IB Biology Transcription and Translation

Summary of translation

1. The tRNA containing the matching anticodon to the start codon binds to P site of small sub unit of ribosomes 2. The small sub unit binds to the 5' end of the mRNA and moves along in a 5' to 3' direction until it reaches the start codon 3. The large sub unitthen binds to the smaller one 4. The next tRNA with the matching anticodon to the next codon on the mRNA binds to the A site 5. The amino acids on the two tRNA molecules form a peptide bond 6. The larger sub unit moves forward over the smaller one 7. The smaller sub unit rejoins the larger one, this moves the ribosome 3 nucleotides along the mRNA and moves the first tRNA to the E site to be released 8. The second tRNA is now at the P site so that another tRNA with the matching anticodon to the codon on the mRNA can bind to the A site 9. As this process continues, the polypeptide is elongated 10. Once the ribosome reaches the stop codon on the mRNA, translation ends and the polypeptide is released 11.Many ribosomes can translate a single mRNA at the same time, these groups of ribosomes are called polysomes

Summary of tRNA choosing amino acid

1.Each tRNA activating enzyme recognises a specific tRNA molecule 2.The tRNA molecule is made up of double stranded sections and loops 3.At the 3' end of the tRNA there is the nucleotide sequence CCA to which the amino acid attaches to 4.The diffferent chemical properties and three dimensional structure of each tRNA allows the tRNA-activating enzymes to recognise their specific tRNA 5.Each tRNA enzyme binds a specific amino acid to the tRNA molecule 6.The tRNA-activating enzyme will bind the amino acid to the tRNA with the matching anticodon 7.Energy from ATP is needed during the process

Summary of transcription

1.RNA polymerase binds to the promoter region 2.This initiates transcription 3.RNA polymerase uncoils the DNA 4.Only one strand is used, the template strand 5.Free nucloside triphosphates bond to their complementary bases on the template strand 6.Adenine binds to uracil instead of thymine 7.As the nucleoside triphosphates bind they become nucleotides and release energy by losing two phosphate groups 8.The mRNA is built in a 5'-3' direction 9.RNA polymerase forms covalent bonds between the nucleotides and keeps moving along the DNA until it reaches the terminator 10.The terminator signals the RNA polymerase to stop transcription 11.RNA polymerase is released and mRNA seperates from the DNA 12.The DNA unwinds`

Draw and label a diagram showing the structure of a peptide bond between two amino acids

NH3-C+R-C++O-N+H-C+R-C++0-OH peptide bond between a carbon doubled bonded to oxygen and a nitrogen bonded to a hydrogen

Outline the structure of ribosomes, including protein and RNA composition, large and small sub units, three tRNA binding sites and mRNA binding sites

Ribosomes have a particular structure. They are made up of proteins and ribosomal RNA. They have two sub units, one large the other small. On the surface of the ribosome there are three site to which tRNA can bind to. However not more than two tRNA molecules can bind to the ribosome at one time. Also there is a site on the surface of the ribosome to which mRNA can bind to.

Distinguish betweeen the sense and antisense strands of DNA

The antisense strand is the template DNA strand which is transcribed. The sense strand on the other hand is the DNA strand which has the same base sequence as the mRNA with thymine instead of Uracil

Explain that each tRNA molecule is recognized by a tRNA-activating enzyme that binds a specific amino acid to the tRNA, using ATP for energy

There are many different types of tRNA and each tRNA is recognized by a tRNA-activating enzyme. This enzyme binds a specific amino acid to the tRNA by using ATP as an energy source. The tRNA molecule has a specific structure. It contains double stranded sections (due to base pairing via hydrogen bonds) and loops. It has an anticodon loop which contains the anticodon and two other loops. The nucleotide sequence CCA is found at the 3' end of tRNA there are 20 different tRNA-activating enzymes as there are 20 different amino acids. Each enzyme will attach a specific amino acid to the tRNA which has the matching anticoden for that amino acid. When the amino acid binds to the tRNA molecule a high energy bond is created . The energy from this bond is used later on to bind the amino acids to the growing polypeptide chain during translation.

Explain the process of translation, including ribosomes, polysomes, start codons and stop codons

Translation occurs in the cytoplasm. It starts off with the tRNA containing the matching anticodon for the start codon AUG binding to the small subunit of the ribosome. This tRNA carries the amino acid methione and is always the first tRNA to bind to the P site. The small sub unit of the ribosome then binds to the 5' end of the mRNA. This is because translation occurs in a 5'-3' direction. The small sub unit will move along the mRNA until it reaches the start codon AUG. The large sub unit of the ribosome can then bind to the small sub unit . The next tRNA with the matching anticodon to the second codon on the mRNA binds to the A site of the small sub unit of the ribosome. The amino acids on the two tRNA molecules then form a peptide bond. Once this is done, the large sub unit of the ribosome moves forward over the smaller one. The smaller sub unit moves forward to join the large sub unit and as it does so the ribosome moves 3 nucleotides along the mRNA and the first tRNA is moved to the E site to be released. The second tRNA is now at the P site so that another tRNA with the matching anticodon can then bind to the A site. As this process continues the polypeptide is elongated. Once the ribosome reaches the stop codon on the mRNA translation, will end as no tRNA will have a matching anticodon to the stop codon. The polypeptide is then released. many ribosomes can translate the same mRNA at the same time. hey will all move along the mRNA in a 5' to 3' direction. These groups of ribosomes on a single mRNA are called polysomes.

State that eukaryotic RNA needs the removal of introns to form mature mRNA

eukaryotic RNA needs the removal of introns to form mature mRNA

State that free ribosomes synthesize proteins for use primarily within the cell, and that bound ribosomes synthesize proteins primarily for secretion or for lysosomes

free ribosomes synthesize proteins for use primarily within the cell, and that bound ribosomes synthesize proteins primarily for secretion or for lysosomes

Explain the process of transcription in prokaryotes, including the role of the promoter region, RNA polymerase, nucleoside triphosphates and the terminator

mRNA is produced during transcription. In prokaryotes, RNA polymerase recognises a specific sequence of DNA called the promoter. The promoter basically "tells" the RNA polymerase where to start the transcription process. Transcription is initiated with the binding of RNA polymerase to the promoter site. The RNA pokymerase then uncoils the DNA and seperates the two strands. One of the strands is used as the template strand for transcription. The RNA polymerase will thenn use free nucleoside triphosphates to build the mRNA in a 5'-3' direction. These nucleoside triphosphates bond to their complementary base pairs on the template strand. As they bind they become nucleotides by losing 2 phosphate groups to release energy. Since RNA does not contain thymine, uracil pairs up with adenine instead. RNA polymerase forms covalent bonds between these nucleotides. It moves along the DNA to keep elongating the sequence of mRNA until it reaches a sequence of DNA called the terminator. This sequence of DNA "tells" the RNA polymerase to stop transciption. The RNA polymerase is then released from the DNA and the newly created mRNA seperates from the template DNA strand. Finally, the DNA rewinds back to ts original double helical structure.

State that transcription is carried out in a 5' to 3' direction

transcription is carried out in a 5' to 3' direction

State that translation consists of initiation, elongation, translocation and termination

translation consists of initiation, elongation, translocation and termination

State that translation occurs in a 5' to 3' direction

translation occurs in a 5' to 3' direction