Life Processes in Living Organisms Part 1Class 10 Science Part 2 Chapter 2 Notes – Maharashtra Board

Summary: Life Processes in Living Organisms Part 1

Life processes are activities that maintain life. Nutrition is the process by which organisms obtain and use food. In autotrophic nutrition, organisms like plants make their own food through photosynthesis using sunlight, water, and carbon dioxide. Heterotrophic nutrition occurs when organisms like animals eat other organisms. The human digestive system breaks down food into simple nutrients that are absorbed in the small intestine and distributed to all cells.

Respiration is the process by which organisms release energy from food. Aerobic respiration uses oxygen and occurs in the mitochondria of cells; it produces more ATP (energy) than anaerobic respiration. Anaerobic respiration occurs without oxygen and is less efficient. Breathing (external respiration) brings oxygen into the body and removes carbon dioxide; cellular respiration (internal) uses oxygen to break down glucose in mitochondria.

The circulatory system transports nutrients, oxygen, and other materials throughout the body. Blood consists of plasma, red blood cells (carry oxygen), white blood cells (fight infection), and platelets (stop bleeding). The heart pumps blood through arteries to the body and receives it back through veins. Capillaries allow exchange of gases and nutrients with cells. The lymphatic system helps in immunity and returns fluid to the blood.

Key points to remember

• Nutrition is the process of obtaining and using food; autotrophic organisms (plants) make their own food; heterotrophic organisms (animals) consume other organisms.
• Photosynthesis in plants: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Occurs in chloroplasts using light energy; produces glucose and oxygen.
• In humans, digestion breaks food into simple nutrients: proteins → amino acids, carbohydrates → glucose, fats → fatty acids and glycerol.
• The small intestine is the main site of nutrient absorption; villi increase surface area for absorption.
• Respiration releases energy from food: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP). Occurs in mitochondria.
• Aerobic respiration produces ~38 ATP molecules per glucose; anaerobic respiration produces only 2 ATP molecules per glucose.
• Breathing (ventilation) brings O₂ into lungs and removes CO₂; occurs 12-16 times per minute in humans at rest.
• Blood components: plasma (carries nutrients), RBCs (oxygen transport), WBCs (immunity), platelets (clotting).
• Hemoglobin in red blood cells binds oxygen; one RBC survives ~120 days and is replaced by bone marrow.
• Heart rate: ~72 beats per minute in resting humans; increases with exercise, fever, and excitement.
• Systolic pressure (~120 mmHg): heart contracts; diastolic pressure (~80 mmHg): heart relaxes.
• Arteries carry blood away from heart at high pressure and speed; veins return blood at low pressure and speed; capillaries connect them.
• The lymphatic system drains tissue fluid, fights infection via lymphocytes, and returns fluid to the circulatory system.

Life Processes in Living Organisms Part 1 – Notes

1. Nutrition and photosynthesis

• Autotrophic nutrition: organisms produce their own food (plants, some bacteria) using energy from sun or chemicals.
• Heterotrophic nutrition: organisms consume other organisms for food (animals, fungi, most bacteria).
• Photosynthesis uses light energy to convert CO₂ and H₂O into glucose and O₂. Occurs in two stages: light reactions (in thylakoids) and dark reactions/Calvin cycle (in stroma).
• Light reactions: chlorophyll absorbs light energy, splits water, releases O₂, and produces ATP and NADPH.
• Calvin cycle: uses ATP and NADPH to fix CO₂ into glucose. Does not directly need light (called 'dark reactions').
• Factors affecting photosynthesis: light intensity, CO₂ concentration, temperature, chlorophyll content, water availability.

2. Human digestive system

• Digestion breaks large food molecules into small absorbable molecules. Mechanical digestion (chewing, churning) and chemical digestion (enzymes) both occur.
• Salivary glands: amylase enzyme breaks down starch to maltose.
• Stomach: gastric juice (HCl + pepsin) breaks proteins into peptides. Churning mixes food into chyme.
• Pancreas secretes pancreatic juice with enzymes (amylase, lipase, protease) into the small intestine.
• Liver secretes bile to emulsify fats; bile is stored in gallbladder and released as needed.
• Small intestine: main absorption site. Villi and microvilli increase surface area. Simple sugars, amino acids, fatty acids, vitamins, minerals, and water are absorbed here.
• Large intestine: absorbs water and remaining minerals; forms feces.

3. Respiration and energy production

• Respiration is controlled breakdown of glucose to release energy in usable form (ATP). Different from breathing (ventilation).
• Aerobic respiration: glucose + oxygen → CO₂ + water + energy (~38 ATP). Occurs in mitochondria in multiple steps.
• Glycolysis (cytoplasm): glucose → 2 pyruvate + 2 ATP + 2 NADH. Does not require oxygen.
• Citric acid cycle/Krebs cycle (mitochondrial matrix): oxidizes pyruvate, releases CO₂, produces NADH and FADH₂.
• Electron transport chain (inner mitochondrial membrane): NADH and FADH₂ donate electrons; energy used to pump H⁺ ions; creates gradient for ATP synthase.
• Anaerobic respiration: glucose → lactate (in muscles) or ethanol (in yeast) + 2 ATP. Occurs during intense exercise when oxygen is limited.

4. Breathing and gas exchange

• Breathing brings air into lungs and removes air from lungs. Normal breathing rate: 12-16 breaths per minute at rest.
• Diaphragm (muscle below lungs) contracts downward; intercostal muscles lift ribcage. These increase lung volume, decreasing pressure, so air flows in (inspiration).
• Relaxation of diaphragm and intercostal muscles decreases lung volume, increasing pressure, forcing air out (expiration).
• Gas exchange in lungs: deoxygenated blood in capillaries gives CO₂ to alveoli; oxygenated air in alveoli gives O₂ to blood.
• Hemoglobin (protein in RBCs) reversibly binds O₂. Each hemoglobin carries 4 O₂ molecules. At high O₂ (lungs), binds readily; at low O₂ (tissues), releases O₂.
• CO₂ is transported in blood as dissolved CO₂, bound to hemoglobin, or as bicarbonate (HCO₃⁻) in plasma.

5. Circulatory system and blood

• Circulatory system: heart (pump), arteries (carry blood away), capillaries (exchange), veins (return blood), and blood.
• Blood composition: plasma (55% - water with dissolved salts, glucose, proteins, hormones, antibodies), RBCs (40% - carry O₂), WBCs (4% - defend), platelets (1% - clot).
• RBCs: no nucleus in mammals; contain hemoglobin; live ~120 days; produced in bone marrow at rate of 2-3 million per second.
• WBCs: have nucleus; include neutrophils (engulf bacteria), lymphocytes (antibodies), monocytes (large phagocytes); survive days to years.
• Platelets: fragments of megakaryocytes; help form blood clots by aggregating and releasing clotting factors.
• Blood types: determined by antigens on RBC surface (A, B, AB, O) and Rh factor. Type O is universal donor; AB is universal recipient.
• Heart: four-chambered (two atria, two ventricles). Right side pumps deoxygenated blood to lungs; left side pumps oxygenated blood to body.
• Cardiac cycle: atria contract, ventricles fill (atrial systole); ventricles contract, atria fill (ventricular systole); diastole: both relax. One cycle = one heartbeat.

Formulas at a glance

Key terms

Life Processes in Living Organisms Part 1 – Flashcards

Read the question, answer it in your head, then tap the card to check. 20 cards.

Life Processes in Living Organisms Part 1 – MCQ Quiz

15 questions. Tap an option — you will see at once if it is right and why.

How to study Life Processes in Living Organisms Part 1

⏱ About 5 hours over 3-4 days

1. Day 1 — Photosynthesis and respiration
   Study light reactions, Calvin cycle, glycolysis, Krebs cycle, electron transport chain.
2. Day 2 — Enzyme kinetics
   Learn enzyme structure, substrate specificity, factors affecting activity (temperature, pH, concentration).
3. Day 3 — Nutrition and digestion
   Study mechanical and chemical digestion, digestive enzymes in each organ.
4. Day 4 — Practice
   Complete flashcards and quiz. Draw energy diagrams and digestion pathways.

✍️ Diagrams to practise

• Light reactions on thylakoid membrane with ATP/NADPH production
• Calvin cycle in stroma fixing CO2 to glucose
• Aerobic respiration: glycolysis, Krebs, electron transport with ATP yield
• Enzyme-substrate complex and product release
• Enzyme activity vs temperature and pH graphs
• Alimentary canal with organs and digestive enzymes