CBSE Class 11 · Biology
Cell : The Unit of Life
Official NCERT chapter from Biology (book code kebo1). ExamMaster notes are original teaching at CBSE Class 11 depth.
This lesson follows the official chapter “Cell : The Unit of Life” in Biology. The words below are ExamMaster’s teaching, not a paste from the book. Use the NCERT chapter for the classroom sequence; use these notes to hold the idea without copying exercises or figures.
- CBSE Class 11
- Medium level
- 8 concepts
1What is a Cell?
A cell is the school unit of structure and function — the smallest living bit that still runs the living-tests as taught. Unicellular versus multicellular is a number-of-units split. A cell is not a drawing-box.
A tissue named as “the cell” is a scale-jump.
Figure. A cell is the smallest living unit. A body claim is not automatically a cell claim — keep the scale.
How it works
- Name the smallest living unitThe cell.
- Split one-celled versus many-celled if askedThe number.
- Refuse a whole organ as the unitUnit-talk.
2Cell Theory
Cell theory (school): all living things are made of cells; new cells from older cells as taught. A theory here is a two-line claim, not a biography of the namers. Viruses sit at the edge if the lesson said so.
“Everything is cells including rocks” is a steal.
Figure. School cell theory is three claims: living bodies are cellular, the cell is the unit, and new cells come from old cells.
How it works
- Write living → cells, and cells from cellsThe theory.
- Keep rocks outLiving only.
- Name the virus-edge only if taughtHonest extra.
3An Overview of Cell
An overview: plasma membrane, cytoplasm, a control-region (nucleus or nucleoid as the kind). Overview is the three-part map before you zoom. A colour-blob with no names is not an overview.
Starting at a ribosome without the three-part map is a zoom-skip.
Figure. Overview split: a prokaryote has no nucleus box; a eukaryote keeps DNA inside a membrane-bound nucleus.
How it works
- Name membrane, cytoplasm, control-regionThe overview.
- Then zoom if askedOrganelles next.
- Keep the three names in the sentenceThe map.
4Prokaryotic Cells
Prokaryotic: no membrane-bound nucleus as taught; a nucleoid, often a cell wall, smaller. Bacterium is the school case. Prokaryote is a control-region look, not “harmful”.
A plant cell as prokaryote because it has a wall is a miss.
Figure. A prokaryotic cell has a nucleoid — DNA without a nuclear membrane — not a second cell inside.
How it works
- Name no true nucleus / nucleoidProkaryotic.
- Keep a bacterium as the caseThe example.
- Refuse harmful as the testA cell-kind.
5Eukaryotic Cells
Eukaryotic: membrane-bound nucleus and organelles as taught — plant (wall + chloroplast + big vacuole) versus animal (centrosome as taught) if split. Eukaryote is a nucleus-plus-rooms story.
A bacterium with a drawn circle labelled nucleus is a lying sketch.
Figure. A eukaryotic cell keeps the nucleus as a membrane-bound compartment inside the cytoplasm.
How it works
- Name true nucleus + organellesEukaryotic.
- Split plant / animal looks if askedThe extra test.
- Refuse a prokaryote as this headingWrong kind.
6A membrane is a boundary with jobs
A membrane is a boundary with jobs: hold in, let some bits pass (selectively permeable as taught). Fluid mosaic if named. Membrane is a gate-and-skin, not a stone wall.
A wall and a membrane swapped in a plant cell is a miss.
Figure. The plasma membrane is a rim with jobs: some things are selected in, others kept out. A name without a job is a glossary.
How it works
- Name boundary + selective passThe membrane.
- Keep wall as a separate plant/prokaryote extraTwo words.
- Refuse “nothing passes” as the school membraneA gate.
7An organelle has a job you can name
An organelle has a job you can name: mitochondrion (energy as taught), chloroplast (food-make), ER, Golgi, ribosome as listed. Organelle is name-plus-job. A mute labelled blob is not this heading.
A nucleus called “an organelle that is the cell” is a scale-mash.
Figure. An organelle earns its name from a job: nucleus for control, mitochondrion for energy. Topology boxes, not a stained cell.
How it works
- Name the organelleThe word.
- Attach the jobWhy it sits there.
- Refuse a name-only claimJob-talk.
8A miss: treating the drawing as the living cell
A miss: treating the drawing as the living cell. The figure is a map; the cell still does the jobs. A perfect textbook colour is a teach-sketch.
A printed mitochondrion as “this is my cheek cell” is the miss.
Figure. The textbook sketch is a map. The living cell is the jobs running. Treating the drawing as the cell is the miss.
How it works
- Keep the drawing as a mapA teach-sketch.
- Keep the living cell as the objectTwo things.
- Refuse a swap of figure for cellThe miss named.
Prokaryotic cells lack
- A membrane-bound nucleus as taught
- Cytoplasm always
- A membrane of any kind
Nucleoid, not a true nucleus.
Notes
- Mapped to the official NCERT chapter “Cell : The Unit of Life”. Original teaching only — no textbook sentences.
- Science here is Physics, Chemistry and Biology ideas at this class, never a language or social-science chapter.
Recap
Hold these pegs from the official chapter “Cell : The Unit of Life”. The wording is ExamMaster’s teaching, not a textbook recap.
- What is a Cell?
- A cell is the school unit of structure and function — the smallest living bit that still runs the living-tests as taught.
- Cell Theory
- Cell theory (school): all living things are made of cells; new cells from older cells as taught.
- An Overview of Cell
- An overview: plasma membrane, cytoplasm, a control-region (nucleus or nucleoid as the kind).
- Prokaryotic Cells
- Prokaryotic: no membrane-bound nucleus as taught; a nucleoid, often a cell wall, smaller.
- Eukaryotic Cells
- Eukaryotic: membrane-bound nucleus and organelles as taught — plant (wall + chloroplast + big vacuole) versus animal (centrosome as taught) if split.
- A membrane is a boundary with jobs
- A membrane is a boundary with jobs: hold in, let some bits pass (selectively permeable as taught).
Practise Cell : The Unit of Life
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- A 4-question practice set that ends the chapter
- 1 quick check with worked explanations
- Timed mocks scored with the real marking scheme
- Readiness tracked per topic, kept on your device