Eukaryotic Cells and Organelles

Cell Overview

Eukaryotic cells are typically 10-100 micrometres in size, many times larger than prokaryotic cells.
They are characterised by their complex internal structure, including their compartmentalisation of functions into discrete organic structures known as organelles.
Their genetic material is held within a nucleus, separated from the rest of the cell.

The Nucleus

The nucleus is a double membrane-bound organelle that contains the cell’s DNA.
It controls the activities of the cell through regulating gene expression and mediates DNA replication during the cell cycle.
The nucleus also contains the nucleolus, a dense region where ribosomal RNA is produced and combined with proteins to form the subunits of ribosomes.

Mitochondria

Mitochondria are responsible for producing ATP, the primary energy currency of the cell, through the process of oxidative phosphorylation.
They have a double membrane, with the inner membrane being highly folded into cristae to increase surface area for ATP production.

Endoplasmic Reticulum

The endoplasmic reticulum (ER) is a series of interconnected membranous sacs and tubules that serve as a production and transport system within the cell.
The smooth ER is involved in the synthesis of lipids and the detoxification of harmful substances.
The rough ER, dotted with ribosomes, is where proteins are synthesised and transported to the Golgi apparatus.

Golgi Apparatus

The Golgi apparatus is a complex of membranous sacs that modify, package and sort proteins received from the rough ER.
It sends the repackaged proteins to their final destinations within or outside the cell, either via transport vesicles or by incorporating them into the plasma membrane.

Lysosomes

Lysosomes are membrane-bound sacs that contain powerful digestive enzymes.
They play a crucial role in recycling cellular waste, breaking down old or damaged organelles, and defending the cell against pathogens.

Plant Cell Exclusives: Chloroplasts and Cell Wall

Chloroplasts are found solely in plants and algae and are responsible for photosynthesis.
They are bound by a double membrane and have numerous membrane structures within named thylakoids, where light-dependent reactions occur.
Plant cells also possess a rigid cell wall, consisting mainly of cellulose, that provides structural support and helps regulate water movement.

It is paramount to tackle past papers and critical thinking questions to better understand how organelles interact and function within the eukaryotic cell.