L2 Lipids Flashcards
What are lipids?
Lipids are organic substances relatively insoluble in water but soluble in organic solvents.
What are lipids composed of?
They are formed of long chain hydrocarbon groups.
They can contain phosphorus, sulfur, oxygen, nitrogen.
What are the 8 functions of lipids?
- Triglycerides are the major storage form of energy 9 cal/gm.
- Provide essential fatty acids; phospholipids, hormones
- Form important constituents of cell membrane and helps to maintain the membrane structure and integrity
- Essential for the absorption of vitamin A, D, E and K
- Acetyl CoA [basic unit of lipids] is used for the synthesis of cholesterol and hence steroid hormones.
- Protects internal organs from shock because of its
insulating effect . - Helps in blood coagulation
- Dipalmitoyl lecithin, a phospholipid act as surfactant and is required for the normal functioning of the lung alveoli
What are the four classifications of lipids?
- Simple lipids
- Compound lipids
- Derived lipids
- Complex lipids
What are simple lipids?
2 examples?
Esters of fatty acids with glycerol or higher alcohols.
Fats and waxes
What are fats?
Esters of fatty acids with glycerol
What are fats also called?
Triglyceride
Triacylglycerol
What is a Triacylglycerol?
Fats and oils of animal and plant origin consist exclusively of the simple lipid class triacylglycerols
What is triacylglycerol composed of?
Composed of esters of fatty acids with glycerol and trihydric-alcohol
Monoacylglycerol
One molecule of fatty acd
Diacylglycerol
Two molecules of fatty acids
Triglyceride
Three molecules of fatty acids
What are compound lipids?
Simple lipids + additional groups (nitrogenous base (phosphate), protein or carbohydrate)
What are the two divisions of compound lipids?
- phospholipids
2. glycolipids
What are phospholipids?
compound lipids containing fatty acid,
phosphoric acid, alcohol and a nitrogenous base or
other alcoholic group
Lecithin is also called?
Phosphatidylcholine
What are the components of phosphatidylcholine?
simple lipid + phosphoric acid + choline
Where is phosphatidylcholine? found?
brain and nervous tissue
Dipalmitoyl lecithin?
lung surfactant that lowers surface tension and
prevents the collapse of lung alveoli
Absence of Dipalmitoyl lecithin results in?
2
- respiratory distress syndrome in premature babies
- hyaline membrane disease
What is another name for Phosphatidylethanolamine?
Cephalins?
What are the components of phosphatidylethanolamine?
simple lipid + phosphoric acid + ethanolamine
or serine as nitrogenous base
Where is phosphatidylethanolamine found?
brain, erythrocytes and other tissues.
What are the components of phosphatidylinositol?
simple lipid + phosphoric acid + inositol (alcohol)
Where is phosphatidylinositol found?
cell membrane
What is function of phosphatidylinositol?
Action of certain hormones like oxytocin & vasopressin is mediated through phosphatidylinositol (PI).
In response to hormonal action,
PI is cleaved to diacylglycerol (DAG) and inositol triphosphate (IP3).
Both these compounds act as second messenger for hormonal action.
What is Sphingomyelin?
A sphingophospholipid
What does Sphingomyelin contain?
A molecule of choline, phosphoric acid and a
fatty acid.
Where is Sphingomyelin found?
Sphingomyelin makes up a large part of the myelin sheath.
These are also present in brain, lungs, nerve and other tissues
Disease associated with Sphingomyelin?
Niemann-Pick disease
Cause of Niemann-Pick disease?
Deficiency of sphingomyelinase enzyme
What is Niemann-Pick disease?
Deposition of sphingomyelin in liver, lymph nodes, bone marrow and central nervous system.
What do glycolipids contain?
Contains fatty acid, sphingosine (amino alcohol), carbohydrate or carbohydrate derivative.
Examples of glycolipids?
Cerebroside
Ganglioside
What do cerebrosides contain?
Contains fatty acid, sphingosine and a sugar (usually galactose).
Where are cerebrosides found?
Present in white matter of brain and myelin sheath of nerves.
What disease is associated with cerebrosides?
Gaucher’s disease
What is Gaucher’s disease?
Elevated levels of cerebrosides in tissues
like reticuloendothelial cells of spleen, liver, lymph node and bone.
What do gangliosides contain?
Contains N-acetylneuramininc acid, fatty acid, sphingosine and three
molecules of hexoses (glucose or galactose)
Where are gangliosides found?
Found in grey matter of the brain.
What is Tay Sach’s disease?
Ganglioside level increases
What are derived lipids?
Substances derived from simple or compound lipids on hydrolysis.
Examples of derived lipids?
E.g. fatty acid, glycerol, alcohol and cholesterol
What are fatty acids?
Aliphatic monocarboxylic organic acid with chain length usually ranging from C-4 to C-24 and it is a constituent of lipid.
General formula of fatty acids?
Fatty acids have the general formula R-CO –OH.
What are Lipoproteins?
Are conjugated proteins, composed of core and surface.
What does the Lipoproteins core consist of?
- Triglycerides
2. Cholesterol esters
What does the Lipoproteins surface consist of?
- Phospholipids
- Proteins
- Cholesterol
How are lipoproteins separated into its distinct groups?
Separated by ultracentrifugation based on
their density and by electrophoresis based on size.
What are the four different types of lipoproteins?
- Chylomicron
- Very low density lipoprotein (VLDL)
- Low density lipoprotein(LDL)
- High density lipoprotein (HDL)
What does Chylomicron(type of lipoprotein) transport?
Transports dietary triglyceride and cholesterol esters from intestine to peripheral tissues and liver
What do very low density lipoprotein (VLDL) transport?
Transports endogenous
triglyceride from liver to extrahepatic tissues.
What do Low density lipoprotein (LDL) transport?
Transports cholesterol from liver to extrahepatic tissues
What do High density lipoprotein (HDL) transport?
Transports cholesterol from
extrahepatic tissues back to the liver in an esterified form
What is the effect of high consumption of saturated and trans fat?
Raise blood cholesterol levels, increasing a person’s
risk of developing heart disease.
What foods contain saturated fat?
Butter, fat on meat products. Oils like palm kernel oil and coconut oil.
What foods contain trans fats?
Pre-packaged items, like cookies, crackers and potato
chips ,many fried foods such as french fries and doughnuts.
What are the three ways fatty acids can be classified?
- Depending on the total number of carbon chains.
- Depending on the length of hydrocarbon chain.
- Depending on the nature of hydrocarbon chain.
What is classification of fatty acids based on the total number of carbon chains?
Even Chain: 2, 4, 6
Odd Chan: 3,5,7
What is classification of fatty acids based on the length of hydrocarbon chain?
Short chain: <6 carbons
Medium chain: 8-14 carbons
Long chain: 16 -24 carbons
What is classification of fatty acids based on nature of hydrocarbon chain?
Saturated: No double bonds
Unsaturated: presence of double bonds
Do saturated fatty acids have double bonds?
Examples?
No
Palmitic acid (C16),stearic acid (C18) & lignoceric acid
(C24)
Do unsaturated fatty acids have double bonds?
Examples?
Yes
Linoleic acid, linolenic acid arachidonic acid
What are fatty acids having 2 or more double bonds called?
PUFA (polyunsaturated fatty acids)
What type of configuration do all the naturally occurring edible fatty acids have
cis-configuration
How are the carbons of fatty acids numbered?
Carboxyl group carbon is C1 (-COOH)
The carbon that comes next is C2 aka alpha carbon, beta is next.
What is the last carbon
atom or methyl (CH3) group called?
omega carbon
Explain the notation in the numbering of fatty acids.
E.g oleic acid 18:1;9 or delta^9, 18:1
Fatty acid has 18 carbons
One double bond at carbon atom 9.
The position of the double can also be indicated by
the symbol delta followed by the position of the double bond in superscript.
How is the omega series numbered?
Start counting carbons from the methyl group(omega) this will be the first carbon atom
Continuing counting carbons as usual
The carbon where the first double bond is present will be the number of the series.
What are 5 benefits of omega 3 and 6?
- Improve brain function, and decreases risk of alzheimer’s
- Helps to maintain a good mood and preventing depression
- Prevention of excessive blood clotting
- Helping to prevent cancer cell growth
- By lowering the amount of fats (as cholesterol and
triglycerides) in circulation decreasing the risk of heart
disease
What are essential fatty acids of PUFA (polyunsaturated fatty acids)?
Fatty acids having 2 or more double bonds
Not synthesized in the body due to lack of the
desaturase enzyme, which introduces double bonds beyond 9th
and 10th carbon atoms.
Should be supplied through diet.
What are four functions of PUFA?
- Are required for the membrane structure and function.
- Transport of cholesterol.
- Formation of lipoproteins.
- Synthesis of Eicosanoids
What are steroids?
Found in association with lipids.
Having special ring in nucleus.
e.g steroid hormone, bile acid, vitamin D.
What is cholesterol?
Found?
Structure?
One of the important steroids present in the body.
In all cells of the body but nervous tissue is rich in cholesterol.
Has 27 carbon, an -OH group, a double bond, two methyl groups at C10 and C13 and a side chain at C17.
What are 5 functions of cholesterol?
- It is a 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.
- Form 7-dehydrocholesterol in skin, it is converted to
vitamin D3 by UV rays. - It is a poor conductor of heat and hence acts as an insulator
- Functions as an insulating covering for structure, which generates and transmits electrical impulse in brain and nervous tissue.
What is an effect of excess cholesterol in body?
It gets deposited in the intima of the arteries producing atherosclerosis. This can narrow the lumen of
blood vessel impeding blood flow, which cause thrombosis.
What is the normal fasting serum cholesterol level?
150-200 mg/dl
What is the name for Steroids containing one or more -OH groups?
Sterols
How does cholesterol get esterified?
Through esterase enzymes
How is cholesterol synthesized in the body?
Using acetyl CoA as precursor
