Lecture 7 - Lipids 1 Flashcards
(24 cards)
Lipids are an:
___ if it is liquid at RT
___ if it is solid at RT
Oils - liquid
Fat - solid
How many kJ and calories per g of lipid?
37kJ, 9 calories
Dietary fat is comprised mostly of what 3 things?
- Triglycerides (90% of total dietary lipids)
- Phospholipids
- Sterols
Triglycerides are made up of ____ + _____.
3 fatty acids + a glycerol backbone
What are the 3 types of FAs (which are what comprise triglycerides)?
Saturated, monounsaturated, polyunsaturated
What are the 3 main series of unsaturated FAs? What is the name based on?
Omega-9 (aka n-9), omega-6 (n-6) and omega-3 (n-3). Based on first double bond counting from methyl carbon (omega/n).
3 common SATURATED FAs?
Palmitic (palm oils), stearic (animal fats), myristic (butter, coconut oil)
2 common MONOUNSATURATED FAs?
Oleic (olive oil), palmitoleic (fish/animal fats, vege oils)
3 common POLYUNSATURATED FAs?
Linoleic (sunflower/corn/soybean oil), alpha-linoleic (chia/flax oil), pentanoic (fish/fish oils)
What are the 5 main dietary sources of saturated fat?
- Dairy
- Butter, margarine, vege oils
- Meat products
- Poultry
- Desserts e.g. cake
What are the only 2 essential FAs to humans? What biochemical process happens when we ingest them?
Linoleic (n-6) and alpha-linoleic (n-3) acid. They undergo transformation into other FAs using enzymes
What are trans fatty acids?
What is a benefit of it?
What is a source of naturally occurring trans FAs?
- Hydrogen is added across a double bond in a polyunsaturated FA (‘hydrogenated’). This causes the configuration to change from cis to trans.
- Prolongs shelf life as fat remains solid at RT
- Small amount in milk and dairy products
What are 2 main types of PHOSPHOLIPIDS?
What are 2 functions of phospholipids?
What are 2 sources?
- Phosphatidylserine, phosphatidylcholine
- Emulsifier, a component of cell membranes
- Egg yolk, peanuts
Main type of STEROL in animals?
Main type of STEROL in plants?
Cholesterol
Phytosterols (then further subcategories)
4 key steps in the absorption of fat?
- Triglycerides mixed with ampipathic compounds (bile acids, phospholipids) in which it is EMULSIFIED (broken down from large droplets to small droplets)
- Pancreatic lipase removes 2 FAs (increases SA)
- Phospholipase + cholesteryl ester hydrolase help to further break down the droplet into monoglycerides + FAs.
- These monoglycerides + FAs can diffuse across enterocytes (mucosal cells of small intestine)
Are lipids soluble in plasma? Why/why not? To combat this lipids are bound with ____ for transport and this unit is termed _____?
This unit can be formed using 2 pathways, what are they each called?
No - plasma is an aqueous solution. Lipids are hydrophobic.
Bound with protein to form lipoproteins.
Exogenous pathway: lipoproteins formed in mucosal cells after the fat has being absorbed (chylomicrons)
Endogenous pathway: lipoproteins are formed in the liver and then transported (via VLDLs) to the tissues
In a lipoprotein, what comprises the:
Outer layer?
The core?
OL: apolipoproteins, cholesterols + phospholipids
C: triglycerides + cholesterol ester rich
LDL-c is positively/negatively associated with _______. Is the relationship linear or non-linear?
Positively atherosclerosis, non-linear
Doctors commonly prescribe meds that target the rate limiting step of cholesterol synthesis. What is this step and what are the meds called?
HMG-CoA reductase
Statins - HMG-CoA reductase inhibitors
HDL-c is positively/negatively associated with _______.
HDL-c is positively/negatively/not associated with _______.
Negatively, atherosclerosis.
No association, CVD (still used as a risk marker though).
Triglycerides are positively/negatively/no associated with _______.
What 3 things lower triglycerides?
Not associated (still used as a risk marker though) with CVD. Niacin, omega-3 FAs, fibrates.
SFAs and MUFA + PUFAs affect LDL levels through the endogenous pathway. What is the mechanism behind this for:
SFAs?
MUFA + PUFAs?
SFA: downregulates LDL receptors on both liver and body tissues hence higher amounts of LDL is left circulating. Saturated fat is the main dietary driver of LDL-c
M/PUFA: upregulates LDL receptors on both liver and body tissues but this is coupled with an increase in endogenous cholesterol synthesis hence these 2 mechanisms cancel eachother out.
SFAs increase LDL-c. So does dietary cholesterol and trans-fats. Which of the 3 increases it the most, which increases it the least.
Trans fats > SFAs > dietary cholesterol
- ** Trans fats do this by increasing endogenous cholesterol synthesis
- ** Dietary cholesterol and SFAs co-inhabit/they are found together
Phytosterols decreases blood cholesterol by ___% at highest dose.
What is the mechanism behind this?
What are some dietary sources of phytosterols?
10%
Competes with cholesterol for absorption in the gut hence less cholesterol is absorbed.
Margarine, brekkie cereals, low-fat yoghurt + milk.
*** There is a dose-dependent reduction in LDL-c and phytosterol concentration in margarine. Greater reduction seen in higher [phytosterol]. There is an increase in LDL-c when butter is used (butter contains SFAs).
