they can stack and block arteries over time.
-double bonds kink FA chains making it difficult for packing
-makes for fluid and flexible cell membranes, and transportation in the blood stream (less sticky and packy which decreases implications for heart disease).
Saturated FAs
Has no double bonds between carbon atoms (no carbon-carbon double bonds).
All carbons saturated with hydrogen.
Solid at room temperature because of the straight chains, making them stackable (due to shape).
-implications for heart disease
Higher percentage in animal fats.
Includes coconut oil, palm kernel oil, butter, cream, whole milk, beef.
Monounsaturated FA
Has one double bond between carbon atoms (carbon-carbon double bond).
Double bond identified from carboxyl or methyl carbon.
Double bond kinks the molecule.
Includes olive oil, canola oil, cashews.
Polyunsaturated FA
Has more than one double bond between carbon atoms (carbon-carbon double bond).
More than one kink.
Includes canola oil, corn, and safflower oil.
Trans-FA
Trans-arrangement
-hydrogenation
-hydrogen atoms on the opposite side (for carbon-carbon double bonds)
-unkinks molecule
-monounsaturated FA that behaves like a saturated FA
-not found often in nature
Cis-arrangement
-hydrogen atoms on the same side (for carbon-carbon double bonds)
-responsible for kink
Trans-fats gave us margarine
Shift away from trans-fat led to use of palm oil.
Essential FAs
Fats that the body cannot synthesize.
FAs with double bonds close (less than 9 carbons) to methyl/omega carbon.
Omega 6 FA
Linoleic acid = omega 6 FA.
Includes vegetable and nut oils.
Consumed at 25:1 ratio to omega 3.
Optimal is 5:1 ratio to omega 3.
Sources of Omega 6
In 100 grams…
-soybean oil = 50 grams
-corn oil = 49 grams
-mayonnaise = 39 grams
-walnuts = 37 grams
-sunflower seeds = 34 grams
-almonds = 12 grams
-cashew nuts = 8 grams
Omega 3 FAs
Alpha-linolenic acid = omega 3
Includes dark leafy greens, flax, canola, fish.
Increase HDL-C.
EPA = may reduce risk of death from a heart attack.
DHA = critical for CNS and retina development.
Sources of Omega 3
In 100 grams…
-salmon = 4 grams of EPA and DHA.
-mackerel = 3 grams of EPA and DHA
-sardines = 2.2 grams of EPA and DHA
-Anchovies = 1 gram of EPA and DHA
-chia seeds = 4.9 grams of ALA
-walnuts = 2.5 grams of ALA
-flaxseeds = 2.3 grams of ALA
Phospholipids
Soluble in water.
Aid in digestion of fats (component of bile).
Transport fats in bloodstream.
Make up cell membranes.
Have a hydrophilic component and hydrophobic component which allows for them to be soluble in water.
Includes egg yolks, peanuts, soybeans, and emulsifiers used in processed food (lecithin).
Sterols
Found in plants and animals.
Ringed structure.
Cholesterol is most common sterol.
Cholesterol
Found only in animals.
Part of every cell membrane.
Butter, egg yolks, whole milk, meats, and poultry.
Good Sterols
Plant sterols appear to block the absorption of cholesterol in the small intestine.
Most people don’t consume enough plant sterols.
Manufacturers add plant sterols to some foods.
How is cholesterol essential to human health?
Body uses endogenous and exogenous cholesterol to produce sex hormones (estrogen, testosterone, and progesterone), adrenal hormones, vitamin D, and bile salts.
Digestion Enzymes
Lingual lipase (mouth)
Gastric lipase (stomach)
Bile and pancreatic lipases (small intestine)
Digestion Purpose
To create 2 FAs and a monoglyceride.
Build FAs, break them down to move them around the body, then rebuild FAs again
Lipids in the Duodenum
Emulsified by bile
-allows for more lipid surface area accessible to pancreatic lipase.
-stops the fats from grouping together which makes it harder for the pancreatic lipase to break it all down.
Triglycerides broken into a monoglyceride and 2 FAs.
Lipid Absorption
Bile salts and phospholipids surround products of lipid digestion creating a micelle.
-contains free FAs, monoglycerides, cholesterol, and phospholipids.
Micelle components taken into enterocyte by endocytosis.
-binds to the cell surface where it gets absorbed (enveloped) by the cell (at the brush border)
-doesn’t require any energy
-medium and short chain fatty acids can bind to protein called albumin which takes it right into the bloodstream to be transported to rest of body
-other micelles get broken down into its parts and go into endoplasmic reticulum where the molecules get packaged together
Chylomicron (chylomicron much bigger than micelles).
-transported through the lymph to rest of the body (lymph is open ended vessels where fluid pushes us through the body and valves stop it from going backwards)
Lipids in the Enterocyte
We can’t transport water-insoluble long-chain FAs and monoglycerides in the blood.
MGs and Fas reformulated into triglycerides in the endoplasmic reticulum where they are then packed together with other components to make chylomicrons.
Lipid Transport
Chylomicrons are formed (similar to micelle but with protein).
-are lipoproteins (fat protein)
-made up of phospholipids and protein on the outside, and triglycerides and cholesterol on the inside
Chylomicrons leave enterocyte and travel through lacteal and lympathetic system.
Enter the bloodstream through the thoracic duct.
-carry triglycerides to cells in need
Circulating chylomicrons travel the bloodstream dropping off triglycerides to cells.
Lipoprotein lipase is an enzyme on cells that breaks apart the triglyceride in the chylomicron.
-binds to cell resulting in protein channels to open so triglycerides can be broken down by enzymes
Cells uptake the FAs and MGs
Short and Medium Chain FAs
Enter bloodstream directly attached to proteins or phospholipids.
-butyric acid
-caprylic acid
-lauric acid
Structure of lipoprotein
Protein and phospholipid bilayer on the outside.
Triglycerides and cholesterol on the inside.
Lipid Fate
Triglycerides taken up by cells (FAs and MGs) and used for energy.
Made into lipid containing compounds.
Stored in muscle, liver, or adipose tissue and triglycerides.
Lipoproteins (aka Cholesterol)
Includes chylomicrons, very low-density lipoproteins, low-density lipoproteins, and high-density lipoproteins.
Fat proteins.
Hydrophobic lipids need an escort to travel in the blood.
Composed of triglycerides, free cholesterol, cholesterol esters, phospholipids, and apolipoprotiens.
Phospholipids and apolipoproteins form the outer layer and allow it to be soluble in water.
High, low, and very low density refers to lipoprotein structure (protein:lipid ratio) and has functional implications.
VLDL Structure and Function
Mostly triglycerides
Produced in liver and intestines.
Transport triglycerides for use for energy or other things in other cells.
May only need some components of the triglycerides.
When have more cholesterol than triglycerides then it becomes LDL.
LDL-C Structure and Function
Bad cholesterol.
-usually when we have an abundance of cholesterol and triglycerides.
Higher proportions of protein than VLDL.
Produced in liver or derived from VLDLs that have released triglycerides.
Circulate in blood and deliver cholesterol to cells with specialized receptors.
-not always bad, do need cholesterol for functioning.
-but we usually have an abundance of cholesterol from animal sources which is where it can be a problem
LDLs not taken up degrade and release cholesterol into the blood.
-If there’s injury to our arteries, cholesterol can bind to stickiness of wound which can build an internal scab (part of formation of atherosclerosis) creating a cap and decreases diameter of artery (usually occurs in high animal consumption diets and sedentary lifestyles).
HDL-C Structure and Function
Good cholesterol.
Higher density of proteins.
Low cholesterol, high lipoprotein content.
Released from liver and intestines (only a little bit from intestines).
Pick up cholesterol from dying cells and arterial plaques (like LDLs).
-transfer to other lipoproteins which return it to the liver
-cleans up everything
Total Serum Cholesterol
Normally, body adjust cholesterol production based on consumption.
-increase consumption = decrease production
Doesn’t work for everyone
Must reduce dietary cholesterol, reduce saturated fat (animal products), and increase fiber and plater sterol consumption.
Food Sources of Fat
Visible fat and invisible fat
Visible Fat
Fats we knowingly add to foods.
Includes butter, cream, mayonnaise, dressings.
Invisible Fats
Fats hidden in foods.
Naturally occurring or added during processing.
Cardiovascular Disease
Risk factors include being overweight, physical inactivity, smoking, high blood pressure, and diabetes.
Cardiovascular Disease Issues in the General Population
Consumption of saturated fats and trans fats increases the risk of CHD.
-cholesterol high in foods with saturated fats (animal products)
-saturated fats increase LDL-C in the blood
-trans-fats increase LDL-C and reduce HDL-C
Six Strategies for Preventing CHD
1) Limit animal products or eat low-fat animal products
-saturated fat less than 7% of dietary intake
-cholesterol less than 300mg/day
2) Limit trans fat consumption as it reduces HDL-Cs and increases LDL-Cs
3) Increase fibre consumption (20-30g/day)
4) Maintain blood glucose levels in the normal range
-eat a diet low in fat, simple sugars, and moderate in energy
5) Get active
-meet guidelines for health benefits
-increase HDLs
6) Increase Omega-3 FA consumption to increase HDLs
