amino acids, proteins and DNA

Question 1

at nuetral pH and in solid state amino acids exist as

Answer 1

zwitterions
H from COOH removed so COO- and added to NH2 forming +NH3

Question 2

structure of amino acid

Answer 2

H2N-CHR-COOH

Question 3

at low pH amino acids exist as

Answer 3

+NH3-CHR-COOH gained h has more acidic

Question 4

at high pH amoni acids exist as

Answer 4

NH2-CRH-COO- as more alkaline so loses H

Question 5

proteins are

Answer 5

condensation polymers of amino acids joined by peptide links

Question 6

the importance of hydrogen bonding and disulphite bonds in proteins

Answer 6

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

Question 7

primary structure of protiens

Answer 7

number and order of amino acids in polypepetide chain

Question 8

seconday structure of protiens

Answer 8

peptide links form hydrogen bonds with each other resulting in alpha helix or beta pleated sheets

Question 9

tertiary structure of proteins

Answer 9

3D tertiary structure
disulphite bonds
hyrogen bonds
ionic bonds

Question 10

hydrolysis of the peptide link produces

Answer 10

the constituent amino acids

Question 11

how can amino acids be sperated and identified

Answer 11

thin layer chromotgraphy
used developing agents such as ninhydrin or UV light to locate then caluculate Rf values

Question 12

enzymes are

Answer 12

proteins

Question 13

action of enzymes as catalysts

Answer 13

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

Question 14

principle of a drug acting as an enzyme inhibitor

Answer 14

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

Question 15

how can drugs’ acting as enzymes inhibitor be deigned

Answer 15

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)

Question 16

explain why a stereospecific active site can only bind to one enantiomeric form of a substrate of drug

Answer 16

as active site made up of amino acids so contain chiral centers

Question 17

a nucleotide is made up from

Answer 17

a phosphate ion bonded to 2-deoxyribose which is bonded to one of the 4 bases (adenine, cytosine, guanine and thymine)

Question 18

a single strand of DNA is a polymer of

Answer 18

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

Question 19

DNA exist as

Answer 19

2 complemtnetory strands arranged in the form of double helix

Question 20

explain how the hydrogen bonding between base pairs leads to the two complemtnetory stands of DNA

Answer 20

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

Question 21

expample of anti-cancer drug and how it works

Answer 21

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

Question 22

consisderations of cisplatin

Answer 22

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