AP Biology Period 1
Take Home Essay #3
Eukaryotes contain many unique and different membrane-bound organelles such as the endoplasmic reticulum and lysosomes which are specialized for specific jobs that help the cell survive and operate. One key membrane-bound organelle contained in eukaryotes is the endoplasmic reticulum (ER) which is responsible for the synthesizing and storing of proteins. The endoplasmic reticulum consists of a lattice of membranes that folds upon itself. The folding within the endoplasmic reticulum assists the production of proteins because as it folds upon itself it increases the amount of surface area for reactions to occur. There are also two types of ER, which are known as the rough ER and the smooth ER. The rough ER is responsible for synthesizing proteins which will then be secreted, while the smooth ER is responsible for the synthesizing of lipids and for detoxification. Another important membrane-bound organelle is the lysosome. Lysosomes are spherical sac shaped organelles, which are lined with a plasma membrane and contain hydrolytic enzymes responsible for breaking down things. Lysosomes serve to break down unneeded material entering or already within the cell and can destroy the cell if necessary, which is why it is often referred to as the suicide sac. Proteins made in ribosomes on the endoplasmic reticulum are specialized for digestion, which is how a lysosome is initially made. While only eukaryotic cells contain membrane-bound organelles, similar to prokaryotic cells, they each have non-membrane bound organelles such as ribosomes and cell walls. Ribosomes are made up of a large and small subunit of RNA and proteins. The function of ribosomes is to create proteins and they are often found floating around the cell. These are called free ribosomes because they wander around the cell randomly and produce proteins for inside the cell. There are also bound ribosomes which are attached to the rough ER and make proteins which are secreted from the cell. Ribosomes are found in both prokaryotes and eukaryotes, the only difference is that since prokaryotes have no membrane bound organelles the ribosomes float in the cytosol.