I/GCSE Biology - Protein Synthesis

Here are the basic structure of a nucleotide.

In I/GCSE, there are some key terms in protein synthesis.

RNA

• Ribonucleic acid
• Made from 
• phosphate groups and ribose sugars linked together with one of four base

RNA polymerase

• An enzyme that creates mRNA from DNA

• Separates 2 DNA strands

mRNA

• Messenger RNA
• A single strand of RNA produced in transcription

Polypeptide

• A chain of amino acids

Codon

• A set of 3 bases found in DNA and RNA

• The genetic code is formed from patterns of codons

tRNA

• Transfer RNA

• A molecule of RNA that carries amino acids

Protein synthesis 

There are 2 stages in protein synthesis.

The FIRST stage: Transcription

• The process by which the gentic code in one strand of DNA molecules is used to make mRNA

Process:

1. RNA Polymerase binds to DNA and separates the strands in a non-coding region. These regions don't code for a protein.
2. The enzyme then moves along one DNA strand (template strand) adding complementary RNA nucleotides. These contain the same bases as DNA, except that Uracil (U) is used instead of Thymine (T).
3. The nucleotides link to form a strand of mRNA.

The SECOND stage: Translation

• The process by which the genetic code in a molecule of mRNA is used to make a polypeptide

Process:

1. The mRNA strands 
2. travel out of the nucleus through nuclear pores.
3. In the cytoplasm, the mRNA strands attach to ribosomes.
4. A ribosome moves along the mRNA strand a codon at a time. At each codon, a molecule of tRNA with complementary bases line up, Each tRNA molecule carries a specific amino acid.
5. As the ribosome moves along it joins the amino acids from the tRNA molecules together, forming a polypeptide.

That's the end of today's topic!

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Drafted by Yoshi (Biology)

Reference:

1. https://www.thoughtco.com/thmb/D_lJSgs883cnxS0-biPtfkfx5UI=/1500x1000/filters:no_upscale():max_bytes(150000):strip_icc()/nucleotide_base-5b6335bdc9e77c002570743e.jpg