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CH 8 Class 8

The document provides an overview of cell structure and functions, highlighting the discovery of cells by Robert Hooke in 1665 and the distinction between unicellular and multicellular organisms. It details the basic components of cells, the differences between prokaryotic and eukaryotic cells, and contrasts plant and animal cells based on their organelles. Key concepts include the cell membrane, cytoplasm, nucleus, and specific features unique to plant and animal cells.

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24 views3 pages

CH 8 Class 8

The document provides an overview of cell structure and functions, highlighting the discovery of cells by Robert Hooke in 1665 and the distinction between unicellular and multicellular organisms. It details the basic components of cells, the differences between prokaryotic and eukaryotic cells, and contrasts plant and animal cells based on their organelles. Key concepts include the cell membrane, cytoplasm, nucleus, and specific features unique to plant and animal cells.

Uploaded by

chughhemang
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as DOCX, PDF, TXT or read online on Scribd
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Here’s a helpful visual diagram illustrating the differences between plant

and animal cells, including key organelles like the cell wall, vacuoles,
and plastids.

Class 8 Science – Chapter 8: Cell — Structure and Functions

Here's a student-friendly summary of the chapter’s most important


concepts:

1. Introduction to Cells

 Cells are the basic structural and functional units of life.


Robert Hooke discovered them in 1665 by observing cork through a
primitive microscope.(ncert-books.com, askIITians)

 Organisms can be:

o Unicellular (single-celled, e.g. amoeba, paramecium), which


perform all life functions by themselves.

o Multicellular, where specialized cells form tissues, then


organs, each performing specific functions.(PendulumEdu,
Learn CBSE, askIITians)

2. Cell Shapes and Sizes

 Shapes vary widely:

o Amoeba (no fixed shape and moves using pseudopodia)

o Red blood cells (spherical), muscle cells (spindle-shaped),


neurons (branched)(Mentor At Home, PendulumEdu)

 Sizes differ too:

o Smallest: Bacterial cell (~0.1–0.5 μm)

o Largest: Ostrich egg cell (visible to the naked eye)(Mentor At


Home, ncert-books.com)

3. Structure of the Cell


Every cell comprises three basic components:

 Cell Membrane – a porous layer that encloses cell contents and


regulates material exchange.(PendulumEdu, Mentor At Home)

 Cytoplasm – a jelly-like fluid where organelles are suspended (e.g.,


mitochondria, Golgi bodies).(PendulumEdu)

 Nucleus – often centrally located; enclosed by a nuclear membrane


and contains chromosomes and the nucleolus. It controls cell
activities and heredity.(NCERT.App, PendulumEdu, ncert-books.com)

 Protoplasm – refers to all living components of the cell (cytoplasm


+ nucleus)(PendulumEdu, askIITians)

4. Cell Types: Prokaryotic vs Eukaryotic

 Prokaryotic cells: No nuclear membrane, e.g., bacteria and blue-


green algae. Genetic material exists freely in the cytoplasm.
(PendulumEdu)

 Eukaryotic cells: True nucleus bound by a membrane; found in


plants, animals, fungi, etc.(PendulumEdu, askIITians)

5. Differences: Plant vs Animal Cells

Feature Plant Cell Animal Cell

Cell Wall Present Absent

One large central Multiple small


Vacuoles
vacuole vacuoles

Plastids (e.g.,
Present Absent
chloroplasts)

Centrioles Absent Present

6. Extra Notes & MCQs

 MCQs for practice:

o Living substance of the cell?

 Answer: Protoplasm.(PendulumEdu)

o Feature unique to plant cells?


 Answer: Large central vacuole, plastids, cell wall.
(PendulumEdu)

TL;DR (Quick Recap)

 Cell = smallest living unit

 Discovered by Hooke (1665)

 Can be unicellular or multicellular

 Key parts: cell membrane • cytoplasm • nucleus

 Cell types: prokaryote (no nucleus) vs eukaryote (nucleus)

 Plant vs animal cells differ in structure and organelles

Would you like this in a website-ready HTML format? I can help rephrase it
or add flashcards, diagrams, or question sets too!

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