The Structure of Eukaryotic Cells

The Structure of Eukaryotic Cells

Part 1: Eukaryotic Cells

Eukaryotic cells are more complex, having evolved from a prokaryote-like predecessor. Most of the living things that we are familiar with, including the cells of our own body, are composed of eukaryotic cells. In addition to multi-cellular eukaryotic organisms, such as plants and animals, there are also a multitude of tiny, single-celled eukaryotes, including paramecium, amoeba and yeasts, to name a few (Nelson, 2005).

Organelles of Eukaryotic Cells

Mitochondria

Specialized organelles of all eukaryotic cells that use oxygen (see illustration). Often called the powerhouses of the cell, mitochondria are responsible for energy generation by the process of oxidative phosphorylation. In this process, electrons produced during the oxidation of simple organic compounds are passed along a chain of four membrane-bound enzymes (the electron transport or respiratory chain), finally reacting with and reducing molecular oxygen to water (Blumenthal, 2002). The movement of the electrons releases energy that is used to build a gradient of protons across the membrane in which the electron transport chain is situated.

Electron micrograph of a thin section through the pancreas of a bat, showing a typical mitochondrion in profile

Mitochondria are bounded by two concentric membranes referred to as the outer and the inner. This creates two distinct compartments, the matrix and the intermembrane space. The outer membrane consists of a bilayer containing about 80% lipid. It is freely permeable to molecules smaller than about 5000 daltons. The inner membrane is also a lipid bilayer. It is extremely rich in protein (about 75%) and is impermeable to even the smallest of ions. The inner membrane contains the enzymes of the electron transport chain and the ATP synthase, together with a set of transporter proteins that regulate the movement of metabolites in and out of the matrix space (Blumenthal, 2002). ...