Amino acids, proteins, DNA

Question 1

are amino acids acidic or basic? why?

Answer 1

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

Question 2

what are the bonds called in proteins?

Answer 2

peptide bonds

Question 3

by what method can amino acids be separated and identified?

Answer 3

thin-layer chromatography

Question 4

how can amino acids be identified?

Answer 4

by their Rf values

Question 5

what is a nucleotide made up of?

Answer 5

a phosphate ion, 2-deoxyribose and a nitrogenous base

Question 6

what are the 4 nitrogenous bases in DNA?

Answer 6

adenine
cytosine
guanine
thymine

Question 7

what is the bonding in a single strand of DNA?

Answer 7

covalent bonding between the phosphate group of one nucleotide and the 2-deoxyribose sugar of another (phosphate - sugar backbone)

Question 8

how does DNA exist?

Answer 8

as 2 complementary strands in a double helix

Question 9

what is used as an anti-cancer drug?

Answer 9

the Pt(II) complex cisplatin

Question 10

how does cisplatin act as an anti-cancer drug?

Answer 10

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

Question 11

when does a zwitterion form?

Answer 11

when the overall pH of the molecule is zero (the isoelectric point)

Question 12

how do disulfide bridges help keep a protein structure stable?

Answer 12

by losing 2 hydrogen atoms

Question 13

what does it mean ‘enzymes are stereospecific’?

Answer 13

they will only break down one enantiomer and will have no effect on the optical isomer

Question 14

what type of polymer is DNA?

Answer 14

condensation polymer

Question 15

how many hydrogen bonds do cytosine and guanine form?

Answer 15

3 (pyrimidines)

Question 16

how many hydrogen bonds do adenine and thymine form?

Answer 16

2 (purines)

Question 17

what is a zwitterion?

Answer 17

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

Question 18

what is the isoelectric point dependent on?

Answer 18

the R group of the amino acid (different amino acids have different isoelectric points)

Question 19

what happens to amino acids in pH lower than the isoelectric point (acidic solution)?

Answer 19

the COO- accepts a H+

Question 20

what happens to amino acids in pH higher than the isoelectric point (alkaline solution)?

Answer 20

the NH3+ loses a H+

Question 21

how many naturally occurring amino acids are there?

Answer 21

20

Question 22

what bonding is present in secondary structure of proteins?

Answer 22

hydrogen bonding

Question 23

what bonding is present in tertiary structure of proteins?

Answer 23

hydrogen
disulfide
ionic
hydrophilic and hydrophobic interactions

Question 24

what is the tertiary structure of proteins?

Answer 24

when an alpha-helix or beta-pleated sheet folds into a 3D structure

Question 25

how can a drug (good or bad) act as an enzyme inhibitor?

Answer 25

by blocking the active site of the enzyme

Question 26

what is a side effect of cisplatin as an onto-cancer drug? why?

Answer 26

hair loss
because it also binds to DNA in healthy cells and hair follicles replicate very quickly like cancer cells so the effect on them is greater than other cells