Cell Structure - IGCSE Biology Revision Notes

Animal and Plant Cells

Animal Cell Structure

• Nucleus: Contains DNA within a distinct membrane.
• Cell Membrane: Holds the cell together and controls substance entry and exit.
• Cytoplasm: Gel-like substance where chemical reactions occur.
• Ribosomes: Site of protein synthesis.
• Mitochondria: Site of aerobic respiration.
• Carbohydrates: Stored as glycogen.
• Lack of Cell Walls and Chloroplasts: No photosynthesis capability.

Plant Cell Structure

• Nucleus: With a distinct membrane.
• Cell Wall: Made of cellulose, provides support.
• Chloroplasts: Contains chlorophyll for photosynthesis.
• Permanent Vacuole: Contains cell sap, supports the cell.
• Carbohydrates: Stored as starch or sucrose.

Differences between Animal and Plant Cells

• Animal cells don’t have cell walls or chloroplasts, plant cells do.
• Plant cells store carbohydrates as starch or sucrose, animal cells store them as glycogen.

Diagrams

• Animal and plant cell diagrams illustrate cell structures.

Bacteria Cells

Bacteria Cell Structure

• Microscopic single-celled organisms with varying shapes and sizes.
• Cell wall: Made of peptidoglycan, not cellulose.
• Cell membrane, cytoplasm, ribosomes present.
• Lack a nucleus: Have a circular chromosome of DNA in cytoplasm.
• Plasmids: Small rings of DNA for extra genes.
• Lack membrane-bound organelles such as mitochondria.

Additional Features

• Flagella: Whip-like tails for movement.

Examples

• Lactobacillus: Used in yogurt production.
• Pneumococcus: Causes pneumonia.

Diagram

• Illustration of typical bacterial cell.

Identifying Cell Structures & Functions

Using Microscopes

• Mitochondria: Found throughout cytoplasm.
• Ribosomes: Free or attached to Rough Endoplasmic Reticulum (R.E.R.).
• Vesicles: Visible with higher magnification.

Diagrams

• Structures in animal and plant cells visible under light and electron microscopes.

Additional Information

• This section also includes references to the educators involved:
  • Author: Lra Marie McIvor
  • Reviewer: Lucy Kirkham

These notes provide a foundational understanding of the differences between animal, plant, and bacterial cells, and the specific functions of their components as relevant to the IGCSE Biology syllabus.