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A2 Chemistry Unit 2 > Amino Acids And Proteins > Flashcards

Amino Acids And Proteins Flashcards

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1
Q

What is an amino acid

A

A compound whose molecules contain bird an amino and a carboxyl group

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2
Q

How many amino acids occur naturally and in what form

A

20 occur naturally and they combine to form proteins

All naturally occurring amino acids are a amino acids

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3
Q

What does alpha amino acid mean

A

NH2 and COOH are bonded to same C atom

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4
Q

What is the definition of a zwitterion

A

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

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5
Q

Why do amino acids exist as zwitterions

A
  • they all contain a basic group and an acidic carboxyl group
  • undergo internal acid-base reaction
  • forms a dipolar ion
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6
Q

Draw the diagram of a zwitterion amino acid

A

See page 22

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7
Q

State the physical properties of amino acids

A

⭕️ High mp - dipolar ions - strong forces of attraction - lot of energy
⭕️ water soluble - dipolar ions - interact w polar water molecules
⭕️ white crystalline solids
⭕️ insoluble in organic solvents

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8
Q

What group is involved in the reaction when an amino acid reacts with sodium carbonate

A

The COOH group

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9
Q

What are the products for the reaction of an amino acid with sodium carbonate

A

Metal salt
Water
Carbon dioxide

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10
Q

What are he observations for amino acid reaction with sodium carbonate

A

Bubbles of colourless has evolved

Solid disappears

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11
Q

What group is reacted when amino acids react with nitrous acid

A

The NH2 group is replaced by an OH

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12
Q

What are the products when amino acid is reacted with nitrous acid

A

N2
H2O
Hydroxycarboxylic acid

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13
Q

How is nitrous acid produced

A

In situ
NaNO2 and HCl
Below 5°C

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14
Q

What is formed when amino acids react with copper (II) sulfate

A

A complex

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15
Q

What are the observations when amino acid is reacted with nitrous acid

A

Bubbles of colourless has given off (N2)

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16
Q

What are the observations when amino acid reacts with copper (II) sulfate

A

Dark blue solution formed

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17
Q

Write the structural equation of amino acid reaction with copper (II) sulfate

A

See notes

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18
Q

Draw the structure of an amino acid in acid conditions and alkaline conditions

A

See notes

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19
Q

Describe the structure of a neutral amino acid

A

Contains one amine and one carboxyl group

20
Q

Describe an acidic amino acid

A

Contains additional carboxyl group

21
Q

Describe a basic amino acid

A

Contains additional amine group

22
Q

What kind of reaction forms a peptide (polyamide)

A

Condensation polymerisation of amino acids

23
Q

What is a peptide link

A

Link between -NH2 of one amino acid and -COOH of another

24
Q

What is a condensation reaction

A

When two molecules combine to form one single molecule. Resulting in the loss of a small molecule eg water

25
Q

Draw the peptide group

A

See notes

26
Q

What happens during acid hydrolysis of protein

A
  • acids formed are protonated
  • NH2 ➡️ NH3+
  • positive amino acid ions
  • COOH stays same
27
Q

What happens during alkaline hydrolysis of a proteins

A
  • acids formed are deprotonated
  • COOH ➡️ COO-
  • negative amino acid ions
  • NH2 stays the same
28
Q

What is the definition of primary structure of proteins

A

Sequence of amino acids joined by peptide links in the chain

29
Q

What is the definition of secondary structure

A

Twisting/coiling of the chain to form a B-pleated sheet/a helix by intramolecular hydrogen bonding

30
Q

Between which parts of the molecule does H bonding occur in the secondary structure

A

NH and C=O

31
Q

What is the definition of tertiary structure in proteins

A

Bending / folding of secondary structure to give a precise 3D shape held together by Hydrogen bonding / disulphide bridges / ionic interactions / VDW forces

32
Q

How does the tertiary structure occur

A

Interactions between R-group side chains

33
Q

How to sulfer bridges form

A
  • cystine

- side group of SH ➡️ oxidised to form dimer

34
Q

What type of bond is a sulfer bridge

A

Covalent - stronger than H bond

35
Q

How do ionic interactions occur in tertiary structure

A

Ionic bonds between adjacent acidic and basic amino acids

36
Q

How do VDW forces occur in tertiary structure

A

Between non polar side groups

37
Q

How do dipole dipole interactions occur in tertiary structure

A

Between polar side chains

38
Q

How do hydrophobic interactions occur in tertiary structure

A
  • Between non polar side chains and water
  • repel water
  • chain folds and hydrophobic on inside folds and hydrophilic polar groups on outside
39
Q

What is the definition of an enzyme

A

A protein which is a biological catalyst

40
Q

What do enzymes do

A
  • Speed up reaction without being used up

- alternative reaction pathway of lower activation energy

41
Q

What is the definition of active site

A

Site on surface of enzyme into which the substrate fits

42
Q

What is the induced fit theory

A

Substrate induces a change of the active site of the enzyme

43
Q

What does it mean that enzymes are stereospecific

A

Only one optical isomer will fit

44
Q

Why are enzymes specific

A

Due to tertiary structure - specific shape needed to fit active site

45
Q

Why are enzymes in washing powder

A
  • Break down biological molecules in stains
  • break down by hydrolysis ➡️ makes them more water soluble so easier washed
  • allows powder to work at lower temp - more cost effective
46
Q

What effect does pH have on enzyme activity

A
  • optimal pH
  • if H+ added ➡️ active site protonated
  • if OH- added then active side deprotonated
  • changes structure of active site
47
Q

What effect does temp have on enzyme activity

A
  • optimal temp
  • changes active site
  • break interactions eg H bonds
  • v high = denatured

A2 Chemistry Unit 2 (12 decks)

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