Protein Synthesis for Middle School Science

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Protein synthesis is the process cells use to build proteins, which are essential for nearly everything your body does. This process turns the instructions stored in your DNA into working proteins. It happens all the time in almost every cell of your body, mainly in the cytoplasm, using information copied from DNA in the nucleus. Without protein synthesis, your body couldn’t grow, repair itself, or carry out basic life functions.

DNA and Proteins

DNA, or deoxyribonucleic acid, is found inside the nucleus of almost every cell in your body. It contains all the instructions a cell needs to build and run the body, like a giant instruction manual. DNA is made up of sections called genes, and each gene contains a specific code that tells the cell how to make a particular protein. Not all parts of DNA code for proteins—some sections help control when and how genes are used, and others have roles scientists are still studying. The parts that code for proteins are called coding regions, and they are read during protein synthesis to build the proteins your body needs. Even though DNA never leaves the nucleus, its instructions are copied into mRNA, which carries the message out to the ribosome, where proteins are made.

DNA and RNA

DNA and RNA are both molecules that carry genetic information, but they have different roles and structures. DNA (deoxyribonucleic acid) stays in the nucleus of the cell and holds the long-term instructions for how to build all the proteins the body needs. RNA (ribonucleic acid), on the other hand, is made as a copy of a small section of DNA and can leave the nucleus to help make proteins. One major difference is their structure—DNA is a double helix (two strands twisted together), while RNA is single-stranded. Also, DNA uses the base thymine (T), but RNA uses uracil (U) instead. Despite these differences, they work together closely: DNA stores the genetic code, and RNA helps carry out the instructions to build proteins.

Base pairs are the building blocks of DNA and RNA. They are made up of nitrogenous bases that pair together in a specific way to form the "rungs" of the DNA ladder or to match bases during RNA transcription. In DNA, the four bases are adenine (A), thymine (T), cytosine (C), and guanine (G). These bases always pair up the same way: A pairs with T, and C pairs with G. These pairs are held together by weak chemical bonds called hydrogen bonds, which help stabilize the structure of the DNA double helix.

In RNA, the base uracil (U) replaces thymine. So when RNA is made during transcription, A on the DNA pairs with U on the RNA instead of T. C still pairs with G, and G still pairs with C. These base-pairing rules are important because they ensure the genetic code is copied accurately. This code is made up of sequences of three bases (called codons) on the mRNA, and each codon tells the cell which amino acid to add next when building a protein. So, base pairs are a key part of how cells read and follow the instructions written in DNA.

Transcription

Transcription is the first step in protein synthesis, and it happens inside the nucleus of the cell. During transcription, a section of DNA that contains the instructions for making a specific protein is copied into a molecule called messenger RNA (mRNA). The enzyme RNA polymerase helps by unzipping the DNA and building the mRNA strand using the DNA as a template. Instead of using the base thymine (T), mRNA uses uracil (U) to pair with adenine (A). Once the mRNA copy is made, it carries the genetic instructions out of the nucleus and into the cytoplasm, where the next step—translation—takes place. Transcription is important because it allows the cell to use the DNA’s information without removing or damaging the original DNA inside the nucleus.

Translation

Translation is the second step of protein synthesis, and it takes place in the cytoplasm of the cell, where the ribosomes are located. Ribosomes are tiny structures made partly of ribosomal RNA (rRNA) that read the instructions carried by the messenger RNA (mRNA). The mRNA provides the sequence of codons, or three-base codes, that tell the ribosome which amino acids to put together.

Another type of RNA, called transfer RNA (tRNA), brings the correct amino acids to the ribosome. Each tRNA has a special region called an anticodon that matches up with the codon on the mRNA. When the tRNA and mRNA match up, the ribosome helps link the amino acid to the growing protein chain. This process continues until the ribosome reaches a stop codon, signaling the protein's end. Once finished, the protein can fold into its correct shape and begin doing its job in the cell.

Proteins

Proteins are incredibly diverse and are found in every part of the body. Some proteins, like enzymes, help speed up chemical reactions. Others, like antibodies, help fight off germs and protect us from getting sick. Hemoglobin, a protein in red blood cells, carries oxygen throughout the body. Some proteins build and repair body structures, like muscles, skin, and bones. Still others act as hormones, which send signals to control different body processes. In short, proteins are the workhorses of the cell, making life possible by doing nearly every important task in the body.

Hemoglobin: Found in red blood cells, hemoglobin carries oxygen from the lungs to the rest of the body and helps remove carbon dioxide.
Insulin: A hormone that helps regulate blood sugar levels by signaling cells to absorb glucose from the bloodstream.
Amylase: An enzyme found in saliva and the small intestine that helps break down starches into simple sugars during digestion.
Antibodies (Immunoglobulins): Proteins produced by the immune system that recognize and fight harmful bacteria, viruses, and other invaders.
Actin and Myosin: Proteins in muscle cells that work together to allow muscles to contract and help us move.
Keratin: A strong protein that makes up hair, nails, and the outer layer of skin, providing structure and protection.
Collagen: The most abundant protein in the human body, collagen provides strength and flexibility to skin, bones, and connective tissues.
DNA Polymerase: An enzyme that helps copy DNA during cell division, ensuring each new cell gets the correct genetic information.
Ferritin: A protein that stores iron in the body and releases it when needed for making red blood cells and other processes.
Growth Hormone: A protein hormone that stimulates growth, cell reproduction, and repair in humans and other animals.

Each of these proteins is made through protein synthesis and is vital for keeping your body healthy and working properly. By understanding this process, scientists can learn how cells work and even how to treat certain diseases caused by protein problems.