Lipids Flashcards
What is a lipid?
Lipids are soluble in organic solvents
-includes hormones, vitamins, structural components of cell membranes
-eicosanoids
Eicosanoids
Carboxylic acids acting as second messengers in inflammatory responses
-synthesized from highly unsaturated fatty acids
Triacylglycerols
-Esters of 3 carboxylic acids= fatty acids with glycerol
Fatty acid nomenclature for C18:3 n-3
Unsaturated fatty acids
double bonds present in the cis formation
*if 2 or more= polyunsaturated
How do you get trans-fatty acids?
Hydrogenation of fatty acids
Unsaturated fatty acids
Have kinks… prevent solid formation because cannot line up neatly together
3 major physiological roles of fatty acids
- source of fuel
- Building blocks of phospholipids and glycolipids
- precursors for hormones and intracellular messengers, signalling
How are fatty acids stored?
Triacylglycerols (TAG)
TAG digestion
- Fat globules mix with bile salts to form emulsion droplets
- Emulsion droplets digested by lipases
- Form free fatty acids (monoglycerides) and bile salts… which can combine together again for transport and eventually monoglycerides diffuse into the epithelial cell layer for digestion by lipase
Bile salts
Emulsifying agents
-have both hydrophobic and hydrophilic components which allow for interaction with the fat globules
-allows fat to be broken down into smaller parts which make it easier for lipases to work
Digestion by pancreatic lipases
Lipases hydrolyze triacylglycerols into 1 molecule of glycerol and 3 fatty acid molecules
Absorption of fatty acids
FFAs are emulsified again with bile salts into micelles (Small droplets) then these micelles diffuse into the epithelial cell
*no energy required
Transport into the lymphatic system
1.Triacylglycerols are reformed
2. TAGs combine with proteins
3. chylomicrons are formed and diffuse into lacteals in the lamina propria of the villus
Transport of chylomicrons in the bloodstream
How do you get lipoprotein lipase into the blood?
Hormone induced release of lipoprotein lipase
-eg. stress
Storage of triacylglycerols in adipose tissue
The fat reservoir of adipocytes is the main energy storage in the body
*stored in the cytoplasm of adipose tissue
Why are TAGs the preferred energy source?
High concentrated stores- more than proteins and carbohydrates because they are anhydrous and highly reduced (less need to break them down for use)
What do FA yield in terms of energy compared to carbohydrates and proteins?
FA= 9kcal/g
Carbohydrates and proteins= 4kcal/g
Intermediary metabolism of TAGs
if single chained, can be broken into acetyl-coA and go into the TCA cycle for eventually ATP production
Medium chain triglycerides
Any triglyceroles with fatty acids that have 6-12 carbons (C6, C8, C10, C12)
-palm oil and coconut oil rich in MCTs
-fatty acids too short to easily be used for storage or synthesis of essential fatty acids
-catabolized for energy instead (keto diet)= theoretically less likely to cause weight gain
Essential fatty acids
Produced by plants (18 carbons) and are needed for production of metabolites in animals
-C18:2 n-6 Linoleic acid
-C18:3 n-3 Linolenic acid
**low in western diets
Why do vertebrate animals need essential fatty acids?
Need C18 FAs to make metabolites
-can be used by animals to elongate fatty acids .. otherwise can not make these longer chains
Varying FAs of oils
What are eicosanoids?
Omega 6 and omega 3 (linoleic and linolenic acids)
How are eicosanoids synthesized?
From arachidonic acid (20:4 n-6) and EPA (20:5 n-3)
Balance between omega-6 and omega 3s
Omega 6= pro inflammatory
Omega 3= anti-inflammatory
Need balance between them
Best= 4:1
*avg American= 12-25:1
What are EPA and DHA?
EPA: 20:5 n-3
DHA: 22:6 n-3
**From Omega 3 (linolenic acid)
Importance of EPA and DHA
Nutritionally desirable; decrease heart disease, cancer, inflammatory conditions. Critical in the brain.
**also important in fetal brain and eye development in pregnancy!
Importance of DHA and EPA in brain
Dry matter of brain= 9% DHA
dry matter of Retina= 12%DHA
Sources of EPA and DHA
-Made by algae
-fatty fish like salmon are rich in EPA and DHA
How to get omega 3s when not eating fish ?
Can provide chickens or other food animals with flax oil, which results in an increase in EPA and DHA in the meat or eggs and is therefore a source for humans
What is the conversion rate from ALA to EPA and DHA?
~2.5%
Cat specific fatty acids requirements
Need Arachidonic acid 20:4 n-6 which is not present in plant oils
*makes vegan diets very difficult
