Edexcel iGCSE Biology-2.2 cell structures- Study Notes- New Syllabus

Cell Structures

📝 Introduction

Cells are the basic units of life.
Different parts inside a cell are called cell structures (organelles), and each one has a specific function.

🧠 Nucleus

• Control centre of the cell.
• Contains DNA → genetic material that controls cell activities (e.g., protein production).
• Surrounded by a nuclear membrane that protects it.
• Present in animal, plant, and protoctist cells (not in bacteria/viruses).

💧 Cytoplasm

• Jelly-like fluid inside the cell.
• Many chemical reactions (like respiration, protein synthesis) happen here.
• Contains organelles floating in it.

🛡️ Cell Membrane

• Thin layer surrounding the cell.
• Partially permeable → controls what enters and leaves the cell (nutrients, gases, waste).
• Found in all cells (plants, animals, fungi, protoctists, bacteria).

🧱 Cell Wall

• Provides support and shape to the cell.
• In plants → made of cellulose.
• In fungi → made of chitin.
• Bacterial cell walls → not cellulose, different material.
• Animal cells don’t have cell walls.

🔋 Mitochondria

• Known as the “powerhouse of the cell”.
• Site of aerobic respiration → releases energy from glucose.
• More mitochondria = higher energy demand (e.g., muscle cells, sperm cells).

🌱 Chloroplasts (Plants only)

• Contain chlorophyll → green pigment that absorbs light.
• Site of photosynthesis → makes glucose.
• Found in green parts of plants (leaves, sometimes stems).

⚙️ Ribosomes

• Tiny organelles (too small to see with light microscopes).
• Site of protein synthesis (making proteins from amino acids).
• Found in cytoplasm or attached to rough ER (in eukaryotes).

💦 Vacuole (Plants mainly)

• Large central vacuole in plants, filled with cell sap (water, sugars, salts).
• Helps maintain turgor pressure → keeps the plant upright.
• In animal cells → vacuoles are small and temporary.

📊 Summary Table – Cell Structures

⚡ Quick Recap
Nucleus → controls cell, holds DNA.
Cytoplasm → chemical reactions.
Cell membrane → controls movement in/out.
Cell wall → structure & support (plants, fungi, bacteria).
Mitochondria → respiration = energy.
Chloroplasts → photosynthesis (plants).
Ribosomes → make proteins.
Vacuole → storage, keeps plant upright.