(O) Topic 30 - Amino Acids, Proteins and DNA
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Draw the structure of an amino acid
refer to notes for answers. should include C bonded to an amine group, a carboxyl group, a Hydrogen and an R group
How many naturally occuring amino acids are there?
20
What state are amino acids usually at room temperature and why?
Solid, due to the ionic attraction between the zwitterions that the amino acids form.
What is the net charge of a zwitterion?
0
What isomerism do amino acids display and why?
Optical Isomerism due to the chiral centre, causing each amino acid to exist as two enantiomers
Which groups on amino acids are basic and which are acidic?
Basic - Amine group Acidic - Carboxyl group
Which reactions can occur with the acidic group of an amino acid?
• Deprotonated by bases • esterfication with alcohols (with acid catalysts)
Which reactions can occur with the basic group of an amino acid?
• Protonated by acids • Acylation with acyl chloride/ acid anhydride • Nucleophilic substituion with halogenoalkanes
What is a dipeptide?
Two amino acids joined together in a condensation reaction.
What is a polypeptide?
Many amino acids joined together in a condensation reaction
What is a protein?
one or more polypeptide chain, made up of many amino acids joined together
Describe the process of breaking down proteins and peptide chains
Hydrolysis reactions occur, breaking peptide bonds through the addition of water, forming their constituent amino acids
Describe the primary structure of a protein
The primary structure is a sequence of amino acids bonded by peptide bond through condensation reactions to form a polypeptide chain
Describe the secondary structure of a protein
Hydrogen bonds form between peptide links in the polypeptide chain, pulling the straight chain into either an alpha helix or beta pleated sheets
Describe the tertiary structure of a protein
The polypeptide chain coils itself up, forming a unique shape for that protein. It is formed by interactions between the R groups of each amino acid, including ionic interaction, disulphide bridges, van der waals, hydrophillic/ hydrophobic interactions and hydrogen bonding.
Describe how a polypeptide with only hydrophobic and hydrophillic R groups may form a tertiary structure
the amino acids containing hydrophobic R group will be folded into the middle, and will be surrounded by the amino acids containing hydrophillic R groups, protecting them.
Describe the Quaternary structure of a protein
Many polypeptide chains interact together forming a complex protein molecule
How many hydrogen bonds are between cytosine and guanine?
3
How many hydrogen bonds are between adenine and thymine?
2
Describe the lock and key hypothesis
Enzymes have specific active sites for which a specifc substrate temporarily bonds too, holding it in a precise orientation required for a reaction to occur. It is bonded temporarily with intermolecular forces, which promote the movement of electrons within the substrate, lowering the activation energy for the reaction.
What is enzyme denaturing
When the teritiary structure of the enzyme breaks down due to a change in the temperature or pH, meaning theat the active site is no longer complementary to the substrate.
Explain how enzyme inhibition works?
A molecule of a similar shape to the substrate can bind and block the active site.
What is the shape of cisplatin?
Square Planar
What is cisplatin?
Cisplatin is an anticancer drug