Biology 1st Year Book PDF Download (Punjab Board FSC)

Biology 1st Year book (Class 11) is published by the Punjab Education, Curriculum, Training and Assessment Authority (PECTAA). The latest 2025–26 edition is based on the Updated/Revised National Curriculum of Pakistan 2023. It covers twelve chapters ranging from Biodiversity and Classification to Human Skeletal and Muscular Systems.

For FSC Part 1 students, this book is the core resource for the Punjab Board Biology paper. Each chapter builds a clear understanding of biological concepts through theory, diagrams, and structured exercises. The PDF makes it easy to revise key topics, go over diagrams, and prepare chapter by chapter before the final board exam.

Book Overview

Class	11 (FSC Part 1 / First Year)
Subject	Biology
Category	FSC
Board	Punjab Board (PECTAA, Lahore)
Curriculum	NCP 2023 (Updated/Revised)
Edition	2025–26
Total Chapters	12
Total Pages	282
Format	PDF

Chapter List

Chapter 1 – Biodiversity and Classification

This chapter opens with the three-domain system proposed by Carl Woese, which groups all organisms into Archaea, Bacteria and Eukarya based on differences in cell membrane lipids, cell wall composition and genetics. It then works through the taxonomic hierarchy from domain down to species, and outlines the salient features of the Eukarya kingdoms — Protista, Fungi, Plantae and Animalia — along with the major animal phyla from Porifera to Chordata. The chapter also explains virus classification by host range, morphology, genetic material and replication strategy, and covers biodiversity assessment levels and the mechanisms of speciation.

Important Questions:

• What are the three domains of life and how do they differ? Archaea, Bacteria and Eukarya; Archaea and Bacteria are prokaryotic but differ in cell membrane lipids and cell wall composition, while Eukarya has membrane-bound organelles and a true nucleus.
• What type of speciation occurs when populations are separated by a physical barrier? Allopatric speciation, as seen in Darwin’s finches on the Galápagos Islands.
• What is the difference between a sac-like and a tube-like digestive system? A sac-like system (as in cnidarians) has one opening for both food intake and waste removal, while a tube-like system has separate mouth and anus for one-way food passage.
• Which kingdom has cell walls made of chitin and is mostly decomposers? Kingdom Fungi, whose members absorb nutrients from their surroundings instead of ingesting food.

Chapter 2 – Bacteria and Viruses

Chapter 2 details the structure of a generalized bacterial cell, from the peptidoglycan cell wall and Gram staining reaction to the nucleoid, plasmids and mesosomes in the cytoplasm. It explains how bacteria form dormant endospores to survive harsh conditions, and describes the different ways bacteria move — flagellar swimming, twitching, gliding and axial filaments — along with flagellar structure and arrangement. The chapter also covers the ecological and economic importance of bacteria as recyclers, product-makers and biopesticides, the concept of normal flora, and the structure of a model bacteriophage and HIV.

Important Questions:

• What is the main structural component of the bacterial cell wall? Peptidoglycan (murein), a polysaccharide chain cross-linked with short peptide fragments.
• What is sporulation? The process by which a bacterium forms a dormant, thick-walled endospore to survive unfavourable conditions.
• Which enzyme converts HIV’s RNA into DNA? Reverse transcriptase, the defining enzyme of retroviruses like HIV.
• What is normal flora and how does it benefit the body? The mixture of microorganisms that normally live on body surfaces; it produces vitamins like K and B12 and prevents colonization by pathogens.

Chapter 3 – Cells and Subcellular Organelles

This chapter builds on the seven properties of life to establish the cell as the basic unit of biology, and traces cell theory from Hooke’s cork observations to Virchow’s principle that cells arise only from pre-existing cells. It compares light and electron microscopy, then works through the structure and function of every major organelle — nucleus, endoplasmic reticulum, ribosomes, mitochondria, chloroplasts, Golgi apparatus, lysosomes and peroxisomes — before contrasting prokaryotic and eukaryotic cells. The chapter closes with cell signalling pathways, the four membrane transport mechanisms, and the categories and medical uses of stem cells.

Important Questions:

• What are the three points of cell theory? All organisms are made of cells; cells are the basic unit of structure and function; cells arise only from pre-existing cells.
• How does facilitated diffusion differ from active transport? Facilitated diffusion moves substances down their concentration gradient through transport proteins without using energy, while active transport uses ATP to move substances against their gradient.
• Why do mitochondria and chloroplasts have their own DNA? Because they are believed to have originated as free-living prokaryotes engulfed by a larger cell in an endosymbiotic relationship.
• What is the difference between pluripotent and multipotent stem cells? Pluripotent stem cells can become almost any cell type, while multipotent stem cells can only differentiate into a closely related family of cells.

Chapter 4 – Molecular Biology

Chapter 4 (titled Biomolecules in the book) introduces the types of chemical bonds that hold biomolecules together, and the condensation and hydrolysis reactions that build and break macromolecule polymers. It explains why water’s polarity, hydrogen bonding and high specific heat make it the medium of life, then classifies carbohydrates, proteins, lipids and nucleic acids in detail — including monosaccharide isomers, the four levels of protein structure, the classes of lipids, and Watson and Crick’s double-helix model of DNA. The chapter ends with the central dogma of transcription and translation, and conjugated molecules like glycoproteins and lipoproteins.

Important Questions:

• How is a peptide bond formed? By dehydration synthesis between the amino group of one amino acid and the carboxyl group of another, releasing a water molecule.
• What is the difference between structural isomers and stereoisomers, using glucose as an example? Glucose and fructose are structural isomers (same formula, different atom arrangement); glucose and galactose are stereoisomers (differ only in the orientation of one OH group).
• What causes sickle cell anaemia at the molecular level? A single amino acid substitution — valine replacing glutamic acid at position six of the beta chain of haemoglobin.
• What are the two steps of the central dogma? Transcription (DNA to RNA) and translation (RNA to protein).

Chapter 5 – Enzymes

This chapter explains how the active site of an enzyme binds a specific substrate, and how cofactors and coenzymes like NAD+ assist in catalysis. It compares the lock-and-key and induced fit models of enzyme action, and shows how enzymes lower activation energy to speed up reactions. Detailed sections cover how temperature, pH, and enzyme and substrate concentration affect reaction rate, along with competitive, non-competitive, reversible and irreversible inhibition and feedback inhibition. The chapter closes by classifying enzymes into six classes by reaction type and by the substrates they act on.

Important Questions:

• What is the difference between competitive and non-competitive inhibitors? A competitive inhibitor resembles the substrate and blocks the active site directly, while a non-competitive inhibitor binds elsewhere on the enzyme and changes its shape.
• How does the induced fit model differ from the lock-and-key model? The lock-and-key model treats the active site as rigid, while the induced fit model says the active site changes shape slightly when the substrate binds.
• What is activation energy? The minimum energy needed to start a chemical reaction; enzymes lower this energy to speed up reactions.
• Give one example each of an oxidoreductase and a hydrolase enzyme. Cytochrome oxidase (oxidoreductase) catalyses oxidation; lipase (hydrolase) breaks down fats by adding water.

Chapter 6 – Bioenergetics

Chapter 6 explains ATP as the universal energy currency before covering photosynthesis in depth — the role of light, CO2 and water, photosynthetic pigments and photosystems I and II, and the Z-scheme of cyclic and non-cyclic photophosphorylation that produces ATP and NADPH for the Calvin cycle. It then details the four stages of aerobic cellular respiration — glycolysis, pyruvic acid oxidation, the Krebs cycle, and the electron transport chain with chemiosmosis — and contrasts this with anaerobic fermentation. The chapter ends with photorespiration and the C4 and CAM adaptations plants use to reduce it in hot climates.

Important Questions:

• What is chemiosmosis? The mechanism by which the energy of an H+ ion gradient across a membrane, built up by the electron transport chain, is used by ATP synthase to make ATP.
• Why is aerobic respiration far more efficient than anaerobic respiration? Aerobic respiration fully oxidizes glucose and yields about 36 ATP per molecule, while anaerobic respiration (fermentation) yields only 2 ATP.
• What is the difference between cyclic and non-cyclic photophosphorylation? Non-cyclic uses both photosystems and produces ATP, NADPH and oxygen; cyclic uses only photosystem I and produces only ATP, with no oxygen released.
• Why do C4 plants have an advantage over C3 plants in hot climates? C4 plants concentrate CO2 in bundle-sheath cells, which reduces photorespiration and the loss of fixed carbon at high temperatures.

Chapter 7 – Structural and Computational Biology

This new NCP-2023 chapter introduces structural biology — how determining the 3D shapes of proteins and nucleic acids helps identify drug targets and active sites, understand host-pathogen interactions like the coronavirus spike protein binding to human receptors, and explain diseases caused by protein misfolding. It explains the steps of X-ray crystallography, from growing a protein crystal to building a 3D structure from its diffraction pattern. The chapter then introduces computational biology — genomics, proteomics and bioinformatics — key databases like GenBank, PDB and Ensembl, tools like BLAST and FASTA, and the concepts of sequence and structural homology.

Important Questions:

• What is the first step in an X-ray crystallography experiment? Growing a good-quality protein crystal, since a regular repeating pattern of molecules is needed for a clear diffraction pattern.
• What is the difference between genomics and proteomics? Genomics studies an organism’s complete set of DNA (the genome), while proteomics studies the complete set of proteins (the proteome) it produces.
• What is GenBank? A comprehensive public database of nucleotide sequences with biological annotations, used for genetic research and comparative genomics.
• What is the difference between orthologs and paralogs? Orthologs are homologous sequences in different species that arose through speciation, while paralogs are homologous sequences within the same species that arose through gene duplication.

Chapter 8 – Plant Physiology

Chapter 8 covers plant nutrition, including the roles of macro- and micronutrients and how insectivorous plants like the pitcher plant and Venus flytrap supplement their diet. It explains gas exchange through stomata, the supporting tissues, and water potential, before detailing how water moves from roots to leaves through xylem via the TACT mechanism and how sugars move through phloem by the pressure-flow theory. The chapter also covers primary and secondary growth, plant hormones, osmotic and thermal adaptations in different plant habitats, tropic movements, and the roles of photoperiodism and vernalisation in flowering.

Important Questions:

• What is the TACT mechanism? It explains how water rises through xylem via Transpiration, Adhesion, Cohesion and Tension, pulling an unbroken column of water from roots to leaves.
• What is the difference between long-day and short-day plants? Long-day plants flower when the dark period is shorter than a critical length, while short-day plants flower when the dark period is longer than a critical length.
• What is vernalisation? Exposure of a plant to low temperature to stimulate flowering, required by many biennial and perennial plants.
• Which plant hormone inhibits stem and root growth during stress like drought? Abscisic acid (ABA), which also promotes stomatal closure during water stress.

Chapter 9 – Human Digestive System

This chapter follows food through the entire human digestive tract, from mechanical and chemical digestion in the oral cavity and the role of the epiglottis in swallowing, to the three-layered structure of the stomach wall and the hormonal (gastrin) and nervous control of gastric juice secretion. It details the three regions of the small intestine, the action of pancreatic juice and bile, and how absorbed sugars, amino acids, fatty acids and glycerol reach the blood and lymph through villi. The chapter closes with the large intestine’s role in water absorption, the reflex of egestion, and the liver’s storage and metabolic functions.

Important Questions:

• What is the difference between bolus and chyme? Bolus is the moist mass of food formed after chewing in the mouth; chyme is the semi-liquid, acidic mass formed after food mixes with gastric juice in the stomach.
• What is the role of bile in digestion? Bile, produced by the liver and stored in the gallbladder, emulsifies fats into small droplets so lipase enzymes can digest them more effectively.
• Which hormones control the release of bile and pancreatic juice? Secretin and cholecystokinin (CCK), released by the duodenal walls when chyme enters from the stomach.
• What is the difference between physical and chemical digestion? Physical digestion breaks food into smaller pieces mechanically, while chemical digestion uses enzymes to break down molecules into absorbable units.

Chapter 10 – Human Respiratory System

Chapter 10 defines the properties of an ideal respiratory surface and traces air through the upper respiratory tract (nasal cavity, pharynx, larynx) and lower respiratory tract (trachea, bronchi, bronchioles) down to the alveoli, where gas exchange actually occurs. It explains the mechanics of inspiration and expiration through the diaphragm and intercostal muscles, and how oxygen and carbon dioxide are transported in blood — including the roles of haemoglobin, the Bohr effect, and bicarbonate ions. The chapter ends with the causes, symptoms and treatment of respiratory infections like sinusitis, otitis media, pneumonia and tuberculosis, and lung disorders like COPD and emphysema.

Important Questions:

• What is the role of surfactant in the alveoli? It lines the inside of alveoli and prevents them from collapsing and sticking together when air moves out.
• What is the Bohr effect? The lowering of blood pH by CO2 reduces haemoglobin’s affinity for oxygen, causing it to release oxygen more readily to tissues.
• What is the main difference between haemoglobin and myoglobin? Haemoglobin has four polypeptide chains and four haem groups and transports oxygen in blood; myoglobin has one chain and one haem group and stores oxygen in muscle.
• What happens to the alveoli in emphysema? Their inner walls are damaged and rupture, forming fewer, larger air spaces and reducing the surface area available for gas exchange.

Chapter 11 – Human Circulatory System

This chapter covers the structure of the heart — its walls, chambers, valves and the pericardium — and traces the flow of blood through the double pump of pulmonary and systemic circulation. It explains the cardiac cycle, the role of the SA node, AV node and Purkinje fibres in controlling heartbeat, and how to read an ECG. The chapter details the structure of arteries, capillaries and veins, systolic and diastolic blood pressure and its regulation, and covers cardiovascular disorders like atherosclerosis, thrombosis and hypertension along with treatments such as angioplasty and coronary bypass. It closes with the lymphatic system.

Important Questions:

• What is the difference between systolic and diastolic pressure? Systolic pressure is the highest arterial pressure during ventricular contraction (about 120 mm Hg); diastolic pressure is the lowest pressure between beats (about 80 mm Hg).
• What is the role of the SA node? Known as the pacemaker, it initiates each heartbeat by sending electrical impulses that cause the atria to contract.
• What is the difference between a thrombus and an embolus? A thrombus is a blood clot that forms and stays in a vessel; an embolus is a thrombus that breaks loose and travels to another location.
• How does atherosclerosis lead to a heart attack? Fatty deposits narrow the coronary arteries and increase the risk of a thrombus, which can block blood flow to heart muscle and cause a myocardial infarction.

Chapter 12 – Human Skeletal and Muscular Systems

The final chapter compares the structure of bone and cartilage, and the roles of osteoblasts, osteocytes and osteoclasts in bone growth and repair. It covers the axial and appendicular skeleton, the three types of joints, and skeletal disorders like disc slip, spondylosis, sciatica, arthritis and osteoporosis along with first aid for dislocations and sprains. The chapter then compares skeletal, smooth and cardiac muscle, explains the ultrastructure of skeletal muscle fibres, and details the sliding filament model of contraction step by step. It closes with the antagonistic action of muscles at the knee joint and disorders like fatigue, cramps and tetany.

Important Questions:

• What is the sliding filament model of muscle contraction? It explains that a muscle contracts when thin actin filaments slide past thick myosin filaments and overlap more, shortening each sarcomere.
• What is the difference between tetany and tetanus? Tetany is involuntary muscle spasm caused by conditions like low blood calcium; tetanus is a bacterial infection (Clostridium tetani) that causes muscle stiffness through a toxin.
• What is the role of osteoblasts and osteoclasts in bone remodelling? Osteoblasts build new bone tissue, while osteoclasts break down old bone and release calcium and phosphate — together they continuously remodel bone.
• Why can muscles only pull and not push? Because muscle fibres generate force only by contracting and shortening, pulling on tendons; they are attached to bone at one end so cannot push it away.

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Download Biology Class 11 Book PDF

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2025–26 Edition (NCP 2023 — PECTAA)

⬇ Download PDF (2025–26)

E-Learn Punjab Edition

⬇ Download PDF (E-Learn Punjab)

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Who Should Read This

This book is for FSC Part 1 (First Year) science students preparing for the Punjab Board annual exam. It is also highly relevant for students planning to appear in MDCAT, as Biology from Class 11 forms a major portion of the MDCAT syllabus. Topics like cell biology, molecular biology, enzymes, and human body systems are directly tested in the entry test.

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Applicable Boards

This textbook is published by PECTAA and is used in Punjab Board colleges. Students from the Federal Board (FBISE) and AJK Board can also use it as a reference, since the FSC Biology syllabus is largely the same. The chapter content also aligns well with Sindh and KPK board syllabi for first-year Biology.

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