MCAT Biology > Cellular Organelles
The cell is the most basic structure of life. Each cell is composed of specific organelles which act just like human organs do in the body. Each organelle serves a specific function within the cell.
There are many different organelles throughout the cell that are necessary to know for the MCAT exam. These organelles include:
- Cellular Membrane
- Endoplasmic Reticulum
- Golgi Apparatus
- Cell Wall
- Plant Cell Organelles
Organelles between plant and animal cells are generally similar with the exception of the cell wall and chloroplasts in plants. These provide the unique structure and ability to perform photosynthesis that distinguish plants and are not found in animal cells.
The ribosome is responsible for protein production. It takes orders from the nucleus and mRNA. It then sends out the products to the endoplasmic reticulum to be processed and sent out throughout the cell.
There are two types of ribosomes, bound and unbound. Bound ribosomes are bound to the endoplasmic reticulum while unbound ribosomes can float freely throughout the cytoplasm.
Eukaryotic ribosomes consist of 60s/30s subunits while prokaryotic ribosomes have 50s/30s and deal with the newly created rRNA molecule.
Ribosomes contain three major binding sites, (1) for mRNA, and (2) for tRNA.
- The A-site holds the aminoacyl-tRNA complex
- The P-site binds to tRNA attached to a growing polypeptide chain
Proteins are distinguished based on the signal sequence on the cells surface or a unique carbohydrate chain. If there is no signal, the protein is excreted from the cell. At the end, the vesicle of a protein is released to mature in the lysosomes
See Golgi Apparatus