Lipids Flashcards
What are the three major groups of dietary lipids?
- triglycerides
- phospholipids
- sterols
All of these are insoluble in water.
What is the predominant type of dietary lipid?
- Most lipids (~95%) are consumed as mixed triglycerides
- FA can be 2 to 24 carbons in length: 18C = most commonly consumed
What are the two groups of triglycerides/fatty acids?
Saturated fat (all carbon saturated with Hydrogen)
Unsaturated fat
What are saturated fatty acids?
- all carbons (except acid end) are saturated with hydrogen atoms
- linear, pack well, solid at room temperature
- higher amounts in animal foods, tropical oils, chocolate, milk fats
What happens when 1 fatty acid is hydrolyzed off a triglyceride?
A DIGLYCERIDE (DG) results
What happens when 2 fatty acids are hydrolyzed off a triglyceride?
A MONOGLYCERIDE (MG) results
What are the two major groups of unsaturated fatty acids?
Monounsaturated and Polyunsaturated
What are mixed triglycerides?
- major fuel source for body
- ~95% of lipids in diet and in body are mixed TG
What are Monounsaturated FA?
- 1 double bond in carbon chain
- cis double bonds occur in nature – hydrogens are on the same side of the double bond – creates a bend in the molecule
- MUFA don’t pack as tightly as SFA
- semi-solid at room temperature
- Omega-9
What are some food sources for monounsaturated fatty acids?
- Olive oil
- Canola oil
- Avocado oil
- Peanut oil
- Almond oil
- Sunflower oil
Where do you find oleic acid?
monounsaturated fatty acids
What are polyunsaturated fatty acids?
- greater than 1 double bond in C chain
- multiple cis bonds, multiple bends in molecule, liquid at room temp.
- Linoleic acid
- Linolenic acid (α-LnA)
Where do you find Omega-6 EFA, linoleic acid?
Polyunsaturated fatty acids
What are dietary sources of Linolenic acid (α-LnA) Omega-3 EFA?
- Flaxseed oil
- Walnut oil
- Canola oil
- Hemp oil
- Wheat germ
- Fish oil
What are food sources for linoleic acids?
- Corn oil
- Soybean oil
- Sunflower oil
- Sesame oil
Is Linoleic acid essential?
Yes!
What can linoleic acid be elongated into?
LA can be elongated & desaturated to longer chain Omega-6 FA - Arachidonic acid, C20:4
Linoleic acid is essential but Arachidonic acid is not!
Where do long-chain omega-3 fatty acids accumulate, where are they active, when are they essential, and where are they found?
- DHA is active in the retina of the eye and cerebral cortex of the brain
- ~ half accumulates in human brain before birth
- lipids are essential during pregnancy & lactation for growth and development of the fetus/infant
- EPA and DHA are found in human milk, shellfish, fish/oils, algae
What can linoleic acid be elongated into?
Linoleic acid can be elongated & desaturated to longer chain Omega-6 FA – Arachidonic acid, C20:4
What can linolenic acid be elongated into?
α-LnA can be elongated & desaturated to longer chain w3 FA
- Eicosapentaenoic acid, C20:5 (EPA)
- Docosahexaenoic acid, C22:6 (DHA)
How does chain length override the effects of saturation?
- Chain length overrides the effects of saturation with SFA only
- Expect all lipid sources that are predominantly SFA to be solid at room temperature
- Exceptions are tropical oils: palm oil (C10:0) and coconut oil (C12:0) – both semi-solid at room temperature – firmer than most oils, softer than most animal fat, less likelihood for SC-SFA to pack together due to shorter chain length
What are they essential fatty acids?
Polyunsaturated fatty acids
- Linoleic acid (Omega-6)
- Alpha-linolenic acid (Omega-3)
What are the dietary recommendations for the essential fatty acids?
- DRI-AI: recommended EFA intake ratio ~10:1 (Omega-6 : Omega-3)
- Males: 17:1.6 g/day
- Females: 12:1.1 g/day (10.9:1 g/day)
Which essential fatty acid do we get a lot of easily, and which do we need to focus on increasing our intake?
We typically get a lot of Omega-6 and need to focus on increasing intake of Omega-3
We’re looking for a ratio of about 10:1 (Omega-6:Omega-3)
What happens if you heat an oil to its smoke point?
Peroxides form, which can act as free radicals
What is the chain length of a short chain fatty acid?
- <6 carbons in length
- ex., 2C = acetic acid, 3C = propionic acid, 4C = butyric acid
- liquid at room temperature
- SCFA that are 4C in length are found in dairy foods
- SCFA are produced by our gut bacteria as they digest dietary fibre.
What is the chain length of a medium-chain fatty acid?
- 6-12C in length
- ex., palm oil (C10:0), coconut oil (C12:0)
- MCFA also found in dairy products
What is the chain length of a long-chain fatty acid?
- 14-24C in length
- if SFA, then solid at room temperature (ex., meat)
- if un-SFA, then semi-solid or liquid at room temperature (ex., oleic acid in olive oil (C18:1); alpha-linolenic acid (C18:3) or linoleic acid (C18:2) in canola or camelina oil)
How do food manufacturers extend the shelf-life of fat-containing products?
- Fats going rancid is a problem in food manufacturing
- Hydrogenation (partial) of inexpensive plant oils extends the shelf life of fat-containing products (e.g., crackers, cookies)
- Hydrogenation produces trans FA and increases the degree of saturation in the FA
- partially hydrogenated oil banned in Canadian food supply, effective fall 2020
What is hydrogenation?
- bubble hydrogen gas under pressure using a metal catalyst into inexpensive plant oil (e.g., soybean, corn)
- extends shelf-life by saturating the fatty acids
What are the functions of fatty acids?
- Integrity and fluidity of cell membranes
* FA (as part of phospholipids) provide structural and functional capacity to cell membranes - Participate in functionality of the immune system andvision
- Enhanced white blood cell response to foreign substances
- Visual problems with deficiency of essential FA (EFA)
- Essential FA (EFA) precursors to LC-PUFA
- Conversion to LC-PUFA inefficient (~10%), more efficient to consume LC-PUFA in diet
- EPA, DHA (Omega-3)
- Arachidonic Acid (Omega-6)
- EFA precursors to EICOSANOIDS
* Hormone-like substances using 20C FA derived from EFA
How are eicosanoids derived?
Formed using Omega-6 or Omega-3 essential fatty acids as a precursor.
What are the regulatory effects of ecosanoids?
Ecosanoids will have different effects depending on the precursor.
- Prostaglandins (PG) – constrict/dilate blood vessels; affect blood pressure – immune assistance – transmission of nerve impulses – smooth muscle contraction, required in childbirth
- Thromboxanes (TX) – affect blood clotting
- Leukotrienes (LK) – mediators of many inflammatory or hypersensitivity reactions (e.g., asthma)