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Science & Mathematics · Class 11

Class 11 Biology 2025–26: Cell Biology, Plant Physiology & Human Physiology — Chapter Weightage, Strategy & Key Terms Reference

Human Physiology carries 18 marks, Cell Biology 15, and three chapters are deleted from the 2025–26 syllabus. Learn the NCERT-first strategy, unit weightage, must-draw diagrams, and key Biology terms for CBSE and NEET.

By Genelis Team 14 min read Updated 2026-07-16T09:00:00+05:30

Class 11 Biology has a preparation advantage that almost no other Class 11 subject offers: the exam is almost entirely from NCERT. Not paraphrased, not adapted — directly from NCERT text, NCERT diagrams, and NCERT in-text questions. A student who reads NCERT carefully, practises every diagram from memory, and uses precise NCERT terminology in their answers is fully prepared for the annual exam. A student who reads summaries, uses shortcut notes, and skips diagram practice is not.

The second advantage — and the second urgency — is NEET. Nearly 45% of NEET Biology content comes from Class 11, especially cell biology and physiology. Class 11 Biology is not just an annual exam subject — it is half of the most important competitive exam for medical students. The preparation overlap is so complete that a student who genuinely masters Class 11 Biology for boards is simultaneously building their NEET Biology foundation.

Before opening a textbook: know which chapters are NOT in your annual exam. Three have been deleted from the 2025–26 rationalised NCERT syllabus. Studying them for annual exam purposes wastes time that should go to Human Physiology (18 marks) and Cell Biology.

Stop. These Three Chapters Are Not in Your Annual Exam.

⚠️ Deleted from CBSE Class 11 Biology annual exam 2025–26

  • Digestion and Absorption — deleted from Human Physiology unit (was Chapter 16)
  • Transport in Plants — deleted from Plant Physiology unit (was Chapter 11)
  • Mineral Nutrition — deleted from Plant Physiology unit (was Chapter 12)

Chapters like Digestion and Absorption, Transport in Plants, and Mineral Nutrition are DELETED and will not be asked in the annual exam. These are assessed only formatively at school level. Students targeting NEET must study them regardless — NEET follows the complete NCERT syllabus. For annual exam preparation: redirect that time to Human Physiology (18 marks), Cell Structure and Function, and Plant Physiology chapters that remain in the exam.

Human Physiology Is 18 Marks. Cell Biology Is 15. Here's the Complete Unit Weightage.

Human Physiology carries the highest weightage with 18 marks. There are 22 chapters divided across 5 major units. Diagrams account for around 25–30 marks and are compulsory in many questions. The theory paper carries 70 marks total.

CBSE Class 11 Biology — unit-wise marks distribution (theory, 70 marks) 2025–26
Human Physiology
Highest — 25.7%
18 marks ★
Structural Organisation in Animals & Plants
18.6%
13 marks
Cell Structure & Function
21.4%
15 marks
Diversity of Living Organisms
17.1%
12 marks
Plant Physiology
17.1%
12 marks

Source: CBSE official 2025–26 curriculum. Unit V (Human Physiology) carrying the highest weightage of 18 marks, understanding the official curriculum is crucial for both Board Exams and NEET.

Class 11 Biology contribution to NEET — by unit
Cell Biology
~28% of Class 11 NEET Qs
Human Physiology
~25%
Plant Physiology
~22%
Diversity & Classification
~15%
Structural Organisation
~10%

Nearly 45% of NEET Biology content comes from Class 11, especially cell biology and physiology.

The NCERT-First Rule — Why It Applies Even More Strongly in Class 11 Than Class 12

Every CBSE Biology annual exam question — from 1-mark MCQs to 5-mark diagram questions — is sourced from NCERT text, NCERT diagrams, NCERT in-text questions, or NCERT chapter-end exercises. This is not an approximation. It is a structural fact about how CBSE Biology papers are set. The rationalised NCERT textbook is the only source material available to question setters for the annual exam.

The three NCERT habits that produce the most marks:

1. In-text questions. NCERT Biology has questions embedded within the chapter text, not just at chapter end. Most students skip these because they appear too simple or informal. CBSE tests them directly — sometimes using the exact same question phrasing. Every in-text question should be answered in writing at least once.

2. Diagram captions. Every diagram in NCERT Biology has a caption explaining what is shown. These captions are frequently tested as "identify this structure" MCQs or "label the diagram" questions. Read every caption. Understand every label. Diagrams in Biology are not illustrations — they are testable content.

3. Exact NCERT terminology. CBSE Biology evaluators mark answers against expected NCERT language. Writing "the cell divides" instead of "the cell undergoes mitosis" loses a mark. Writing "DNA copies" instead of "DNA undergoes semi-conservative replication" loses a mark. Build a terminology list for each chapter. Revise it weekly. Use only NCERT terms in written answers.

💡 Diagrams account for around 25–30 marks and are compulsory in many questions. This is the single most mark-significant preparation habit in Class 11 Biology. A student who practises 12–15 key diagrams weekly from memory, with accurate labels and correct structure, can secure 25–30 marks from diagrams alone — more than one-third of the theory paper.

Cell Biology, Plant Physiology, Human Physiology — What Each Unit Demands

Cell Structure & Function — 15 marks

Diagram accuracy + process understanding

Cell biology tests two things: the structure of organelles (draw and label the cell, chloroplast, mitochondria) and the process of cell division (mitosis and meiosis — stages, significance, differences). Both require diagram mastery and precise NCERT language.

  • Cell organelles — structure and function of all (ER, Golgi, ribosome, lysosome, mitochondria, chloroplast, nucleus)
  • Mitosis — 4 stages with diagrams, significance (growth and repair)
  • Meiosis — overview, crossing over, significance (variation)
  • Biomolecules — carbohydrates, proteins, lipids, nucleic acids — structure and function
Plant Physiology — 12 marks (after deletions)

Process description + Z-scheme diagram

With Transport in Plants and Mineral Nutrition deleted, Plant Physiology now covers: Photosynthesis (the highest-returning chapter — Z-scheme diagram, light and dark reactions, C3 vs C4), Respiration in Plants (glycolysis, Krebs cycle, oxidative phosphorylation), and Plant Growth and Development (auxin, gibberellin, cytokinin — their roles and interactions).

  • Photosynthesis — light reactions (Z-scheme), Calvin cycle (dark reactions), C3 vs C4, CAM plants
  • Respiration — aerobic vs anaerobic, RQ values for different substrates
  • Plant growth regulators — 5 types, their specific roles, seed germination, fruit development
Human Physiology — 18 marks (after deletions)

Process explanation + diagram-based questions

With Digestion deleted, Human Physiology covers: Breathing (mechanism, lung volumes), Circulation (heart structure and cardiac cycle, blood groups, coagulation), Excretion (nephron structure, urine formation process — ultrafiltration, reabsorption, secretion), Locomotion (muscle contraction — sliding filament theory, sarcomere), and Neural Control (neuron structure, impulse transmission, reflex arc). Each chapter has a major diagram and a process explanation question.

  • Breathing — lung volumes (TV, IRV, ERV, RV), mechanism of breathing, oxygen and CO₂ transport
  • Circulation — cardiac cycle, ECG, blood groups (ABO + Rh), coagulation
  • Excretion — nephron (must draw), urine formation (3 steps with exact NCERT terms)
  • Locomotion — sarcomere (must draw), sliding filament theory, types of muscles
  • Neural — neuron (must draw), resting and action potential, reflex arc

12 Diagrams That Decide Your Biology Score — Learn to Draw Every One from Memory

Diagrams account for around 25–30 marks and are compulsory in many questions. Every diagram in this list has appeared in CBSE Class 11 annual papers or NEET papers — many appear in both every year. The preparation method: once per week, pick four diagrams, close all notes, draw from memory with all labels, check against NCERT, note missing labels, return to those the next day.

Cell Biology

Animal & Plant Cell

All organelles labelled: nucleus, ER (rough and smooth), Golgi, ribosome, mitochondria, lysosome, centriole (animal), chloroplast and cell wall (plant)

Every year
Cell Biology

Mitosis Stages

Prophase, Metaphase (chromosomes at equatorial plate), Anaphase, Telophase. Chromosomes must be drawn accurately at each stage.

Every year
Cell Biology

Chloroplast Ultrastructure

Outer and inner membrane, stroma, grana (stacked thylakoids), thylakoid membrane, stroma lamellae. Site of light reactions = thylakoid; dark reactions = stroma.

High frequency
Cell Biology

Mitochondria Ultrastructure

Outer membrane, inner membrane, cristae (invaginations), matrix, F₀F₁ particles on cristae. Krebs cycle = matrix; oxidative phosphorylation = inner membrane.

High frequency
Plant Physiology

Z-Scheme (Light Reactions)

P680 (PSII) → electron transport → P700 (PSI) → NADPH. Water splitting at PSII releasing O₂. ATP synthesis via photophosphorylation. Cyclic vs non-cyclic.

Every year (NEET)
Plant Physiology

Stomatal Apparatus

Guard cells (bean-shaped), subsidiary cells, stomatal pore. Opening mechanism: K⁺ ion accumulation → water enters guard cells by osmosis → turgid → pore opens.

High frequency
Human Physiology

Nephron Structure

Bowman's capsule, glomerulus, PCT (proximal convoluted tubule), loop of Henle (ascending and descending), DCT, collecting duct. Vasa recta alongside.

Every year
Human Physiology

Human Heart

4 chambers, 4 valves (tricuspid, bicuspid/mitral, pulmonary semilunar, aortic semilunar), major vessels, blood flow direction with arrows (deoxygenated and oxygenated paths).

Every year
Human Physiology

Neuron Structure

Cell body (soma), dendrites, axon, myelin sheath, nodes of Ranvier, axon terminals. Multipolar neuron is the most commonly tested form. Include synapse with neurotransmitter vesicles.

Every year
Human Physiology

Sarcomere Structure

A-band, I-band, H-zone, Z-line, M-line. Thick filaments (myosin) in A-band; thin filaments (actin) in I-band and A-band overlap. During contraction: I-band and H-zone shorten; A-band stays constant.

High — NEET essential
Human Physiology

Reflex Arc

Receptor → sensory (afferent) neuron → spinal cord (integration centre) → motor (efferent) neuron → effector (muscle/gland). Label synapse between neurons in spinal cord.

High frequency
Structural Organisation

TS of Dicot Root

Epidermis, cortex (parenchyma cells), endodermis (Casparian strips), pericycle, xylem (star-shaped, exarch), phloem (between xylem arms). Include root hair on epidermis.

High frequency

Biology Has Five Units. A Single Score Tells You Nothing About Which One Is Failing.

What a Genelis weak area map looks like after a Class 11 Biology test

Diversity — biological classification
85%
Cell Biology — organelle functions
73%
Plant Physiology — Z-scheme and Calvin cycle
52%
Human Physiology — nephron and urine formation
38%

Next session: Human Physiology nephron (38%) — not Diversity (85%). Genelis builds this map automatically after every practice session and test.

Genelis is an AI-powered personalized learning platform built on Adaptive Personalized Intelligence. The Genelis learning system tracks your accuracy separately across all five Class 11 Biology units — distinguishing diagram errors from process explanation errors, and terminology gaps from conceptual misunderstanding. Every wrong answer is logged to your wrong-question notebook, tagged by unit and question type. The next session is directed at the lowest-accuracy unit — not the most comfortable one.

Step 1 Attempt Biology session
→
Step 2 Unit-level gap detected
→
Step 3 AI notes for weak concept
→
Step 4 Wrong Qs auto-logged
→
Step 5 Reattempt those questions
→
Result Gap closed. Map updates. ✓
Start your personalised Class 11 Biology study plan on Genelis — free →

Complete Class 11 Biology Key Terms & Process Reference — Cell Biology, Plant Physiology & Human Physiology

Every definition below is in NCERT-aligned language — the exact phrasing that earns full marks in CBSE Biology answers. Method: cover the definition, state it from memory, check, return to gaps weekly.

C

Cell Structure & Function — Key Terms

15 marks · Diagram + process

Cell Organelles

Endoplasmic Reticulum
A network of membranous tubules and sacs (cisternae) throughout the cytoplasm. Rough ER (with ribosomes) synthesises and transports proteins. Smooth ER synthesises lipids and detoxifies drugs and poisons.
Golgi Apparatus
Stack of membrane-bound flattened sacs (cisternae) involved in processing, packaging, and secretion of proteins and lipids. Cis face receives from ER; trans face dispatches to destinations. Functions: glycosylation of proteins, formation of lysosomes, secretory vesicle production.
Lysosome
Membrane-bound vesicles containing hydrolytic enzymes (acid hydrolases, active at pH 5). Function: intracellular digestion of phagocytosed material. Called "suicide bags" because rupture releases enzymes that digest the cell itself.
Ribosome
Non-membranous organelle consisting of rRNA and proteins. Site of protein synthesis (translation). 80S in eukaryotes (60S + 40S subunits); 70S in prokaryotes (50S + 30S). Mitochondria and chloroplasts have 70S ribosomes — evidence of endosymbiotic origin.

Cell Division

Mitosis
Type of cell division producing two daughter cells genetically identical to the parent cell and to each other. Occurs in somatic (body) cells. Four stages: Prophase (chromatin condenses), Metaphase (chromosomes align at equatorial plate), Anaphase (chromatids separate to poles), Telophase (nuclear envelope reforms). Significance: growth, repair, and asexual reproduction.
Meiosis
Two-stage cell division (Meiosis I and Meiosis II) producing four haploid daughter cells from one diploid parent cell. Occurs in reproductive organs (gonads) to produce gametes. Crossing over in Prophase I creates genetic recombination. Significance: maintains chromosome number across generations and creates genetic variation.
Crossing Over
Exchange of segments between non-sister chromatids of homologous chromosomes during Prophase I (at the pachytene stage). Occurs at points called chiasmata. Results in new combinations of alleles (recombinant chromosomes). Major source of genetic variation in sexually reproducing organisms.
P

Plant Physiology — Key Terms & Processes

12 marks · Z-scheme + Calvin cycle essential

Photosynthesis

Light Reactions (Z-scheme)
Occur in thylakoid membranes. P680 (Photosystem II) absorbs light → water is split (photolysis) releasing O₂, electrons, and H⁺. Electrons pass through electron transport chain to P700 (Photosystem I) → electrons reduce NADP⁺ to NADPH. ATP is produced by photophosphorylation. Products: ATP, NADPH, O₂. Cyclic photophosphorylation: only PSI involved; only ATP produced; no NADPH, no O₂.
Calvin Cycle (Dark Reactions)
Occurs in stroma. CO₂ is fixed by RuBisCO enzyme onto RuBP (5C) → 3-phosphoglycerate (3C) → reduced to G3P using ATP and NADPH → G3P used to regenerate RuBP and form glucose. Net: 3CO₂ + 9ATP + 6NADPH → 1 G3P.
C3 vs C4 Plants
C3 plants: CO₂ first fixed into 3C compound (3-PGA) by RuBisCO in mesophyll cells. Photorespiration occurs — wasteful. Examples: wheat, rice, potato. C4 plants: CO₂ first fixed into 4C compound (oxaloacetate) in mesophyll cells; transferred to bundle sheath cells where CO₂ is released and refixed by RuBisCO. No photorespiration. Examples: maize, sugarcane.

Respiration in Plants

Glycolysis
Occurs in cytoplasm. Glucose (6C) → 2 pyruvate (3C). Net yield: 2 ATP and 2 NADH per glucose. Common to both aerobic and anaerobic respiration. Substrate-level phosphorylation.
Respiration Quotient (RQ)
RQ = volume of CO₂ released / volume of O₂ consumed. RQ for carbohydrates = 1 (equal volumes). RQ for fats < 1 (more O₂ needed). RQ for proteins ≈ 0.9. RQ > 1 for anaerobic respiration of carbohydrates. CBSE frequently asks "what does an RQ of X indicate" — know the RQ values for each substrate.

Plant Growth Regulators

Auxin (IAA)
Promotes cell elongation in shoots (positive phototropism, apical dominance). Inhibits lateral bud growth — removing apical bud releases lateral buds (apical dominance). High concentration inhibits root growth while promoting shoot growth. Produced at shoot apex.
Gibberellin
Promotes stem elongation, seed germination (breaking dormancy), and fruit development without fertilisation (parthenocarpy). Application on dwarf mutants restores normal height. Promotes bolting in long-day plants.
Cytokinin
Promotes cell division (cytokinesis). Delays leaf senescence (aging). Produced mainly in roots. Works synergistically with auxin — ratio of auxin:cytokinin determines differentiation (high ratio → root formation; low ratio → shoot formation in tissue culture).
Abscisic Acid (ABA)
The "stress hormone" — promotes seed dormancy, causes stomatal closure during water stress (triggers K⁺ ion efflux from guard cells → water leaves → stomata close). Promotes leaf abscission. Called the "inhibitor" growth regulator.
H

Human Physiology — Key Terms & Processes

18 marks ★ Highest unit · After deletions

Breathing & Exchange of Gases

Lung Volumes
Tidal Volume (TV) = 500 mL (normal breath). Inspiratory Reserve Volume (IRV) = ~2500 mL. Expiratory Reserve Volume (ERV) = ~1000 mL. Residual Volume (RV) = ~1100 mL (air that cannot be expelled). Vital Capacity = TV + IRV + ERV = ~4000 mL. Total Lung Capacity = VC + RV = ~5100 mL.
Oxyhaemoglobin dissociation
Haemoglobin has higher affinity for O₂ at high pO₂ (lungs) and releases O₂ at low pO₂ (tissues). CO₂ and H⁺ decrease Hb's affinity for O₂ (Bohr effect) — promoting O₂ release at metabolically active tissues. CO transport: 70% as bicarbonate (HCO₃⁻), 20–25% as carbaminohaemoglobin, 7% dissolved.

Body Fluids & Circulation

Cardiac Cycle
One complete heartbeat lasting ~0.8 seconds. Atrial systole (0.1s) → Ventricular systole (0.3s, lub sound = AV valves close) → Joint diastole (0.4s, dub sound = semilunar valves close). Stroke volume ≈ 70 mL. Heart rate ≈ 72 beats/min. Cardiac output = 70 × 72 ≈ 5 L/min.
ABO Blood Groups
Determined by presence of antigens (A and/or B) on RBC surface and antibodies in plasma. Group A: antigen A, antibody anti-B. Group B: antigen B, antibody anti-A. Group AB: both antigens, no antibodies (universal recipient). Group O: no antigens, both antibodies (universal donor).

Excretory Products & Their Elimination

Urine Formation — 3 Steps
Step 1 — Ultrafiltration: blood filtered under high pressure in glomerulus → glomerular filtrate (GFR ~125 mL/min = ~180 L/day). Step 2 — Selective reabsorption: glucose, amino acids, 70–80% water, Na⁺ reabsorbed in tubules. Step 3 — Tubular secretion: H⁺, K⁺, creatinine, ammonia secreted into tubule. Final urine: ~1–1.8 L/day.

Locomotion & Neural Control

Sliding Filament Theory
Muscle contraction occurs when myosin heads (thick filaments) attach to actin (thin filaments) and pull them toward the M-line, shortening the sarcomere. Requires ATP (for myosin detachment and movement) and Ca²⁺ (released from sarcoplasmic reticulum to expose actin binding sites by moving tropomyosin). I-band and H-zone shorten; A-band length remains constant.
Resting Membrane Potential
In resting neuron: inside is −70mV relative to outside (polarised). Maintained by Na⁺-K⁺ ATPase pump (3 Na⁺ out, 2 K⁺ in) and selective permeability. Stimulus → Na⁺ channels open → Na⁺ rushes in → depolarisation → action potential generated → propagates along axon.
Synapse
Junction between two neurons (or neuron and effector). Action potential reaches presynaptic terminal → Ca²⁺ influx → neurotransmitter (acetylcholine) released from synaptic vesicles into synaptic cleft → binds to receptors on postsynaptic membrane → generates new action potential. Neurotransmitter then broken down by acetylcholinesterase.
💡 How to use this reference sheet: For each definition — cover and reproduce in writing from memory. For process descriptions (Z-scheme, urine formation, cardiac cycle) — reproduce as a numbered step sequence without looking. Practise weekly from August. By December, all terms and processes should come to mind in under 10 seconds. In the exam, that speed is the difference between completing long-answer questions fully and running out of time.
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Frequently Asked Questions

Questions Students Commonly Ask

Quick answers to the most common questions related to this guide.

Which unit has the highest weightage in Class 11 Biology CBSE 2025–26?

Human Physiology (Unit V) carries the highest weightage at 18 marks out of 70 theory marks. It covers Breathing and Exchange of Gases, Body Fluids and Circulation, Excretory Products and Their Elimination, Locomotion and Movement, and Neural Control and Coordination. This unit is also critically important for NEET, where physiology questions appear in every paper.

Which chapters are deleted from Class 11 Biology CBSE 2025–26?

Three chapters are deleted from the Class 11 Biology 2025–26 rationalised NCERT syllabus and will NOT appear in the annual exam: (1) Digestion and Absorption — previously in Human Physiology unit; (2) Transport in Plants — previously in Plant Physiology unit; (3) Mineral Nutrition — previously in Plant Physiology unit. Students targeting NEET must study these chapters regardless, as NEET follows the complete NCERT syllabus. For CBSE board/annual exam preparation, do not allocate significant time to these three deleted chapters.

Is NCERT enough for Class 11 Biology CBSE annual exam?

Yes — unequivocally. CBSE Class 11 Biology annual exam questions are almost entirely from NCERT text, NCERT diagrams, and NCERT in-text questions. The rationalised NCERT textbook is the only resource students need for board/annual exam preparation. Read every line, every diagram caption, every in-text question. Do not rely on reference books or additional guides for board preparation. For NEET, supplement NCERT with MCQ practice but keep NCERT as the primary resource.

What diagrams are most important for Class 11 Biology CBSE and NEET?

The must-draw diagrams for Class 11 Biology, ranked by frequency: cell structure (animal and plant cell with all organelles), mitosis stages (especially metaphase and anaphase), meiosis overview, chloroplast ultrastructure, mitochondria ultrastructure, photosynthesis Z-scheme (light reactions), nephron structure, human heart, neuron structure with synapse, reflex arc, sarcomere structure (muscle contraction), stomatal apparatus cross-section, and TS and LS of dicot and monocot roots/stems. Each must be drawn from memory with minimum 6 accurate labels.

How much of NEET Biology comes from Class 11?

Approximately 45% of NEET Biology questions come from Class 11 content, making Class 11 Biology preparation critically important for medical entrance. The highest-contributing Class 11 chapters for NEET are Cell Structure and Function (cell organelles, cell cycle, cell division), Plant Physiology (photosynthesis, respiration, growth and development), Human Physiology (breathing, circulation, excretion, nervous system, locomotion), and Diversity of Living Organisms (biological classification and plant kingdom). The Class 11 Biology foundation directly determines NEET Biology performance.

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