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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 the structure of a globular protein?

A

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

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23
Q

What makes a globular protein soluble in water?

A

Hydrophobic interactions cause the R groups to face centre

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24
Q

What are the functions of a globular protein?

A

Biochemical
Enzymes
Pigments
Receptors
Antibodies

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25
What does the function of a globular protein depend on?
The specific 3D shape
26
What is a congregate protein and an example of one?
A protein that contains a non-protein group which is called the prosthetic group eg: haemoglobin contains iron
27
What causes proteins to denature?
High temperatures breaks H bonds pH breaks ionic bonds
28
What does denaturing a protein mean?
The bonds have been broken so it changes shape therefore stops functioning properly
29
What is the impact of fibrous proteins denaturing?
They lose their structural strength
30
What is the impact of globular proteins denaturing?
They become inactive and/or insoluble because the R groups move
31
What are the 4 bonds that maintain a proteins shape?
Peptide bonds Ionic bonds Hydrogen bonds Disulphide bridges
32
What is a biological catalyst?
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
33
What is catabolic enzyme action?
Breaks down something in the reaction
34
What is anabolic enzyme action?
Builds up something in the reaction
35
What does it mean by enzyme specificity?
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
36
What is intracellular enzyme action and examples?
Happens inside the cell Eg: Lysosomes Cytoplasm Organelles like the mitochondrial membrane
37
What is extra cellular enzyme action and examples?
Happens outside of the cell Eg: The alimentary canal in the digestive system
38
How does an enzyme catalyse a reaction?
Does not react with the substrate and is not involved in the reaction It lowers the activation energy
39
What is an exergonic reaction?
Products have less energy than reactants - energy is released
40
What is an endergonic reaction?
The reaction requires energy
41
What must the substrate shape be like to join the active site?
The substrate shape must be complementary to the active site and the shape must be maintained and specific
42
What is is called when the subtracted joins the enzyme?
Enzyme-substrate complex
43
What is the lock and key model of enzyme action?
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
44
What is the induced fit theory?
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
45
What type of reaction is the formation of enzyme-substrate complexes?
Catabolic
46
What is an example of the induced fit model?
Lysosymes in lysosomes digest bacterial cell wall
47
What type of protein are enzymes?
Globular
48
What makes the substrate more stable ?
Forming an enzyme-substrate complex
49
What type of reaction is ATP hydrolysis?
Exergonic
50
What might you observe in an enzyme controlled reaction?
The product appearing The substrate disappearing Bubbles - O2
51
What effect does temperature have on enzyme action?
Increases KE More successful collisions between substrate and active site
52
What happens if there is excess substrate in an enzyme controlled reaction?
The no. Of active sites becomes a limiting factor because all the active sites are occupied
53
Why does substrate conc become a limiting factor in an enzyme controlled reaction?
Because it has been converted into product
54
How do you calculate the rate of production of a product from a graph?
Change in y/ change in x
55
What is the units for rate?
Mg dm-3 min-1
56
How do you calculate the percentage change in a reaction?
Original - new / original X100
57
How do you calculate the initial rate of reaction?
Draw a tangent and y/x Tangent starts from 0
58
What does it mean if the reaction has stopped?
Not all the substrate was converted into product
59
What does it mean if the reaction has finished?
All the substrate has been converted into product
60
How do you calculate rate of reaction from the time taken?
1/T
61
What are the units for rate of reaction calculated from time?
S-1 x10-3
62
How do you calculate rate of reaction from mass or volume?
Volume/ T Mass/T
63
What are the units for rate of reaction calculated from volume?
Cm3s-1
64
Describe the graph showing the effect of temp on rate of reaction in an enzyme controlled reaction.
1. Initially, as temp increases, ROR increases 2. Max ROR occurs at the optimum temp 3. As temp increases beyond optimum, ROR decreases
65
Why does ROR initially increase with temp?
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
66
Why does ROR decrease as temp increases beyond the optimum?
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
67
Describe the graph showing the effect of pH on ROR in exams controlled reactions
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
68
Explain the pH and ROR graph with enzyme action
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 and hydrogen bonds
69
Describe the the ROR and substrate conc graph
Substrate conc increases so ROR increases After a certain substrate conc, a further increase in substrate conc the ROR remains constant
70
Describe the enzyme conc and ROR graph
Enzyme conc increases so ROR increases After a certain enzyme conc, a further increase in enzyme conc the ROR remains constant
71
Explain the substrate conc and ROR graph
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
72
Explain the enzyme conc and ROR graph?
Initially the enzyme conc is the limiting factor Then the substrate conc becomes the limiting factor as there are excess enzymes to bind to
73
What is an enzyme inhibitor?
A chemical or molecules that slows down enzyme activity
74
What are the two types on enzyme inhibitors?
Competitive and non-competitive
75
What is competitive inhibition?
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
76
What is an example of a competitive inhibitor?
The resp inhibitor - malonate
77
What is non-competitive inhibition?
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
78
How can you get max ROR with a competitive inhibitor present?
Increase substrate conc
79
What is an example of a non-competitive inhibitor?
The resp inhibitor - cyanide
80
How can you reach max ROR with non-competitive enzymes present?
Max ROR cannot be reached
81
What is a metabolic pathway?
A series of reactions in which each step is catalysed by an enzyme
82
What is end-product inhibition?
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
83
What is a conjugated protein?
a protein to which another chemical group (e.g., carbohydrate) is attached by either covalent bonding or other interactions
84
What organelle helps translate the primary structure of a protein?
Ribosomes
85
How does an enzyme act as a catalyst by the induced fit model?
substrate binds to the active site active site changed shape so it is complementary to the substrate reduces the activation energy
86
How can you stop an enzyme catalysed reaction?
boil - denature enzyme put in freezer - reduces KE add high conc of inhibitor - E-S complexes do not form
87
How does a competitive inhibitor reduce ROR?
inhibitor is similar in shape to substrate binds to the active site prevents E-S complexes forming
88
How does a structure of a protein depend on the amino acids?
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 
89
How does non-competitive inhibition reduce ROR?
Attaches to the enzyme at a site other than the active site  Changes shape of active site  No longer complementary so no more binding 
90
How is there always a NH2 and COOH at the end of a polypeptide?
peptide bonds join amino acids there is a free NH2 and COOH at either end
91
Why do enzymes denature at a faster rate at higher temps?
more kinetic energy
92
How does the active site of an enzyme cause a high rate of reaction?
lowers activation energy induced fit causes active site to change shape so E-S complex causes bonds to form or break
93
How is a secondary structure formed by bonds b/w amino acids?
hydrogen bonds between the NH and C=O group
94
How does forming an E-S complex increase rate of reaction?
reduces activation energy due to bending bonds
95
What bonds are broken when an ezyme is denatured?
H bonds in tertiary structure ionic bonds between amino acids
96
What is the structure of a fibrous protein?
long strands of polypeptide chains that have cross-linkages due to hydrogen bonds

Biology A level (36 decks)

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