Medical Chemistry

Medical Chemistry Lecture By : Asst. Lect. Tariq Al Mgheer College of Medicine- Babylon University

of its position. For example, water at the top of a waterfall has potential energy as a result of its position above the surface of the earth. An object has kinetic energy as a result of its motion. A moving car and an airplane in flight all have kinetic energy. Chemical energy is the energy stored in the molecule as a result of the kinds and positions of its atoms. Atomic or nuclear energy is associated with the structure of atoms. Radiant energy is the energy of light.
The energy of any object changes whenever it undergoes a chemical reaction or physical change. This energy change occurs by transferring energy. For example, part of the energy of wood is transferred to the surrounding air when it is burned. The energy is transferred by several methods. Four of the most common are work, heat, sound, and light These are all visible signs of a transfer of energy.
It is important to realize that, although a substance may contain energy, it never contains heat or work. Heat and work are evident only when the energy of the material changes and a transfer of energy occur. The terms heat content and work content of substances are often used. These terms mean that the change in energy of a substance will occur in the form of heat or work.
Chemical reactions involved in our body also demonstrate the transfer of energy. The food we eat provides the energy that allows our bodies to carry out the normal work of contraction and motion Food also provides us with heat to maintain a constant body temperature. Food undergoes a series of chemical reactions in our bodies that result in the transfer of part of the chemical energy to muscles to do work and to the surroundings as heat.

UNITS OF ENERGY
Heat is one of the most easily measured forms of energy. The most common unit of measurement of heat is the calorie. Its symbol is cal. A calorie is defined as the amount of heat needed to raise the temperature of 1 g of water from 14.5° to 15.5° C. Although is the exact definition of a calorie, approximately 1 calorie is needed to raise the temperature of 1 g of water by 1° C at any temperature between 0 and 70° C. Most chemical reactions release several thousand calories; as a result, quantities of heat are usually reported as kilocalones (1 kcal = 1000 cal). The Sl unit of energy is the joule. Its symbol is J There are exacdy 4.184 J in 1 cal. Be careful in using the calorie as a unit, because there are actually two calories in use:
the one defined above, and the Calorie (with a capital C), used in nutrition. One Calorie is equal to 1 kcal.
EXARCISE: How much heat, in cai and kcal, is needed to raise the temperature of 1000