Amino acids, proteins, DNA Flashcards
(26 cards)
are amino acids acidic or basic? why?
they have both acidic and basic properties (they are amphoteric) because the carboxylic acid group can act as an acid while the amine group can act as a base
what are the bonds called in proteins?
peptide bonds
by what method can amino acids be separated and identified?
thin-layer chromatography
how can amino acids be identified?
by their Rf values
what is a nucleotide made up of?
a phosphate ion, 2-deoxyribose and a nitrogenous base
what are the 4 nitrogenous bases in DNA?
adenine
cytosine
guanine
thymine
what is the bonding in a single strand of DNA?
covalent bonding between the phosphate group of one nucleotide and the 2-deoxyribose sugar of another (phosphate - sugar backbone)
how does DNA exist?
as 2 complementary strands in a double helix
what is used as an anti-cancer drug?
the Pt(II) complex cisplatin
how does cisplatin act as an anti-cancer drug?
it prevents DNA replication in cancer cells by a ligand replacement reaction with DNA by distorting the shape of the DNA strand - it binds to nitrogen atoms on 2 adjacent guanine bases
when does a zwitterion form?
when the overall pH of the molecule is zero (the isoelectric point)
how do disulfide bridges help keep a protein structure stable?
by losing 2 hydrogen atoms
what does it mean ‘enzymes are stereospecific’?
they will only break down one enantiomer and will have no effect on the optical isomer
what type of polymer is DNA?
condensation polymer
how many hydrogen bonds do cytosine and guanine form?
3 (pyrimidines)
how many hydrogen bonds do adenine and thymine form?
2 (purines)
what is a zwitterion?
a molecule with both positive and negative ions (with amino acids, both the carboxyl and amino groups are ionised) but the molecule is neutral overall
what is the isoelectric point dependent on?
the R group of the amino acid (different amino acids have different isoelectric points)
what happens to amino acids in pH lower than the isoelectric point (acidic solution)?
the COO- accepts a H+
what happens to amino acids in pH higher than the isoelectric point (alkaline solution)?
the NH3+ loses a H+
how many naturally occurring amino acids are there?
20
what bonding is present in secondary structure of proteins?
hydrogen bonding
what bonding is present in tertiary structure of proteins?
hydrogen
disulfide
ionic
hydrophilic and hydrophobic interactions
what is the tertiary structure of proteins?
when an alpha-helix or beta-pleated sheet folds into a 3D structure
