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Clinical biochemistry > Lecture: Lipids > Flashcards

Lecture: Lipids Flashcards

1
Q

What are lipoproteins

A

clusters of lipids associated with proteins that serve as transport vehicles for lipids in the lymph and blood

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2
Q

What type of reaction is the formation of lipids

A

Condensation reaction (water is eliminated)

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3
Q

What is a triglyceride

A

One glycerol molecule & 3 fatty acids

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4
Q

What are fatty acids

A

Long carbon chains with CH3 at one end and COOH at the other

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5
Q

Three types of fatty acids

A

Saturated
Monounsaturated
Polyunsaturated

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6
Q

When do cis fatty acids occur

A

When the hydrogen atoms are at the same side of the double bond

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7
Q

When do trans fatty acids occur

A

When hydrogen atoms are on the opposite side of the double bond.

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8
Q

What happens fatty acids when cooking

A

Cis fatty acids are converted to trans

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9
Q

Why are lipids oxidised in the liver and muscles

A

To produce heat and energy

Form cell membranes

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10
Q

Why are excess lipids stored in the adipose tissue under the skin

A

Insulate the body
Act as an energy reserve in absence of carbohydrates
Protects delicate organs

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11
Q

What can triglyceride determination and other lipid assays diagnose

A

Primary/secondary hyperlipoproteinemia

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12
Q

What is hyperlipoproteinemia

A

Abnormally elevated fat in blood

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13
Q

What are the standard methods for measuring triglyceride concentrations

A

Enzymatic or alkaline hydrolysis to liberate glycerol

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14
Q

Is triglyceride level effected by meals

A

Yes, TG needs 12hrs fating prior

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15
Q

How long are triglycerides stable in serum

A

three days when stored at 2-8degrees

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16
Q

What could happen TG if serum sample left too long at room temperature

A

Glycerol containing compounds may hydrolyse, releasing glycerol with and apparent increase in total triglycerides content.

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17
Q

Enzymatic reaction sequence in TG assay

A

Triglycerides + H2O - Glycerol + Fatty acids

Glycerol + ATP - Glycerol-3-phosphate + ADP

Glycerol-3-phosphate + O2 - DAP + H2O2

H2O2 + 4AAP + 4 chlorophenol - quinoneimine dye + 2H2O2

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18
Q

How is glycerol concentration calculated in enzymatic assay

A

Coupled with trinder reaction that terminated the formation of quinoneimine dye. Dye formed = tg concentration

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19
Q

What breaks down fats

A

Liver, pancreas, illeum.

bile) (pancreatic lipase) (intestinal lipase

20
Q

Where is cholesterol found

A

Blood, bile and brain tissue

21
Q

How is cholesterol carried in the blood

A

Attached to HDL, LDL or VLDL.

22
Q

What functions is cholesterol vital for

A

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

23
Q

How much of cholesterol is dietary

A

15%

85% is endogenous

24
Q

What is atherosclerosis

A

When special cells catch LDL and deposit the cholesterol out of it in the walls of the blood vessels

25
Q

Function of HDL

A

Collect bad cholesterol and takes it back to the liver.

Helping prevent heart attack

26
Q

Name 2 types of blood tests that determine high cholesterol

A 
Total cholesterol (non fasting)
Lipid profile (fasting 12 hrs)
27
Q

Normal total cholesterol levels

A

Below 6.2 mmol/L

28
Q

Normal LDL cholesterol levels

A

Below 4.1 mmol/L

29
Q

Normal HDL cholesterol

A

Greater than 1.56 mmol/L

30
Q

High cholesterol related conditions

A

Diabetes
Hypothyroidism
Kidney/Liver disease

31
Q

What do low cholesterol levels indicate

A

Liver disease
Malnutrition
Hyperthyroidism

32
Q

What HDL level puts individuals at greater risk to developing coronary artery disease

A

Less than 1.04 mmol/L

33
Q

Effect if dietary cholesterol on blood cholesterol:

A

No effect

34
Q

Effect of saturated fats

A

Raise LDL

35
Q

Effect of trans fats

A

raise LDL and lower HDL

36
Q

Effect of monounsaturated fats

A

Lowers LDL

37
Q

Effect of omega-3 polyunsaturated fats

A

lowers blood cholesterol

38
Q

Risk factors for high cholesterol

A 
family history 
age
gender
diet
cigarette smoking 
obesity 
medical conditions
stress
39
Q

What is the relationship between serum HDL cholesterol and coronary heart disease risk

A

inverse relationship

40
Q

How is HDL cholesterol measured

A

Enzymatic methods involving cholesterol esterase and oxidase and trinders colour system.

41
Q

Colour of quinoneimine

A

red

42
Q

Principle of HDL cholesterol determination

A

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.

43
Q

How to prepare HDL cholesterol sample for assay

A

React with polyethene glycol reagent, all LDL and VLDL are precipitated.
HDL fraction remains in the supernatant.

44
Q

Plasma lipoproteins can be separated by their

A

ultracentrifugation (based on density)

or on the basis of their electrophoretic mobility

45
Q

What is lipoprotein mobility dependent on

A

Protein content.

High protein content = moves faster

Clinical biochemistry (11 decks)

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