Notes prepared by
Ashaq Hussain Bhat
Teacher Education
Department
Jammu And Kashmir
LIFE PROCESSES
AN INTRODUCTION
It is really very difficult to distinguish a living organism from a non-living object and it is equally difficult to give a proper definition of life. If we see a frog jumping, or a monkey eating fruits, or the children playing in the park, we know that these are living beings. We come to know this on the basis of
some assumptions in our mind. We have certain criteria to assign an object as living or as non-living. Those criteria are, infact, the characteristic features of living beings. We know that plants do not jump, or ent fruits, or shout or play in the parks. But still, they are living beings because they possess the characteristic features of living organisms. Viruses, on the other hand, do not show any characteristic feature of living beings when remain outside the host. They are, therefore, regarded as non-living particles. The same non-living particles of viruses become active and start their molecular movements and other features of living organisms when reach inside the host cells. It is because of this dual nature, they are considered as connecting links between living and non-living. There is a controversy about whether viruses are alive or not. On the basis of the characteristic features of living beings a definition of living things may be given as follows:
“Living things are complex organisations of molecules, which perform certain life processes such as growth, metabolism, reproduction, etc., that distinguish them from non-living matter."
WHAT ARE LIFE PROCESSES ?
All living organisms perform some basic functions or processes in order to remain alive. These processes are needed for the maintenance of their bodies and catching to their daily activities. Some of these processes continue to occur even when the organisms are not doing any activities. The maintenance processes continue to occur even when we are just sitting sleeping. This is because when we are asleep, a large number of biological processes continue to occur which require energy. All the processes which together keep the living organisms alive and perform the job of body maintenance are called life processes.
SOME IMPORTANT LIFE PROCESSES
NEEDED FOR LIVING
1. Nutrition. It is a process by which the organisms obtain and utilise the nutrients (food). These nutrients are the source of energy which come from outside the body of the individual organism. Since the life on earth depends mainly on carbon-based molecules (e.g., carbohydrates, proteins, fats, etc.), most of these nutrients are also carbon based. Nutrition of different organisms involves different processes. Plant nutrition involves the process of photosynthesis in which the green plants synthesize carbohydrates with the help of carbon dioxide and sunlight Animal nutrition involves taking of food inside the body and its digestion.
2. Respiration. It is a process that involves breakdown of nutrients through oxidation and release of energy for cellular needs. For this, many organisms take oxygen from outside the body
3. Transport. In the case of single-celled organisms (e.g., Amoeba), no specific organs for getting nutrients, oxygen, water or removal of wastes are needed because the entire body surface of such organisms remains in contact with the environment. They enter into the cell by simple diffusion. However, in case of multicellular organisms like humans and higher plants, simple diffusion is not sufficient to meet the oxygen and nutritional requirement of all the cells. Such organisms develop specific organs and tissues for transportation of materials from one part of the body to another part. This process is called transport.
4. Excretion. The biochemical reactions involved in assimilation of carbon dioxide, digestion of nutrients and oxidation of digested nutrients generate some by-products which are not only useless for the cells, but also cause toxic effects if not thrown out. Removal of the excess or toxic wastes from the body is called excretion and the system consisting of tissues and organs related with excretion is called excretory system. detail.
NUTRITION
All living organisms need nutrients (food) to build up most of their own body molecules and to get energy for doing work. Nutrients are inorganic as well as organic substances which the organisms obtain from their surroundings in order to synthesize their body constituents and use them as a source of energy.
Nutrition ( word was derived from the term nutrient) is defined as the process of intake of nutrients and its utilization by an organism in various biological activities.
MODES OF NUTRITION
Autotrophic nutrition:
It is that type of nutrition in which an organism prepares own food material from some simple inorganic substances like water and carbon dioxide (CO2) in presence of sunlight and chlorophyll by a process known as photosynthesis. The organisms which adopt this mode of nutrition are called autotrophs. All plastid bearing plants and some bacteria like sulphur bacteria are considered as autotrophs.
Heterotrophic nutrition:
It is that type of nutrition in which an organism depends on another organism (plant or animal) for its food supply. The organisms which adopt this mode of nutrition are called heterotrophs. All animals' non green plants like fungi and some parasitic plants like Cuscutta plants are considered as heterotrophs.
TYPES OF HETEROTROPHIC NUTRITION
On the basis of the mode of obtaining food, heterotrophic nutrition has been divided into the following types:
1. Saprozoic nutrition. It is that type of Heterotrophic nutrition in which an organisin obtains its food from dead and decaying organic matter. The organisms which adopt this mode of nutrition are called S'apro-boints. These organisms secret some enzymes which act upon the dead and decaying organic matter and convert it into simple and soluble form and then use it. Agricus Compestris, Rhizopus, Mucor and some bacteria are the various examples of Sapro-boints.
2. Parasitic nutrition: It is that type of heterotrophic nutrition in which an organism obtains the food which is already prepared in the body of the host. The organism which adopts this mode of nutrition is called parasite and the one from which from material is obtained is called the host. Tape worm, Round worm, louse. Cuscutid plant are some of the examples of parasites.
3. Symbiotic nutrition: It is that type of heterotrophic nutrition in which two interdi- pendent members come close to each other and form a type of association called symbiotic association and then shares the nutrien themselves. One of the partners provides one nutrient and gets the other nutrients from the other partner. Lichen is a best example of symbiotic nutrition. Fungi and algae are the two partners in this association.
4. Holozoic nutrition: In this type of heterotrophic nutrition, food is first ingested, digested then absorbed and finally the undigested food is egested out from the body though anus. The various examples loft e organisms which undergo holozoic nutrition are man, dog, cat, sheep ete.
STEPS INVOLVED IN DIGESTION OF FOOD IN HUMAN BEINGS
(1.) Ingestion. The process of intake of food by an organism is called ingestion, Ingestion takes place differently in different organisms e.g, in unicellular organisms like Amoeba,.food is ingested at any place on the body surface as there is no special opening. In multicellular, food is ingested through a special opening called mouth,
(2) Digestion:- Digestion involves physical and chemical break down of complex, non diffusible food materials into simple soluble food materials. Digestion of food starts in oral cavity continues in stomach and is finally completed in small intestines. In the buccal cavity food mixes with saliva secreated by salivary glands which contains enzymes namely ptylin' or 'salivary amylase and maltase. These enzymes convert starch into glucose. The partially digested food called "bolus" enters into the stomach. In the stomach, food is treated mechanically by peristalatic movements and chemically by gastric juice. Gastric juice contains Hcl, and enzymes like pepsin, rennin etc. the HCl provides acidic medium for the action of enzymes. The enzyme pepsin converts proteins into peptones and proteoses, while as enzyme renin converts milk into curd. The churned food called chyme passes from stomach into small intestines. In small intestines the chyme is treated with secreation of pancrease, liver and intestinal glands These glands release enzymes like trypsin,carbohydrases, lipase etc.
Tryprin converts proteins into peptones and then peptones into aminoacids while as carbohydrases convert starch into glucose. Lipases converty fats into fatty acids and glycerol. In the small ihtestines the food changes into diffusible form called chyle. So during digestion, carbohydrates are converted into glucose, proteins into aminoacids and fats into fatty acids and glycerol.
(3)Absorption:-
Diffusion of digested food through the walls of alimentary canal into the blood is called absorption The digested food is absorbed mainly in small intestines. The inner surface of small intestines is provided with millions of fingers like projection called villi. The villi increases the surface area of small intestines through which absorption of digested food takes place. Each villus has lymph vessel in the centre called Lacteal, which is surrounded by a network of capillaries, which in turn is surrounded by a layer of epithelial cells. Digesied lipids are absorbed into lacteal while as sugar, and amino acids, are absorbed by blood capillaries.
(4) Assimilation: -
Convertion of digested glucose into living protoplasm is called assimilation .The blood caries digested food to all parts of the body where it becomes assimilated in to the cells. In the cells, most of the glucose is oxidized to release energy required for various metabolic activities. The remaining glucose is converted in to glycogen which is in liver and muscle cells. The glycogen can be used as source of energy by the body and when required. The amino acids are converted into proteins while as fatty acids and glycerol is converted into fats.
(5) Egestion :-
Removal of undigested food out of the body is called egesting. In human beings it is carried out by large intestines. In large intestines water is absorb into the blood, thus concentrating chyle into semi-solid faeces, Which is passed out the body through the anus by the relaxation of sphincter muscles.. .
DIGESTIVE SYSTEM IN HUMAN BEINGS
All the organs in the body of man that help in nutrition collectively constitute the digestive system it can be divided in to two parts
(1)Alimentary Canal.
(2) Digestive glands.
(1) Alimentary canal -
Alimentary canal in man is a long tube about 22 feet in length and is highly coiled, muscular structure starts from mouth and terminates as anus. It isdifferentiated in to into 8 parts:
(1) Mouth
(II) Buccal cavity
(III) Pharynx
(IV) Oesophagus
(V) Stomach
(VI) Small intestine
(VII) Large intestine.
(VIII) Anus
(i) . Mouth:- The slit between two lips is called mouth. The lips prevent the loss of food from the buccal cavity during Mestication of food
(ii) . Buccal Cavity or Oral Cavity: it is the large cavity bounded above by palate on the lower side by throat & the lateral walls formed by the jaws. The jaws bear teeth. The teeth are 32 in number in an adult human being.
(iii)Tongue: Tongue is a muscular sense organ. It is attached at the posterior end with throat and free in the front .Tongue contains papillae and taste buds. The tongue is essential for mastication, speech and secretion of mucous.
.(iv) Pharynx : - The pharynx is about 12cm-14cm long funnel shaped vertical canal. it serves as passage for iood from the cavity to oesophagus. It is commonly called the throat.
(V) . Oesophagus: - The oesphagus is also called food pipe. It is about 25cm long muscular narrow track which lies behind the trachea and heart. The oesophagus opens into the stomach. The junction of Oesophagus & stomach is called cardiac oriface. It is guarded by cardiac sphincter. The oesophagus passes food from pharynx to stomach.
(VI) Stomach: - The stomach is 'J' shaped muscular sac present on the left side of the
abdomen. The stomach has three regions namely Fundus, Body and Pylorus. The
posterior end of stomach opens into small intestines by pyloric oriface & is guarded by
pyloric sphincter
(VII) Small intestine: It is the narrow tube measuring about (25 feet) and arises from
pyloric part of stomach Small intestine is differentiated into three parts.
a) Duodenum -
b) Jejunum
c) Illeum.
(a) Duodenum:- The stomach opens into 'C' shaped narrow tube measuring about
25cm. Duodenum receives pancreatic juice from panceraes and bile from liver
through the common duct called as hepato pancreatic duct.
(b) Jejunum: It is the middle part of small intestines that measures about two
meters in length.
( c) Illeum:- It is the last part of small intestine measuring about 3-3.5 meters long
The mucous membrane of intestines is produced into numerous finger like projection called villi, there are about 50 lacs villi, in human intestine. These villi, increasey the surface area of the small intestine for absorption of food.
(VIII) Large intestines
The illeum enters into wide tube called large intestine that measures about 1.5 meters
it is differentiated into 3 parts.
a. Caecum
b. Colon
c. Rectum.
(a) Caecum:- Small almost rounded blind sac measues about 6 cm. from caecum arises
a blind worm like structure called vermiform appendix, Which measures about 3-8cm.
(b) Colon:- Is largest part of large intestines and is divided into four regions they are:
Assending Colon, Transverse Colon, Descending colon &Sigmoid colon.
(c) Rectum:- It is “S” shaped tube measuring about 12cm that opens to outside as anus.
(IX) Anus:- Opening of alimentary canal at lower end is called anus. It is bounded by
anal sphincter. Anus is meant for passing out faeces.
(2) Digestive Glands
The glands which are associated with alimentary canal and 'secrentsisome enzymes that helps in the process of digestion are called digestive glands. Human digestive glands include
(i)Salivary glands,
(ii)Gastric glands,
(iii)Liver,
(iv)Pancreas,
(V)Intestinal glands.
(1)Salivary Glands:-
Salivary glands are present in mouth. There are three types of salivary glands in man.
(i) Parotid Glands:-
Parotid Glands are the largest salivary glands, which are present below and in front of each pinna (ear).
(ii) Sub-maxillary:-
it is located on the inner side of Jaw, one on either side.
(iii)Sublingual Glands:
These are present below the tongue. Salivary glands secreats fluid called saliva through salivary duct into the oral cavity. Saliva is slightly alkaline (PH=6.8) and its daily secretion is about 1 to 1.5 liters Saliva contains two enzymes.
(a) Salivary amylase or ptylin:- It converts starch into maltose.
(b) Maltase - It converts maltose into glucose.
Mucus of saliva helps to lubricate the food for swallowing.
(2)Gastric Glands -
Gastric Glands are tubular multicellular glands present in the internal surface of stomach. There are about 35 million gastric glands in stomach. Gastric glands scerets gastric juice which is highly acidic and has PH 0.1-1.5. Gastric juice contains Hel and two inactive enzymes and an active enzyme called gastric lipase.
(a) HCI:- It provides an acidic medium and activates in- active enzymes pepsinogen
and prorenin into pepsin and rennin respectively.
(b) Renin:- It coverts soluble casein into paracasein. This process is called curding of
milk.
(c) Pepsin - It converts proteins into peptones and proteases.
(d) Gastric lipase:- It splits fats into faty acids and gylcerol.
(3) Liver:-
Liver is the largest gland of our body. It is bilobed reddish, brown gland which lies on the right side of the abdominal cavity. Liver is formed of hepatic cells. Numerous capillaries are present in between these cells called bile capillaries. The
hepatic cells join together to form hepatic duct. The two hepatic ducts join together to form common bile duct. The liver secrets bile which is stored in the gall bladder until needed in the duodenunm. The bile is clear yellow alkline fluid and has bitter taste About 500ml to 1 litre of bile is secreted by liver in a day. Bile contains bile pigment and bile salts.
Bile salts emulsify the fat and facilitate absorption of vitamins. The only enzym
present in bile is alkaline-phosphatase but it has no digestive function.
(4)Pancreas: -
Pancreas: - It is the second largest gland in our body. Pancreas is a heterocrine pinkish, leaf like triangular gland present in 'C' shaped loop of duoedenum. The pancreas secreats the panereatic juice which is poured into the doedonum through hepatopancreatic duct. The exocrine region of Pancreeas secreates sodium bi- carbonate and many digestive enzymes. The bicarbonate ions make the mediu alkaline favourable for the action of Pancreatic enzymes.
The some important enzymes present in Panereatic Juice are:
1. Trypsin - It converts proteins into proteoses, peptones and peptides.
Chrymotryprin :- it acts on proteins and converts them into polypeptides and fre
unino acids.
1.Amylase: - It converts starch into maltose and small amounts of glucose.
v.Steapsin or lipase:- It converts fats into fatty acids and glycerol.
v.Sucrase:- It converts sucrose into glucose and fructose.
vi. Maltase :- it converts maltose into glucose.
vii Nucleases ;- These act on polynucleotide chains of RNA and DNA and convert them into nucleotides.
(5) Intestinal Glands -
There are two types of numerous, microscopic glands present the in mucos of small intestines. They are
(a) Crypts of liberkuun.
(b)Brunner's glands.
These glands secrets intestinal juice. Intestinal juice is alkaline in nature (PH=8.3 Man secrets about 2-3 lit. of intestinal juice. Intestinal juice contains following enzymes:
(1) Erepsin:- It converts peptones into amino acids.
(ii) Carbohydrases:- They convert carbohydrates into glucose.
(iii)Nucleases:- Which changes nucleic acids into nucleotides.
(iv)Lipase:_- which converts lipids into fatty acids and glycerol.
PROCESS OF DIGESTION IN HUMAN BEINGS
Digestion is a process in which the complex non-diffusible molecules such as
proteins, fats, starch and nucleic acids are converted into simple diffusible molecules
like amino-acids, fatty acids, glycerol and glucose with the help of enzymes. The process of digestion can be studied under the fallowing headings:-
(1) Digestion of food in buccal cavity:
First the food is taken into the buccal cavity
through mouth. In the buccal cavity, food is masticated with the help of teeth, whic
breaks it into smaller pieces in order to provide more surface area for the action
enzymes (Physical digestion). The tongue mixes the saliva, secreted by salivary gland
with food. The saliva contains mucus which serves to moist the food and make slippery for easy swallowing. The saliva contains two enzymes namely ptylin or salivary amylase and maltase. The enzyme Ptylin converts the starch present in food into maltase and the another enzyme namely naltase converts maltose in
glucose. Therefore, only the digestion of carbohydrates take place in the mouth. This partially digested food which is called bolus passes into stomach through oesophagus or
food pipe. There is no digestion of food in the pharynx and esophagus.
(ii) Digestion of food in stomach:-
The gastric juice secreted by gastric glands pre-
in the wall of stomach contains mucous, Hydrocholric acid (HCI),and enzymes
pepsin, rennin and gastric lipase.
(a) The HCl neutralizes the saliva mixed food and makes the medium acidic for action of gastric enzymes.
b) The mucous present in the gastric juice protects the inner lining of the stomach from the action of acid (HCI)
(c). The pepsin present in the gastric juice changes the proteins present in the foc
peptones and proteoses
(d) The gastric juice also contains the small amount of lipase which changes fats in to
fatty acids and glycerol.
(3) Renin helps to change milk into curd.
The stomach churns the food into a slippery semi-solid mixture called chyme. which
passes into small intestines, by the peristalic movements of stomach.
(iii)Digestion of food in small intestine:
The duodenum is the first part of smali
facts as the duodenum food mixes with two important juices, the bile juice
secreted by fiver and pancreatic juice secreted by pancreas.
Bile which is alkaline in nature contains pnly one enzyme called alkaline phosphatase,
which has no digestive function. Bile neutralizes the action of HCl and helps in
digestion of fats by emulsifying them. Bile also helps in the digestion of fat soluble
vitamins.
The pancreatic juice contains the following enzymes:-
Pancreatic amylase:-Pancreatic amylase converts starch into maltore
Pancreatic lipase:- Pancreatic lipase changes fats (lipids) in to fatty acids and glycerol.
Trypsin:- Trypsin converts peptones and proteases into amino acids.
The inner lining of small intestine is glandular in nature and it secretes intestinal juice.The intestinai juice contains following enzymes:-
(i) Erepsin:- (Mixture of di-peptidases and amino peptidase which changes peptones (lower peptides) into amino acids.
(ii) Sucrose changes sucrose into glucose.and fructose
ii) Maltase changes maltose into giucose.
iv) Lactase changes lactose into glucose. and glactose.
v) Nucleolitic enzymes(Nucleases) which changes nuclic acids into nucleotides.
vi) Lipase which converts lipids into fatty acids.
In the small intestine the food changes into liquid food called as "chyme” which is
diffusible and is absorbed by intestinal wall. Thus the digestion started in mouth is completed in the small intestine.
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