Topic 30: Amino acids, proteins and DNA

Question 1

Amino acid

Answer 1

a carboxylic acid group (-COOH) and an amine group (-NH₂) usually around a chiral carbon

Question 2

Naming amino acid

Answer 2

2-aminoethanoic acid
anoic acid plus whatever groups

Question 3

Zwitterion

Answer 3

A molecule containing both a positively charged group (cation) and a negatively charged group (anion)
Can come from amino acids. Isoelectric point

Question 4

Amino acid with no optical isomerism

Answer 4

Glycine - hasn’t got a chiral carbon centre

Question 5

Boiling points of zwitterons

Answer 5

Higher than their amino acids as have more imfs

Question 6

Amino acids acids/ bases

Answer 6

Act as both as have both functional groups

Question 7

Amino acids acid and base reactions

Answer 7

Form salts

Question 8

Chromatography of amino acids developing agent

Answer 8

Ninhydrin makes the spots of aas more visible (purple)

Question 9

Peptides

Answer 9

Amino acids joining together via an amide (peptide) links

Question 10

Hydrolysis of peptides

Answer 10

Attack takes place at slightly positive C of C=O
The C-N bond broken
Broken into their amino acids

Question 11

Hydrolysis of peptides water

Answer 11

Very slow

Question 12

Hydrolysis of peptides acid/alkaline conditions

Answer 12

Quick, produces salts
Acid- amine group protonated
Alkaline - acid group becomes sodium salts

Question 13

Mechanism of peptide synthesis

Answer 13

Addition- elimination

Question 14

Proteins IMFs

Answer 14

Hydrogen bonding
C=O and N-H bonds are polar so H bonding between chains

Question 15

DNA structure elements

Answer 15

Deoxyribose sugar, Phosphate and Nitrogenous organic base

Question 16

Nucleotide

Answer 16

Monomers of DNA

Question 17

Making nucleotide

Answer 17

Two condensation reactions joining the 3 parts together making water

Question 18

Bond between nucleotides

Answer 18

Phosphodiester, covant bond between phosphate group and pentose sugar on neighbouring nucleotide

Question 19

Why are DNA bases bases?

Answer 19

They accept a proton

Question 20

Why is DNA acidic

Answer 20

Can donate a proton from phosphate

Question 21

IMFs between DNA bases

Answer 21

H bonding
3 between C and G
2 between A and T

Question 22

DNA replication

Answer 22

Basic expaination
H bonds break
Free nucleotides pair
Recoils
2 New strands

Question 23

Cisplatin

Answer 23

Anti-cancer drug
cis-[Pt(NH3)2Cl2]

Question 24

Cisplatin shape

Answer 24

Square planar

Question 25

How cisplatin works

Answer 25

Lone pairs on nitrogen on G dative bond with Pt water displaces Cls on Pt Water ligands displaces in ligand substitution by N on G Distorts the shape of DNA preventing replication

Question 26

Cisplatin side affects

Answer 26

Works on normal DNA but mostly on cancer as faster, hair follicles have fast DNA replication so hair falls out

Question 27

Primary structure of protein

Answer 27

Amino acid sequence

Question 28

Secondary structure of protein

Answer 28

H bonding Alpha helix/ beta pleated sheet

Question 29

Bonding in proteins

Answer 29

Hydrogen Ionic between different groups Disulphide bridge (sulfur-sulfur bond

Question 30

Tertiary structure of protein

Answer 30

3D shape Mixture of different bonds

Question 31

Determining protein structure

Answer 31

Reflux in conc. HCl to break into its amino acids

Question 32

How enzymes work

Answer 32

Lock and key Substrate must fit and be at right orientation to react. Also temp. have IMFs between E- move within substrate lowering activation energy

Question 33

Stereospecificity of enzymes

Answer 33

Will only catalyse the reaction for one of the other enantiomer of a molecule.

Question 34

Enzyme competitive inhibition

Answer 34

Similar structure to substrate Competes with substrate for active site Stops harmful enzyme catalysed reactions in the body