The circulatory system transports nutrients and blood cells to and from cells throughout the body. Blood is oxygenated in the lungs then sent back to the heart to be pumped to the rest of the body in blood vessels. The types of blood vessels include veins, arteries and capillaries. Veins carry blood to the heart while arteries carry blood away from the heart. Oxygen diffuses into the cells directly from the capillaries.
RNA molecules are produced in the nucleus of our cells and can also be found in the cytoplasm. The three primary types of RNA molecules are messenger RNA, transfer RNA and ribosomal RNA. Some RNAs, known as small regulatory RNAs, have the ability to regulate gene expression.
No, really. In eukaryotic cells, the first stage of this process takes place in the nucleus and consists of specific portions of the DNA, called genes, being copied, or transcribed, into small strands of ribonucleic acid, or RNA. RNA containing a copy, or transcript, of DNA is called messenger RNA, or mRNA.