How the lipids absorbed in intestine ?

In order for the body to make use of dietary lipids, they must first be absorbed from the small intestine. Since these molecules are oils, they are essentially insoluble in the aqueous environment of the intestine. The solubilization (or emulsification) of dietary lipids is therefore accomplished by means of bile salts, which are synthesized from cholesterol in the liver and then stored in the gallbladder; they are secreted following the ingestion of fat.

The emulsification of dietary fats renders them accessible to pancreatic lipases (primarily lipase and phospholipase A₂; PLA₂). These enzymes, secreted into the intestine from the pancreas, generate free fatty acids and a mixtures of mono- and diacylglycerols from dietary triacylglycerols. Pancreatic lipase degrades triacylglycerols at the 1 and 3 positions sequentially to generate 1,2-diacylglycerols and 2-acylglycerols. Phospholipids are degraded at the 2 position by pancreatic PLA₂ releasing a free fatty acid and the lysophospholipid. The products of pancreatic lipases then diffuse into the intestinal epithelial cells, where the re-synthesis of triacyglycerols occurs.

Dietary triacylglycerols and cholesterol, as well as triacylglycerols and cholesterol synthesized by the liver, are solubilized in lipid-protein complexes. These complexes contain triacylglycerol lipid droplets and cholesteryl esters surrounded by the polar phospholipids and proteins identified as apolipoproteins. These lipid-protein complexes vary in their content of lipid and protein.

Theories Contributing to Modern Biology

Modern biology is based on several great ideas, or theories:

• The Cell Theory
• The Theory of Evolution by Natural Selection
• Gene Theory
• Homeostasis

Robert Hooke (1635-1703), one of the first scientists to use a microscope to examine pond water, cork and other things, referred to the cavities he saw in cork as "cells", Latin for chambers. Mattias Schleiden (in 1838) concluded all plant tissues consisted of cells. In 1839, Theodore Schwann came to a similar conclusion for animal tissues. Rudolf Virchow, in 1858, combined the two ideas and added that all cells come from pre-existing cells, formulating the Cell Theory. Thus there is a chain-of-existence extending from your cells back to the earliest cells, over 3.5 billion years ago. The cell theory states that all organisms are composed of one or more cells, and that those cells have arisen from pre-existing cells.

Figure : James Watson (L) and Francis Crick (R), and the model they built of the structure of deoxyribonucleic acid, DNA. While a model may seem a small thing, their development of the DNA model fostered increased understanding of how genes work. Image from the Internet.

In 1953, American scientist James Watson and British scientist Francis Crick developed the model for deoxyribonucleic acid (DNA), a chemical that had (then) recently been deduced to be the physical carrier of inheritance. Crick hypothesized the mechanism for DNA replication and further linked DNA to proteins, an idea since referred to as the central dogma. Information from DNA "language" is converted into RNA (ribonucleic acid) "language" and then to the "language" of proteins. The central dogma explains the influence of heredity (DNA) on the organism (proteins).

Homeostasis is the maintenance of a dynamic range of conditions within which the organism can function. Temperature, pH, and energy are major components of this concept. Thermodynamics is a field of study that covers the laws governing energy transfers, and thus the basis for life on earth. Two major laws are known: the conservation of matter and energy, and entropy. These will be discussed in more detail in a later chapter. The universe is composed of two things: matter (atoms, etc.) and energy.

These first three theories are very accepted by scientists and the general public. The theory of evolution is well accepted by scientists and most of the general public. However, it remains a lightening rod for school boards, politicians, and television preachers. Much of this confusion results from what the theory says and what it does not say.

Indian Nobel Prize Winners in science

India has its own share of Nobel Prize winners over the decades in several fields. The Nobel Prize is the most respected award the world over and here is a list of those Indians who have won this award and made the country proud.

Sir Chandrasekhar Venkata Raman (C.V. Raman)-Nobel Prize for Physics (1930)

C V Raman was born in Thiruvanaikkaval, in the Trichy district of Tamil Nadu. He was the first Asian scientist to win the Nobel Prize.he was awarded the Nobel Prize in Physics in 1930 for his discovery of “RAMAN effect”.Raman effect is useful in the study of molecular energy levels, structure development, and multi component qualitative analysis.

Venkatraman Ramakrishnan –Nobel Prize for Chemistry (2009)

Born in Chidambaram, Tamil Nadu in 1952.He was awarded Nobel Prize in Chemistry in 2009. He is a structural biologist who received the Nobel Prize for his studies in the structure and function of the ribosome.

Dr. Har Gobind Khorana –Nobel Prize for Medicine and Physiology (1968)

He was born in 1922 in Raipur in Punjab of eastern Pakistan. He was awarded the Nobel Prize in Medicine in 1968 for producing the first man-made gene in his laboratory in the early seventies. His discovery won him the Nobel Prize sharing it with Marshall Nuremberg and Robert Holley for interpreting the genetic code and analyzing its function in protein synthesis.

Dr. Subramanyan Chandrasekhar – Nobel Prize for physics (1983)

He was born on October 19, 1910 in Lahore, India (now part of Pakistan) in a Tamil hindu family. He was awarded the Nobel Prize in 1983 for Physics. He was recognized for his theoretical studies of the physical processes of importance to the structure and evolution of stars.

Sir Ronald Ross –Nobel Prize for Physiology (1902)

 
He was a Scottish physician who was born in Almora in India in 1857. Though he finished his education in England, Ross had also spent a number of years in India while he was making progress in his search for his discovery of the malarial parasite and its prevention. He was awarded by Nobel prize in 1902 for his work on malaria.