LIFE PROCESSES
NUTRITION
All living organisms require energy to carry on various maintenance processes. This energy comes from the outside the body of the individual organism. Some organism utilize simple inorganic substances such as carbon dioxide and water, whereas other organisms utilize complex substances which are required to be digested before they can be utilized for various life processes such as growth, maintenance and repair. So, “Nutrition” is a process by which a source of energy from outside the body of the organism, which we call food, is transferred to inside the body of the organism.
MODES OF NUTRITION
There are two modes of nutrition - Autotrophic and Heterotrophic.
Autotrophic Nutrition - In this type of nutrition food is synthesized by the organism itself (autotrophs) from simple inorganic raw materials such as CO2 and H2O. The essential elements of Autotrophic Nutrition are the presence of green pigment (Chlorophyll) and Sunlight. All green plants and some bacteria have this type of nutrition.
Heterotrophic Nutrition - Some organisms are unable to synthesize their own food. These organisms rather obtain their food directly or indirectly from autotrophs. This food is then broken down with the help of some enzymes. This mode of nutrition is called ‘Heterotrophic Nutrition’. In this type of nutrition no pigment or sunlight is required. All animals, fungi and some bacteria have this type of nutrition.
PHOTOSYNTHESIS
Photosynthesis is the process by which chlorophyll-containing cells in plants synthesize food in the form of carbohydrates, carbon dioxide and water using sunlight. The raw materials required for photosynthesis are carbon dioxide and water and the products formed are carbohydrates and oxygen. The process can be represented as:
The process of photosynthesis occurs in two phases -
1. Light Reactions : This reaction takes place in the presence of light. Events occuring during Light Reactions are -
a. absorption of light energy by chlorophyll molecules.
b. splitting of water molecules into hydrogen and oxygen atoms.
c. formation of ATP and NADPH2
2. Dark Reactions : This reaction does not require direct light and occurs in the stroma of the chloroplasts. During this phase, reduction of CO2 takes place to form carbohydrates.
NUTRITION IN AMOEBA
Fig - Nutrition in Amoeba
Amoeba takes in food using temporary finger-like extensions of the cell surface, calledpseudopodia, which fuse over the food particle forming a food - vacuole. Inside the foodvacuole, complex substances are broken down into simpler ones which then diffuse into the cytoplasm.
NUTRITION IN HUMAN BEINGS
Fig - Human Alimentary Canal
Eating nutritious food is healthy because it supplies essential nutrients required to sustain life. It is by the process of digestion that the nutrients present in the food are utilized by the human body. The following are the different digestive organs and their functions -
MOUTH
Digestion of food begins in the mouth. It comprises of the following parts -
Teeth: Tear and break down the food.
Saliva: Contains a digestive enzyme called salivary amylase, which help to break down starch into sugar.
Tongue: It is a sense organ with taste buds. Its muscular movements help to move the foodfrom the mouth into inside.
PHARYNX
It opens into the oesophagus (which leads to the stomach) and trachea (which leads to the lungs). Pharynx is a common passageway for food and air.
OESOPHAGUS
The peristaltic movements of the longitudinal smooth muscles in oesophagus push the foodinto the stomach and also prevent the chewed food material from moving back into the mouth.
STOMACH
The stomach stores and mixes the food from oesophagus with the gastric juice. The main components of gastric juice, which is secreted by gastric glands present in the walls of the stomach, are HCl, mucus, and pepsynogen.
SMALL INTESTINE
1. It is the longest part of the elementary canal and is made up of three parts - duodenum, jejunum, and ileum.
2. The length of the small intestine depends on the type of food consumed by the organism and hence, differ ijn various animals.
3. It also produces intestinal juice from glands present in the wall which helps in further digestion of the food.
4. Other digestive juices like - bile juice (which causes emulsification of fats) and the pancreatic juice (for digesting proteins and emulsified fats) mix with the food in the small intestine.
5. The small intestine is the site for complete digestion of carbohydrates, proteins and fats.
6. The digested food is then absorbed through the intestinal walls and transported to the various parts of the body.
LARGE INTESTINE
The indigestible material and water enters the large intestine. The large intestine performs the function of storage of wastes (faeces) before they are excreted from the body via the anus.
ATP
The energy released during the process of respiration is used to form high energy ATP (adenosine tri-phosphate) molecules. ATP is known as energy currency of the cell and it is used as cellular fuel for most cellular processes. ATP is called ‘energy currency’ of the cell because the energy required for various life activities is released by mitochondria in the form of ATP molecules, which is used by the body performing various activities. For example, energy stored in ATP is used to bring about energy requiring activities of cell such as photosynthesis, protein synthesis and muscle contraction.
LYMPHATIC SYSTEM
Lymph is another fluid connective tissue, which helps in the process of transportation. Some pores are present in the walls of the capillaries and through these pores, small amounts of plasma, proteins, and blood cells escaped into the intercellular spaces in the tissues to form the tissue fluid or lymph. It is similar to the plasma of blood but colourless and contains less protein. Lymph drains into lymphatic capillaries from the intercellular spaces, which joined to form large lymph vessels.
Functions of the Lymph:
1. It acts as a reservoir of water, salts and digested food.
2. It carries digested food and fats from the small intestine. Lymphatic vessels present in the intestinal villi absorb fatty acids.
3. It contains phagocytes that can engulf and destroy bacteria. and other foreign particles.
FUNCTION OF KIDNEYS
Kidneys form a part of human excretory system. Different functions of kidneys are as follows:
1. Kidneys filter waste products from the blood e.g. various nitrogenous wastes such as urea,uric acid etc.
2. Kidneys play an important role in the formation of urine.
3. It helps us in maintaining the water balance of our body by removing excess fluids.
4. It is the basic filtration unit of the excretory system.
5. They also make hormones that keep the bones strong and healthy.
Sample Questions
Q.1: Which pigment captures solar energy?
Ans: Chlorophyll
Q.2: Name any three life processes.
Ans: Nutrition, respiration and blood circulation
Q.3: Answer the following questions:
(i) What is the first reaction in photosynthesis?
(ii) In which form do plants store food?
Ans: (i) The first reaction in photosynthesis is the photolysis of water.
(ii) The product of photosynthesis is glucose, which is stored in plants in the form of starch.
Q.4: What are the inorganic sources used by plants for making food?
Ans: Carbon dioxide, water and sunlight.
Q.5: What are the outside raw materials used by an organism?
Ans: Various outside raw materials used by an organism are as follows:
1. Food as a source of supplying energy and materials.
2. Oxygen for the break-down of the food to obtain energy.
3. Water for proper digestion of food and other functions inside the body.
The raw materials required by an organism will vary depending on the complexity of the organism and its environment.
Q.6: Plants have lower energy need and relatively slow transportation system than those of animals. Give reasons.
Ans: Energy needs differ between different body designs. Unlike animals, plants do not move and plant bodies have also a large proportions of dead cells in many tissues. As a result, plants have lower energy needs and also relatively slow transportation than those required by animals.
Q.7: Briefly describe the digestive functions of liver and pancreas.
Ans: Energy needs differ between different body designs. Unlike animals, plants do not move and plant bodies have also a large proportions of dead cells in many tissues. As a result, plants have lower energy needs and also relatively slow transportation than those required by animals.
Q.7: Briefly describe the digestive functions of liver and pancreas.
Ans: Liver :
1. The liver secretes bile which is stored in the gall bladder from where it is sent to the duodenum whenever needed.
2. The bile breaks down the fat droplets into small fat globules. This phenomenon is known as emulsification of the fat.
Pancreas :
1. Pancreas secretes a juice which is sent to the duodenum.
2. Pancreatic juice contains different enzymes. The Trypsin, which digests proteins into peptones, and the pancreatic amylase, which digests starch into sugar. The lipase which breaks down the emulsified fats.
3. It also produces hormones - insulin and glucagon. This insulin is a very important hormone that regulates the sugar level in blood.
