Biochemistry: Amino Acids, Proteins, Water and pH Flashcards

1
Q

what shape is water

A

tetrahedral

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2
Q

hydrophilic

A

dissolves in water

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3
Q

how do hydrophilic molecules dissolve in hydrophilic substances

A

electrostatic interactions - ion-dipole, dipole-dipole interactions

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4
Q

hydrogen bond

A

covalent bond between a hydrogen atom and a more electronegative one creating a polarised bond

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5
Q

what is the strength of a hydrogen bond compared to covalent

A
  • individually weaker

- collectively strong

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6
Q

hydrophobic

A

non-polar substances are insoluble in water

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7
Q

what is the hydrophobic effect

A

2 layers form when polar and non-polar substances are mixed

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8
Q

ampipathic

A

molecules with both hydrophilic and hydrophobic parts

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9
Q

describe an ampipathic molecule

A

polar ‘head’, hydrophobic ‘tail’

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10
Q

what do ampipathic molecules form in water

A

micelles

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11
Q

what if the function of the proteins in the phospholipid bilayer

A
  • confer selectivity

- involved inrecognition

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12
Q

what are amino acids made of

A

proteins and polypeptides

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13
Q

in an amino acid what is bonded to the central carbon atom

A
  • amide group
  • R group
  • carboxyl group
  • hydrogen
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14
Q

steroisomer

A

non-superimposable mirror images

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15
Q

what are the 4 types of amino acids

A
  • polar (uncharged)
  • non-polar (uncharged)
  • acidic
  • basic
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16
Q

describe peptide bond formation

A
  • the carboxyl and amino group of 2 amino acids bond via peptidyl transferase
  • this forms an amide group
17
Q

what direction does peptide bond formation occur in

A

towards the C terminal

18
Q

what is a peptide bond

A

partial double bond character electrons, form the N and C terminal but arent covanlently bonded

19
Q

describe peptide bonds

A

planar, strong and rigid

20
Q

acid

A

substance that donates a proton

21
Q

base

A

proton acceptor

22
Q

what does the strength of an acid depend on

A

how readily it donates a proton

23
Q

what equation is used to measure an acids strength

A

dissociation constant

Ka= [H+][A-]/[HA]

24
Q

what is pH a measurement of

A

the amount of protons in a solution

25
Q

what is the equation for measuring pH

A

pH = -log10[H+]

26
Q

what is the equation to measure an acids strength with pKa

A

pKa = -log1o[Ka]

27
Q

how do you work out the log of a pH to use in an equation

A

the log of no.x to its base n is the no. of times n has to be multiplied with itself to get x
log10^100 = log 10^10^2 - pH7 = 10^-7

28
Q

what equation is used to connect the pKa of a weak acid with the pH of its solution

A

Henderson Hasselbach

29
Q

what is the Henderson Hasselbalch used to calculate

A

properties of a buffer solution

30
Q

what is the Henderson Hasselbalch equation

A

pKa - pH = log10[HA]/[A]

31
Q

buffer

A

solution that controls the pH of a reaction mixture by resisting a change in pH with moderate amounts of acid or base added at their pKa value

32
Q

when [acid] = [conjugate base] what else is equal

A

pH = pKa

33
Q

describe a titration curve

A

the graph shows that at the buffers pKa value it resists a change in pH

34
Q

what are zwitterions

A

amino acids without a charged side group in a neutral solution, no net charge
contain 2 titratable groups

35
Q

isoelectric pH

A

pH at which a molecule has no net charge

36
Q

zwitterions with 2 titratable groups means what in terms of pKa

A

2 pKa values

proteins can act in a different way as pH varies

37
Q

what part of proteins can be ionised

A

the ends

38
Q

what can a change in pH do to the ionisation of a proetin

A

change the ionisation and therfore structure and function