The Control Centre and Protein Factory

The nucleus is basically the cell's brain - it's the control centre that runs everything. Surrounded by a double membrane with nuclear pores, it houses the cell's DNA in structures called chromosomes. These pores act like gatekeepers, controlling what molecules can enter and leave the nucleus.

Inside the nucleus, you'll find the nucleolus, which is like a specialised protein factory. This is where ribosomes are made, and since ribosomes produce proteins throughout the cell, the nucleolus plays a crucial role in keeping the cell functioning.

Mitochondria are often called the powerhouses of the cell because that's where respiration happens - the controlled release of energy from food. Cells that need lots of energy (like muscle cells) are packed with mitochondria, whilst cells that don't do much work (like fat cells) have very few.

Exam Focus: The more cristae (folded inner membranes) a mitochondrion has, the more energy it can produce - this is a common exam question!