MYTUTOR SUBJECT ANSWERS

520 views

What are the levels of protein structure?

The structure of proteins, especially those of enzymes, is extremely important in allowing them to carry out their duties in the cell and body. Protein folding needs to be specific, and repeated exactly the same way every time for the same protein.

The primary structure of a protein is the newly translated polypeptide strange of amino acids, which are in the order as dictated by its mRNA. Each amino acid (also referred to as a residue when it is in a polypeptide) is attached by a covalent peptide bond one either side, and each amino acid has specific properties which will allow for the protein to take the correct shape. At the moment, it is a shapeless strand.

The secondary structure of a protein can either be an alpha helix or a beta pleated sheet. A alpha helix is a tight coil (like a spring), with the peptide groups of residues forming hydrogen bonds with the ones above and below it. This bonding stabilises the structure, and is intra-molecular hydrogen bonding (the same strand forms bonds to itself). Meanwhile, beta pleated sheets are a bit looser, and have inter-molecular hydrogen bonding, where many polypeptides can be bound together.

Tertiary structure is concerned with the 3D folding of the protein. This is where amino acid specificity comes in; the R-groups of the residues (that is, the variable groups attached to the alpha-carbon of amino acids) allow for certain bonds to form. Salt bridges/ionic bonds/charge-charge interactions form between positively charged (usually basic residues such as lysine) and negatively charged (such as glutamic acid) residues. Disulphide bonds/bridges are covalent bonds between the R groups of two cysteines, which have a -S-H (thiol) group on the end. The thiol groups are oxidised to form a sulphur-sulphur bond, and this helps maintain the 3D shape of the protein. There are also hydrophobic interactions, where hydrophobic residues prefer to be in the center of the protein, and the hydrophilic ones face outwards. Finally, there are also hydrogen bonds between R-groups (not between the peptide groups but the R-groups - peptide group hydrogen bonds are used in secondary structure).

Lastly, the quarternary structure is the combination of many tertiary structure proteins and sometimes, a prosthetic group. In the case of haemoglobin, there are four polypeptides: two alpha chains, two beta chains and one prospethic group, haem, per polypeptide (so four in total on one molecule). The polypeptides are bound non-covalently, and the prosthetic group assists the protein carry out its function better. Not all proteins have a quaternary structure, especially not structural proteins.

Giulia Z. A Level Biology tutor, GCSE Biology tutor, A Level History ...

11 months ago

Answered by Giulia, who tutored A Level Biology with MyTutor


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

164 SUBJECT SPECIALISTS

£22 /hr

Nicola C.

Degree: Medicine MBChB (Other) - Birmingham University

Subjects offered:Biology, Maths+ 2 more

Biology
Maths
Chemistry
-Medical School Preparation-

“About me I have an incredible passion for science and am currently studying Medicine at the University of Birmingham. Having always shown great enthusiasm for the science subjects, I hope that I would be able to pass this on to other ...”

£20 /hr

Idrees A.

Degree: Medicine (Bachelors) - Bristol University

Subjects offered:Biology, Science+ 4 more

Biology
Science
Human Biology
Chemistry
-Personal Statements-
-Medical School Preparation-

“Hi, my name is Idrees and I am a medical student at the University of Bristol. I am a friendly, enthusiastic and approachable person with an unmoveable passion for science and teaching. I have tutored Biology and Chemistry to many GCS...”

£20 /hr

Josh H.

Degree: Natural Sciences (Bachelors) - Lancaster University

Subjects offered:Biology, Physics+ 1 more

Biology
Physics
Maths

“Hello! I'm in my third year of a Natural Sciences degree and my aim as a tutor is to give you an intuitive understanding of your subject.”

MyTutor guarantee

About the author

Giulia Z.

Currently unavailable: for new students

Degree: Biological Sciences (Bachelors) - Durham University

Subjects offered:Biology, Human Biology+ 1 more

Biology
Human Biology
History

“A bit about meI'm studying biology at Durham University, with a passion for science! I've been volunteering with primary and secondary students for the past three years and so have a lot of experience in communicating ideas. I'm very...”

MyTutor guarantee

You may also like...

Posts by Giulia

How do I write a history essay?

What are the levels of protein structure?

What happens to the blood when it enters the heart?

Other A Level Biology questions

Name the three components of a nucleic acid

What is a nerve synapse and how does it work?

Describe the ways in which LDLs and HDLs affect the formation of atheromas.

What is meant by the semi-conservative replication of DNA?

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