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Lecture 1
Energy balance & caloric value of food By Dr. Doaa samy
Metabolism
Metabolism means literally change. It is used to refer to all chemical and energy transformations that occur in the body to continue living . It is divided into 2 major processes:
Anabolism Catabolism
Energy transfer
energy liberated by catabolism
Energy transfe r
High energy compounds
High energy compounds
High energy phosphate Compounds
adenosine triphosphate (ATP), creatine phosphate (CP), others.
ATP
Structure of ATPadenosine Pi Pi Pi
ATP ATP
ADP
AMP
12 Kcal
12 Kcal
ATP is present everywhere in the cytoplasm and nucleoplasm of all cells.
ATP ATP
ADP
AMP
12 Kcal
12 Kcal
Creatine phosphate (CrP)
This compound contains a high energy bond which upon hydrolysis liberates about 13Kcal/mole However, this energy cannot be used directly by the cells. It is used to reform ATP from ADP.
Also , when extra amounts of ATP are available, much of its energy is used to reform creatine phosphate.
Creatine phosphate (CrP)
CrP CrP + ADP
Cr + Pi + energy ATP + Cr
CrP is 3-8 times as abundant as ATP
Units used to measure heat energy
calorie (cal, with a small c): It is the amount of heat energy necessary to raise the temperature of 1 gram of water, 1 degree, from 15 degrees centigrade to 16 degrees centigrade. The kilocalorie (Kcal, Calorie, with a capital C). It equals 1000 cal. It is the unit commonly used in physiology and in medicine.
Energy balanceIn the body, there is an energy balance between the caloric intake and the energy output
intake
output
Energy balance
caloric intake
>
energy output
=
Positive energy balance
the individual gains weight
Energy balance
caloric intake