National Five Biology - Unit 1: Cell Biology

Key Area 1: Cell Structure

Unit 1 is divided into six key areas, and the first one is cell structure, focusing on:

• Different types of cells
• Organelles inside them
• Functions of these organelles
• Comparison of four types of cells: Animal, Plant, Bacterial, Fungal

Animal Cell Structure

• Cell Membrane: Surrounds the cell.
• Mitochondria: Oval-shaped structure.
• Ribosomes: Small dots scattered within the cell.
• Nucleus: Central, often black-colored region.
• Cytoplasm: Jelly-like fluid filling the cell.

Plant Cell Structure

• Contains all organelles present in animal cells.
• Unique to Plant Cells:
  • Chloroplasts: Green dots; contain chlorophyll for photosynthesis.
  • Vacuole: Large central structure containing cell sap.
  • Cell Wall: Provides support and surrounds the cell membrane.

Bacterial Cell Structure

• Cytoplasm: Fills the space between organelles.
• Cell Membrane: Present like other cells.
• Plasmids: Rings of genetic material, replace nucleus.
• Bacterial Chromosome: Ribbon-like genetic material.
• Cell Wall: Present similarly to plant cells.

Fungal Cell Structure

• Similar to animal cells but with a cell wall.
• Yeast Cells: Type of fungal cell.
• Contains ribosomes, cytoplasm, cell membrane, mitochondria, and cell wall.

Functions of Cell Organelles

• Cell Wall: Supports and strengthens the cell; made of cellulose.
• Cell Membrane: Selectively permeable, found in all cell types.
• Cytoplasm: Site of chemical reactions.
• Mitochondria: Site of aerobic respiration and ATP production; found in animal, plant, and fungal cells.
• Chloroplasts: Site of photosynthesis, only in plant cells.
• Vacuole: Contains cell sap, supports cell, only in plant cells.
• Ribosomes: Site of protein synthesis, found in all four cell types.
• Plasmids: Found in bacterial cells; location of genetic material.
• Nucleus: Found in animal, plant, and fungal cells; stores genetic information and controls cell activities.

Study Tips

• Familiarize yourself with cell diagrams and structures.
• Practice identifying and naming organelles.
• Understand functions of organelles to answer questions effectively.

Practice Questions

1. Identify plant cells among given options by looking for cell walls, membranes, and vacuoles.
2. Recognize structures like cell walls and determine their composition (e.g., cellulose).
3. Differentiate cells based on presence of plasmids and other unique features.

Follow-up

• Complete quizzes on cell structures (1.1).
• Prepare for the next lesson: Transport across the Cell Membrane (1.2).