📚 NEET MDS Lecture Notes
CLASSIFICATION OF LIPIDS
BiochemistryCLASSIFICATION OF LIPIDS
Lipids are classified as follows:
1. Simple lipids: Esters of fatty acids with various alcohols.
(a) Fats: Esters of fatty acids with glycerol. Oils are fats in the liquid state. A long-chain carboxylic acid; those in animal fats and vegetable oils often have 12–22 carbon atoms.
(b) Waxes: Esters of fatty acids with higher molecular weight monohydric alcohols. Waxes are carboxylic acid esters, RCOOR’ ,with long, straight hydrocarbon chains in both R groups
2. Complex lipids: Esters of fatty acids containing groups in addition to an alcohol and a fatty acid.
(a) Phospholipids: Lipids containing, in addition to fatty acids and an alcohol, a phosphoric acid residue. They frequently have nitrogen containing bases and other substituents,
Eg glycerophospholipids the alcohol is glycerol
sphingophospholipids the alcohol is sphingosine.
(b) Glycolipids (glycosphingolipids): Lipids containing a fatty acid, sphingosine, and carbohydrate. These lipids contain a fatty acid, carbohydrate and nitrogenous base. The alcohol is sphingosine, hence they are also called as glycosphingolipids. Clycerol and phosphate are absent
e.g., cerebrosides, gangliosides.
(c) Other complex lipids: Lipids such as sulfolipids and aminolipids. Lipoproteins may also be placed in this category.
3. Precursor and derived lipids: These include fatty acids, glycerol, steroids, other alcohols, fatty aldehydes, and ketone bodies, hydrocarbons, lipid soluble vitamins, and hormones. Because they are uncharged, acylglycerols (glycerides), cholesterol, and cholesteryl esters are termed neutral lipids
4. Miscellaneous lipids: These include a large number of compounds possessing the characteristics of lipids e.g., carotenoids, squalene, hydrocarbons such as pentacosane (in bees wax), terpenes etc.
NEUTRAL LIPIDS: The lipids which are uncharged are referred to as neutral lipids. These are mono-, di-, and triacylglycerols, cholesterol and cholesteryl esters.
Fatty Acid Synthesis
BiochemistryThe input to fatty acid synthesis is acetyl-CoA, which is carboxylated to malonyl-CoA.
The ATP-dependent carboxylation provides energy input. The CO2 is lost later during condensation with the growing fatty acid. The spontaneous decarboxylation drives the condensation.
fatty acid synthesis
acetyl-CoA + 7 malonyl-CoA + 14 NADPH → palmitate + 7 CO2 + 14 NADP+ + 8 CoA
ATP-dependent synthesis of malonate:
8 acetyl-CoA + 14 NADPH + 7 ATP → palmitate + 14 NADP+ + 8 CoA + 7 ADP + 7 Pi
Fatty acid synthesis occurs in the cytosol. Acetyl-CoA generated in the mitochondria is transported to the cytosol via a shuttle mechanism involving citrate
Drugs Used in Diabetes -pramlintide -Amylin mimetics
Pharmacology
Pramlintide -Amylin mimetics
Mechanism
synthetic analogue of human amylin that acts in conjunction with insulin
↓ release of glucagon
delays gastric emptying
Clinical use
type I and II DM
Cytopathologic techniques
General PathologyCytopathologic techniques
Cytopathology is the study of cells from various body sites to determine the cause or nature of disease.
Applications of cytopathology:
- Screening for the early detection of asymptomatic cancer
2. Diagnosis of symptomatic cancer
3. Surveillance of patients treated for cancer
Cytopathologic methods
There are different cytopathologic methods including:
1. Fine-needle aspiration cytology (FNAC) -In FNAC, cells are obtained by aspirating the diseased organ using a very thin needle under negative pressure.
Superficial organs (e.g. thyroid, breast, lymph nodes, skin and soft tissues) can be easily aspirated.
Deep organs, such as the lung, mediastinum, liver, pancreas, kidney, adrenal gland, and retroperitoneum are aspirated with guidance by fluoroscopy, ultrasound or CT scan.
- Exfoliative cytology
Refers to the examination of cells that are shed spontaneously into body fluids or secretions. Examples include sputum, cerebrospinal fluid, urine, effusions in body cavities (pleura, pericardium, peritoneum), nipple discharge and vaginal discharge.
- Abrasive cytology
Refers to methods by which cells are dislodged by various tools from body surfaces (skin, mucous membranes, and serous membranes). E.g. preparation of cervical smears with a spatula or a small brush to detect cancer of the uterine cervix at early stages.