Lipids Flashcards
1
Q
What is the AMDR of fat for adults and children?
A
Adults: 20-35%
Children: 30-40% for 1-3 years, 25-35% for 4-18 years
2
Q
What is the basic structure of triglycerides?
A
- Three fatty acids attached to one glycerol
- Fatty acids don’t have to be the same
3
Q
Saturated vs. unsaturated fatty acids
A
- Saturated FAs have no double bonds
- Unsaturated FAs have one or more double bonds between the carbons
- Can be monounsaturated and polyunsaturated
4
Q
Omega-3 vs. Omega-6 fatty acids
A
- Omega-3 refers to the 1st double bond at C3=C4 from the methyl end (called alpha linoleic acid)
- Omega-6 denotes the 1st double bond at C6=C7 (called linoleic acid)
- Both are important for production of cellular regulators that control inflammation, blood clotting and smooth muscle contractility
- These FAs are essential, we need to take them in through our diet; they are needed for brain development during growth
- The balance of ω-3 and ω-6 is also important
5
Q
What are sources of omega-3 FAs?
A
ALA: found in plant foods such as flaxseed, canola oil, walnuts, almonds, etc.
EPA/DHA: found in seafood such as salmon, shrimp, tuna, mussels, etc.
- DHA is easier for our bodies to utilize
- Seafood also has more ω-3 than ω-6, while the reverse is true for plant foods
6
Q
Why is the ratio of ω-3:ω-6 important?
A
- The ratio affects the types and amounts of eicosanoids produced
- Eicosanoids are the molecules made from the oxidation of arachidonic acid and other polyunsaturated FAs
- Arachidonic acid is formed from omega-6 and is pro-inflammatory and thus we should consume less of it
- Recommended ratio is 5:1 to 10:1 for ω-3:ω-6
- Difficult for our bodies to convert omega-6 into omega-3
- Diets such as the Mediterranean are higher in omega-3
7
Q
How are eicosanoids synthesized?
A
- Linoleic acid (omega-6 FA) is required to make arachidonic acid
- Arachidonic acid is the most common precursor of eicosanoids
- It is oxidized by COX and LOX to make pro-inflammatory molecules such as PGs and LTs
- COX-1 and/or COX-2 is the enzyme inactivated by aspirin and NSAIDs
8
Q
What are trans fatty acids?
A
- These are mostly produced by the hydrogenation of unsaturated fats
- Rather than becoming saturated, the type of bond is changed
- Similar orientation to saturated fatty acids but with a double bond between two carbons, which makes the molecule kinked
- Increases cholesterol and CVD risk
9
Q
Cis vs trans arrangement of FAs
A
- A cis arrangement denotes that where the C=C occurs, the H atoms branch out on the same side
- This creates a kink in the molecule that prevents close packing and thus these FAs tend to be liquid at room temperature
- A trans arrangement denotes that where the C=C occurs, the H atoms branch out on opposite sides, causing a slight kink but still allowing close packing
10
Q
Is coconut oil healthy?
A
- Not as healthy as other plant oils b/c of the large proportion of saturated FAs
- Was thought that coconut oil had more medium chain triglycerides but this was not accurate because it was specialized blends used in the study
11
Q
What are phosphoglycerides?
A
- Have a structure like TGs but contain 2 fatty acids and a polar phosphate group, along with a glycerol backbone
- They are amphipathic - they have a polar head and a hydrophobic tail
- Allows the formation of the lipid bilayer of the cell membrane
12
Q
What are sterols?
A
- The structure of sterols is a series of rings, they are not water-soluble
- Cholesterol present in ANIMAL CELLS not in PLANTS
- Cholesterol is a precursor for hormones such as testosterone and estrogen as well as for vitamin D and bile acids
13
Q
How are lipids absorbed?
A
- Lipids travel from the GI tract in chylomicrons
- Lipoprotein lipase (LPL) lines the capillaries in muscle and adipose tissue; fatty acids are removed by these tissues and the chylomicron remnants travel to the liver for disposal by lysosomes
- VLDL is produced in the liver from excess carbohydrates
- VLDL circulates and as triglycerides are removed by LPL in the capillaries, the density increases
14
Q
What is the effect on lipids when blood glucose is low vs when it is high?
A
- Low blood glucose: muscles decrease glucose uptake, increase FFA uptake, and adipose tissue increases FFA release
- High blood glucose: increased LPL activity, results in increased uptake of fat in adipose tissue, but decreased FFA uptake in muscles
- Inverse relationship between BG and FFAs
15
Q
How are lipids metabolized?
A
- β-oxidation is the first step
- Fatty acids are broken down into 2-carbon molecules of acetyl CoA
- FAs yield a lot more acetyl CoAs - a 16-C FA would give 8 acetyl CoAs, vs only 2 from a glucose molecule
- Acetyl CoA can then enter the citric acid cycle and electrons are shuttled to the ETC
