Biology — Cell and Organ Systems

Overview

Cell and Organ Systems is a foundational topic in the Science section of KAR TET Paper II, bridging basic biology with human physiology. Questions typically test your understanding of cell structure, tissue classification, and the functions of major organ systems. This topic carries significant weight because it connects microscopic biology to observable body functions — a key conceptual link for upper-primary science teaching.

For the exam, you must know the structural differences between plant and animal cells, the four basic tissue types, and the components and functions of human organ systems. Expect questions that ask you to identify organelles, match tissues to their functions, or explain how organ systems work together. Mastery here also supports pedagogy questions about teaching life sciences through models, diagrams, and activity-based learning.

Key Concepts

• **Cell is the structural and functional unit of life** — all living organisms are made of cells; cells carry out all life processes.

• **Prokaryotic vs Eukaryotic cells** — prokaryotes (bacteria) lack a membrane-bound nucleus; eukaryotes (plants, animals, fungi) have a true nucleus and membrane-bound organelles.

• **Plant cells have cell wall, chloroplasts, and large central vacuole** — animal cells lack these but have centrioles for cell division.

• **Tissues are groups of similar cells performing a specific function** — four basic types in animals: epithelial, connective, muscular, and nervous.

• **Organs are made of multiple tissue types working together** — example: stomach has epithelial lining, muscular wall, connective tissue, and nerve supply.

• **Organ systems are groups of organs performing related functions** — eleven major systems in humans work in coordination.

• **Division of labour** — in multicellular organisms, different cells specialise for different functions, increasing efficiency.

Formulas / Key Facts

| Cell Organelle | Function | |----------------|----------| | Nucleus | Controls cell activities; contains genetic material (DNA) | | Cell membrane | Selectively permeable; controls entry and exit of substances | | Mitochondria | Powerhouse of cell; site of cellular respiration (ATP production) | | Ribosomes | Protein synthesis | | Endoplasmic Reticulum (ER) | Smooth ER — lipid synthesis; Rough ER — protein transport | | Golgi apparatus | Packaging and secretion of proteins | | Lysosomes | Digestive enzymes; waste disposal ("suicide bags") | | Chloroplasts | Photosynthesis (only in plant cells) | | Vacuole | Storage; large in plant cells, small in animal cells | | Cell wall | Provides rigidity and protection (only in plant cells) |