MYTUTOR SUBJECT ANSWERS

766 views

How are proteins synthesised?

There are two main steps involved in protein synthesis: transcription and translation. Transcription occurs in the nucleus of a cell whereas translation takes place in the cytoplasm.

Transcription begins when the hydrogen bonds between the bases of a DNA strand (A-T, C-G) break. This causes the strand to 'unzip' resulting in two single strands. In the nucleus are free, activated RNA nucleotides which line up to the complementary bases on each strand. A reaction occurs which causes the formation of the sugar-phosphate back bone between the RNA nucleotides. Nucleotides continue to be added until the stop codon is reached and the now mRNA (messenger RNA) can leave the nucleus via a nuclear pore.

In the cytoplasm, there are free amino acids as well as tRNA. tRNA has a specific amino acid binding site as well as an anticodon on the other end (three unpaired bases). An enzyme catalyses the reaction binding the amino acid to tRNA.

Meanwhile, the mRNA attaches to a ribosome in the cytoplasm by a specific subunit of rRNA.This subunit covers six bases which are now 'exposed'. The first three exposed bases (always AUG) attracts the tRNA with the anticodon UAC and the next exposed mRNA bases attract the complementary tRNA molecule so two are lined up against each other. As two amino acids are now in close proximity, the enzyme peptidyl transferase from the rRNA molecule catalyses the formation of a peptide bond. This allows the ribosome to move along the mRNA strand. Subsequently, the first three bases are released from the ribosome allowing the tRNA molecule to leave but leave its amino acid behind. As more bases are exposed, more tRNA is attracted and the process starts again. The polypeptide grows with each amino acid added until a stop codon is reached and the appropriate protein has been synthesised.

Alana F. Uni Admissions Test .LNAT. tutor, GCSE Biology tutor, A Leve...

1 year ago

Answered by Alana, an A Level Biology tutor with MyTutor


Still stuck? Get one-to-one help from a personally interviewed subject specialist

175 SUBJECT SPECIALISTS

£20 /hr

Holly S.

Degree: Bachelor of Dental Surgery (Bachelors) - Glasgow University

Subjects offered:Biology, Maths

Biology
Maths

“Hi! I am studying Dentistry at the University of Glasgow, and have an in-depth knowledge and keen interest in the sciences and maths (and teeth!). ”

MyTutor guarantee

£24 /hr

Pooja D.

Degree: Medicine (Bachelors) - Birmingham University

Subjects offered:Biology, Science+ 6 more

Biology
Science
Physics
Maths
Chemistry
.UKCAT.
-Personal Statements-
-Medical School Preparation-

“I have tutored for the past 4 years and have gathered many ways of teaching concepts to students in a way that is easily-digestible and understandable. ”

£36 /hr

Els D.

Degree: Veterinary Science BVSC (Bachelors) - Bristol University

Subjects offered:Biology, Science+ 4 more

Biology
Science
Dutch
Chemistry
.BMAT (BioMedical Admissions)
-Personal Statements-

“Often students are too shy to ask questions in the classroom - and this can be detrimental to their learning. During my own studies at both GCSE and A-Level, I found one to one tutition to be invaluable in helping me get to grips with all those...”

About the author

£22 /hr

Alana F.

Degree: Law (Bachelors) - Durham University

Subjects offered:Biology, Geography+ 3 more

Biology
Geography
Extended Project Qualification
English
.LNAT.

“About me I am currently studying law at Durham University. I have always enjoyed reading and so a degree with this at its centre is perfect for me! In the past two years I have tutored a number of Biology and English students tackling...”

You may also like...

Posts by Alana

How are proteins synthesised?

How do I approach the essay section?

How do I choose which short answer questions to answer in the exam (AQA)?

How to quickly and effectively analyse a poem?

Other A Level Biology questions

Outline some of the evidence for evolution

What are the stages of mitosis?

Describe and explain the main function of the proximal convoluted tubule in filtration/absorption.

How is mRNA produced in the nucleus of a cell?

View A Level Biology tutors

We use cookies to improve your site experience. By continuing to use this website, we'll assume that you're OK with this. Dismiss

mtw:mercury1:status:ok