Lipids Biochemistry Flashcards
What is xanthelasma?
Yellow deposit of cholesterol underneath the skin. Usually on or around the eyelids
What is xanthelasma result of?
High levels of cholesterol in bloodstream
Describe cholesterol
White crystalline
Soft yellow appearance
What chemical group does cholesterol contain and why is this important?
Hydroxyl group
Very fat soluble
Are the rings of cholesterol planar?
NO
What is “stacking”?
Sit on top of each other
Can cholesterol stack?
YES
Forms crystals in blood + urine
What happens when cholesterol is in the blood?
Cause precipitation
Coagulation
Blood vessel blockage
Heart disease
How do you form cholesterol?
3 molecules of acetic acid activated Becomes acetyl CoA Combine using HMG-CoA reductase Form mevalonic acid Converted to cholesterol
What is HMG-CoA reductase?
Enzyme in mevalonic acid pathway (produce cholesterol)
What do drugs do that lower cholesterol?
Inhibit HMGCR = lower serum cholesterol = reduce cardiovascular diseases
What are examples of statins
Lovastatin (Mevacor)
Fluvastatin (Lescol)
Pravastatin (Pravachol)
Atorvastatin (Lipitor)
Describe statins
All share similarities with mevalonic acid
Block HMG-CoAR
What are the best statins + why?
Rosuvastatin, Pitavastatin + Atorvastatin
= tightest bound to enzyme = best at reducing cholesterol
What is acetic acid?
2 carbon
Vinegar
When are fatty acids saturated?
C=O
When are fatty acids unsaturated?
C=C
What can long chain fatty acids do?
Stack = form crystalline solids
Why is olive oi liquid at RT?
Contains oleic acid = cis C=C = "kink" in the chain = no stacking = no crystalline solid
What do solid fats do?
Form clots in blood vessels more readily than liquid fats
What do trans fats do?
For straight chain fatty acids
= stack
= form crystalline solids
What do manufactures do to make their food crispy?
Convert unsaturated CIS oil + convert into solid tarns fats
Process = hydrogenation
What are triglycerides?
3 fatty acids combined with glycerol
Are triglycerides inert?
YES BUT esters “unstable”
= can be reversibly broken down
How are triglycerides broken down?
1st —-> 2nd —-> 3rd
Then glycerol left
What is the process of breaking down triglycerides regulated by?
Epinephrine (adrenaline)
What is a mixed triglyceride?
2 saturated fatty acids attached to one unsaturated fatty acid
What are lipoproteins?
Complex particles with central core containing cholesterol esters + triglycerides surrounded by free cholesterol, phospholipids + apolipoproteins, which facilitate lipoprotein formation + function
What are apolipoproteins?
Proteins that bind to lipids
What are lipoproteins spheres?
Allow for unreactive transport of lipids
= smallest SA = less area for it to react
What are the 4 classes of lipoproteins?
Chylomicrons Very-low density lipoproteins (VLDL) Low-density lipoproteins (LDL) Intermediate density lipoproteins (IDL) High-density lipoproteins (HDL)
How much lipid in chylomicrons?
99%
How much lipid in VLDL?
85%
How much lipid in LDL?
82%
How much lipid in IDL?
80%
How much lipid in HDL?
50%
Why do the high density lipoproteins have less fat?
Proteins denser than fats
Describe absorption in small intestine
Through striated border epithelium covering villi
Diffusion + active transport
What is absorbed into capillaries?
Amino acids, sugars, minerals, glycerol, some fatty acids + vitamins
What is absorbed into lacteals?
Glycerides, some fatty acids + fat soluble vitamins
What do fatty acids + triglycerides do in the intestine?
Form emulsion
= achieved by bile secretion
What happens to fats in intestine?
Emulsion forms micelles
Micelles approach cells of intestine wall + collapse
Fats + triglycerides absorbed into epithelial cells
Chylomicrons pass into lymph system
What are bile salts made from?
Cholesterol
How do LDL contribute to heart disease?
Transported through blood
Stick yo blood vessels
Absorbed by cell wall of blood vessel = its oxidised
How does our body try to protect from oxidised fats?
Engulf with macrophages
“blow up” in size = foam cell
What happens when foam cell trapped in protein matrix of blood vessel wall?
Form lump distorts blood vessel
Makes lumen narrower
Lump = plaque
Process = atherosclerosis
Describe atherosclerosis
Plaque with fibrous cap
Cap ruptures
Blood clot forms around rupture = blocks artery
Where are bile salts produce from?
Gall bladder
What is the problem with bile salts being made from cholesterol?
For crystals
= gall stones
= block gall bladder