Lipids Flashcards
(32 cards)
What is a lipoprotein?
Clusters of lipids associated with proteins that serve as transport vehicles for lipids in the lymph and blood
Production of a triglyceride?
-Formed when one glycerol molecule joins with 3 fatty acids to produce a triglyceride and water
-Water is eliminated (condensation rxn)
Look at lipid classification diagram
Lipid functions?
-Lipids are oxidised in the liver and muscles to produce heat and energy and form cell membranes
-Excess lipids are stored in the adipose tissue underneath the skin this insulates the body, acts as an energy reserve in absence of carbs amd protects delicate organs
What are triglyceride determinants when preformed in conjunction with other lipid assays useful in the diagnosis of?
Primary and secondary hyperlipoproteinemia
(abnormally elevated fat in blood)
Standard methods for measuring triglyceride conc invoolve either enzymatic or alkaline hydrolysis to liberate glycerol
Do TG test need fasting?
Yes needs 12 hrs fasting as level is effected by meal - fatty meal, high carbs meal
What specimen is collected and how is it stored for triglyceride measurement?
-Fresh non-hemolyzed serum from fasting patients is recommened
-Triglycerides in serum appears stable for 3 days when stored at 2-8 degrees C
-Prolonged storage of the samples at room temp is not recommended since other glycerol containing compounds may hydrolyze, releasing free glycerol with an apparent increase in total TG content
Principle of enzymatic sequence reaction in assay of TG?
triglycerides + H20 –lipase-> glycerol + FAs
glycerol + ATP –glycerol kinase-> glycerol-3-phosphate + ADP
glycerol-3-phosphate + O2 –G-1-P oxidase-> DAP +H202
H2O2 + 4AAP + 4 chlorophenol –peroxidase-> quinoneimine dye + 2H2O
What product from the TG enzymatic reaction is measured to assess TG conc?
(procedure involves hydrolysis of triglycerides by lipase)
Glycerol conc is determined by enzymatic assay coupled with Trinder reaction that terminates the formation of a quinoneimine dye
-Amount of dye formed is tested at 505nm and is directly proportional to conc of TG in sample
What is produced by the liver, pancreas and illeum for lipid digestion?
Liver - produces bile, contains salts, bile salts break down lipids into emulsified fats
Pancreas - pancreatic juice contains pancreatic lipase which breaks lipids into 1 glycerol molecule and 3 fatty acids
Illeum - intestinal juices contain intestinal lipase which continues breakdown of lipids into 1 glycerol molecule and 3 fatty acids
What is cholesterol?
-A type of fat (lipid) found in the blood, bile and brain tissue
-It is carried in the blood attached to a protein in the form of high density lipoprotein (HDL-Cholesterol), low density lipoprotein (LDL-Cholesterol) and very low density lipoprotein (VLDL-Cholesterol)
Functions of Cholesterol?
-formation and maintenance of cell membranes
-formation of several hormones-steroids
-production of bile salts which help digest food
-conversion into vitD in the skin when exposed to sunlight
Liver vs diet cholesterol?
85% of cholesterol is endogenous (liver) and 15% from diet
Effect of high cholesterol?
-Specialised cells catch LDL and deposit the cholesterol out of it in the walls of the blood vessels - athersclerosis
Effect of HDL?
HDL usually collects the bad cholesterol and takes it back to the liver - known as good cholesterol - helps prevent heart attack
Types of measuring Cholesterol?
2 types of blood tests
- Total cholesterol (nonfasting) - total amount of cholesterol in your blood
- Lipid profile (lipoprotein analysis) - have to fast 12 hours before
i)Total cholesterol
ii)HDL cholesterol
iii) LDL cholesterol
iv) triglycerides
High cholesterol levels in total cholesterol and LDL cholesterol?
Risk levels for HDL?
Total cholesterol levels: 6.2mmol/L or more is high cholesterol - high risk for heart disease
LDL cholesterol levels: 4.1mmol/L or more is high cholesterol - higher risk for heart disease
HDL cholesterol levels: less than 0.9 mmol/L
Desirable levels of total cholesterol, LDL, HDL?
Total: <5.2mmol/L
LDL: <3.4mmol/L
HDL: >1.56 mmol/L
What causes high cholesterol and TG levels?
-inherited form of high cholesterol (hypercholesterolemia or hyperlipidemia)
-Diabetes
-Hypothyroidism
-Kidney or liver disease
High levels of HDL?
HDL cholesterol greater than 1.56mmol/L can help protect a person from developing coronary artery disease ad stroke (neg risk factor)
Why may somone have unusually low cholesterol levels?
-liver disease (cirrhosis or hepatitis)
-malnutrition
-hyperthyroidism
Low HDL levels?
-HDL cholesterol levels lower than 1.04 mmol/L (<40mg/dL) increase a persons ris´k of developing coronary artery disease, especially in people who also have high total cholesterol levels
Risk factors and goal LDL levels?
-If you are at risk for coronary heart disease and diabetes - goal is LDL less than 2.6mmol/L
-If have multiple risk factors (2+) then LDL goal is less than 3.4mmol/L
-If have zero to 1 risk factor - goal LDL is less than 4.1mmol/L
What effect do lipids have on lipoproteins and CVD risk?
-Dietary cholesterol - no effect on blood cholesterol
-Saturated fats - raise LDL
-Trans fats - raise LDL and lower HDL
-Monounsaturated fats - lowers LDL
-Omega-3-polyunsaturated fats - lowers blood cholesterol
