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