Protein structures

Question 1

Proteins are essential for..?

Answer 1

Cell growth
Cellular sensing & responding to their environment
Store & convert genetic information
Contain organelles for chemical/biological functions
Maintain shape/integrity
Developmental alterations
Controlled cell death (apoptosis)

Question 2

Name the 3 major technics to solve protein structures

Answer 2

1. X-ray crystallography
2. Nuclear magnetic resonance (NMR)
3. Single particle cryo-electron microscopy

Question 3

Describe the protein primary structure.

Answer 3

Sequences of amino acids.

Amino acids:
Building blocks of proteins
Amino group, carboxyl group, R chain
Peptide bonds
20 different amino acids
Side chains gives each amino acid unique properties

Question 4

Describe the protein secondary structure.

Answer 4

Alfa helixes / beta sheets

Skapar ionic bonds, hydrogen bonds, van Der walls attractions

Alpha-helix:
Hydrogen bond between every 4th peptide bond
One turn is 3.6 amino-acids
Common in transmembrane proteins
Can create coiled coil (icke polära delar inåt)

Beta-strands:
Hydrogen bonds between peptide bonds in different strands
Often found inside proteins
Rigid structure
Two ways: antiparallel / parallel

Question 5

Describe the protein tertiary structure.

Answer 5

Fold helixes & strands into domains.
Domains: portion of protein that has a tertiary structure of its own

Question 6

Describe the protein quarternary structure.

Answer 6

Functional assemblies of chains.
Subunits comes together - creating a larger unit.

Question 7

Describe how proteins form complexes.

Answer 7

Proteins bind to each other by noncovalent bonds
The region of interaction is a binding site
Each polypeptide chain in such a complex is a subunit

Question 8

Microtubules consist of..?

Answer 8

Heterodimers of alfa & beta-tubulin

Question 9

Proteins activity is often regulated by …? And is reversed by …?

Answer 9

Phosphorylation & phosphatases