Chapter – 5

Life Processes

In this post we have given the detailed notes of class 10 Science Chapter 5 (Life Processes) in English. These notes are useful for the students who are going to appear in class 10 board exams.

Chapter 5: Life Processes

Life Processes 🌱

• All those activities of the body which help it maintain itself and protect it from wear and tear, and together carry out the work of maintenance, are called life processes. Together, all the processes necessary for an organism to live and maintain itself — such as excretion, nutrition, transportation, etc. — come under life processes. In nutrition, organisms take in nutrients that are required from nature, which are then digested inside or outside the body, providing energy for the organism to live. In excretion, the toxic substances produced during metabolism inside the body are removed from the body.

The Processes Included in Life Processes Are:

• Nutrition
• Respiration
• Transportation
• Excretion

All living organisms need energy to survive and carry out different functions. This energy is obtained through the process of nutrition. In this process, a biochemical activity called metabolism takes place inside cells, and it requires oxygen, which the organism obtains from its external environment. The use of oxygen in this process, and the removal of the carbon dioxide (CO₂) produced, is called respiration. Some unicellular organisms do not need special organs for the transport of oxygen and carbon dioxide because their cells are directly in contact with the environment. But in multicellular organisms, there is a respiratory system for exchange of gases, and to carry them to the cells there is a transport system called the circulatory system. When chemical reactions use a carbon source and oxygen to release energy, products are also formed that are not only useless but can also be harmful to the body’s cells. Removing these waste products from the body is essential — this process is called excretion. Since all these processes together carry out the maintenance of the body, they are collectively called life processes.

Biochemical Processes

In all these processes, an organism obtains energy from an external energy source, and inside the body, complex substances obtained from that energy source are broken down or built up, forming molecules necessary for the maintenance and growth of the body. For this, a series of chemical reactions takes place in the body, which is called the biochemical process.

Process of Nutrition

Intake of energy from an external source (complex substances)

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Breakdown of complex substances obtained from the energy source

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Conversion into simple useful molecules by the biochemical process

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Consumption as energy

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Further different biochemical processes taking place

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Formation of new complex molecules (protein synthesis)

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Growth and maintenance of the body

General Chemical Mechanism for Breakdown of Molecules

• The breakdown of molecules in the body happens through a chemical mechanism called metabolism.
• Metabolic activities are biochemical activities that take place in all living organisms to sustain life.
• Metabolic activities are of two types.

Anabolism: This is a group of constructive chemical reactions in which the energy produced by catabolism is used to build complex molecules from simple molecules. Through this process, all the required nutrients are delivered to different parts of the body as needed, forming new cells or tissues.

Catabolism: In this process, complex organic substances are broken down to form simple molecules, and energy is released during cellular respiration. Under life processes, the following processes together carry out maintenance: nutrition, respiration, transportation, excretion.

Nutrition

• The process occurring in living organisms in which an organism converts complex substances into simple substances through a biochemical process to obtain and use energy is called nutrition.

Examples of biochemical processes:

• Photosynthesis in plants
• Digestion in animals

The process by which plants obtain food is called photosynthesis. In this process, organisms obtain simple substances from inorganic sources in the form of carbon dioxide and water; such organisms are called autotrophs. Example: green plants and some bacteria.

Enzymes: To break down complex substances into simple substances, organisms use certain biological catalysts called enzymes.

Types of Nutrition

Nutrition Is of Two Types:

• Autotrophic nutrition
• Heterotrophic nutrition

1. Autotrophic nutrition: Autotrophic nutrition is a type of nutrition in which organisms synthesize their own biological substances (food) from inorganic sources. This type of nutrition is carried out by green plants and autotrophic bacteria.

Example: Green plants and some photosynthesizing bacteria.

Photosynthesis: Green plants use raw materials like water and carbon dioxide, in the presence of sunlight and chlorophyll, to make food.

2. Heterotrophic nutrition: The method of nutrition in which an organism obtains its food from other sources. It obtains food either from plant sources or animal sources. Example: fungi, humans, all animals, etc.

Heterotrophic Nutrition Is of Three Types:

(i) Saprophytic nutrition: The method of nutrition in which organisms obtain their nutrition from dead and decaying organic matter is called saprophytic nutrition. This type of nutrition is found in fungi and most bacteria.

(ii) Parasitic nutrition: Parasitic nutrition is a method of nutrition in which an organism obtains food and shelter from another organism and absorbs its source of nutrition; this is called parasitic nutrition.

Two types of organisms participate in this process:

• Host: The organism from which the parasite absorbs food is called the host.
• Parasite: A parasite is an organism that lives in or on a host’s body and absorbs its food and shelter. Examples: Plasmodium found in mosquitoes, tapeworm and roundworm found in the human intestine, lice, etc.; in plants, Cuscuta (amarbel).

(iii) Holozoic nutrition: A method of nutrition in which an organism obtains energy by ingesting and digesting organic material obtained from plant and animal sources. That is, the organism takes in food, digests it and then excretes the waste. Example: humans, amoeba and all animals.

Nutrition in amoeba: Amoeba obtains nutrition similarly to humans and digests food inside its body.

Nutrition in Humans

Nutrition in humans occurs by the holozoic method, which involves the following processes:

• Ingestion: Taking food into the mouth.
• Digestion: Digesting the food.
• Absorption: Converting the digested food into necessary nutrients and absorbing them.
• Assimilation: The absorbed nutrients reaching the cells and being used for cellular respiration.
• Egestion: After absorption of the required nutrients, the remaining waste is removed from the body.

Human Digestive Process

(i) Mouth → Ingestion of food
Teeth → Chewing of food
Tongue → Mixing food thoroughly with saliva
Salivary glands → Saliva secreted by salivary glands converts starch into maltose sugar in the presence of the enzyme salivary amylase.

(ii) Passage of food through the oesophagus → We have a food pipe from the mouth to the stomach called the oesophagus. Food reaches the stomach through peristaltic movement in this pipe.

(iii) Stomach → The human stomach is also a gland that secretes gastric juice, which is a mixture of digestive juices like pepsin, hydrochloric acid and mucus.

Action Taking Place in the Stomach

Gastric juice

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Hydrochloric acid provides an acidic medium

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Breaks food into smaller pieces

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Pepsin digests proteins

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Mucus protects the inner lining of the stomach from the acid

(iv) Small intestine → The small intestine is the longest part of the alimentary canal.

The small intestine has three parts:

(i) Duodenum: This is the part of the small intestine attached to the stomach, which further connects to the jejunum. The bile duct from the liver and the duct from the pancreas open into this part of the alimentary canal. This part of the small intestine receives secretions from the liver and pancreas.

a) Liver: The liver is the largest gland in the body. It secretes bile juice, which contains bile salts. This mixes with food in this part of the alimentary canal and helps digest fats.

Function of bile juice:

i) The food coming from the stomach is acidic, and bile juice secreted by the liver makes it alkaline so the pancreatic enzymes can act on it.

ii) Bile juice converts large fat globules into smaller globules through emulsification.

b) Pancreas: The pancreas is also a gland with two parts.

i) Endocrine part: The endocrine part of the pancreas secretes a hormone called insulin.

ii) Exocrine part: The exocrine part of the pancreas secretes enzymes that mix with food in the small intestine through a duct and digest various nutrients. The enzymes released from the pancreas make up pancreatic juice.

These enzymes are:

• Amylase enzyme: Digests starch and converts it into glucose.
• Trypsin enzyme: Digests protein into peptones.
• Lipase enzyme: Digests fat into fatty acids.

Jejunum: The part between the duodenum and ileum is called the jejunum, and it digests the fine particles of food that have been digested by the stomach and duodenum.

Ileum: This is the longest part of the small intestine, and most food is digested here. Its last end joins the large intestine.

Villi

• Many finger-like projections are found on the inner lining of the small intestine of humans; these are called villi.

Function of villi:

• They increase the surface area for absorption.
• They absorb water and food and deliver them to the cells.

Respiration

• (Peristaltic movement): The movement of the alimentary canal by which food moves from one part of the canal to another is called peristaltic movement.

• During the process of nutrition, the food material we consume provides energy that is used by cells. The organism uses this energy for various life processes.

(i) Cellular respiration: The breakdown of food inside cells for the production of energy is called cellular respiration.

(ii) Breathing: This process of respiration occurs in the lungs, where the organism takes in oxygen and releases carbon dioxide.

Energy for Various Life Processes

Cells obtain energy for various life processes during cellular respiration, through different pathways in different organisms:

• In the absence of oxygen: Some organisms, like yeast, obtain energy during fermentation.

The pathway is as follows:

6-carbon glucose ⇒ broken down into 3-carbon pyruvate ⇒ ethanol, carbon dioxide and energy are released.

Since this process occurs in the absence of oxygen, it is called anaerobic respiration.

• In lack of oxygen: During vigorous exercise or strenuous physical activity, our body’s muscles experience a lack of oxygen when the supply of oxygen is less than the demand.

The pathway is as follows:

6-carbon glucose ⇒ broken down into 3-carbon pyruvate ⇒ lactic acid and energy are released.

• In the presence of oxygen: This process takes place in the mitochondria of our cells in the presence of oxygen. The pathway is as follows:

6-carbon glucose ⇒ broken down into 3-carbon pyruvate ⇒ carbon dioxide, water and a large amount of energy are released.

Since this process occurs in the presence of oxygen, it is called aerobic respiration.

Flow Diagram for Breakdown of Glucose by Different Pathways

• Aerobic respiration: The process of glucose breakdown that occurs in the presence of oxygen is called aerobic respiration.
• Anaerobic respiration: The process of glucose breakdown that occurs in the absence of oxygen is called anaerobic respiration.

Difference Between Aerobic and Anaerobic Respiration:

Anaerobic respiration:

• It produces energy (ATP) with a lower net yield.
• This process takes place in the cytoplasm.
• It occurs in lower organisms such as yeast cells.
• This type of respiration occurs in the absence of oxygen.
• Along with energy, ethanol and carbon dioxide are released.

Aerobic respiration:

• It produces energy (ATP) with a much higher net yield.
• This process takes place in the mitochondria.
• It is found in all higher organisms.
• This type of respiration occurs in the presence of oxygen.
• Along with energy, carbon dioxide and water are released.

Utilisation of energy: The energy released during cellular respiration is immediately used to synthesise a molecule called ATP, which is used as fuel for other cellular activities.

• The breakdown of ATP releases a fixed amount of energy, which drives the endothermic reactions taking place in the cell.
• This energy is also used by the body to make various complex molecules, which is how protein synthesis occurs. This protein synthesis leads to the formation of new cells in the body.
• ATP is also used for the contraction of muscles, transmission of nerve impulses, and many other activities.

Requirements for aerobic respiration in aerobic organisms:

• Take in a sufficient amount of oxygen.
• The respiring cells should be in contact with air.

Difference Between Respiration and Breathing

Respiration:

• It is a complex biochemical process in which digested food is oxidised.
• This process takes place in the mitochondria.
• Energy is produced through this process.

Breathing:

• The process of taking in oxygen and releasing carbon dioxide is called breathing.
• This process takes place in the lungs.
• This does not produce energy directly. It oxygenates the blood and removes carbon dioxide.

Diffusion

The exchange of certain selected gases through cell membranes is called diffusion.

Direction of Diffusion in Plants

The direction of diffusion depends on environmental conditions and the needs of the plant.

• Plants respire at night: When photosynthesis is not taking place, they release carbon dioxide and take in oxygen.
• Plants photosynthesize during the day: The CO₂ released during respiration is used up in photosynthesis, so no CO₂ is released. At this time, the release of oxygen is the main event.

Breathing rate increases during strenuous exercise: During strenuous exercise, the breathing rate increases because the rate of respiration in cells increases, leading to more energy consumption. The demand for oxygen in cells increases and more CO₂ is released, which increases the breathing rate.

Transportation in Humans 🩸

Blood vessels: Our body has different kinds of blood vessels to carry out transportation. There are three types:

• Arteries: Blood vessels that carry blood from the heart to other parts of the body are called arteries. Example: aorta, pulmonary artery, etc.
• Veins: Blood vessels that carry blood from other organs of the body back to the heart are called veins. Example: vena cava, pulmonary vein, etc.
• Capillaries: Blood vessels that connect arteries and veins are called capillaries.

Difference Between Arteries and Veins:

Human Heart ❤️

The heart is a muscular organ, roughly the size of our fist. It is divided into several chambers to prevent oxygenated and deoxygenated blood from mixing during blood flow. Its function is to collect blood from various parts of the body and pump it to other parts of the body.

The heart has four chambers, two on the left and two on the right, with the following names and functions:

• Right atrium: This collects blood from the upper and lower parts of the body and pumps it into the right ventricle.
• Right ventricle: This sends blood to the lungs for oxygenation through the pulmonary artery.
• Left atrium: Blood is brought here from the lungs via the pulmonary vein; it collects the blood and sends it to the left ventricle.
• Left ventricle: The left ventricle pumps the blood received from the left atrium to the entire body through the aorta.

Working of the human heart: The functioning of the heart involves the following steps:

• When deoxygenated blood comes from the body into the right atrium, it contracts, and the corresponding chamber below it, the right ventricle, expands and receives the blood. This chamber then pumps the blood to the lungs for oxygenation. When it pumps, its valves prevent the backward flow of blood.
• When the oxygenated blood returns from the lungs to the heart, it enters the left atrium, which relaxes while collecting it. When the next chamber, the left ventricle, expands, the left atrium contracts, transferring blood into it. In turn, when the muscular left ventricle contracts, blood is pumped out into the body.

Function of Heart Valves

Valves prevent the backward flow of blood.

Division of the heart into chambers: The separation of the right and left sides of the heart is useful in preventing oxygenated and deoxygenated blood from mixing. Such a separation allows a highly efficient supply of oxygen to the body.

Use of Chambers in Other Animals:

• This is very beneficial for animals like birds and mammals that need a continuous supply of energy to maintain their body temperature. In animals that do not use energy for this purpose, body temperature depends on the environment. Amphibians and many reptiles have a three-chambered heart and can tolerate some mixing of oxygenated and deoxygenated blood. On the other hand, fish have a two-chambered heart, from where blood is sent to the gills, gets oxygenated, and is sent directly to the rest of the body. In this way, blood in fish passes through the heart only once in one cycle.

Double Circulation

• Our heart pumps blood twice in each cycle to send it out and blood also comes back to the heart twice in each cycle. This is called double circulation.

Blood Cells

Our blood contains three types of blood cells:

• White blood cells (WBC)
• Red blood cells (RBC)
• Platelets

1) Function of white blood cells: These fight against foreign substances or infections in our body.

2) Function of red blood cells: Red blood cells are mainly made of haemoglobin, which gives blood its red colour.

Function of haemoglobin:

• It gives blood its red colour.
• It has a high affinity for oxygen and carries oxygen and carbon dioxide from one place to another.

3) Function of platelets: Platelets are cells that circulate throughout the body and help stop bleeding from any part of the body by forming a clot at the site of injury, blocking the flow.

Plasma

Besides blood cells, blood also contains another connective tissue that provides a liquid medium for the blood cells, called plasma.

Function of plasma: Cells remain suspended in it. Plasma transports food, carbon dioxide and nitrogenous waste in a dissolved form.

Blood Pressure

The pressure exerted by blood against the walls of blood vessels is called blood pressure.

Blood Pressure Is of Two Types:

i) Systolic pressure: The pressure of blood inside an artery when the ventricle contracts is called systolic pressure.

ii) Diastolic pressure: The pressure inside an artery when the ventricle relaxes is called diastolic pressure.

• Normal human blood pressure is 120mm of mercury (systolic) to 80mm of mercury (diastolic).
• Blood pressure is measured with an instrument called a sphygmomanometer.

Lymph

Through pores present in the walls of capillaries, some plasma, proteins and blood cells come out into the intercellular spaces of the tissues and form tissue fluid, or lymph. This is a colourless fluid, similar to plasma, called lymph. It is also called a fluid tissue.

Lymph flows in one direction in the body, i.e. from bottom to top, and instead of flowing through blood vessels, it flows through the intercellular spaces, from where it enters the lymph capillaries. This forms a system called the lymphatic system. In this system, all the lymph capillaries join lymph nodes to form a junction. The lymph node filters out foreign agents present in lymph that are responsible for infection.

Intercellular space: The empty space between two cells is called the intercellular space.

Function of Lymph:

• It strengthens the body’s immune system and helps in transportation.
• Digested fat absorbed by the small intestine is transported through lymph.
• It carries excess fluid collected in the extracellular space back to the blood.
• The lymphocytes found in lymph fight against infection.

Transportation in Plants 🌿

The raw materials required for building the plant body are obtained separately. For plants, soil is the closest and most abundant source of nitrogen, phosphorus and other mineral salts. So these substances are absorbed by the roots, which are in contact with the soil. If the distance between the parts in contact with soil and the chlorophyll-containing parts is very small, energy and raw material can easily diffuse into all parts of the plant body. A large part of a plant’s body consists of dead cells, so plants need less energy and can use a relatively slower transport system. In this, the conducting tissues xylem and phloem play an important role.

Function of Xylem and Phloem

Function of xylem: It carries water and mineral salts obtained from the soil to other parts of the plant such as the leaves.

Function of phloem: It transports products formed by photosynthesis in the leaves to other parts of the plant.

Transport of water in plants:

• Xylem tissue forms a continuous network of water-conducting cells connecting roots, stems and leaves throughout the plant. Root cells in contact with soil actively take up ions, creating a difference in ion concentration between the root and the soil. To eliminate this difference, water from the soil moves into the root. This means water continuously moves into the root xylem, forming a column of water that is continuously pushed upward.
• For taller plants, this method alone is not sufficient. So another method exists in which loss of water from stomata in leaves creates a suction that pulls water upward through the xylem cells present in the roots. This causes water to move upward. Thus, transpiration causes absorption and the upward movement of water and dissolved minerals from the roots to the leaves.

Transport of food and other substances: Substances like sucrose are transferred in phloem tissue using energy from ATP. This increases the osmotic pressure of the tissue, causing water to enter it. This pressure moves substances in phloem to tissues that have less pressure. This allows phloem to transport material according to the needs of the plant. For example, in spring, sugar stored in root and stem tissues is transported to buds that need energy for growth.

Excretion

• Excretion: The life process in which harmful metabolic waste products are removed from the body is called excretion.
• Excretion in amoeba: A unicellular organism removes waste from its body by diffusion into water through the body surface.
• Excretion in multicellular organisms: In multicellular organisms, the process of excretion is complex, so they have special organs to carry out this function.

Excretion in Humans:

Names of excretory organs: The organs that take part in excretion are called excretory organs. They are:

• Kidneys
• Ureters
• Urinary bladder
• Urethra

Kidneys: Humans have a pair of kidneys located in the abdomen, one on each side of the backbone.

Process of excretion: Urine formed in the kidneys passes through the ureter into the urinary bladder, where it is stored until it is released through the urethra.

Excretory substances: The waste substances released after excretion are called excretory products.

Names of excretory substances:

• Nitrogenous waste substances like urea
• Uric acid
• Ammonia
• Creatinine

Functions of the kidney:

• It maintains the balance of water and other fluids in the body, which controls blood pressure.
• It regulates and filters minerals and salts from the blood.
• It filters out waste products from food, medicines and toxic substances.
• It helps regulate the amount of acid and base in the body.

Nephron: The filtration unit in each kidney is called a nephron.

Regulation of urine formation: This depends on the following factors:

• Reabsorption of the amount of water.
• The amount of extra water available in the body.
• How much dissolved waste needs to be excreted.

Function of the kidney during dehydration: During dehydration, the kidney reduces the process of urine formation; this is regulated by a special hormone.

Kidney failure: Due to infection, injury or reduced blood flow to the kidney, sometimes the kidney reduces or stops functioning. This is called kidney failure. As a result, toxic waste products accumulate in the body, which can even cause death. In this inactive state of the kidney, an artificial kidney is used to remove nitrogenous wastes from the body.

Artificial kidney: The technique of removing nitrogenous waste from blood using an artificial device is called dialysis.

How Dialysis Works

An artificial kidney consists of many tubes with a semi-permeable lining. These tubes are placed in a tank filled with dialysis fluid. The osmotic pressure of this fluid is similar to that of blood but does not contain nitrogenous wastes. The patient’s blood is passed through these tubes. Along this path, waste products from the blood diffuse into the dialysis fluid. The purified blood is then pumped back into the patient’s body.

Difference between kidney and artificial kidney: Reabsorption takes place in the kidney, whereas reabsorption does not take place in an artificial kidney.

Excretion in plants:

• Plants remove excess water through transpiration.
• Many plant waste products are stored in cellular vacuoles.
• Waste products are also stored in leaves that fall off the plant.
• Other waste products are stored as resins and gums, especially in old xylem.
• Plants also excrete some waste substances into the surrounding soil.

Key Points to Remember

• Life processes essential for maintaining the body are nutrition, respiration, transportation and excretion. 🌱
• Nutrition is of two types — autotrophic (self-synthesizing, e.g. green plants) and heterotrophic (saprophytic, parasitic and holozoic).
• Human digestion involves ingestion, digestion, absorption, assimilation and egestion, aided by saliva, gastric juice, bile and pancreatic enzymes.
• Respiration can be aerobic (in presence of oxygen, in mitochondria, produces more energy) or anaerobic (in absence of oxygen, in cytoplasm, produces less energy). 🫁
• The human heart has four chambers and shows double circulation to keep oxygenated and deoxygenated blood separate. ❤️
• Blood consists of RBCs, WBCs, platelets and plasma, each performing distinct transport and defence functions.
• In plants, xylem transports water and minerals while phloem transports food (translocation).
• Excretion in humans is carried out by the kidneys, ureters, bladder and urethra, with the nephron as the functional filtration unit.

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