Revision: Life Processes Science English Medium Class 10 CBSE

The process by which organisms obtain energy and materials from external sources for growth, repair, and maintenance of life processes is called nutrition.

Biological substances that speed up the breakdown of complex food into simpler forms to aid in digestion are called enzymes.

The mode of nutrition in which organisms prepare their own food from simple inorganic substances like carbon dioxide and water using sunlight in the presence of chlorophyll is called autotrophic nutrition.

The mode of nutrition in which organisms obtain their food from other organisms because they cannot synthesize it themselves is called heterotrophic nutrition.

An enzyme in saliva that breaks down starch (a complex carbohydrate) into simple sugars is called salivary amylase.

A digestive fluid secreted by salivary glands that moistens food and contains the enzyme salivary amylase to break down starch is called saliva.

The circulatory system is a transport system moving substances throughout our body with the help of blood.

Veins are the blood vessels that carry deoxygenated (impure) blood from the body cells to the heart.

Arteries are the blood vessels in which oxygenated blood is going away from the heart to all parts of the body.

As the blood flows in the capillaries of the tissues, the plasma and the leukocytes "leak out" through their walls. This fluid bathes the cells and is called the tissue fluid or the intercellular or extracellular fluid.

The loss of water vapour from the aerial parts of a plant, mainly through stomata, is called transpiration.

Micturition is the process of expelling urine out of the body through the urethra by opening the sphincter muscles and passing urine, involving the relaxation of the sphincter muscles between the urinary bladder and urethra. 

The kidney while removing wastes like urea from the blood also regulates its composition, i.e., the percentage of water and salts. This function is called osmoregulation.

Excretion is the process that biological organisms use to expel or eliminate the waste products produced by their metabolism.

• The process of removal of chemical wastes (mainly nitrogenous wastes) from the body is known as 'excretion' (ex: out, crete: flow).
• Excretion is the process of removal of harmful and unwanted nitrogenous waste products from the body.
• Excretion is defined as the process by which organisms expel metabolic waste products and other toxic substances from the body.

Organs which are concerned with the formation, storage and elimination of urine constitute the 'excretory system'.

The apex of each pyramid in the medulla of the kidney that projects into the pelvis is called the papilla.

The kidney is composed of an enormous number of minute tubules called uriniferous tubules or nephrons or renal tubules or just kidney tubules. These are the structural and functional units of the kidney. 

Bowman's capsule is a thin-walled, cup-shaped structure in the nephron that surrounds the glomerulus and collects the filtrate from the blood.

The glomerulus is a knot-like network of blood capillaries located inside the Bowman's capsule, where blood filtration occurs.

The Malpighian capsule is the combined structure of the Bowman's capsule and glomerulus, forming the filtration unit of the nephron.

An artificial kidney is a dialysis machine that removes urea and excess salts from the blood when both kidneys fail, and returns the purified blood back into the body.

Dialysis is a medical process in which nitrogenous wastes and toxic substances are removed from the blood using an artificial machine when the kidneys fail to function properly.

1. Autotrophic organisms like green plants synthesize their own food through photosynthesis using carbon dioxide, water, sunlight, and chlorophyll.
2. The process of photosynthesis involves absorption of light by chlorophyll, splitting of water into hydrogen and oxygen, and conversion of carbon dioxide into carbohydrates.
3. The general equation of photosynthesis is: \[\ce{{6CO_2+12H_2O} ->[Chlorophyll][Sunlight] \underset{Glucose}{C6H12O6} + 6O2 +6H2O}\]
4. Carbon dioxide required for photosynthesis enters the plant through stomata, whose opening and closing is regulated by guard cells.
5. Along with water absorbed by roots, plants require minerals like nitrogen, phosphorus, iron, and magnesium from the soil for growth and synthesis of proteins and other compounds.

• ATP formation is called phosphorylation and occurs in three ways: photophosphorylation, substrate-level phosphorylation, and oxidative phosphorylation.
• Photophosphorylation occurs during photosynthesis, while the other two occur during respiration.
• Substrate-level phosphorylation involves direct transfer of a phosphate group to ADP and occurs in the cytoplasm and mitochondrial matrix.
• Oxidative phosphorylation uses energy from oxidation of NADH and FADH₂ and occurs in the inner mitochondrial membrane.
• ATP is hydrolysed to release energy whenever the cell needs it for metabolic activities.

1. The tricuspid valve (right atrio-ventricular valve) is located between the right atrium and right ventricle; it has three cusps held by chordae tendineae attached to papillary muscles.
2. The bicuspid or mitral valve (left atrio-ventricular valve) lies between the left atrium and left ventricle and has two cusps.
3. The pulmonary semilunar valve is located at the opening of the pulmonary artery from the right ventricle; it has three pocket-shaped cusps.
4. The aortic semilunar valve is found at the origin of the aorta from the left ventricle and also has three pocket-shaped cusps.

1. Xylem vessels and tracheids form a continuous network that carries water and minerals from roots to all parts of the plant.
2. Water enters the roots due to active absorption of ions, creating a concentration difference that pulls water in from the soil.
3. Transpiration is the loss of water vapour from the aerial parts of the plant, mainly through stomata, and creates a suction pull that draws water upward.
4. Transpiration pull is the main force for upward water movement during the day, while root pressure plays a bigger role at night.

• Humans have two bean-shaped kidneys located on either side of the vertebral column (from the 12th thoracic to the 3rd lumbar vertebra).
• Kidneys help in maintaining homeostasis by regulating water balance (osmoregulation) and pH of body fluids.
• They also secrete erythropoietin, a hormone important for red blood cell production.
• Each kidney has an outer cortex and an inner medulla; the medulla contains conical structures called renal pyramids.
• Cortex extends into medulla, forming renal columns (columns of Bertini), and pyramids open into minor calyces through renal papilla.
• Kidneys are protected by renal capsule, adipose capsule (fat layer), and renal fascia, and contain nephrons, which are functional units for urine formation.

• Nephrons are the structural and functional units of the kidney, each consisting of a glomerulus and a renal tubule, and measuring about 4–6 cm in length.
• The Malpighian corpuscle (glomerulus + Bowman’s capsule) is the site of ultrafiltration, where blood enters through the afferent arteriole and leaves via the efferent arteriole.
• The proximal convoluted tubule (PCT), lined with cuboidal cells and microvilli, is the main site of selective reabsorption of water, ions, and nutrients.
• The loop of Henle extends into the medulla and helps in concentration of urine; its descending limb is permeable to water, while the ascending limb is impermeable to water but allows movement of electrolytes.
• The distal convoluted tubule (DCT) carries out tubular secretion and regulation of ions, and opens into the collecting duct, which reabsorbs water and transports urine to the renal pelvis.
• Nephrons are of two types: cortical nephrons with short loops of Henle and juxtamedullary nephrons with long loops that play a key role in urine concentration.
• The kidneys receive rich blood supply and filter large volumes of blood daily, with most filtrate reabsorbed and about 1–1.5 litres of urine excreted per day.