1
Q
What are Lipids?
A
- Organic substances relatively insoluble in water, but soluble in organic solvents such as alcohol and ether.
- Found in animals and plants
- Formed of long-chain hydrocarbon groups (also contain oxygen, phosphorus, nitrogen and sulfur)
2
Q
What are the functions of Lipids?
A
- major storage form of energy (9cal/gm)
- provides essential fatty acids like phospholipids and hormones
- form importantconstituents of cell membranes and helps to maintain the membrain structure and integrity
- Essential for the absorption of vitamin A,D,E, and K
- Acetyl CoA is used for the synthesis of cholesterol and hence steroid hormones
- Protects internal organs from shock due to insulating effect
- Helps in blood coagulation
- Dipalmitoyl lecithin (phospholipid) act as a surfactant and is required for the normal functioning of the lung aveoli
3
Q
What are the classification of Lipids?
*objective
A
Bloor’s Classification:
1. Simple
2. Compund
3. Derived
4. Complexed
4
Q
What are Simple Lipids?
A
The esters of fatty acids with glycerol or higher alcohols (eg. fats and waxes)
*fats are also called triacylglycerols/ triglycerides
5
Q
What are glycerols and the types of glycerol compound with FA?
A
Glycerol is made up of a three carbon- alcohol chain that is able to form bonds with three R groups (usually FAs)
Glycerol with:
- one molecule of FA is called monoacylglycerol
- two molecules of FAs are called diacylglycerol
- three molecules of FAs are called triacylglecerol
6
Q
What are Compound Lipids?
A
Simple lipids + additional groups such as phosphate, notrogenous base, carbohydrate and protein besides esters of FAs with alcohols
7
Q
What are the two groups Compound Lipids are further divided?
A
- Phospholipids
- Glycolipids
8
Q
What are Phospholipids?
A
- Compound lipids containing alcohol, fatty acid, phosphoric acid and a nitrogenous base or other alcohol group:
9
Q
What are the main examples of Phospholipids?
A
- Lecithin (phosphatidylcholine)
- Cephalins (phosphatidylethanolamine)
- Phosphatidylinositol
- Sphingomyelin
10
Q
What is Lecithin (Phosphatidylcholine)? what are the uses?
A
- Simple Lipid + Phosphoric acid + Choline (nitrogenous base)
- Present in the brain and nervous tissue
- Dipalmitoyl lecithin is a lung surfactant (lowers surface tenstion) which presvents the collaps of the ling alveoli
11
Q
What is Cephalins (phosphatidylethanolamine)?
A
- Simple Lipid + Phosphoric acid + Ethanolamine/ serine (nitrogenous base)
- present in the brain, erythrocytes and many other tissues
12
Q
What is Phosphatidylinositol? What are the uses?
A
- Simple Lipid + Phosphoric acid + inositol (alcohol)
- An important component of cell membranes
- Action of certain hormones like oxytocin and vasopressin is mediatedthrough phosphatidyl inositol (PI). In response to hormonal action, PI is cleaved to disacyl glycerol (DAG) and inositol triphosphate (IP3). Both these compunds act as second messengers for hormonal action.
13
Q
What is Sphingomyelin? What are its uses?
A
- Is a type of sphingolipid
- Fatty acid + Phosphoric acid + Choline + Sphingosine (unsaturated amino alcohol)
- Makes up a large part of the myelin sheth
- Present in the brain, lungs, nerve and other tissues
- Difficiency leads to Niemann- Pick Disease
14
Q
What is Niemann- Pick Disease?
A
Cause: deficiency of sphingomyelinase enzyme
Clinical problem: Deposition of sphingomyelin in liver, lymph nodes, bone marrow and central nervous system
15
Q
What are Glycolipids?
A
- Fatty acids + Sphingosine (amino alcohol) +
carbohydrate/ carbohydrate derivative - Two major types:
1. Cerebrosides
2. Gangliosides
16
Q
What are Cerebrosides?
A
- Fatty Acids + Sphingosine + Sugar (usually galactose)
- Present in white matter of brain and myelin sheath of nerves
- Can cause Gaucher’s Disease
17
Q
What is Gaucher’s Disease?
A
- Elevated levels of cerebrosides in tissues like reticuloendothelial cells of spleen, liver, lymph nde and bone
18
Q
What are Gangliosides?
A
- N-acetylneuramininc acid + fatty acid + sphingosine + 3 molecules of hexoses (glucose or galactose)
- found in grey matter of the brain
- Can cause Tay Sach’s Disease
19
Q
What is Tay Sach’s Disease?
A
- Ganglioside level increases
20
Q
What are Derived Lipids?
A
- Subsances derived from simple or compound lipids on hydrolysis
- the use of water (H2O) to break down the chemical bonds that exist between simple/ compound lipids
- Examples:
1. Fatty acids
2. Glycerol
3. Alcohol
4. Cholesterol
21
Q
What is the structure of FAs in Derived Lipids?
A
- Aliphatic (open chain) monocarboxylic organic acid with chain length usually ranging from C-4 to C24 and it is a constituent of lipid
- Geberal formula: R-CO-OH
22
Q
What are Complexed Lipids?
A
- a type of compund lipid
- for example; lipoproteins
23
Q
What are lipoproteins and what are they made up of?
A
- conjugated proteins, compsed of core and surface
- LP Core
- Triglycerides
- Vholesterol esters
*LP Surface - Phospolipids
- Proteins
- Cholesterol
+ The outer polar surface makes them water soluble - since lipids are water insoluble they are present in the blood as lipoprotein form which are water soluble
+ Seperated by ultracentrifigation into 4 distinct groups based on density and by electrophoresis (cation and anion charge)
24
Q
What are the 4 different types of Lipoproteins?
A
- Chylomicron
- Very Low Density Lipoprotein (VLDL)
- Low Density Lipoprotein (LDL)
- High Density Lipoproyein (HDL)
25
What is Chylomicron?
- Type of Lipoprotein
- Transports dietary triglyceride and cholesterol esters from intestine to peripherol tissues and liver
26
What is Very Low Density Lipoprotein (VLDL)?
- Type of Lipoprotein
- Transports endogenous triglyceride from liver to extrahepatic tissues
27
What is Low Density Lipoprotein (LDL)?
- Type of Lypoprotein
- Transports cholesterol from liver to extrahepatic tissues
28
What is High Density Lipoprotein (HDL)?
- Type of Lipoprotein
- Transports cholesterol from extrahepatic tissues back to the liver in an esterified form
29
What are the Types of FAs?
Ther are two types:
1. Saturated FAs
2. Unsaturated FAs (Cis and Trans fats)
30
What are Saturated Fats?
Examples?
- Lack of carbon-carbon double bonds
- Higher melting points compared to unsaturated acids of the corresponding size due to their ability to pack their molecules together thus leading to a straight rod-like shape and stronger intermolecular bonds
- found in butter, fat on meat products, oils.
31
What are Unsaturated Fats?
Examples?
- Indicated when a fatty acid has more than one double bond
1. Trans Fats- two H on opp side of double bond (less healthy)
2. Cis Fats- two H on same side of double bond (more healthy)
32
Are Saturated Fats and Trans Fats good for the body?
No!
- raises blood cholesterol levels, increases a person's risk of developing heart disease
- Cis- unsaturated Fats are more healthy as they tend to increase the amount of good cholesterol in the body
33
How do you classify FAs?
(Classification of FAs)
1. depending on the total number of carbon chains (even or odd chains)
2. depending on the length of hydrocarbon chain (short- <6C, medium- 8-14C, long- 16-24C)
3. depending on the nature of hydrocarbon chain (saturated or unsaturated)
34
How do you number FAs?
- Start from the -COOH numbering it C1
- C2 follows and is also called the alpha carbon... C3- beta carbon
- The last carbon is called the omega carbon
- eg. Oleic acid- 18:1;9
Omega Series
- Start from omega carbon
- Count carbons until you reach the carbon with the first carbon- carbon double bond
- at this stage - Omega 3/ 6 series
35
What are the Benifits and Importance of Omegas 3 and 6?
1. Improving brain function and decreases risk of alzheimer's
2. Helping to maintain a good mood and preventing depression
3. Prevention of excessive blood clotting
4. Helping to prevent cancer cell growth
5. By lowering the amount of fat (as cholesterol and triglycerides) in circulation decreasing the risk of heart disease
36
What are Essential Fatty Acids or PUFA?
- FAs that are not synthesised in the body and should be supplied through diet
- Contain more than one double bond
37
What are some examples of Essential FAs.
Why are they Essential?
Eg. Linoleic Acid, Linolenic acid and Arachidonic Acid
- Not synthesised in the human body due to the lack of the desaturase enzyme- introduces double bonds beyond 9th and 10th carbon atoms
38
What are the Functions of Essential FAs/ PUFA?
1. Are required for the membrane structure and function
2. Transport of cholesterol
3. Formation of Lipoproteins
4. Synthesis of Eicosanoids (derived from a 20 carbon polyunsaturated fatty acids)
39
What are Steroids?
Any of a class of natural or synthetic organic compounds characterized by a molecular structure of 17 carbon atoms arranged in four rings
- found in association with lipids
- having special ring, cyclopentanoperhydrophenanthrene
- eg. steroid hormone, bile acid, vitamin D
40
What is Cholesterol?
A compound of the sterol type found in most body tissues.
- one of the most important steroids present in the body
- has 27 carbon, an -OH group, a double bond, two methyl groups at C10 and C13 and a side chain at C17
- precursor of various compounds such as vitamin D3, bile acids and adreocortical and sex hormones
- widey distributed in all cells of the body but nervous tissue is rich in cholesterol
- steroids containing one or more -OH groups are known as sterols
- normal fasting serum cholesterol level is 150-200 mg/dl
- synthesised in our body using acetyl CoA as precursor
- cholesterol exists in free and ester form; gets esterified through esterase enzymes
- excess is harmful to the body, it gets deposited in the intima of the arteries producing atherosclerosis narrowing the lumen of blood vessels impeeding blood flow (causes thrombrosis)
41
What are the functions of Cholesterol?
If maintained in normal levels it has a number of good effects:
- precursor for the synthesis of bile acids in liver
- the steroid hormone in adrenal cortex and sex hormones in gonads are mainly synthesized from cholesterol
- forms 7-dehydrocholesterol in skin which is converted to vitamin D3 by UV rays
- a poor conductor of heat and hence acts as an insulator
-abundant in the brain and nervous tissue where it functions as an insulating covering for structure, which generated and transmits electrical impulse
42
What are the Properties of Lipids?
-Triglycerides, which contain a higher proportion of unsaturated FAs or short chain FAs, are liquid at 20 degrees Celcius and are usually called as oils
- Fats, however, are solid at room temp and contain saturated long chain FAs (eg animal fat)
43
What are the Clinical Applications of Lipids?
Excessive fat deposits cause abnormality in cholesterol and lipoprotein metabolism leading to:
- atherosclerosis
- obesity
- diabetes mellitus
... all important risk factor for cardiovascular diseases
Biochemistry I
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