There are some basic essential activities performed by an organism to survive, these processes are called life processes, or these may be called basic functions performed for the survival of organisms. The life processes are respiration, nutrition, transportation, excretion, control, and coordination.
Life processes are the main criteria to decide whether something is alive or not. If someone is performing life processes can be called alive. i.e. breathing, movement, nutrition, excretion, etc.
Life processes can be categorized as–
Some others which are may or may not be seen in some organisms like plant and microscopic organisms as
Nutrition In Organisms
Nutrition in organisms: Every organism needs energy to perform their life processes, and these energies are acquired by proteins and ATP formation, for this we need raw material in the form of food.
So food is the source of energy by which we get energy. This is different in plants and animals as Plants manufacture their own food by photosynthesis, but animals including humans have to take in ready-made food.
The process by which organisms obtain and utilize food for their growth, development, and maintenance is called nutrition and the chemical substances present in the food are called nutrients. There are six basic components of nutrients: carbohydrates, proteins, fats, vitamins, minerals, and water.
Two types of nutrition: Autotrophic nutrition and heterotrophic nutrition.
|Autotrophic nutrition||Heterotrophic nutrition|
|(AUTO: self, TROPHOS: food)||(Hetero: different, Trophos: food)|
|Green plants and certain bacteria manufacture their own food (organic substances) from inorganic substances like CO2 and H2O using energy from sunlight||Food – Organic and inorganic substances obtained by feeding on other organisms are called heterotrophic. In other words, the organisms cannot produce their food and are dependent on others.|
In autotrophic nutrition, the food is synthesized by the organism itself, and in the process of food production photosynthesis takes place in the presence of sunlight and carbon-di-oxide with the help of chlorophyll.
With the help of chlorophyll, carbohydrates are produced as the product of photosythesis. The remaining carbohydrates which are not utilized by the plant, are stored in the form of starch. The starch serves as the internal energy reserve to be used as and when required by the plant.
Process photosynthesis– These are the events that occur during photosynthesis
- Chlorophyll Absorbs of light energy.
- Conversion of light energy into chemical energy and water molecules splits into hydrogen and oxygen.
- Reduction of carbon dioxide to carbohydrates.
In the whole process of photosynthesis chlorophyll, water, carbon-di-oxide and sunlight are the essential elements. Water for photosynthesis is taken from the soil by the roots in terrestrial plants, from soil other important materials like nitrogen, phosphorus, iron, and magnesium are taken.
As we know nutrition differs depending on the type and availability of food materials as well as how it organism obtains that food.
- In single-celled organisms, the food may be taken in by the entire surface. But as the organism becomes complex, different parts become specialized to perform different functions.
- For example, Amoeba takes food in using temporary finger- Food particles such as minute bacteria are enclosed (caught) by pseudopodia (pseudo = false, podia = feet) to form a food vacuole (Ingestion).
Types of heterotrophic nutrition
- Holozoic– Organisms engulf food into the body, digest it and absorb the soluble products of digestion, e.g. humans.
- Saprophytic– Organisms secrete digestive enzymes onto dead organic material and absorb the products of digestion, e.g. certain bacteria and fungi.
- Parasitic– Food is derived from other living organisms by living on or inside their body e.g., certain bacteria, roundworm, tapeworm, Cuscuta, etc.
Nutrition in human
The digestive system of humans consists of an alimentary canal which is associated with digestive glands.
The human alimentary canal is a continuous muscular digestive tube that runs through the body. It opens at two ends with openings, which are the mouth at the anterior, and anus at the posterior end.
- The digestion in humans takes place through various organs by many processes.
Organs associated with the human digestive system
Having associated organs (teeth, tongue)- Minute quantities of water, water-soluble vitamins, and simple sugars like glucose (as in honey) are absorbed in the mouth. Saliva contains only a single enzyme Amylase (old name Ptyalin) which acts on starch.
2. Pharynx (or throat):
A cavity inside of the mouth. It is a common passage for the inhaled air and swallowed food.
A narrow tube arising from the pharynx, continuing through the thorax and ending in the stomach, food moves in the stomach through the esophagus in the form of the bolus through the movement of peristalsis. These peristaltic movements occur all along the gut.
- An elastic bag-like structure with highly muscular walls, located below the diaphragm.The muscular walls of the stomach help in mixing the food thoroughly with more digestive juices.
- The stomach churns the food mixing it with gastric juice and thus produces a creamy chyme (partially digested food). It contains Water (98%), some salts, hydrochloric acid (0.5%), lubricant mucin, and two enzymes pepsin. Water, glucose, ethanol (alcohol), certain minerals, vitamins, and certain drugs may be absorbed into the cells lining the stomach.
- This absorption occurs by osmosis, diffusion (down the concentration gradient), and active transport (against a concentration gradient
5. Small intestine:
- It is the longest part of the alimentary canal, a tube about 7 meters long and about 2.5 cm wide.
- The exit of food from the stomach is regulated by a sphincter muscle which releases it in small amounts into the small intestine. From the stomach, the food now enters the small intestine.
- The small intestine is the site of the complete digestion of carbohydrates, proteins, and fats. The liver and pancreas help the small intestine for digestion by their juices, pancreatic enzyme makes the food alkaline, as it was acidic from the stomach.
- Bile juice comes from the liver which acts on fats as, by the help of bile, fat molecules break in small globules, and enzymes work on it effectively.
- pancreatic juice contains enzymes like trypsin for digesting proteins and lipase for breaking down emulsified fats. The enzymes present in it finally convert the proteins to amino acids, complex carbohydrates into glucose, and fats into fatty acids and glycerol.
- Many folds (finger-like projection) in its wall called villi (singular, villus) further increase the surface area of absorption,
- The epithelial cells have microvilli which are projections of the plasma membrane to further increase the absorptive surface.
- It is narrow for the slow movement of nutrients allowing absorption.
- Nutrients absorbed into the blood is carried by veins into the liver, and the nutrients absorbed by the lacteals (small lymph vessels) enter the lymphatic system.
The three subdivisions of the small intestine are:
(I) Duodenum–Short upper part, next to the stomach
(ii) Jejunum–Slightly longer part, about 2 meters long.
(iii) Ileum–Longest, about 4 meters long, coiled and twisted.
6. Large Intestine: About 1.5 meters long, It has three parts:
(i) Caecum–Small blind pouch found at the junction of the small and large intestine. A narrow worm-shaped tube (vermiform appendix) projects from the caecum.
(ii) Colon: A little over 1-meter-long, it has three parts termed ascending, transverse, and descending limbs of the colon.
(iii) Rectum: Last part, about 15 cm. long. It has two parts, the rectum proper and the anal canal. The anus is the external opening surrounded by circular muscles (sphincters).
Most of the water present in the food is absorbed in the colon by diffusion. Unabsorbed food sent here, some mineral ions are absorbed by the colon through active transport, rest material is removed from here through the anus.
Note- The vermiform appendix is a vestigial (functionless) organ in humans, but is large and functional in herbivorous mammals.
1.Parotid glands- located in front of and below each ear, produces watery saliva rich in amylase
2.Submaxillary glands– close to the inner side of the lower jaw, produce water and mucus
3.Sublingual glands –below the tongue, produce water and mucus.
4.Liver–Liver is the largest gland, located in the upper right side of the abdomen below the diaphragm. It secretes bile.
5.Pancreas-located in the bend of the duodenum. Its digestive secretion (pancreatic juice) is poured into the duodenum by the pancreatic duct.
Some enzymes and their role in indigestion-
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