NEET MDS Lessons
Biochemistry
BIOLOGICAL ROLES OF LIPID
Lipids have the common property of being relatively insoluble in water and soluble in nonpolar solvents such as ether and chloroform. They are important dietary constituents not only because of their high energy value but also because of the fat-soluble vitamins and the essential fatty acids contained in the fat of natural foods
Nonpolar lipids act as electrical insulators, allowing rapid propagation of depolarization waves along myelinated nerves
Combinations of lipid and protein (lipoproteins) are important cellular constituents, occurring both in the cell membrane and in the mitochondria, and serving also as the means of transporting lipids in the blood.
CHOLESTEROL AND ITS IMPORTANCE
Cholesterol is an important lipid found in the cell membrane. It is a sterol, which means that cholesterol is a combination of a steroid and an alcohol .
It is an important component of cell membranes and is also the basis for the synthesis of other steroids, including the sex hormones estradiol and testosterone, as well as other steroids such as cortisone and vitamin D.
In the cell membrane, the steroid ring structure of cholesterol provides a rigid hydrophobic structure that helps boost the rigidity of the cell membrane.
Without cholesterol the cell membrane would be too fluid. In the human body, cholesterol is synthesized in the liver.
Cholesterol is insoluble in the blood, so when it is released into the blood stream it forms complexes with lipoproteins.
Cholesterol can bind to two types of lipoprotein, called high-density lipoprotein (HDL) and low-density lipoprotein (LDL).
A lipoprotein is a spherical molecule with water soluble proteins on the exterior. Therefore, when cholesterol is bound to a lipoprotein, it becomes blood soluble and can be transported throughout the body.
HDL cholesterol is transported back to the liver. If HDL levels are low, then the blood level of cholesterol will increase.
High levels of blood cholesterol are associated with plaque formation in the arteries, which can lead to heart disease and stroke.
FLUORIDE
The safe limit of fluorine is about 1PPM in water. But excess of fluoride causes Flourosis
Flourosis is more dangerous than caries. When Fluoride content is more than 2 PPM, it will cause chronic intestinal upset, gastroenteritis, loss of weight, osteosclerosis, stratification and discoloration of teeth
Titration of a weak acid with a strong base
• A weak acid is mostly in its conjugate acid form
• When strong base is added, it removes protons from the solution, more and more acid is in the conjugate base form, and the pH increases
• When the moles of base added equals half the total moles of acid, the weak acid and its conjugate base are in equal amounts. The ratio of CB / WA = 1 and according to the HH equation, pH = pKa + log(1) or pH = pKa.
• If more base is added, the conjugate base form becomes greater till the equivalance point when all of the acid is in the conjugate base form.
Amino acids
Proteins are linear polymers of amino acids. Participate in virtually every biological process. Perform diverse functions:
1. Enzymes: catalyze all reactions in living organisms
2. Storage and transport
3. Structural
4. Mechanical work ( flagella, muscles, separation of chromosomes)
5. Decoding information (translation, transcription, DNA replication)
6. Cell-signalling (hormones and receptors)
7. Defence (antibodies)
HORMONES
A hormone is a chemical that acts as a messenger transmitting a signal from one cell to another. When it binds to another cell which is the target of the message, the hormone can alter several aspects of cell function, including cell growth, metabolism, or other function.
Hormones can be classified on three primary ways as following:
1. Autocrine: An autocrine hormone is one that acts on the same cell that released it.
2. Paracrine: A paracrine hormone is one that acts on cells which are nearby relative to the cell which released it. An example of paracrine hormones includes growth factors, which are proteins that stimulate cellular proliferation and differentiation.
3. Endocrine: An endocrine hormone is one that is released into the bloodstream by endocrine glands. The receptor cells are distant from the source. An example of an endocrine hormone is insulin, which is released by the pancreas into the bloodstream where it regulates glucose uptake by liver and muscle cells.
Polyprotic Acids
• Some acids are polyprotic acids; they can lose more than one proton.
• In this case, the conjugate base is also a weak acid.
• For example: Carbonic acid (H2CO3 ) can lose two protons sequentially.
• Each dissociation has a unique Ka and pKa value.
Ka1 = [H+ ][HCO3 - ] / [H2CO3]
Ka2 = [H+ ][CO3 -2 ] / [HCO3- ]
Note: (The difference between a weak acid and its conjugate base differ is one hydrogen)