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Biology Core concepts > enzymes > Flashcards

enzymes Flashcards

1
Q

primary structure

A

formed from the order of amino acids

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2
Q

condensation

A

reaction occurs joining two molecules together into a larger one with the elimination of water

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3
Q

secondary structure

A

formed from the folding of the primary structure into two main forms the alpha helix or beta pleated sheet

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4
Q

tertiary structure

A

formed from the folding of the secondary structure into a 3D shape

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5
Q

hydrolysis

A

the breaking down of large molecules into smaller ones by the addition of a molecule of water

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6
Q

What is a metabolism

A

a series of enzyme controlled reactions in the body

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7
Q

What are the two main types of enzyme controlled reactions in the body

A
  • anabolic reactions - building up reactions - anabolism
  • catabolic reactions - breaking down reactions - cataboilism
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8
Q

What are the type of anabolic reactions

A

protein synthesis where amino acids are built up into more complex polypeptides

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9
Q

what are the type of catabolic reactions

A

digestion of proteins where complex polypeptides are broken down into simple amino acids

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10
Q

Name the key properties of enzymes

A
  • proteins that speed up chemical reactions
  • lower the activation energy needed for the reaction to take place
  • don’t actually take part in the reaction
  • only needed in small quantitites
  • can be used over and over again
  • convert substrates into products
  • biological catalysts
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11
Q

Describe the structure of an enzyme

A
  • complex folded polypeptide chains that are held togeher in a complex 3D shape
  • basic structure is the primary structure formed from the order of different amino acids organised into chains called polypeptides
  • each amino acid joined to the next one via a condensation reaction forms a peptide bond
  • structure is then folded into either an alpha helix or beta pleateed sheet held together by hydrogen bonds called the secondary stryctyre
  • enzymes have a tertiary structure whereby the the secodary structure is folded again to form a 3D shape that is held together by hydrogen,ionic and disulpide bonds
  • this created an active site where substrates bing
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12
Q

What are the bonds holding the tertiary structure susceptible to

A
  • temperature
  • pH
  • action of reducing agents
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13
Q

What environment do enzyes work in

A
  • aqueous environemtns
  • soluble and catalyse many reactions including hydrolysis
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14
Q

enzyme substrate complex

A

an intermediate structure formed during an enzyme catalysed reaction in which the substrate and enzyme bind temporarily such that the substrates are close enough to react

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15
Q

activation energy

A

the minimum energy that must be put into a chemical system for a reaction to occur

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16
Q

How do enzymes work

A
  • in a cataboilic reactions the substrate binds to the active site forming an enzyme substrate complex
  • reaction proceeds and products are relased
  • enzyme now free to catalyse another reaction
  • in anabolic reactions several substrates bind to one of more produces are relased
  • as biological catalysts enzymes lower the activation energy needed to start a reaction by providing energy to break bonds in existing molecules so new one can form in new molecules so chemical reaction are sped up
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17
Q

Where do enzymes work and give an example of each reaction

A
  • intracellularly - within a cell - during protein synthesis where the formation of a peptide bond between two amino acids is catalysed
  • extracellularly - outsode a cell - pancreatic amylase released from pancreativ cell and travels to the small intestine via pancreatic duct where it then catalsyes the breakdown of starch to maltose
18
Q

What is the lock and key model

A
  • the substrate has a complementary shape to the enzyme’s active site
  • explains the specificitys of many enzymes - that many can only catalyse one substrate
19
Q

What is the induced fit model

A
  • enzyme’s active site was being altered by the binding of a substrate molecules
  • active site is able to change slightly to accomodate the substrate
  • change places strain on the substrate molecule helping to break bonds and so lowering the activation energy
  • explains why several molecules with similar shapes are able to bind to the active site
20
Q

How does lysozyme show the induced fit model and what is it

A
  • anti bacterial enzymes found in human tears and saliva
  • active site consists of a groove which closes over the polysaccharides found in the bacterial cell walls
  • the enzyme molecule changes shape which allows hydrolysis to occur
21
Q

What are the five factors affecting the rate of enzyme action

A
  • substrate concentration
  • temperature
  • pH
  • enzyme concentration
  • prescence of inhibitors
22
Q

kinetic energy

A

energy that it possessed due to its motion

23
Q

denaturing

A

results in permanent changes to the shape of the active sute prevents substrate from binding

24
Q

How does substrate concentration affect enzyme controlled reactions

A
  • as substrate concentration increases greater chance of successful collision between substrate and the enzyme
  • resulting in more enzyme substrate complexes forming
  • increasing the rate of reaction
  • when all enzyme active sites are occupied a plateu is reached whcih represents the maximum rate of reaction for the conditions
25
Q

Describe how does temperature affect enzyme controlled reactions

A
  • when temperature of an enzyme and substrate increases both enzyme and substrate gain more kinetic energy
  • so move faster increasing the chance of a successful collission between them
  • as more enzyme substrate complexes are formed the rate of reaction increases up to an optimum
  • above this rate of reaction decreases rapidly as hydrogen bonds in tertiary structure breaks due to increase vibrations resulting in a change to the shape of the active site - denaturing
  • rate of enzyme controlled reaction doubles per 10 degree rise in temperature until optimum reached
26
Q

Decribe how pH affects rate of enzyme controlled reaction

A
  • when pH of an enzyme increases of decreases either side of the optimum the rate of reaction decreases
  • the charge on amino acid side chains - r groups that make up the active enzymes active site are influenced by free H+ and OH- ions
  • if too many H+ or OH- ions are present the substrate can be repelled from the active site preventing it from binding
  • if changes are relativley minor then it is reversible
  • more excessive changes in pH will result in ionic bonds in tertiary structrue breaking causing denaturing by creating permanent change to the shape of the active site
27
Q

Describe the use of buffers in enzyme experiments, why

A
  • when carrying out enzyme experiments where pH is not the independednt variable pH is controlled so it at its optimum and not limiting rate of reaction
  • achieved using a pH buffer
28
Q

Describe the affect of enzyme concentration on enzyme controlled reaction

A
  • when substrate concentration increases greater chance of successful collision between substrate and enzyme so more enzyme substrate complexes formed
  • increasing rate of reaction
  • as long as substrate is present in excess this will continue to rise so long as there no limiting factors
29
Q

what is a buffer

A
  • buffer is a solution that can resist changes in PH by neutralising acid/alkalis that are added to the solution
30
Q

What are the two buffers maintaining pH of blood

A
  • we buffer pH of blood using carbonic acid and bicarbonate
31
Q

Decribe the rate of product formation

A
  • diffferent from rate of reaction
  • shows total product made
  • once plateu reached no more product is formed and reaction has stopped however with rate of reaction graph rate would drop to zero at this point
32
Q

Describe how inhibitors affect rate of enzyme controlled reaction

A
  • enzymes can be inhibited by other substances
  • either combine with the active site directly or bind to anothr part of enzyme preventing formation of enzyme substrate complex
  • competitive and non competitive inhibition
  • reversible (inhibitor binds temporatrily) or irreversible (inhibitor binds permanently)
33
Q

Describe competitive inhibition and how it is overcome

A
  • molecule has a similar shape to the substrate
  • complementary shape to the active site
  • first molecules to collide successfully with active site will form a complex
  • by increasing concentration of substrate inhibition is overcome as long as it’s reversible as it is more likley that a substrate molecule will form an enzyme substrate complex
34
Q

Describe an example of competitive inhibition

A
  • enzyme succinic dehydrogenase involved in cellular respiration
  • catalyses the breakdown of succinate to fumerate
  • malonate is a competitive inhibitor of this enzyme due to its similar shape to the substrate
35
Q

Describe non competitive inhibition and give an example

A
  • inhibitor binds to another site on the enzyme - allosteric site
  • binding changes shape of the active site preventing substrate molecules forming an enzume substrate complex
  • cyanid binds to cytochrome oxidise inhibiting respiration
36
Q

Describe what end product inhibition is and where it is found

A
  • seen in complex metaboilic pathways where several enzymes involved
  • example of competitive inhibition at work in cells prevents the biuld up of the end product in the pathway which could become harmful
  • product of one reaction acts as the substrate for the next and the end product acts as a competitive inhibitor for an enzyme earlier in the pathway
37
Q

What are immobolised enzymes and how is this achieved

A
  • enzymes that are fixed to an inert matrix
  • entrapment - held inside a gel - silica gel
  • micro encapsulation - trapped inside a micro capsule - alginate beads
38
Q

How are immobolised enzymes used

A
  • beads containing enzyme can be packed into a glass column and substrate added at one end
  • rate of flow of substrate over the beads controlled - slow rate will give more time for enzyme substrate complexes to form therefore yield more produce
  • since enzymes contained within their own micro enviromnent less succeptible to changes in pH and temperature and action of chemicals such as organic solvents
39
Q

What are the advantages to immobolising enzymes

A
  • enzyme can be easily recovered and reused
  • product is not contaminated by the enzyme
  • more stable at higher temperature
  • catalyse reactions in a wider pH
  • several enzymes with different temperatures and pH optima can be used at the same times
  • enzymes can aslo be easily added or removed giving greater control over the reaction
40
Q

biosensor

A

a device that comines a biomolecule such as an enzyme with a transducer to produce an electrical signal which measures the concentration of a chemical

41
Q

What are biosensors and what are they used for

A
  • biosensores contain immobolised enzymes that can be used to detect small concentrations of specific molecules in a mixture eg glucose in a sample of blood
  • consists of a specific immobolised enzyme, selectivley permeable membrane and a transduced connected to a display
  • selectivley permeable membrane allows the metaboilite to diffuse through to the immoboilise enzyme preventing the passage of other molecules
  • metaboilite binds to the active site of the enzyme converted into a product which in turn combines with the transducer turing the chemical energy into an electrical signeal
  • highr concentration of a metaboilite present the greater the electrical signal
  • technique used to accuratle measure the blood glucose of diabetic patients

Biology Core concepts (5 decks)

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