100% satisfaction guarantee Immediately available after payment Both online and in PDF No strings attached
logo-home
Summary Lecture 4 - proteins; structure and function $3.90   Add to cart

Summary

Summary Lecture 4 - proteins; structure and function

 11 views  0 purchase
  • Course
  • Institution
  • Book

Summary of lecture, book and additional material about protein structure and protein function.

Preview 2 out of 13  pages

  • No
  • Chapter 3: page 109-140, not 124-126 and 128-133
  • March 29, 2021
  • 13
  • 2020/2021
  • Summary
avatar-seller
Lecture 4 (BOOK) – Proteins:
structure and function
(Thunnissen)
Chapter 3: page 109-140, not 124-126 and 128-133

CH3 Proteins
The shape and structure of proteins
There are 20 different amino acids bwhich make up a protein molecule. The amino acids are linked to
its neighbours through a covalent peptide bond, proteins are therefore known as polypeptides.
The repeating sequence of atoms along the core of the polypeptide chain is referred to as the
polypeptide backbone. Attached to this are side chains which gave each amino acid its unique
properties.

The folding of a protein is determined by non-covalent bonds formed between the chain and/or side
chains. There are three types of these weak bonds which have all been mentioned before: hydrogen
bonds, electrostatic bonds and van der Waals attractions. Although these bondings may be weak,
the combined forces of large numbers of non-covalent bonds determines the stability of each folded
shape.




Hydrophobic clustering force is a fourth weak force which also has a central role in determining the
shape of a protein. Hydrophobic molecules tend to be forced together in aqueous environments in
order to minimise their disruptive effect on the hydrogen-bonded network of water molecules.




Conformation of lowest energy

, Most proteins have a particular three-dimensional structure which is determined by the order of the
amino acids in its chain. The final folded structure called the conformation is generally the one that
minimises its free energy.
Denaturing is the unfolding of a protein, and renaturing is the refolding of a protein.
Although a protein chain can fold itself without help, proteins called molecular chaperones often
assist in protein folding.

Large proteins usually consist of several protein domains which are structural units that fold more or
the less independently of each other.

The alpha helix and beta sheet
There are two regular folding patterns found called the alfa helix and the beta sheet. Both patterns
result from hydrogen bonding between N-H and C=O groups in the polypeptide backbone, without
involving the side chains.
A beta sheet occurs when two backbones run in the same orientation (parallel chains) and an alpha
helix is generated when a single polypeptide chain twists around on itself to form a rigid cilinder.
Alpha helices can wrap around eachother to form a stable structure called a coiled-coil. This can form
when the a helices have most of their non polar (hydrophobic) side chains on one side so they can




twist around each other with these side chains facing inward.

Four levels of organisation
Scientists distinguish four levels of organisation in the structure of a protein.
The primary structure is the amino acid sequence. Stretches of polypeptide
chain that form alpha helices or beta sheets constitute the protein’s
secondary structure. The full three-dimensional organisation of a
polypeptide chain is referred to as the tertiary structure. If a particular
protein molecule is formed as a complex of more than one polypeptide
chain, the complete structure is said to be the quaternary structure.

The protein domain is a substructure produced by any contiguous part of a
polypeptide chain that can fold independently of the rest of the protein into
a compact, stable structure. The different domains of a protein are often
associated with different functions.



Protein families

The benefits of buying summaries with Stuvia:

Guaranteed quality through customer reviews

Guaranteed quality through customer reviews

Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.

Quick and easy check-out

Quick and easy check-out

You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.

Focus on what matters

Focus on what matters

Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!

Frequently asked questions

What do I get when I buy this document?

You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.

Satisfaction guarantee: how does it work?

Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.

Who am I buying these notes from?

Stuvia is a marketplace, so you are not buying this document from us, but from seller stijnvantrijp. Stuvia facilitates payment to the seller.

Will I be stuck with a subscription?

No, you only buy these notes for $3.90. You're not tied to anything after your purchase.

Can Stuvia be trusted?

4.6 stars on Google & Trustpilot (+1000 reviews)

83430 documents were sold in the last 30 days

Founded in 2010, the go-to place to buy study notes for 14 years now

Start selling
$3.90
  • (0)
  Add to cart