AA, proteins and DNA

Question 1

functional groups of AA

Answer 1

NH2 and COOH

Question 2

how many naturally occurring AA are there in the body

Answer 2

20

Question 3

what type of AA are found in the body

Answer 3

alpha

the NH2 is always on the carbon next to COOH

Question 4

generic formula for an alpha AA

Answer 4

R
            I
H2N - C - COOH
            I
            H

Question 5

which enantiomer do alpha AA exist as in nature

Answer 5

• enantiomer

Question 6

is the product from AA being synthesises naturally optically active

Answer 6

no

a racemix is formed as the CN- can attack from above or below the planar C=O

Question 7

in what form do AA exist as solids

Answer 7

zwitterions

Question 8

what colour are zwitterions

Answer 8

white solids

Question 9

zwitterion

Answer 9

ions which have both a permanent positive and negative charge but are neutral overall

Question 10

zwitterion AA

Answer 10

R
              I
H3N+ - C - COO- 
              I
              H

Question 11

what happens to AA in acidic conditions

Answer 11

gains a proton on NH2 group

Question 12

what happens to AA in alkaline conditions

Answer 12

loses a proton from COOH group

Question 13

peptide linkage

Answer 13

CONH

Question 14

what name is given to chains of AA up to 50 AA

Answer 14

polypeptide

Question 15

what name is given to a chain of AA with more than 50

Answer 15

proteins

Question 16

conditions needed for hydrolysis to occur

Answer 16

6 mol dm3
HCl
reflux for 24 hours

Question 17

primary structure

Answer 17

sequence of AA along the protein chain bonded by covalent bonds

Question 18

secondary structure

Answer 18

shape of the protein chain

Question 19

how is the secondary structure held together

Answer 19

hydrogen bonding

Question 20

tertiary shape of a protein

Answer 20

alpha helix or beta pleated sheet is folded into a complex 3D shape

Question 21

how is the tertiary structure held together

Answer 21

hydrogen bonding
ionic interactions
disulphide bridges
van der waals

Question 22

what is TLC plate made of

Answer 22

plastic sheet coated with silica

this is the stationary phase

Question 23

describe the process of TLC

Answer 23

spot the samples onto a pencil line a few cm above the base
place this in a beaker with solvent lower than the pencil line
wait until the solvent front is almost at the top of the plate
remove and analyse

Question 24

how do you calculate the Rf value

Answer 24

distance moved by that substance divided by the distance moved by the solvent front

Question 25

what is 2D TLC

Answer 25

uses a square TLC plate
spot the AA in one corner then run TLC in first solvent
flip the plate through 90’ and repeat TLC in a second different solvent

Question 26

what is an enzyme

Answer 26

protein based catalyst that speed up reactions in the body by factors of up to 10^10

Question 27

structure of an enzyme

Answer 27

globular protein with a creft/crevice in it, known as an active site

Question 28

how structure help the function

Answer 28

the reacting molecules fit precisely into the active site and are held at exactly the right orientation to react

Question 29

enzymes increase the ror

Answer 29

reacting molecules form temporary bonds to the enzyme

this weakens the bonds in the molecules promotes electron movement and lowers Ea

Question 30

what does the stereospecificity of enzymes mean

Answer 30

active sites are so selective of the shape of substrates that only reactions involving one enantiomer are catalysed

Question 31

example of a drug that works through enzyme inhibition

Answer 31

penicillin

Question 32

DNA

Answer 32

deoxyribonucleic acid

Question 33

what does DNA do

Answer 33

present in all cells and is a blueprint from which all organisms are made

Question 34

cisplatin

Answer 34

Cl NH3
Pt
Cl NH3

Question 35

function of cisplatin

Answer 35

bonds to strands of DNA to distort shape and prevent cell replication
bonds to N atoms on 2 adjacent G bases
N atom replaces Cl- ligand