Lecture: Lipids

Question 1

What are lipoproteins

Answer 1

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

Question 2

What type of reaction is the formation of lipids

Answer 2

Condensation reaction (water is eliminated)

Question 3

What is a triglyceride

Answer 3

One glycerol molecule & 3 fatty acids

Question 4

What are fatty acids

Answer 4

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

Question 5

Three types of fatty acids

Answer 5

Saturated
Monounsaturated
Polyunsaturated

Question 6

When do cis fatty acids occur

Answer 6

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

Question 7

When do trans fatty acids occur

Answer 7

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

Question 8

What happens fatty acids when cooking

Answer 8

Cis fatty acids are converted to trans

Question 9

Why are lipids oxidised in the liver and muscles

Answer 9

To produce heat and energy

Form cell membranes

Question 10

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

Answer 10

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

Question 11

What can triglyceride determination and other lipid assays diagnose

Answer 11

Primary/secondary hyperlipoproteinemia

Question 12

What is hyperlipoproteinemia

Answer 12

Abnormally elevated fat in blood

Question 13

What are the standard methods for measuring triglyceride concentrations

Answer 13

Enzymatic or alkaline hydrolysis to liberate glycerol

Question 14

Is triglyceride level effected by meals

Answer 14

Yes, TG needs 12hrs fating prior

Question 15

How long are triglycerides stable in serum

Answer 15

three days when stored at 2-8degrees

Question 16

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

Answer 16

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

Question 17

Enzymatic reaction sequence in TG assay

Answer 17

Triglycerides + H2O - Glycerol + Fatty acids

Glycerol + ATP - Glycerol-3-phosphate + ADP

Glycerol-3-phosphate + O2 - DAP + H2O2

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

Question 18

How is glycerol concentration calculated in enzymatic assay

Answer 18

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

Question 19

What breaks down fats

Answer 19

Liver, pancreas, illeum.

bile) (pancreatic lipase) (intestinal lipase

Question 20

Where is cholesterol found

Answer 20

Blood, bile and brain tissue

Question 21

How is cholesterol carried in the blood

Answer 21

Attached to HDL, LDL or VLDL.

Question 22

What functions is cholesterol vital for

Answer 22

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

Question 23

How much of cholesterol is dietary

Answer 23

15%

85% is endogenous

Question 24

What is atherosclerosis

Answer 24

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

Question 25

Function of HDL

Answer 25

Collect bad cholesterol and takes it back to the liver. Helping prevent heart attack

Question 26

Name 2 types of blood tests that determine high cholesterol

Answer 26

``` Total cholesterol (non fasting) Lipid profile (fasting 12 hrs) ```

Question 27

Normal total cholesterol levels

Answer 27

Below 6.2 mmol/L

Question 28

Normal LDL cholesterol levels

Answer 28

Below 4.1 mmol/L

Question 29

Normal HDL cholesterol

Answer 29

Greater than 1.56 mmol/L

Question 30

High cholesterol related conditions

Answer 30

Diabetes Hypothyroidism Kidney/Liver disease

Question 31

What do low cholesterol levels indicate

Answer 31

Liver disease Malnutrition Hyperthyroidism

Question 32

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

Answer 32

Less than 1.04 mmol/L

Question 33

Effect if dietary cholesterol on blood cholesterol:

Answer 33

No effect

Question 34

Effect of saturated fats

Answer 34

Raise LDL

Question 35

Effect of trans fats

Answer 35

raise LDL and lower HDL

Question 36

Effect of monounsaturated fats

Answer 36

Lowers LDL

Question 37

Effect of omega-3 polyunsaturated fats

Answer 37

lowers blood cholesterol

Question 38

Risk factors for high cholesterol

Answer 38

``` family history age gender diet cigarette smoking obesity medical conditions stress ```

Question 39

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

Answer 39

inverse relationship

Question 40

How is HDL cholesterol measured

Answer 40

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

Question 41

Colour of quinoneimine

Answer 41

red

Question 42

Principle of HDL cholesterol determination

Answer 42

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.

Question 43

How to prepare HDL cholesterol sample for assay

Answer 43

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

Question 44

Plasma lipoproteins can be separated by their

Answer 44

ultracentrifugation (based on density) | or on the basis of their electrophoretic mobility

Question 45

What is lipoprotein mobility dependent on

Answer 45

Protein content. | High protein content = moves faster