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Biology A level > 1.4 proteins and enzymes > Flashcards

1.4 proteins and enzymes Flashcards

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1
Q

What is the structure of an amino acid?

A

Centra carbon atom
H atom
amino group - NH3
Carboxyl group - HO-C=O
and the r (variable) group

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2
Q

What bond is formed in condenation reaction of amino acids?

A

peptide bond

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3
Q

Where is the peptide bond formed in an amino acid?

A

the C of the carboxyl group of one amino acid and the N of the amino group of another amino acid

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4
Q

What is the N terminal of a polypeptide?

A

the amino group is at the end of the peptide chain

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5
Q

What is the C terminal of a polypeptide chain?

A

the carboxyl group is at the end of the polypeptide chain

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6
Q

What is the primary structure of a protein?

A

the sequence of amino acids in a polypeptide chain that is held in place by peptide bonds

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7
Q

What happens if the amino acid sequence was changed?

A

would change the structure of the protein

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8
Q

What is a secondary structure protein?

A

twisting of secondary structure into regular arrangement
it is either a alpha helix or a beta pleated sheet

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9
Q

What is a tertiary structure protein?

A

further folding of secondary structure into a 3D gobluar shape

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10
Q

What bonding occurs in a secondary structue protein?

A

H bonds between the carboxyl group and amino group

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11
Q

What bonding occurs in a tertiarty structure protein?

A

ionic bonds
h bonds
disulphide bridges occurs between r groups

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12
Q

What is a quaternary structure protein?

A

functional protein composed oof more then 1 polypeptide
the polypeptide might be a 2 or 3 structure

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13
Q

Where is the water removed from two amino acids in a condensation reaction?

A

The OH from the carboxyl group of one amino acid and the H from an amino group from the other amino acid

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14
Q

What is the bond formed in the condensation reaction between amino acids?

A

A peptide bond

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15
Q

What is a peptide bond?

A

The bond between the C from the carboxyl group of one amino acid and the nitrogen from the amino group of the other amino acid

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16
Q

What is the ‘N terminal’?

A

The amino group at the end of the polypeptide chain

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17
Q

What is the ‘C terminal’?

A

The carboxyl group at the end of the polypeptide chain

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18
Q

What is the structure of a fibrous protein?

A

Multiple secondary structure proteins that make a functional protein, folded to make a quaternary structure protein

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19
Q

What is the function of a fibrous protein?

A

Structural function

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20
Q

What are the properties of fibrous proteins?

A

High tensile strength
Insoluble in water

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21
Q

What are two examples of fibrous proteins?

A

Collagen
Keratin

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22
Q

What is Collagen’ structure (fibrous protein structure)?

A

Quaternary = 3 polypeptide chains which are secondary structure alpha helixes that are held in place by H bonds

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23
Q

What is the structure of a globular protein?

A

Single tertiary structure polypeptide
Or
Multiple tertiary polypeptide so a quaternary structure protein

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24
Q

What makes a globular protein soluble in water?

A

Hydrophobic interactions cause the R groups to face centre

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25
Q

What are the functions of a globular protein?

A

Biochemical
Enzymes
Pigments
Receptors
Antibodies

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26
Q

What does the function of a globular protein depend on?

A

The specific 3D shape

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27
Q

What is a congregate protein and an example of one?

A

A protein that contains a non-protein group which is called the prosthetic group eg: haemoglobin contains iron

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28
Q

What causes proteins to denature?

A

High temperatures breaks H bonds
pH breaks ionic bonds

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29
Q

What does denaturing a protein mean?

A

The bonds have been broken so it changes shape therefore stops functioning properly

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30
Q

What is the impact of fibrous proteins denaturing?

A

They lose their structural strength

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31
Q

What is the impact of globular proteins denaturing?

A

They become inactive and/or insoluble because the R groups move

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32
Q

What are the 4 bonds that maintain a proteins shape?

A

Peptide bonds
Ionic bonds
Hydrogen bonds
Disulphide bridges

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33
Q

What is a biological catalyst?

A

A substance that is produced by living tissue, that speeds up the rate of reaction without altering and being used up.
It does not cause a reaction to happen

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34
Q

What is catabolic enzyme action?

A

Breaks down something in the reaction

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35
Q

What is anabolic enzyme action?

A

Builds up something in the reaction

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36
Q

What does it mean by enzyme specificity?

A

The active site is specific to the substrate as they are complementary in shape. The enzymes are specific to 1 reaction for multiple similar groups of reactions

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37
Q

What is intracellular enzyme action and examples?

A

Happens inside the cell
Eg:
Lysosomes
Cytoplasm
Organelles like the mitochondrial membrane

38
Q

What is extra cellular enzyme action and examples?

A

Happens outside of the cell
Eg:
The alimentary canal in the digestive system

39
Q

How does an enzyme catalyse a reaction?

A

Does not react with the substrate and is not involved in the reaction
It provides the environment for reaction to occur
It lowers the activation energy

40
Q

What is an exergonic reaction?

A

Products have less energy than reactants - energy is released

41
Q

What is an endergonic reaction?

A

The reaction requires energy

42
Q

What must the substrate shape be like to join the active site?

A

The substrate shape must be complementary to the active site and the shape must be maintained and specific

43
Q

What is is called when the subtracted joins the enzyme?

A

Enzyme-substrate complex

44
Q

What is the lock and key model of enzyme action?

A

The substrates shape is specific to the active site and will only fit in the active site of one specific site enzyme
The enzyme is unaltered by the reaction

45
Q

What is the induced fit theory?

A

Initially the active site is not complementary in shape to the substrate
When the substrate fits, the active site alters and changes shape to fit the substrate
When the substrate leaves, the active site returns to original shape

46
Q

What type of reaction is the formation of enzyme-substrate complexes?

A

Catabolic

47
Q

What is an example of the induced fit model?

A

Lysosymes in lysosomes digest bacterial cell wall

48
Q

What type of protein are enzymes?

A

Globular

49
Q

What makes the substrate more stable ?

A

Forming an enzyme-substrate complex

50
Q

What type of reaction is ATP hydrolysis?

A

Exergonic

51
Q

What might you observe in an enzyme controlled reaction?

A

The product appearing
The substrate disappearing
Bubbles - O2

52
Q

What effect does temperature have on enzyme action?

A

Increases KE
More successful collisions between substrate and active site

53
Q

What happens if there is excess substrate in an enzyme controlled reaction?

A

The no. Of active sites becomes a limiting factor because all the active sites are occupied

54
Q

Why does substrate conc become a limiting factor in an enzyme controlled reaction?

A

Because it has been converted into product

55
Q

How do you calculate the rate of production of a product from a graph?

A

Change in y/ change in x

56
Q

What is the units for rate?

A

Mg dm-3 min-1

57
Q

How do you calculate the percentage change in a reaction?

A

Original - new / original
X100

58
Q

How do you calculate the initial rate of reaction?

A

Draw a tangent and y/x
Tangent starts from 0

59
Q

What does it mean if the reaction has stopped?

A

Not all the substrate was converted into product

60
Q

What does it mean if the reaction has finished?

A

All the substrate has been converted into product

61
Q

How do you calculate rate of reaction from the time taken?

A

1/T

62
Q

What are the units for rate of reaction calculated from time?

A

S-1 x10-3

63
Q

How do you calculate rate of reaction from mass or volume?

A

Volume/ T
Mass/T

64
Q

What are the units for rate of reaction calculated from volume?

A

Cm3s-1

65
Q

Describe the graph showing the effect of temp on rate of reaction in an enzyme controlled reaction.

A
  1. Initially, as temp increases, ROR increases
  2. Max ROR occurs at the optimum temp
  3. As temp increases beyond optimum, ROR decreases
66
Q

Why does ROR initially increase with temp?

A

Increase in KE of enzymes and substrate so more successful collisions and more enzyme-substrate complexes formed so more product is formed per unit or time

67
Q

Why does ROR decrease as temp increases beyond the optimum?

A

Increase KE amino acids vibrate, H bonds between R groups break in the tertiary structure so the active site changes shape, denatures when not complementary to substrate

68
Q

Describe the graph showing the effect of pH on ROR in exams controlled reactions

A

A slight change in pH decreases or increases the ROR
1. Optimum ph - lots of product produced
2. Inactivation - less product produced between 2 phs
3. Denaturing at lowest and highest pH on x axis

69
Q

Explain the pH and ROR graph with enzyme action

A
  1. Optimum- complementary to active site
  2. Different enzymes work at different pHs, during inactivation, the active site changes shape so it is less complementary
  3. At extreme pHs the tertiary structure changes shape as it breaks the ionic bonds
70
Q

Describe the the ROR and substrate conc graph

A

Substrate conc increases so ROR increases
After a certain substrate conc, a further increase in substrate conc the ROR remains constant

71
Q

Describe the enzyme conc and ROR graph

A

Enzyme conc increases so ROR increases
After a certain enzyme conc, a further increase in enzyme conc the ROR remains constant

72
Q

Explain the substrate conc and ROR graph

A

Substrate conc is the limiting factor initially
Then the conc of enzymes becomes the limiting factor as there is excess substrate past the point of saturation

73
Q

Explain the enzyme conc and ROR graph?

A

Initially the enzyme conc is the limiting factor
Then the substrate conc becomes the limiting factor as there are excess enzymes to bind to

74
Q

What is an enzyme inhibitor?

A

A chemical or molecules that slows down enzyme activity

75
Q

What are the two types on enzyme inhibitors?

A

Competitive and non-competitive

76
Q

What is competitive inhibition?

A

It is complementary to the active site
It binds to the active site and blocks the substrate
The substrate and inhibitor are similar in shape

77
Q

What is an example of a competitive inhibitor?

A

The resp inhibitor - malonate

78
Q

What is non-competitive inhibition?

A

The substrate and inhibitor have different shapes, it binds to the enzyme in a different place than the active site - the allosteric site
The tertiary structure changes shape so the active site changes shape - substrate does not fit - enzyme denatured

79
Q

What is the allosteric site?

A

Once the inhibitor has bonded this is the area it is bonded to is called

80
Q

How can you get max ROR with a competitive inhibitor present?

A

Increase substrate conc

81
Q

What is an example of a non-competitive inhibitor?

A

The resp inhibitor - cyanide

82
Q

How can you reach max ROR with non-competitive enzymes present?

A

Max ROR cannot be reached

83
Q

What is a metabolic pathway?

A

A series of reactions in which each step is catalysed by an enzyme

84
Q

What is end-product inhibition?

A

The product from one enzyme catalyst, acts as a regulator in excess and can become an inhibitor to a different enzyme step in the metabolic pathway

85
Q

What is a conjugated protein?

A

a protein to which another chemical group (e.g., carbohydrate) is attached by either covalent bonding or other interactions

86
Q

What organelle helps translate the primary structure of a protein?

A

Ribosomes

87
Q

How does an enzyme act as a catalyst by the induced fit model?

A

substrate binds to the active site
active site changed shape so it is complementary to the substrate
reduces the activation energy

88
Q

How can you stop an enzyme catalysed reaction?

A

boil - denature enzyme
put in freezer - reduces KE
add high conc of inhibitor - E-S complexes do not form

89
Q

How does a competitive inhibitor reduce ROR?

A

inhibitor is similar in shape to substrate
binds to the active site
prevents E-S complexes forming

90
Q

How does a structure of a protein depend on the amino acids?

A

Structure determined by position of the amino acids

Primary structure is the sequence of amino acids

Secondary structure formed by hydrogen bonding between amino acids

Tertiary structure formed by interactions between R groups

Creates active sites on enzyme

Quaternary structure formed by interactions between polypeptide chains

91
Q

How does non-competitive inhibition reduce ROR?

A

Attaches to the enzyme at a site other than the active site

Changes shape of active site

No longer complementary so no more binding

Biology A level (27 decks)

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