7 – Lipid Nutrition Flashcards
1
Q
What is the classification of lipids?
A
- Soluble in organic solvents
- Diverse calls of molecules
- Ex. steroids, eicosanoids, TAGs
2
Q
What are some examples steroids?
A
- Hormones
- Vitamins
- Structural components of cell membranes
3
Q
What are eicosanoids?
A
- Carboxylic acids acting as second messengers in inflammatory responses
- Synthesized from highly UNsaturated fatty acids
4
Q
What are triacylglycerols (TAGs)
A
- Esters of 3 carboxylic acids with glycerol
- Carboxylic acids are usually called FAs
5
Q
How is FA nomenclature done? Ex. C18:3 n-3
A
- C18 means18C atoms in FA
- :3 means there are 3 double bonds
- N-3 refers to position of first double bond from the methyl end (ex. also called omega-3)
6
Q
Saturated vs. unsaturated fatty acids
A
- Saturated: no double bonds
- Unsaturated: 1 or more double bonds
o Polyunsaturated: 2 or more double bonds
o Cis or trans
o *hydrogenation of FAs results in trans-FAs
7
Q
What are the 3 major physiological roles of FAs?
A
- Source of fuel
- Building blocks of phospholipids and glycolipids (especially brain and retina)
- Precursors for hormones and intracellular messengers and signalling (PGs and eicosanoids)
- **STORED AS TAGs
8
Q
TAG digestion overview
A
- Fat globules (lipids) + bile salts (hydrophilic and hydrophobic portions)
- Emulsion droplets (micelles=smaller=increased SA relative to volume)
- *digestion by lipases occurs at surface of fat globule
- Get FFAs (monoglycerides)
9
Q
Pancreatic lipases
A
- Hydrolyze TAGs into 1 molecule of glycerol and 3 FA molecules
10
Q
Absorption of FAs
A
- FFAs are again emulsified with bile salts into micelles
- Micelles diffuse into epithelial cell
- NO ENERGY REQUIRED
11
Q
TAG transport into lymphatic system
A
- TAGS are reformed
- TAGS combine with proteins
- **Chylomicrons are formed
- Chylomicrons diffuse into lacteals in lamina propria of the villus
12
Q
What is the transport of chylomicrons (after a meal) in the bloodstream?
A
- Join with VLDL from liver
o Lipid rich
o *available TAG (FFAs) to cells (need to be broken down by lipoprotein lipase in the bloodstream)
o *density gets smaller as the lipids are being taken up (get LDL)
13
Q
If LDL is in excess
A
- Remains in blood
- Does not have many TAGs
o Delivers cholesterol to cells instead (more in humans)
14
Q
HDL
A
- Synthesized by liver
- *cholesterol scavengers=remove the stiffness of cell membranes
o More fluid membranes=better
o GOOD cholesterol - Non-human animals have lots of it
15
Q
What causes lipoprotein lipase secretion in the blood?
A
- Have hormone sensitive lipase
o Ex. stress response, in need for energy, anticipation of a meal
16
Q
Storage of TAGs in adipose tissue
A
- Fat reservoir of adipocytes is the main energy storage in the body
17
Q
Why TAGs as an energy source?
A
- Highly concentrated stores of metabolic energy
o More concentrated than proteins and CHO
o Anhydrous (exclude water) and highly reduced - Complete oxidation of FA yields 9kcal/g (vs. 4kcal/g for CHO and proteins)
- *stored in cytoplasm of adipose cells
18
Q
Medium-chain triglycerides (MCTs)
A
- TAGS with FAs that have 6-12 carbons
- Ex. palm oil and coconut oil are rich in them
- FAs to short to easily be used for storage or synthesis of essential FA
- *catabolized for energy instead (KETO diet!)
o “less likely” to gain weight
19
Q
Essential FAs
A
- Plants can only produce FAs with up to 28 carbons
o Linoleic acid (C18:2 n-6): omega-6
o Linolenic acid (C18:3 n-3): omega-3
o *nutritionally essential in vertebrates=precursors for all highly unsaturated FAs
o *LOW in Western diets - *animals require FAs with greater than 18 carbons for metabolites
20
Q
You are what you eat: example with ‘fat types’
A
- If you eat a lot of saturated fats=you store more saturated fat
- *there is a small amount of bioconversion of FAs
- Example to get a ‘balance of omega 3 and 6
o Canola: more omega 6 than omega 3
o Flax (linseed) oil: more omega 3 than omega 6
21
Q
What are eicosanoids synthesized from?
A
- Arachidonic acid
- EPA
22
Q
Omega-3 eicosanoids
A
- Pro-inflammatory
23
Q
Omega-6 eicosanoids
A
- Anti-inflammatory
24
Q
What is the ideal balance of omega-6 : omega-3 FA?
A
- 4:1
- Average American: 12-25:1
25
Q
EPA and DHA (omega-3 FAs)
A
- Nutritionally desirable FAs
- Decreased heart disease, cancer, inflammatory diseases
- *critical in brain and retina
o Vital for fetal brain and eye development during pregnancy
26
Q
EPA and DHA (omega-3 FAs): sources
A
- Made by algae
- Fatty fish (Ex. salmon) are rich in them
27
Q
Omega-3 fats and eggs
A
- Plant oils contain omega-3 alpha linolenic acid (ALA)
o Chickens can convert ALA (from flax) to EPA and DHA and deposit the fat in egg yolk (only about 5% of flax oil is converted) - Animals need EPA and DHA (ex. from salmon)
28
Q
Cats and AA
A
- Nutritionally require it!
o Vegan cat diets are difficult - NOT present in plant oils
