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a level biology > Enzymes > Flashcards

Enzymes Flashcards

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AP® Biology flashcards
1
Q

What do enzymes need help from to catalyse some reactions

A

Cofactor

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2
Q

What part of the enzymes structure is changed if there is a gene mutation

A

Tertiary structure

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3
Q

Examples of enzymes catalysing the formation of structural components

A
  • collagen in bones
  • cartilage
  • blood vessel walls
  • joints
  • connective tissue
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4
Q

What two things do enzymes effect

A

-structural
- functional

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5
Q

Why is the tertiary structure important in active sites

A

Its shape is complementary to the shape of the substrate molecule

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6
Q

What can change the shape of an active site

A
  • temperature
  • pH
  • anything that affects the bonds that hold proteins in the tertiary structure
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7
Q

Where do enzymes work

A
  • intracellular reactions
  • extracellular reactions
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8
Q

What is a metabolic pathway

A

A series of consecutive reactions
- every part is catalysed by a specific enzyme
- these produce a specific product
- these then act as substrates for the next reaction (metabolites)

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9
Q

What is a catabolic in metabolic pathways

A

Metabolites are broken down to smaller molecules and release energy

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10
Q

What is an anabolic in metabolic pathways

A

Energy is used to synthesise larger molecules from smaller ones

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11
Q

Example of a metabolic pathway

A
  • respiration
  • photosynthesis
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12
Q

What is catalase

A

An enzyme that protects cels from damage by reactive oxygen
- quickly breaks hydrogen peroxide into water and oxygen

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13
Q

What is the structure and characteristics of catalase

A
  • four polypeptide chains
  • contains a harm group with iron
  • fastest acting enzyme
  • eukaryotic cells: found in small vesicles called peroxisomes
  • white blood cells use them to help kill microbes
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14
Q

Example of an extracellular enzyme

A
  • amylase
  • trypsin
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15
Q

What is amylase

A
  • produced in the salivary glands
  • digests the polysaccharide starch to the disaccharide maltose
  • made in the pancreas
  • catalyses same reaction as the lumen of the small intestine
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16
Q

What is trypsin

A
  • made in the pancreas
  • acts in the lumen of the small intestine
  • digests proteins into smaller peptides
  • hydrolyses peptide bonds
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17
Q

What is a cofactor

A
  • substrate that has to be present to ensure that an enzyme catalysed reaction takes place at the appropriate rate
  • some cofactors (prosthetic groups) are part of the enzyme structure
  • others (coenzymes) form temporary associations with the enzyme
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18
Q

What is a prosthetic group

A

A cofactor that is permanently bound, covalent bonds, to an enzyme molecule

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19
Q

What is an enzyme-substrate complex

A

Complex formed by temporary bonding of enzyme and substrate come culex’s during an enzyme catalysed reaction

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20
Q

What is the benefit of enzyme substrate complexes

A

Increases rate of reaction

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21
Q

What is a co-substrate

A

When they bind to the substrate to form the correct shape to bind to the active site

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22
Q

What is a coenzymes

A

Small organic non-proteins molecules that bind temporarily to the active site
- chemically charged during the reaction

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23
Q

What happens to a substrate if it is heated

A
  • extra energy causes the molecules to move faster
  • increased rate of collisions between molecules
  • increased force at which they collide
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24
Q

What happens if the reactant mixture containing enzymes and substrate molecules is heated

A
  • both molecules will gain kinetic energy
  • increased rate of successful collisions
  • rate of formations of ES complexes increases
  • increased rate of reaction
  • at a certain temp (optimum temperature) rate of reaction is at its max
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25
Q

What does vibrations lead to in molecules

A
  • break some of the weak bonds: hold the tertiary structure of the active site
  • active site changes = substrate cannot fit
  • temp increases the active site will completely and irreversibly change
  • enzyme is denatured
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26
Q

Formula to work out rate of reaction

A

Rate of reaction = 1 / time taken to reach end point

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27
Q

What is the units for rate of reaction

A

S -1

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28
Q

What is the temperature coefficient (Q10)

A

The increase in the rate of process when the temperature is increased by 10 C

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29
Q

What is the equation for temperature coefficient

A

Q10 = rate of reaction at (T+10)C / rate of reaction at T

30
Q

What does it mean if the Q10 is 2

A

Every 10C the reaction is doubled

31
Q

What is an enzyme product complex

A

Enzyme molecule with product molecules in its active site
- the two are joined temporarily by non-covalent forced

32
Q

What are the steps of the lock and key theory

A
  • substrate molecule bind to the active site of the enzyme
  • temporary hydrogen bonds hold them together
  • this forms a ES complex
  • substrate is broken into smaller products and leave
  • substrate molecules fit in the active site (ES complex)
  • bonds form to create an enzyme product complex
  • larger molecule leaves the active site
33
Q

What is the induced fit hypothesis

A

Explains how the transition state (ES complex) is formed

34
Q

Who suggested the induced fit hypothesis

A

Daniel Koshland (1958)

35
Q

What did Daniel Koshland suggest
Steps of the induced fit hypothesis

A
  • when the substrate fits into the active site it changed shape to mould around the molecule
  • when binding the changes of the side chains (R groups) of amino acids give a more precise shape
  • moulding allows the substrate to bind more effectively
  • ES complex is formed with non-covalent forces binding the substrate to the active site
  • an EP complex is formed
  • products detach from the active site as they have a slightly different shape
  • enzyme can now catalyse other reactions
36
Q

What is the equation for showing how an enzyme catalyses a reaction

A

Enzyme + substrate —> enzyme-substrate complex —> enzyme product complex —> enzyme + product
E+S ESC EPC E+P

37
Q

Do enzymes lower or increase the activation energy

A

Lower

38
Q

What is activation energy

A

the minimum quantity of energy which the reacting species must possess in order to undergo a specified reaction

39
Q

How are enzymes able to lower the activation energy

A
  • bring the substrate molecules close enough together to react
  • increase chance of molecules binding
  • speed up metabolic reactions
40
Q

What is pH

A

Concentration of hydrogen ions in a solution

41
Q

What is a buffer

A

Something that resists changes in pH

42
Q

What are buffers able to

A

Donate or accept hydrogen ions

43
Q

How do changes in pH affect bonds within molecules

A
  • hydrogen ions (proton, + charge)
  • excess hydrogen ions will interfere with these hydrogen bonds so the active site will change shape
  • this will decreases the rate of reaction
  • increased concentration of hydrogen ions will also alter the charged
  • more protons will cluster around negatively charged groups
  • this interferes with the binding of the substrate and active site
44
Q

Do enzymes work within a narrow or wise range of pH

A

Narrow

45
Q

What happens if there are small changes around the optimum pH

A

Slow down the rate of reaction
- shape of the active site is disrupted

46
Q

What happens if the normal pH is restored

A

Hydrogen bonds can re-form and the active site’s shape is restored

47
Q

True or false
All enzymes have the same optimum pH

A

False

48
Q

Why does the rate of reaction increase as substrate concentration is increased

A
  • more ES complexes can form
  • more products are formed
  • it then becomes the limiting factor
49
Q

What happens when substrate concentration is the limiting factor

A
  • all the enzymes active sites are occupied with substrate molecules
  • if more substrate is added they cannot successfully collide with and fit into the active site
50
Q

What does the graph for substrate/enzyme concentration against initial rate of reaction look like

A
  • steep gradient
  • substrate concentration becomes limiting factor
  • line plateaus
51
Q

What controles enzyme synthesis

A
  • cells needs
  • genes for synthesis will be turned on or of
52
Q

What is the advantage of enzyme degrading

A
  • eliminated abnormally shaped proteins that might build up and harm the cell
  • regulation of metabolism in the cell by eliminating any superfluous (surplus to requirements) enzymes
53
Q

What happens as enzyme concentration is increased

A
  • more active sites available
  • more successful collisions between enzyme and substrate
  • more ES complexed can form
  • so increased rate of reaction
  • will later become the limiting factor
54
Q

What happens if enzyme concentration becomes the limiting factor

A
  • there will be no more substrate to bind with the active sites
55
Q

Why is the initial rate of reaction always the greatest

A
  • there is a greater chance of the substrate molecules successfully colliding with an active site
56
Q

Why does initial rate of reaction slow down over time

A
  • the substrate then become product molecules and decreases the substrate concentration
  • frequency of collisions decreased
  • slows down rate of reaction
57
Q

What is a competitive inhibitor

A

Substances whose molecules have simular shapes to an enzymes substrate molecules
- they compete with the substrate for the active site
- blocks the site and prevents the formation of ES complexes

58
Q

What is an inhibitor

A

A substance that reduces or stops reactions

59
Q

What does a competitive inhibitor do

A
  • compete directly with substrate molecules for the active site
  • make the enzyme inactive
  • when in the active site they cannot be changed
  • stops ES and EP complexes from forming
60
Q

What are the different types of enzyme inhibition

A
  • competitive
  • non competitive
  • reversible
  • irreversible
61
Q

What is an inactivator

A

When a competitive inhibitor binds irreversible to an active site

62
Q

What is non-competitive inhibition

A

When the inhibition molecule binds to the enzymes somewhere other than the active site

63
Q

How does non-competitive inhibition work

A
  • attach to the enzyme in the allosteric site
  • this distrusts the enzymes tertiary structure and shape
  • changes the shape of the active site
  • max rate of reaction is reduced
64
Q

What is the place where the inhibitor binds to in non-competitive inhibition called

A

Allosteric site

65
Q

What does the allosteric site do

A

Disrupts the enzymes tertiary structure and shape
- changes shape of active site

66
Q

What is end product inhibition

A

When the reaction is finished the products may stay tightly bound to the enzyme
- engulfed cannot form more of the product than the cell needs

67
Q

How are metabolic sequences controlled

A
  • product of one reaction becomes the substrate of the next
  • bindings change the shape of enzymes 1s active site
  • when concentrations change the inhibitor will leave the enzyme to allow more of the product to be formed
68
Q

What does cyanide inhibit

A

Aerobic respiration

69
Q

What does snake venom inhibit

A

Acetylcholinesterase
- important in neuromuscular synapses

70
Q

What does aspirin do

A
  • catalyses the formation of prostaglandins
  • reduces risk of blood clots
71
Q

What do ATPase inhibitors do

A

Inhibit sodium potassium pump
- allows more calcium ions to enter the cells
- increase muscle contraction
- strengthens the heartbeat

72
Q

What do ACE inhibitors do

A

Inhibit angiotensin converting enzyme (ACE)
- operates in a metabolic pathways that increased blood pressure
- lower blood pressure for hypertension when can’t take beta blockers
- treat heart failure
- minimise second heart attacks

a level biology (13 decks)

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