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Flashcards in Proteins Deck (26):

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?



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