medchem 21

Question 1

the carbon carrying the R substiuent is called —

Answer 1

alpha carbon

Question 2

there are – different alpha amino acids in nature and they differ in the —-

Answer 2

• 20
• r group side chain

Question 3

there are — naturally occurring amino acids which gives rise to —

Answer 3

• 20
• proteins , enzymes , hormones , antibodies

Question 4

carboxylic acid are acidic when they react with — to give —-

Answer 4

• bases
• carboxylate salt
  ( as: c.a + Na+ OH- –> carboxylate salt + h20)

Question 5

amines are — when they react with acids as hydrochloric acid to give —

Answer 5

• basics
• ammonium salt
  ( R-NH2 + h+ cl- –> ammonium salt )

Question 6

are amino acids :
- basics
- acidic
- both

Answer 6

both bc of the acid end of the c.a and the amine end

Question 7

amino acids contains both acidic and basic groups so they undergo —

Answer 7

internal acid base reactions and produce a zwitteron ( aka different charges at the opposite ends )

Question 8

amino acids exist in a dipolar form ( + and -ve charge in one molecule ) which is called —

Answer 8

zwitteron which means hybrid ions

Question 9

for an acid in a graph of pH vs. quantity of the base added is called —-
and we use the – to which the pH is read after the addition of the base

Answer 9

• pH titration curve ( check the graph)
• pH meter

Question 10

-in the pH titration curve we need — equilivent bases to complete the titration and there are – regions of — ( aka the 2 acidic groups ) one w the ph of — and one around —
- the —- of an acidic group is the pH at the point go half neautrilzation of that group

Answer 10

• 2 bases
• 2 regions of neutralisation (check the graph )
• 2.3 of the c.a , 9.7 of the nh3
• the pKa of an acidic group

Question 11

from point A and B:
from point B and C:

Answer 11

• we neautralized the carboxylic group and we formed a zwitteron amino acid with water
• we nevautrallized the amino group from the zwitteron complex and we add more base to give us neutral amino group and -ve carboxylic group with water

Question 12

the — point is the point at which the amino acid has an overall charge of zero and doesn’t migrate to cathode or anodr in electric field

Answer 12

• isoelectric point (pl)

Question 13

for simple amino acid aka one without acidic or basic group the pl is the — of the two pKa

Answer 13

• mean

Question 14

adult humans can synthesise all 20 amino acids except for – these are called the — amino acids and must be included in the diet

Answer 14

• 9
• essential amino acids

Question 15

amino acids can be divided into groups dependent on the —
– natural
– acidic
– basic

Answer 15

• R substituents ( non polar ,aliphatic r groups , aromatic r groups , polar , uncharged r groups , +ve changed r groups and -ve charged r groups )
• 15
• 2
  -3

Question 16

the type of r groups:

Answer 16

• non polar , aliphatic which contains H or many ch2
• polar , uncharged contains OH , CH2-SH , or carboys group so C=O with amino group as: CH2-NH2-C=O
• aromatic has a bezne ring
• +ve charged are basic has +ve or histaidne which doesn’t have the +ve charged
• -vely charged which are acidic has the -ve

Question 17

side chains can be also hydrophobic as:
and they arrange themselves into the centre away from the water phase
side chains can be also hydrophilic which contains — and they arrange themselves into the surrounding water phase

Answer 17

• valine , alanine , phenylaline
• OH groups
  ( CHECK EXAMPLES SLIDE 17)

Question 18

cytosine and methionine have — containing groups side chains as:

the two cytosines are often converted into —- within the protein thereby linking them together

Answer 18

• sulphur containing side chain such as thiol ( -SH)
• disulfied

Question 19

all alpha amino acids are optically active as the alpha carbon has a chiral centre except — -which is an exception

Answer 19

• glycine
  ( R=H)

Question 20

all naturally optically active alpha amino acids have – configuration except —-

Answer 20

• S
• Cys bc the COO- have a higher priority than R , ( CHECK EXAMPLE SLIDE 21)

Question 21

all naturally occurring alpha amino acids including cys ( cystine ) are – in old convention except —

Answer 21

• L
• GLY

Question 22

B-alanine is a naturally occurring amino acids and its the structural isomer for —-
the neurotransmitter ( GABA ) aka gamma-aminobutryic acid is also a naturally occurring and diffency of it causes huntigtons chorea aka a nearological disorder

Answer 22

• alpha alanine
  ( CHECK SLIDE 22)