Unit 1: Proteomics & Protein Structure 2 Flashcards
Protein Structure
The four levels of protein structure are;
- Primary
- Secondary
- Tertiary
- Quaternary
The basic structure of an amino acid is
What are the four classes of amino acids?
- Polar
- Non-Polar
- Acidic
- Basic
What term is used to describe an amino acid, that has both a negative and positive charge?
A Zwitterion
What is the structure of an amino acid zwitterion?
Acids are free to
donate hydrogen ions
Bases are free to
accept hydrogen ions
What is the primary structure of a protein?
A polypeptide chain of amino acids
Describe the formation of the peptide bond in the polypeptide chain of amino acids?
The peptide bond forms between the carboxylic acid (-COOH) and (-NH2) by a condensation reaction.
What is the form of bonding along the backbone of the protein results in alpha-helices and beta sheets?
Hydrogen bonding
In secondary protein structure where does hydrogen bonding occur?
Along the backbone of the protein strand
In an alpha helix hydrogen bonding occurs between what two chemical groups?
N-H and C=O
In beta sheet what are the two types of twisting that can occur?
Antiparallel and Parallel
What are R groups in amino acids?
Residues or Side chains
Hydrophobic molecules are…
non polar
Hydrophillic molecules are…
polar
R groups that are positively charged are
basic
R groups that are negatively charged are
acidic
R groups give the proteins it’s … as they intereact with other structures associated with the protein
function
The conformation of the tertiary structure is decided by
interactions between the R groups
Name the 5 bons/interactions that occur between R groups cause further folding of the polypeptide?
- Hydrophobic interactions
- Ionic bonds
- Hydrogen bonds
- Van Der Waals
- Disulfide bridges
Prosthetic groups do what?
Give proteins added function
Where do hydrophobic interactions occur?
Between non-polar R groups along the length of the polypeptide
Folding of the polypeptide occurs forming a
central hydrophobic core
Hydrophobic sections of proteins are usually found in the
phospholipid bilayer of a cell
The hydrophillic polar parts are free to interact with the
extracellular and intracellular solutions
Ionic bonding occurs between
oppositely charged polar R groups
pH affects _____ bonding
ionic
At extremes of pH what interacts with the chrage across the ionic bond?
The H+ ions and OH-
Hydrogen bonding is a weak
polar interaction
Van Der Waals occurs between
adjacent atoms
Disulfide briges are _____ bonds that from between adjacent _____ amino acids
covalent, cysteine
Disulfide bridges can occur …
within a polypeptide or between adjacent polypeptides
Prosthetic groups are
additional non-protein structures that give the protein molecule it’s function
An example of a prosthetic group is
Haem foudn in red bloods cells in haemoglobin responsible for oxygen carriage
Quaternary structure is made up of
several connected polypeptide subunits held together by various interactions
An example of a quaternary structure is
Haemoglobin
Temperature increases the kinetic energy of the protein molecule placing stress on
bonds and breaking them expecially weak interactions
The r groups at the surface of a protein determine it’s
location within a cell
Regions of hydrophobic R groups allow strong hydrophibic interactions that hold ____ proteins within the phospholipid bilayer
integral
Give an example of a receptor
G-proteins
Give an example of a transporter
Sodium potassium pump
Give an example of a channel proteins
active transport
Peripheral/extrinsic proteins have fewer …
hydrophobic R groups interacting with the phospholipids
Peripheral/extrinsic proteins are responsible for
cell to cell interactions
Peripheral/extrinsic proteins are responsible for junctions
between cells
Name the four junctions between cells;
plasmodesmata, tight junction, gap junction, desmosomes
An example of tight junction could be found in the
stomach where it prevents acid leaking out
Plasmodesmata junctions are found only in
plants
