Edexcel iGCSE Biology-2.3 functions of the nucleus- Study Notes- New Syllabus

Functions of Cell Structures

🧠 Nucleus

• Acts as the control centre of the cell.
• Contains DNA (genetic instructions).
• Controls cell activities (growth, repair, protein production, division).

💧 Cytoplasm

• Jelly-like fluid filling the cell.
• Where chemical reactions happen (e.g., respiration, protein synthesis).
• Holds organelles in place.

🛡️ Cell Membrane

• Thin, partially permeable layer around the cell.
• Controls movement of substances in and out (nutrients, gases, waste).
• Provides some protection and structure.

🧱 Cell Wall

• Provides support and shape to the cell.
• In plants → made of cellulose.
• Prevents bursting when water enters by osmosis.
• Absent in animal cells.

🔋 Mitochondria

• Site of aerobic respiration.
• Releases energy (ATP) for cell activities (movement, active transport, protein synthesis).
• Cells with high energy demand (e.g., muscle, sperm) have many mitochondria.

🌱 Chloroplasts (Plants only)

• Contain chlorophyll → absorbs light for photosynthesis.
• Site of photosynthesis → makes glucose (food for plant).
• Found in green parts of plants (mainly leaves).

⚙️ Ribosomes

• Tiny organelles in cytoplasm.
• Site of protein synthesis → link amino acids to build proteins.
• Essential for cell growth and repair.

💦 Vacuole

• In plants → large, permanent vacuole filled with cell sap (water, sugars, salts).
• Helps maintain turgor pressure → keeps plant firm and upright.
• In animals → small, temporary vacuoles (for storage or transport).

📊 Summary Table – Functions of Cell Structures

⚡ Quick Recap 
Nucleus → DNA + control centre.
Cytoplasm → chemical reactions.
Cell membrane → selective barrier.
Cell wall → support & protection.
Mitochondria → energy (respiration).
Chloroplasts → photosynthesis.
Ribosomes → make proteins.
Vacuole → storage + keeps plant firm.