The mitochondria and nucleus are two organelles inside a cell that share many similarities. Both are made of two membranes. These membranes separate the inside of the organelle from the outside, but have protein channels that allow things to pass in and out. Both contain DNA material that carries genes that encode for proteins. Both have genes that make ribosomes, the machines that read the instructions in RNA to make protein.
The mitochondria and nucleus are pouches whose walls are made of two membranes. A mitochondrion has an outer membrane and an inner membrane. A nucleus also has an outer membrane and an inner membrane. The two membranes of a mitochondrion serve different purposes. The inner membrane is where energy molecules are made. For the nucleus, its outer membrane is connected to the endoplasmic reticulum, another membranous organelle. The outer membrane of the nucleus also has ribosomes on it, similar to the rough endoplasmic reticulum. The inside of the inner nuclear membrane is held in place by a network of proteins that is like the wooden frame of a house.
The two membranes in mitochondria and the nucleus are barriers separating things on the inside from things form the outside, but they have protein channels that allow molecules to move in and out. The nucleus has what is called the nuclear pore complex, which is a protein channel that pokes through both the outer and inner membranes. This pore regulates what goes in and out. The mitochondria have protein channels on the outer membrane that are right above protein channels on the inner membrane. The outer channel passes proteins on the outside of the mitochondrion to the inner channel, which moves the protein to the inside of the mitochondrion.
The nucleus contains the chromosomes of the cell. The main genome of the organism is found in the nucleus. In humans, the nucleus holds 46 chromosomes, which contains about 25,000 genes. However, mitochondria have DNA of their own. The human mitochondrion has DNA in the form of plasmids, which are circular pieces of DNA. Mitochondrial genes encode for 13 proteins and 24 RNA molecules that are only found in the mitochondrion. Interestingly, the mitochondrial genes use a slightly different genetic code compared to the genes in the nucleus, like two dialects of the same genetic language.
Ribosomes are the machines that read the instructions in RNA molecules that came from DNA. Ribosomes translate the information in RNA into proteins. The ribosome itself is made of protein, but is also made of RNA. In fact, ribosomes can be two-thirds RNA and one-third protein. Both the nucleus and the mitochondrion contain DNA that encodes for ribosome building blocks. Ribosome proteins and ribosomal RNA are made by the nucleus and the mitochondrion. The proteins and RNA combine to form mature ribosomes.
