Lecture: Lipids Flashcards
What are lipoproteins
clusters of lipids associated with proteins that serve as transport vehicles for lipids in the lymph and blood
What type of reaction is the formation of lipids
Condensation reaction (water is eliminated)
What is a triglyceride
One glycerol molecule & 3 fatty acids
What are fatty acids
Long carbon chains with CH3 at one end and COOH at the other
Three types of fatty acids
Saturated
Monounsaturated
Polyunsaturated
When do cis fatty acids occur
When the hydrogen atoms are at the same side of the double bond
When do trans fatty acids occur
When hydrogen atoms are on the opposite side of the double bond.
What happens fatty acids when cooking
Cis fatty acids are converted to trans
Why are lipids oxidised in the liver and muscles
To produce heat and energy
Form cell membranes
Why are excess lipids stored in the adipose tissue under the skin
Insulate the body
Act as an energy reserve in absence of carbohydrates
Protects delicate organs
What can triglyceride determination and other lipid assays diagnose
Primary/secondary hyperlipoproteinemia
What is hyperlipoproteinemia
Abnormally elevated fat in blood
What are the standard methods for measuring triglyceride concentrations
Enzymatic or alkaline hydrolysis to liberate glycerol
Is triglyceride level effected by meals
Yes, TG needs 12hrs fating prior
How long are triglycerides stable in serum
three days when stored at 2-8degrees
What could happen TG if serum sample left too long at room temperature
Glycerol containing compounds may hydrolyse, releasing glycerol with and apparent increase in total triglycerides content.
Enzymatic reaction sequence in TG assay
Triglycerides + H2O - Glycerol + Fatty acids
Glycerol + ATP - Glycerol-3-phosphate + ADP
Glycerol-3-phosphate + O2 - DAP + H2O2
H2O2 + 4AAP + 4 chlorophenol - quinoneimine dye + 2H2O2
How is glycerol concentration calculated in enzymatic assay
Coupled with trinder reaction that terminated the formation of quinoneimine dye. Dye formed = tg concentration
What breaks down fats
Liver, pancreas, illeum.
bile) (pancreatic lipase) (intestinal lipase
Where is cholesterol found
Blood, bile and brain tissue
How is cholesterol carried in the blood
Attached to HDL, LDL or VLDL.
What functions is cholesterol vital for
formation/maintenance of cell membranes
formation of several hormones-steroids
production of bile salts
conversion into vitamin D in the skin when exposed to light
How much of cholesterol is dietary
15%
85% is endogenous
What is atherosclerosis
When special cells catch LDL and deposit the cholesterol out of it in the walls of the blood vessels
Function of HDL
Collect bad cholesterol and takes it back to the liver.
Helping prevent heart attack
Name 2 types of blood tests that determine high cholesterol
Total cholesterol (non fasting) Lipid profile (fasting 12 hrs)
Normal total cholesterol levels
Below 6.2 mmol/L
Normal LDL cholesterol levels
Below 4.1 mmol/L
Normal HDL cholesterol
Greater than 1.56 mmol/L
High cholesterol related conditions
Diabetes
Hypothyroidism
Kidney/Liver disease
What do low cholesterol levels indicate
Liver disease
Malnutrition
Hyperthyroidism
What HDL level puts individuals at greater risk to developing coronary artery disease
Less than 1.04 mmol/L
Effect if dietary cholesterol on blood cholesterol:
No effect
Effect of saturated fats
Raise LDL
Effect of trans fats
raise LDL and lower HDL
Effect of monounsaturated fats
Lowers LDL
Effect of omega-3 polyunsaturated fats
lowers blood cholesterol
Risk factors for high cholesterol
family history age gender diet cigarette smoking obesity medical conditions stress
What is the relationship between serum HDL cholesterol and coronary heart disease risk
inverse relationship
How is HDL cholesterol measured
Enzymatic methods involving cholesterol esterase and oxidase and trinders colour system.
Colour of quinoneimine
red
Principle of HDL cholesterol determination
Cholesterol esters are hydrolysed to produce cholesterol.
Hydrogen peroxide is then produced from the oxidation of cholesterol by cholesterol oxidase. Quinoneimine dye is produced in a coupled reaction from 4-aminoantipyrine, phenol and hydrogen peroxide.
How to prepare HDL cholesterol sample for assay
React with polyethene glycol reagent, all LDL and VLDL are precipitated.
HDL fraction remains in the supernatant.
Plasma lipoproteins can be separated by their
ultracentrifugation (based on density)
or on the basis of their electrophoretic mobility
What is lipoprotein mobility dependent on
Protein content.
High protein content = moves faster
