All chemical changes occurring in a living cell are called metabolism. Metabolism may be anabolism or catabolism. Anabolism is the process of synthesis of complex chemical molecule from simpler ones. Photosynthesis is an example of anabolism. Catabolism is the process of breaking down of a large and a complex molecule into the simple form. Respiration and digestion are the example of catabolism .
Anabolism
and catabolism together are called metabolism . Anabolism is called a
constructive process and catabolism is called the destructive process. Metabolism
is indicated by the following processes taking places in the body.
a. Formation of the necessary cells and
tissues takes place in the body as a
result of the chemical reaction of various nutritious food.
b. The blood cells and tissues become useless in the body .
Nutrition in
the Human body:
Human beings
like other animals are unable to prepare their own food so, the nutrition in
the human beings is heterotropic. The human being depend on plants directly or
indirectly for their food.
Digestive
System in Human:
Digestion is
a catabolic process or the process of breaking down of complex food materials
into simple forms which can be directly
absorbed by the body. The organs concerned with digestion is called digestive
system. The digestive system of human body consist of mouth, alimentary canal
and the anus.
Mouth:
It is an
opening through which food is taken inside the body. The food mixes with saliva
inside the mouth and here the mechanical break down food occurs by the help of
teeth and tongue. Saliva contains the enzyme ptyalin which helps to break down
the carbohydrate partially to the glucose.
Alimentary
Canal:
The
alimentary canal is basically a long tube extending from the mouth to anus. It
is necessary to move the foods in a regulated manner along the digestive tube
so that it can be processed properly in each part . The linings of canal have muscles that contract
rhythmically in order to puss the food forward. These peristaltic movements
occur all along the gut. Alimentary canal has the following parts:
a. Food pipe or oesophagus
b. Stomach
c. Small intestine
d. Large intestine
e. Anus
Food Pipe or
Oesophagus:
The food
after chewing in the mouth passes to stomach through the food pipe or
oesophagus.
Stomach:
The stomach
is a large organ which expands when the food enters in it. The muscular walls
of stomach helps in mixing the food thoroughly with more digestive juices. The
digestive functions are carried out by the gastric glands present in the wall
of stomach. The gastric gland release:
a. Hydrochloric acid
b. A protein digesting enzyme called
protein
c. Mucus
The hydrochloric acid creates an acidic medium which
facilates the action of enzyme pepsin. It also kills the bacteria present in
the food.
