Proteins Flashcards
What four groups are attached to the central carbon of an amino acid?
NH2, COOH, H and variable component R
What are the four classes of amino acids?
acidic, basic, polar and non-polar
Which part of the amino acid decides which class the amino acid belongs to?
The R group
Which class of R group gives a hydrophobic reaction with water?
Non-polar
Give examples of Proteins which are, acidic, basic, polar and non-polar, and the functional group which causes this.
Acidic: aspartic acid COOH
Basic: Lysine, NH2
Polar: Serine OH
Non-polar: Alanine CH3
When are amino acids linked together?
During translation of mRNA at the ribosome
What type of reaction is the formation of a peptide bond?
Condensation reaction caused by an enzyme.
What is the the primary structure of a protein?
The sequence of amino acids that make up a polypeptide chain.
What are the two ends of a polypeptide chain known as?
N terminus and a C terminus
What is the secondary structure of a protein stabilised by?
Hydrogen bonds between the atoms of different peptide bonds in the chain.
Which part of the polypeptide with a slight negative and positive charge?
Positive: The hydrogen of the NH2 group.
Negative: Oxygen of the COOH
What are the two type of secondary structure
Alpha Helix and Beta Sheet
Describe the structure of an alpha helix
A spiral with the R groups sticking outwards
What is the structure of a Beta sheet
Parts of polypeptide chain running alongside each other forming a corrugated sheet, with the R groups sitting above and below.
What does an anti-parallel and parallel chain consist of?
anti-parallel: Chains in opposite directions with respect to NC polarity
parallel: Chains in the same direction with respect to NC polarity.
What is the tertiary shape of a protein?
The 3-dimensional shape of a protein
What is the tertiary shape of a protein stabilised by?
Interactions between R groups of amino acids
Why are the R groups close together in the tertiary structure?
Because of the folding in the secondary structure
Name five types of interactions between R groups
Hydrophobic interactions Van der Waals interactions Hydrogen bonding Ionic bonds Disulphide bridges
Describe hydrophobic interactions
Non polar R groups are usually found on the inside of the protein. Other R groups are usually found on the outside.
Describe van der waals interactions
Very weak attractions between the electron clouds of atoms
Describe hydrogen bonding
The weak negative charge of oxygen on C=O is attracted to the weak positive charge of the hydrogen on an OH or NH2 group.
Describe ionic bonds
The COOH and NH2 groups ionise to become COOH- and NH3+. These groups are strongly charged and can attract one another
Describe disulphide bridges
Covalent bonds form due to reactions between the sulphur-containing R groups of cysteines.
What is the name given to the non-protein groups that are incorporated into the polypeptide chain in the tertiary structure
Prosthetic groups
What does the quaternary structure of a protein consist of?
Different polypeptide sub-units linked by R group interactions
