amino acids, proteins and DNA Flashcards
at nuetral pH and in solid state amino acids exist as
zwitterions
H from COOH removed so COO- and added to NH2 forming +NH3
structure of amino acid
H2N-CHR-COOH
at low pH amino acids exist as
+NH3-CHR-COOH gained h has more acidic
at high pH amoni acids exist as
NH2-CRH-COO- as more alkaline so loses H
proteins are
condensation polymers of amino acids joined by peptide links
the importance of hydrogen bonding and disulphite bonds in proteins
hold proteins in shape ,
hydrogen bonding exist between polar groups(-OH and -NH2) stabilize the secondary and tertiary structure of protein
disulphite bonding between cysteine, link diff part of protein chain together help to stabilise the tertiary strucutre
primary structure of protiens
number and order of amino acids in polypepetide chain
seconday structure of protiens
peptide links form hydrogen bonds with each other resulting in alpha helix or beta pleated sheets
tertiary structure of proteins
3D tertiary structure
disulphite bonds
hyrogen bonds
ionic bonds
hydrolysis of the peptide link produces
the constituent amino acids
how can amino acids be sperated and identified
thin layer chromotgraphy
used developing agents such as ninhydrin or UV light to locate then caluculate Rf values
enzymes are
proteins
action of enzymes as catalysts
substrate fit exactly into the active site that is stereospecific so only bond to one enantiomer of a substrate.
enzyme substrate complex forms reducing the Ea to break bonds within the molecule and catalyses’ the reaction
principle of a drug acting as an enzyme inhibitor
similar shape to sunstrate so compete with the substrate to bond to the active site but no reaction follows instead they block the active site so no sunstrate can fit in
how can drugs’ acting as enzymes inhibitor be deigned
computers
if an undesirable biological process occurs which is catalyzed by and enzyme a computer is used to determine the shape of an active site and design another molecule that will fit into the active site (must be correct enantiomers)
explain why a stereospecific active site can only bind to one enantiomeric form of a substrate of drug
as active site made up of amino acids so contain chiral centers
a nucleotide is made up from
a phosphate ion bonded to 2-deoxyribose which is bonded to one of the 4 bases (adenine, cytosine, guanine and thymine)
a single strand of DNA is a polymer of
nucleotides are phosphate group of one nucleotide bonded to the 2-deoxyribose of another nucleotide, this results in a sugar-phosphate-sugar-phosphate polymer chain with baes attached to the sugars in the chain
DNA exist as
2 complemtnetory strands arranged in the form of double helix
explain how the hydrogen bonding between base pairs leads to the two complemtnetory stands of DNA
complementary base pairing exists in DNA helix where adenine always pairs with thymine with 2 hydrogen bonds and guanine always pairs with cytosine with 3 hydrogen bonds
expample of anti-cancer drug and how it works
cisplatin
prevents DNA replication in cancer cells by a ligand replacement reaction with DNA in which a bond is formed between platinum and nitrogen atom on guanine. this prevents DNA from unwinding so cancerous cell cannot replicate
consisderations of cisplatin
will also bind to the DNA in healthy cells which can cause unwanted side effects
the drug can be targeted straight to the cancer cells to reduce the effect on healthy tissue
can also be used in minimal amounts
