Topics
Living World
- Concept of Living
- Taxonomical Aids
Systematics of Living Organisms
- Systematics of Living Organisms (Introduction)
- Systematics of Living Organisms (Introduction)
- Concept of Systematics
- Concept of Systematics
- Classification of Taxonomy
- Classification of Taxonomy
- Three Domains of Life
- Three Domains of Life
- Chemotaxonomy
- Chemotaxonomy
- Numerical Taxonomy
- Numerical Taxonomy
- Cladogram
- Cladogram
- Phylogeny
- Phylogeny
- DNA Barcoding
- DNA Barcoding
- Taxonomic Hierarchy of Living Organisms: Unit of Classification
- Taxonomic Hierarchy of Living Organisms: Unit of Classification
- Taxonomic Hierarchy
- Taxonomic Hierarchy
- Units of Classification
- Units of Classification
- Binomial Nomenclature
- General Features of Five Kingdoms
- General Features of Five Kingdoms
- Acellular Organisms
- Acellular Organisms
Kingdom Plantae
- Kingdom Plantae
- Salient Features of Major Plant Groups Under Cryptogams
- Salient Features of Major Plant Groups Under Phanerogams
- Plant Life Cycle and Alternation of Generations
Kingdom Animalia
- Criteria Used for Animal Classification
- Animal Body Plan
- Animal Classification
Cell Structure and Organization
- Cell: Structural and Functional Unit of Life
- Types of Cells
- Components of Eukaryotic Cell
Biomolecules
- Biomolecules in Living System
- Biomolecules in the Cell
- Biomolecules in the Cell > Carbohydrates
- Biomolecules in the Cell > Lipids
- Biomolecules in the Cell > Proteins
- Biomolecules in the Cell > Nucleic Acids
- Biomolecules in the Cell > Enzymes
- Nature of Enzyme Action
- Biomolecules in the Cell > Enzymes
- Biomolecules in the Cell > Enzymes
- Enzyme - Substrate Interactions
- Factors Affecting Enzyme Activity
- Metabolism
- Metabolic Pool
- Metabolism
Cell Division
Plant Tissues and Anatomy
- Tissues - “The Teams of Workers”
- Meristems or Meristematic Tissues
- Permanent Tissue
- Tissue System
- Secondary Growth in Plants
- Wood
- Cork Cambium and Secondary Growth
- Anatomy of Root, Stem and Leaf
Morphology of Flowering Plants
- Phanerogams > Division II- Angiosperms
- Evidences of organic evolution > Morphology
- Study of Some Important Families
Animal Tissue
Study of Animal Type : Cockroach
- Systematic Position
- External Morphology
- Body Cavity
- Digestive System of Cockroach
- Reproduction System
- Interactions with Mankind
Photosynthesis
- Concept of Photosynthesis
- Chloroplasts
- Nature of Light
- Mechanism of Photosynthesis
- Light Reaction
- Photophosphorylation
- Light-Independent Phase of Photosynthesis
- Photorespiration
- C4 Pathway Or Hatch-slack Pathway
- Cam - Crassulacean Acid Metabolism
- Factors Affecting Photosynthesis
Respiration and Energy Transfer
- Production of ATP
- Glycolysis
- Phases of Respiration: Pyruvate Oxidation (Link Reaction)
- Electron Transport System (Ets) and Oxidative Phosphorylation
- Tricarboxylic Acid Cycle (Citric Acid Cycle or Kreb’s Cycle)
- Phases of Respiration: Electron Transport Chain (Electron Transfer System)
- Fermentation
- Respiratory Balance Sheet
- Amphibolic Pathways
- Utility of Stepwise Oxidation
- Respiratory Quotient
Human Nutrition
- Nutrients and Nutrition
- Component of Food
- Human Digestive System
- The Mouth and Buccal Cavity
- The Salivary Glands
- The Teeth and Its Structure
- Human Digestive System
- The Food Pipe/Oesophagus
- The Stomach
- The Small Intestine
- The Large Intestine
- Human Digestive System
- Physiology of Digestion
- Absorption of Food
- Assimilation of Food
- Egestion of Food
- Nutritional and Digestive Tract Disorders
Excretion and Osmoregulation
- Excretion
- Modes of Excretion: Ammonotelism, Ureotelism, and Uricotelism
- Human Excretory System
- Kidney and Its Internal Structure
- Structure of a Kidney Tubule (Nephrons)
- Function of the Kidney - “Production of Urine”
- Concentration of Urine
- Composition of Urine
- The Excretory Organs
- Common Disorders of the Urinary System
Skeleton and Movement
- Movements and Locomotion
- Location and Structure of Skeletal Muscles
- Working of Skeletal Muscles
- Mechanism of Muscle Contraction
- Physiology of Muscle Relaxation
- Relaxation of Muscle Fibres
- Skeletal System
- Group of Skeleton
- Types of Joints
- Disorders Related to Muscles
- Disorders Related to Bones
Estimated time: 3 minutes
CBSE: Class 12
Key Points: Mechanism of Muscle Contraction
- Muscle contraction follows the sliding filament theory, where thin (actin) filaments slide over thick (myosin) filaments.
- Contraction begins with a signal from the CNS through a motor neuron; the neuron and muscle fibres together form a motor unit.
- The neuromuscular junction (motor-end plate) is the point where the motor neuron connects to the muscle fibre.
- Acetylcholine is released, which generates an action potential and causes the release of Ca²⁺ from the sarcoplasmic reticulum.
- Calcium ions activate actin, allowing myosin heads to bind and form cross-bridges.
- Cross bridges pull actin filaments, causing sliding, shortening of the sarcomere, and muscle contraction (I-band shortens, A-band remains the same).
- ATP helps in breaking and reforming cross-bridges; when Ca²⁺ is pumped back, the muscle relaxes.
