Curriculum

Science Grade 10

Grade 10 Science

0/13

Interactive Worksheets

0/2

Text lesson

Chapter 5: Life Processes

Grade 10 · Chapter 5 · Biology

Life Processes

Every living organism — from a single-celled amoeba to a complex human body — performs a set of essential biological functions to stay alive. These are known as life processes: Nutrition, Respiration, Transportation, and Excretion.

🌿 Nutrition

💨 Respiration

🫀 Transportation

🧹 Excretion

What Are Life Processes?

How do we tell what is alive and what is not? Visible movement — a dog running, a plant growing — is an obvious clue. But many living things show no visible movement at all. A sleeping animal, a dormant seed, or a non-growing plant are still alive. So visible movement is not a reliable definition of life.

Biologists point to molecular movement — the constant rearrangement of molecules within cells — as the true marker of life. Living structures are highly ordered and organised. Without constant maintenance, this order breaks down and the organism dies. These maintenance activities are called life processes.

Life processes require energy. That energy comes from food (external source), which must be broken down inside the body. Oxygen is often needed for this breakdown. Waste products must be removed. In multicellular organisms, specialised tissues and transport systems handle all of this.

📖 Key Definitions

Term	Definition
Life Processes	All maintenance activities that keep a living organism alive, including nutrition, respiration, transportation and excretion.
Nutrition	The process by which an organism obtains food (energy and raw materials) from its environment.
Autotroph	An organism that makes its own food from simple inorganic substances (e.g. CO₂ and water) using an external energy source such as sunlight. Examples: green plants, algae, some bacteria.
Heterotroph	An organism that cannot make its own food and depends on complex organic substances prepared by other organisms. Examples: animals, fungi.
Photosynthesis	The process by which green plants convert carbon dioxide and water into glucose and oxygen, using sunlight and chlorophyll.
Respiration	The process by which food molecules (glucose) are broken down to release energy (stored as ATP). May be aerobic (with oxygen) or anaerobic (without oxygen).
Transpiration	Loss of water in the form of vapour through the stomata of leaves. This helps pull water up from the roots through xylem.
Excretion	The removal of harmful metabolic waste products from the body. In humans this includes urea (removed by kidneys), CO₂ (removed by lungs) and water.
Enzyme	A biological catalyst (protein) that speeds up chemical reactions in living cells without being used up itself.

🌿	Section 1: Nutrition

All organisms need energy and materials to survive. The way they obtain food differs based on their complexity and environment. There are two fundamental modes: autotrophic and heterotrophic nutrition.

Photosynthesis Equation

6CO₂ + 12H₂O

Chlorophyll
→
Sunlight

C₆H₁₂O₆ + 6O₂ + 6H₂O
(Glucose)

🔬 Diagram: Cross-Section of a Leaf

Waxy Cuticle	Outermost waterproof layer. Prevents excess water loss from the leaf surface.
Upper Epidermis	Single layer of transparent cells. Allows light to pass through to the mesophyll below.
Palisade Mesophyll	Densely packed columnar cells. Contains the most chloroplasts — main site of photosynthesis.
Spongy Mesophyll	Loosely arranged cells with large air spaces. Allows CO₂ and O₂ to diffuse freely between cells.
Vascular Bundle	Contains Xylem (carries water up) and Phloem (carries sugars away). Also called the leaf vein.
Guard Cells / Stomata	Pairs of bean-shaped cells that open and close the stomatal pore. Control gas exchange and water loss.

🔬 Diagram: Open vs Closed Stomata

OPEN STOMATA (Day)

Guard cells swell with water → pore opens → CO₂ enters for photosynthesis

CLOSED STOMATA (Night / Drought)

Guard cells lose water → pore closes → prevents excess water loss

🔬 Diagram: Human Alimentary Canal

Organ	Secretion / Enzyme	Function
Mouth (Buccal Cavity)	Saliva / Salivary Amylase	Mechanical chewing; amylase breaks starch → simple sugar (maltose)
Oesophagus	None (muscular movement)	Peristalsis moves food from mouth to stomach
Stomach	HCl, Pepsin, Mucus	HCl creates acidic medium; pepsin digests proteins; mucus protects stomach lining
Small Intestine	Bile, Pancreatic juice, Intestinal juice	Complete digestion of carbs, proteins, fats; absorption via villi into bloodstream
Liver	Bile juice	Emulsifies large fat globules into smaller ones; neutralises stomach acid
Pancreas	Trypsin, Lipase	Trypsin digests proteins; lipase digests emulsified fats
Large Intestine	Water absorption	Absorbs water from undigested material; remaining waste expelled via anus

💨	Section 2: Respiration

Respiration is the process of breaking down food (glucose) to release energy stored as ATP (Adenosine Triphosphate). The first step — breaking glucose into pyruvate — occurs in the cytoplasm. What happens next depends on whether oxygen is available.

🔬 Diagram: Glucose Breakdown Pathways

GLUCOSE (6-carbon) → PYRUVATE (3-carbon) + ENERGY [in cytoplasm]

Aerobic Respiration

Location: Mitochondria

Condition: Oxygen present

Products: CO₂ + H₂O + ATP

Energy yield: HIGH

Anaerobic (in Yeast)

Location: Cytoplasm

Condition: No oxygen

Products: Ethanol + CO₂ + ATP

Energy yield: LOW

Anaerobic (in Muscles)

Location: Cytoplasm

Condition: O₂ shortage

Products: Lactic Acid + ATP

Causes: Muscle cramps

🔬 Diagram: Human Respiratory System

Structure	Role in Breathing
Nostrils	Entry point for air; fine hairs and mucus filter dust and germs
Trachea	Windpipe; kept open by rings of cartilage; carries air to bronchi
Bronchi → Bronchioles	Branching tubes that distribute air to all parts of both lungs
Alveoli	Tiny balloon-like air sacs at tube tips; enormous surface area (~80m²); walls one-cell thick; site of O₂/CO₂ exchange with blood
Diaphragm	Dome-shaped muscle below lungs. Contracts (flattens) to increase chest volume → air rushes in (inhalation)
Haemoglobin	Respiratory pigment in red blood cells; picks up O₂ from alveoli and delivers it to all body tissues

🫀	Section 3: Transportation

In multicellular organisms, food, oxygen and waste cannot simply diffuse to every cell. A dedicated transport system is essential. In humans, this is the circulatory system. In plants, it is the vascular system (xylem and phloem).

🔬 Diagram: The Human Heart (4 Chambers)

Chamber	Blood Type Received	Where It Sends Blood
Right Atrium	Deoxygenated (from body via vena cava)	Right Ventricle
Right Ventricle	Deoxygenated (from right atrium)	Lungs (via pulmonary artery) for oxygenation
Left Atrium	Oxygenated (from lungs via pulmonary vein)	Left Ventricle
Left Ventricle	Oxygenated (from left atrium)	Whole body (via aorta) — thickest muscular wall

🔬 Diagram: Blood Vessels Compared

Feature	Artery	Vein	Capillary
Direction	Away from heart	Toward heart	Between artery & vein
Wall Thickness	Thick and elastic	Thin	One-cell thick
Valves	No valves	Has valves (prevent backflow)	No valves
Function	Carry oxygenated blood (except pulmonary artery)	Carry deoxygenated blood (except pulmonary vein)	Exchange materials between blood and cells

🔬 Diagram: Transport in Plants (Xylem vs Phloem)

Feature	Xylem	Phloem
Transports	Water and dissolved minerals	Sugars, amino acids (products of photosynthesis)
Direction	Upward only (root → leaf)	Both upward and downward
Driving Force	Transpiration pull + root pressure	ATP energy (active transport)
Cell Type	Dead cells (vessels and tracheids)	Living cells (sieve tubes + companion cells)

🧹	Section 4: Excretion

Metabolic reactions produce waste products. Nitrogenous wastes such as urea and uric acid — produced from the breakdown of proteins — are toxic and must be removed. This removal process is called excretion.

🔬 Diagram: Structure of a Nephron (Kidney Filtration Unit)

Part	Function
Glomerulus	Knot of blood capillaries inside Bowman’s capsule. High pressure forces water, urea, glucose and salts into the capsule (filtration).
Bowman’s Capsule	Cup-shaped structure that collects the initial filtrate from the glomerulus. Starts the nephron tubule.
Proximal Tubule	Re-absorbs most glucose, amino acids, salts and water back into the blood.
Loop of Henle	Creates a concentration gradient; re-absorbs additional water. Concentrates the urine.
Distal Tubule	Final selective re-absorption. Secretes additional waste into the tubule.
Collecting Duct	Carries concentrated urine to the ureter → urinary bladder → urethra.

Excretion in Plants

Plants excrete waste in several unique ways: (1) Oxygen released during photosynthesis and CO₂ from respiration leave through stomata. (2) Excess water is lost through transpiration. (3) Waste materials are stored in cellular vacuoles. (4) Wastes are deposited in falling leaves. (5) Resins, gums and latex stored in old xylem. (6) Some wastes are excreted directly into the surrounding soil.

✏️ Worked Examples (10 Questions)

Example 1 — Photosynthesis

Q: What are the three essential inputs for photosynthesis, and what two main products are formed?

Show Answer

Inputs: (1) Carbon dioxide (CO₂) — absorbed from air through stomata. (2) Water (H₂O) — absorbed from soil via roots. (3) Sunlight — captured by chlorophyll in chloroplasts.

Products: (1) Glucose (C₆H₁₂O₆) — stored energy used by the plant. (2) Oxygen (O₂) — released into the atmosphere as a by-product.

Equation: 6CO₂ + 12H₂O + light energy → C₆H₁₂O₆ + 6O₂ + 6H₂O

Example 2 — Respiration

Q: Write the equation for aerobic respiration. Where does it take place in the cell?

Show Answer

Aerobic Respiration Equation:
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy (ATP)

Location: The first step (glycolysis: glucose → pyruvate) occurs in the cytoplasm. The second step (pyruvate breakdown) occurs in the mitochondria.

Key point: Aerobic respiration releases much more energy than anaerobic respiration because the complete breakdown of glucose is achieved.

Example 3 — Anaerobic Respiration

Q: Why do muscles cramp during intense exercise? Explain with chemistry.

Show Answer

During intense exercise, muscle cells consume oxygen faster than blood can supply it. When oxygen runs out, the cells switch to anaerobic respiration.

Anaerobic pathway in muscles:
Glucose → Pyruvate → Lactic acid + small amount of ATP

Cramps occur because lactic acid (a 3-carbon molecule) builds up in the muscle tissue. This build-up lowers pH and interferes with muscle contraction. Rest and increased blood flow (which brings oxygen) allow the lactic acid to be oxidised back to CO₂ and water, relieving the cramp.

Example 4 — Double Circulation

Q: What is double circulation? Why is it important in humans?

Show Answer

Double circulation means blood passes through the heart twice in one complete circuit of the body.

Circuit 1 (Pulmonary): Right side of heart → Lungs → Left side of heart (blood gets oxygenated)
Circuit 2 (Systemic): Left side of heart → Body organs → Right side of heart (oxygen delivered to cells)

Importance: It keeps oxygenated and deoxygenated blood completely separate (septum divides heart). This ensures high-pressure, oxygen-rich blood is delivered efficiently to all tissues — essential for warm-blooded animals (birds and mammals) that need constant energy to maintain body temperature.

Example 5 — Kidney Function

Q: Describe how a nephron filters blood to produce urine.

Show Answer

Step 1 — Ultrafiltration: Blood enters the glomerulus under high pressure. Small molecules (water, urea, glucose, amino acids, salts) are forced into the Bowman’s capsule. Large molecules (proteins, cells) remain in blood.

Step 2 — Selective Reabsorption: As the filtrate travels through the tubule, useful substances (glucose, amino acids, most water, salts) are reabsorbed back into the blood capillaries surrounding the tubule.

Step 3 — Tubular Secretion: Additional waste is secreted into the tubule fluid.

Result: Concentrated urine (water + urea + salts) drains into the ureter. Normally, 180 L is filtered daily but only 1–2 L is excreted — the rest is reabsorbed.

Example 6 — Stomata Function

Q: How do guard cells control the opening and closing of stomata?

Show Answer

Guard cells are a pair of curved cells surrounding the stomatal pore.

Opening (day/well-watered): Water enters guard cells by osmosis → guard cells become turgid (swollen) → their curved shape causes them to bow outward → stomatal pore opens → CO₂ enters for photosynthesis.

Closing (night/drought): Guard cells lose water → become flaccid (limp) → curve collapses inward → stomatal pore closes → prevents water loss by transpiration.

Example 7 — Nutrition Types

Q: Distinguish between autotrophic and heterotrophic nutrition with two examples of each.

Show Answer

Autotrophic Nutrition: The organism makes its own food from simple inorganic materials using an energy source (sunlight or chemicals). Does NOT depend on other organisms for food.
Examples: Green plants (photosynthesis), Cyanobacteria (blue-green algae)

Heterotrophic Nutrition: The organism cannot make its own food and must consume complex organic compounds made by other organisms. Depends directly or indirectly on autotrophs.
Examples: Humans (holozoic — ingest and digest food internally), Mushrooms/Bread mould (saprophytic — digest food outside body and absorb it)

Example 8 — Transpiration

Q: How does transpiration help in the upward movement of water in tall plants?

Show Answer

When stomata are open during the day, water molecules evaporate from leaf cells and escape as water vapour — this is transpiration.

As water leaves the leaf cells, they become less turgid and pull water from nearby xylem cells. This creates a “transpiration pull” — a continuous suction force that draws water upward through the xylem from the roots.

Root pressure also contributes: roots actively absorb ions from soil, creating a concentration gradient that draws water in, pushing it up. Together, transpiration pull (major force in daytime) and root pressure (important at night) move water to the top of even very tall trees.

Example 9 — Small Intestine

Q: How is the small intestine structurally adapted for the efficient absorption of digested food?

Show Answer

The small intestine is adapted for maximum absorption through several features:

(1) Length: It is very long (6–7 metres in humans) — folded into a compact space — giving more time and surface area for absorption.
(2) Villi: The inner lining has thousands of finger-like projections called villi, which dramatically increase the surface area.
(3) Microvilli: Each villus cell has further tiny projections (microvilli/brush border) — further increasing surface area.
(4) Rich blood supply: Each villus contains a dense network of capillaries and a lacteal (lymph vessel). Glucose and amino acids enter capillaries; fats enter lacteals.

Example 10 — ATP

Q: What is ATP and why is it called the “energy currency” of the cell?

Show Answer

ATP (Adenosine Triphosphate) is a molecule that stores and releases energy for use in cellular processes. It is produced during respiration from ADP + inorganic phosphate using the energy released from breaking down glucose.

Why “energy currency”? Just as money can be used for many different purposes, ATP can power many different types of cellular work — muscle contraction, protein synthesis, nerve impulse conduction, active transport of substances across membranes, and more.

When the terminal phosphate bond in ATP is broken (using water), approximately 30.5 kJ/mol of energy is released — a precise, usable amount that drives cellular reactions.

📝 Practice Sets A–D (with Answers)

Set A — Multiple Choice

1. The kidneys in human beings are part of which system?
(a) Nutrition (b) Respiration (c) Excretion (d) Transportation

2. Xylem in plants is responsible for:
(a) Transport of food (b) Transport of water (c) Transport of oxygen (d) Transport of amino acids

3. The breakdown of pyruvate to CO₂, water and energy takes place in the:
(a) Cytoplasm (b) Nucleus (c) Mitochondria (d) Chloroplast

4. The autotrophic mode of nutrition requires:
(a) CO₂ and water (b) Chlorophyll (c) Sunlight (d) All of the above

Show Answers

1. (c) Excretion 2. (b) Transport of water 3. (c) Mitochondria 4. (d) All of the above

Set B — Short Answer (2 marks each)

1. What is the role of saliva in digestion?

2. Why do aquatic organisms breathe faster than terrestrial organisms?

3. What is the function of platelets?

4. What is translocation in plants?

Show Answers

1. Saliva contains salivary amylase which breaks down starch (complex carbohydrate) into simple sugars (maltose). It also moistens food for easy swallowing.
2. Water contains far less dissolved oxygen than the atmosphere (about 1% vs 21%). Aquatic organisms must breathe faster to extract enough oxygen from water.
3. Platelets are cell fragments that circulate in blood. When a blood vessel is damaged, they rush to the site and form a plug (clot) to stop bleeding and seal the leak.
4. Translocation is the transport of dissolved sugars and other organic compounds made during photosynthesis through phloem to all parts of the plant, including roots, fruits and growing buds.

Set C — Long Answer (5 marks each)

1. Describe the complete journey of food through the human alimentary canal, naming the organs and enzymes at each stage.

2. With the help of a labelled diagram description, explain the double circulation of blood in human beings.

3. Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to structure and function.

Show Model Answer Points

Q1 key points: Mouth (salivary amylase → starch to maltose) → Oesophagus (peristalsis) → Stomach (HCl, pepsin → proteins) → Small intestine (bile emulsifies fats; trypsin, lipase, intestinal enzymes complete digestion; villi absorb products) → Large intestine (water absorbed) → Anus (egestion of waste).

Q2 key points: Blood travels through heart TWICE per circuit. Pulmonary circuit: right ventricle → pulmonary artery → lungs (gets O₂) → pulmonary vein → left atrium. Systemic circuit: left ventricle → aorta → body tissues → vena cava → right atrium. Importance: complete separation of oxygenated and deoxygenated blood; efficient oxygen delivery.

Q3 key points: Both are thin-walled structures maximising surface area for exchange. Alveoli: exchange O₂/CO₂ between air and blood; surrounded by capillaries; large surface area (~80m²). Nephrons: filter blood to remove urea/excess salts; Bowman’s capsule + glomerulus = high-pressure filtration; tubules = selective reabsorption; both require rich blood supply.

Set D — Application / Thinking Questions

1. Why is diffusion insufficient to meet the oxygen needs of a large multicellular organism like a human being?

2. A person’s haemoglobin level drops drastically. What effect would this have on their body, and why?

3. Why are carnivores like tigers able to survive with a shorter small intestine compared to herbivores like cows?

4. What would happen if the walls of the alveoli became thick due to disease? How would breathing be affected?

Show Answers

1. Diffusion is a very slow process that works only over very short distances. In a large body, cells deep inside are far from the surface. By the time oxygen diffused from the surface to internal organs, cells would already be dead from oxygen starvation. A circulatory system with haemoglobin dramatically speeds oxygen delivery.

2. Haemoglobin carries oxygen in red blood cells. Low haemoglobin = low oxygen-carrying capacity = less oxygen delivered to cells → the person would feel fatigue, weakness, breathlessness during activity (anaemia symptoms). In severe cases, organs begin to fail.

3. Cellulose in grass is very difficult to digest and requires long exposure to digestive enzymes. Meat (protein and fat) is far easier to digest and is absorbed much more quickly. Therefore herbivores need a much longer small intestine to give enough time for cellulose breakdown and absorption; carnivores do not need this extra length.

4. Thick alveolar walls would slow the diffusion of oxygen into the blood and CO₂ out. Less oxygen would reach the blood despite normal breathing. The person would experience breathlessness, reduced stamina, and potentially dangerous oxygen deprivation — similar to the effects of diseases like emphysema or pulmonary fibrosis.

📋 Chapter Summary

🌿 Nutrition

Autotrophs (plants) use photosynthesis: 6CO₂ + 12H₂O → glucose + O₂. Heterotrophs (animals, fungi) digest organic material. Human digestion: mouth → stomach → small intestine → absorption via villi.

💨 Respiration

Aerobic: glucose + O₂ → CO₂ + H₂O + ATP (mitochondria, HIGH energy). Anaerobic: glucose → lactic acid (muscles) or ethanol + CO₂ (yeast). ATP = energy currency of the cell.

🫀 Transportation

Human: 4-chamber heart, double circulation, blood vessels (arteries / veins / capillaries), lymph. Plants: xylem (water/minerals, upward), phloem (sugars, bidirectional, uses ATP).

🧹 Excretion

Humans: kidneys (nephrons filter blood, produce urine), CO₂ removed by lungs. Plants: O₂/CO₂ via stomata, water via transpiration, wastes stored in vacuoles, leaves, gums/resins.

⚡ 8-Point Exam Quick-Check

#	Must-Know Fact	Remember
1	Photosynthesis equation	6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O (needs chlorophyll + sunlight)
2	Aerobic vs Anaerobic respiration	Aerobic = mitochondria, HIGH ATP, needs O₂ \| Anaerobic = cytoplasm, LOW ATP, no O₂
3	Double circulation	Blood passes through heart TWICE per circuit. Keeps oxygenated and deoxygenated blood separate.
4	Xylem vs Phloem	Xylem = WATER (dead cells, upward only). Phloem = FOOD/SUGAR (living cells, both directions, needs ATP).
5	Blood pressure values	Normal systolic = 120 mm Hg \| Diastolic = 80 mm Hg. Hypertension = high BP (constricted arterioles).
6	Nephron filtration facts	~180 L filtered per day. Only 1–2 L excreted. Rest reabsorbed. Glomerulus filters; tubule reabsorbs.
7	Alveolar surface area	Alveolar surface ≈ 80 m² if spread out. Maximises gas exchange. Walls are one-cell thick.
8	Salivary amylase target	Salivary amylase breaks down STARCH → simple sugar. NOT proteins or fats (those are digested later).

This comprehensive Grade 10 Biology lesson on Life Processes (Chapter 5) covers all major topics including photosynthesis, nutrition in autotrophs and heterotrophs, aerobic and anaerobic cellular respiration, ATP production, human digestive system, human respiratory system, transportation in human beings and plants, double circulation, blood vessels, lymph, excretion in humans via nephrons and kidneys, and excretion in plants. Ideal for students preparing for CBSE Class 10 Science Board Exams, this page includes original worked examples, practice questions with answers, and detailed labelled diagram descriptions — providing complete revision material for the chapter on Life Processes in Class 10 Science.