The endoplasmic reticulum is an extensive network of membranes composed of both regions with ribosomes and regions without ribosomes.Endoplasmic ReticulumWhat are their distinguishing characteristics? There are two regions of the ER that differ in both structure and function. One region is called rough ER because it has ribosomes attached to the...

Ribosomes are organelles that consist of RNA an proteins. They are responsible for assembling the proteins of the cell. Depending on the protein production level of a particular cell, ribosomes may number in the millions.Distinguishing Characteristics: Ribosomes are typically composed of two subunits: a large subunit and a small subunit. Ribosomal...

Mitochondria are the cell's power producers. They convert energy into forms that are usable by the cell. They are the sites of cellular respiration which ultimately generates fuel for the cell's activities. What are their distinguishing characteristics? Mitochondria are bounded by a double membrane. Each of these membranes...

The nucleus is a membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction. It is commonly the most prominent organelle in the cell.Distinguishing Characteristics: The nucleus is bounded by a double membrane called the nuclear envelope. This membrane separates the contents of the nucleus...

In Journey into the Cell, we looked at the structure of the two major types of cells: prokaryotic and eukaryotic cells. Now we turn our attention to the "movers" of a eukaryotic cell, cilia and flagella. What are cilia and flagella? Cilia and flagella are protrusions from some cells that aid in cellular locomotion. They are formed from specialized...

Life is both wonderful and majestic. Yet for all of its majesty, all organisms are composed of the fundamental unit of life, the cell. The cell is the simplest unit of matter that is alive. From the unicellular bacteria to multicellular animals, the cell is one of the basic organizational principles of biology. Let's look at some of the components...

Osmosis is a special case of passive transport. In osmosis water diffuses from a hypotonic (low solute concentrated) solution to a hypertonic (high solute concentrated) solution. Generally speaking, the direction of water flow is determined by the solute concentration and not by the "nature" of the solute molecules themselves. If the blood cells in...

Facilitated diffusion is a type of passive transport that allows substances to cross membranes with the assistance of special transport proteins. Some molecules and ions such as glucose, sodium ions and chloride ions are unable to pass through the lipid bilayer of cell membranes.Through the use of ion channel proteins and carrier proteins that are...

Diffusion Diffusion is the tendency of molecules to spread into an available space. This tendency is a result of the intrinsic thermal energy (heat) found in all molecules at temperatures above absolute zero. Without other outside forces at work, substances will move/diffuse from a more concentrated environment to a less concentrated environment. No...

Animal cells are eukaryotic cells, or cells with a membrane-bound nucleus. Unlike prokaryotic cells, DNA in animal cells is housed within the nucleus. In addition to having a nucleus, animal cells also contain other membrane-bound organelles, or tiny cellular structures, that carry out specific functions necessary for normal cellular operation. Organelles...