DNA - Protein Synthesis: Translation (GCSE Biology)
Protein Synthesis: Translation
Protein Synthesis
DNA’s biggest process is protein synthesis. This is how the growth and repair of our body occurs. DNA provides a template upon which proteins are coded for. There is some slightly confusing terminology in this section.
Protein synthesis is the process by which the base sequence found in genes on DNA is used to make polypeptides.
Protein synthesis occurs in two major phases:
- Transcription – during which a strand of mRNA is synthesised from a particular gene template.
- Translation – during which the mRNA attaches to the ribosome, which recruits tRNAs carrying amino acids in order to make a polypeptide.
RNA
RNA is ribonucleic acid – it is similar to DNA but it is single stranded and contains uracil instead of thymine.
An important part of protein synthesis is that the DNA stays in the nucleus. Now if the DNA stays in the nucleus, how does it reach the organelles to allow protein synthesis to occur?
Transcription
- The DNA molecule is unzipped around the gene. DNA is a double stranded molecule so it needs to be unzipped to expose one strand.
- RNA polymerase helps make a copy of DNA as mRNA. RNA polymerase binds to the non-coding region in front of a gene on one of the DNA strands and uses free nucleotides to produce a complementary mRNA (messenger RNA) strand of the coding part of the gene. The copying of the DNA is known as transcription.
Translation
- mRNA leaves the nucleus, moves into the cytoplasm and attaches to the ribosome. The ribosome is the organelle responsible for protein synthesis.
- tRNA molecules complementary to the mRNA arrive at the ribosome. When the mRNA moves to the ribosome, it recruits tRNA (transfer RNA structures) that are complementary to the base sequence of the mRNA. The tRNA has an anti-codon that is complementary to the mRNA’s codon (sequence of 3 bases).
- The tRNA molecule carry amino acids with it. The bases on the mRNA are read in threes and code for a specific amino acid (the triplet code). The amino acids then bond with another and polypeptides are formed. This is translation.
DNA Base Order and Protein Structure
This therefore means that the order of the bases in the DNA determines what amino acids are recruited and what polypeptides are made. Therefore, the structure of the DNA influences what protein is made.
Protein Shape and Enzymes
Once these protein chains are formed, they are folded in a few ways, so each protein has its own unique shape for example, enzymes, antibodies, receptors, neurotransmitters etc. The unique shape is imperative for enzymes, as they have their own individual active sites. These active sites must be individual to each enzyme as they must have a complementary shape to their substrate, to ensure the functionality of the enzyme.
Gene Expression and Proteins
The expression of proteins can be altered by switching genes on and off. Now how does this occur?
- DNA is separated into coding and non-coding DNA. The DNA that is coding is what directly determines the proteins formed as a copy of it is made. Non-coding DNA on the other hand has a different function. It works to turn on and off genes. Therefore, if it decides to turn off a section of coding DNA, the protein produced would be different. This can lead to differences in the appearance of the expression of the gene.
- As every cell contains all of the DNA in the body, genes must be switched on and off in order to stop every cell producing every protein. Therefore, different cells have different genes turned on and off
DNA stands for deoxyribonucleic acid, and it is the blueprint that contains the instructions for building proteins in our cells. It determines our genetic makeup and helps our bodies function properly.
Protein synthesis is the process of creating proteins from the instructions in DNA. Proteins are essential for many processes in our bodies, including growth and repair, so protein synthesis is crucial for our overall health.
Translation is the second step of protein synthesis, where the instructions in the DNA code are translated into a protein molecule. This is done by ribosomes in the cell, using the genetic code and a molecule called messenger RNA.
Messenger RNA is a molecule that carries the instructions from the DNA to the ribosomes, where it helps the ribosomes read the code and build the protein.
The genetic code is a set of instructions that tells the ribosomes which amino acids to use to build a protein. It is made up of codons, which are sequences of three nucleotides (building blocks of DNA) that specify a particular amino acid. The ribosomes use this code to match the messenger RNA to the right amino acids and build the protein.
Ribosomes are the “workstations” of the cell where proteins are synthesized. They use the information in the messenger RNA to build the protein, matching codons to the right amino acids and linking them together in the correct order.
Translation is carefully regulated to make sure that the right amino acids are used in the right order to build the protein correctly. Any mistakes in the genetic code can cause problems with the protein and potentially lead to health problems.
Yes, there are several ways that translation can go wrong, such as mutations in the DNA code or problems with the ribosomes. These errors can result in the creation of non-functional or harmful proteins, which can cause health problems.
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