5090 Biology Grade 10 and 11 Comprehensive Cell Structure and Organization Notes

• Subject Code: Biology $5090$

• Academic Level: Grade $10/11$ ($2026$ Biology Scheme of Work)

• Paper Structure:

  • Paper $1$ (Multiple Choice):

  • Time: $1$ hour

  • Marks: $40$

  • Paper $2$ (Short-answer):

  • Time: $1$ hour $45$ mins

  • Marks: $80$

  • Paper $3$ (Practical Test):

  • Time: $1$ hour $30$ mins

  • Marks: $40$

Introduction to Biology

• Definition: The science of life and living organisms.

• Origin: From Greek "bios" (life) and "logos" (knowledge).

Cell Classification

• Prokaryotes:

  • What they are: Simple, single-celled organisms without a true nucleus (e.g., bacteria).

• Eukaryotes:

  • What they are: More complex cells with a true nucleus (e.g., plant and animal cells).

Microscopy

• Microscopes: Needed to see cells.

• Light Microscopes: Common in labs; can magnify up to $1500$ times.

• Electron Microscopes: Show tiny details of cells, like ribosomes and mitochondria.

Animal vs. Plant Cells

• Similarities: Both have a cell membrane, cytoplasm, and nucleus.

• Differences:

  • Cell Wall: Plants have it, animals do not.

  • Chloroplasts: Plants have them for photosynthesis; animals do not.

  • Vacuoles: Plants have one large vacuole; animals have many small ones.

Cell Structures

• Protoplasm: Living material in the cell; mostly water.

• Organelles: Small structures inside cells that do specific jobs (e.g., mitochondria for energy).

• Cell Membrane: Thin layer controlling what enters and leaves the cell.

• Cytoplasm: Jelly-like substance where chemical reactions happen.

• Mitochondria: Produce energy for the cell.

• Nucleus: Controls cell activities and contains DNA.

• Cell Wall (Plants): Provides shape and protection.

• Chloroplasts (Plants): Help in photosynthesis.

• Vacuoles: Store food and help support plant cells.