Amino acids, Proteins and DNA

Question 1

what is the structure of glycine

Answer 1

Question 2

what are zwitterions

Answer 2

• a molecular ion which has both positive and negative charges and is neutral overall

Question 3

what property do all amino acids except form glycine have in common

Answer 3

• all of them have a chiral centre and are therefore optically active

Question 4

how does the structure of amino acids change when in acidic conditions

Answer 4

• the NH2 group gains a hydrogen ion forming NH3+

Question 5

how does the structure of amino acids change in basic solutions

Answer 5

• the carboxyl group (COOH) loses a hydrogen forming a negative COO- group

Question 6

what bonds are formed between amino acids to form proteins

Answer 6

• peptide bonds (CONH)

Question 7

what is the primary structure of a protein

Answer 7

• the sequence of amino acids

Question 8

what are the secondary structure of a protein

Answer 8

• folding of the polypeptide chain due to hydrogen bonding to form structures such as alpha-helix and beta-pleated sheet

Question 9

what is the tertiary structure of a protein

Answer 9

• further folding of the chain due to hydrogen ionic and disulfide bridges

Question 10

how can peptide bonds be broken into their separate amino acids

Answer 10

• by hydrolysis in the presence of an aqueous strong acid or an aqueous strong base

Question 11

what are enzymes

Answer 11

• proteins that act as catalysts in biological reactions

Question 12

how would you describe the active site of an enzyme

Answer 12

• stereospecific as it only allows one enantiomer to react

Question 13

how can enzymes be inhibited

Answer 13

• drugs can be synthesised to mimic the substrate which can bind with the active site and block the substrate

Question 14

how can enzyme inhibitors be designed

Answer 14

• by computer modelling

Question 15

what are the monomers that DNA is made from

Answer 15

• nucleotides

Question 16

what bonding occurs between nucleotides

Answer 16

• hydrogen bonding

Question 17

how many hydrogen bonds between adenine and thymine

Answer 17

• 2

Question 18

how many hydrogen bonds between guanine and cytosine

Answer 18

• 3

Question 19

describe the action of anti-cancer drug cisplatin

Answer 19

• Cis-platin bonds with guaine and stops DNA replication during cell division by cross-linking strands of DNA
• the chloride ligands are replaced by the guanine bases in a ligands substitution reaction
• the nitrogen atom uses its lone pair to form a coordinate bond with the Pt

Question 20

why cant transplatin do what cisplatin does

Answer 20

• the chloride ligands are on opposite sides of the complex

Question 21

why does chemotherapy produce side effects

Answer 21

• it kills fast-multiplying cells such as WBC’s, gametes and hair cells leading to side effects such as weak immune system, infertility and hairloss

Question 22

what part of the guanine is involved in forming dative covalent bonds to cis-platin

Answer 22

• the nitrogen atoms not involved in covalent bonding to the deoxyribose or the hydrogen bonding to cytosine
• normally the top N

Question 23

what are the leaving groups when nucleotides join together

Answer 23

• the H of the phosphate on one nucleotide and the OH on the sugar molecule on another nucleotide

Question 24

what are the leaving groups during the formation of a nucleotide

Answer 24

• OH off sugar and H off the phosphate
• OH off sugar and H off amino acid