amino acids, polymers and proteins Flashcards

1
Q

general formula of an amino acid

A

NH2–CHR–COOH

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2
Q

what is a zwitterion

A

ion with both a positive and negative charge that’s overall charge cancels out.

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3
Q

define isoelectric point

A

the pH at which a zwitterion forms in solution

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4
Q

how does an amino acid form a zwitterion

A

the H from the COOH of one molecule will protonate the NH2 group of another molecule

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5
Q

what groups does an amino acid zwitterion contain

A

NH3+ and COO-

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6
Q

what are three physical properties of amino acids

A

white solids
high melting point (around 300)
water soluble

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7
Q

at what pH can an amino acid act as an acid and why

A

low pH
COOH has a proton to donate

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8
Q

at what pH can an amino acid act as a base and why

A

high pH
N has a lone pair of electrons which can accept a proton

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9
Q

what is amphoteric behaviour

A

when a substance can act as both an acid and a base, depending on the chemical environment

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10
Q

which is the only amino acid that is not optically active

A

glycine

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11
Q

why is glycine the only amino acid that is not optically active

A

it does not have a chiral carbon as the R group is a Hydrogen

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12
Q

what is the bond between amino acids in a peptide/polypeptide called

A

an amide link

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13
Q

what type of polymer are polypeptides

A

condensation polymers

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14
Q

two steps to hydrolyse peptide bonds

A

1 heat under reflux with HCl for up to 24hrs
2 followed by addition of water

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15
Q

what does a condensation reaction produce

A

polymer and a small molecule eg H20 or HCl

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16
Q

what are polyesters formed from

A

a dicarboxylic acid and a diol
or a diacyl chloride and a diol

17
Q

what are polyamides formed from

A

a dicarboxylic acid and a diamine

18
Q

what is the ester functional group formed in a polyester

A

O=C-O

19
Q

what is the amide group in a polyamide

A

O=C-NH

20
Q

what is the glycine R group

A

H-

21
Q

what is the alanine R group

A

CH3-

22
Q

what is the valine R group

A

(CH3)2CH-

23
Q

what is the cysteine R group

A

HS-CH2-

24
Q

what is the phenylalanine R group

A

C6H5-CH2-