Enzymes Flashcards
1
Q
What is a metabolism
A
- series of enzyme controlled reactions in the body
2
Q
What are anabolic reactions
A
- anabolism
- building up reactions
- eg protein synthesis where amino acids are built up into more complex polypeptides
3
Q
What are catabolic reactions
A
- catabolism
- breaking down reactions
- eg digestion of proteins complex polypeptides are broken into simple amino acids
4
Q
What are features of enzymes
A
- proteins speed up chemical reactions
- lower activation energy for reaction
- don’t take part in reaction
- only needed in small amounts
- used over and over again
- convert substrates into products
- described as biological catalysts
5
Q
Describe the structure of an enzyme
A
- complex folded polypeptide chains held in complex 3D shape
- most basic is primary structure formed order of different amino acids organised into chains called polypeptides
- each amino acid is joined by condensation reaction forming a peptide bond
- primary structure is folded into alpha helix or beta pleated sheat held by hydrogen bonds
- enzyme have a teritary structure where the secondary strucutre is folded again forming 3D shape hydrogen , ionic and disulphide bonds
- important in enzymes as create an active site where substrates can bind
- bonds holding tertiary structure are suspectible to changes in temp, pH and action of reducing agents
- acts in an aquous environment as they’re soluble and catalyse many reactions eg hydrolysis
6
Q
Where do enzymes work
A
- may act intracellularly within cells eg protein synthesis where formation of a peptide bond between two amino acids is catlysed
- extracelllularlu outside of cells eg pancreatic amylas release form pancreatix cells travels to small intestine via pancreatic duct where caatalyses break down of starch into maltose
7
Q
How do enzymes work
A
- catabolic reactions substrate bind to the active site forming enzyme substrate complex
- reactions proceedss and products are released
- active site is now free to catalyse aanother reaction
- in anabolic reactions several subtrates bind and one or more products are released
- as biologial catalysts enzymes lower the activation energy needed to start a reaction by providing energy to break bond in existing molecule so new ones can form in new molecules
- speeding chemical reactions up
8
Q
Describe the locke and key theory
A
- substrate has a complementary shape to enzyme’s active site
- explain specificity of many enzymes
9
Q
Describe the induced fit model
A
- enzyme’s active site altered by binding substrate molecule
- active site able change slightlu to accomodate substrate a bit
- strain placed on a substrate molecule helping to break bonds lowering the activation energy
- explain severall molecule with similar shapes binding to the active site
10
Q
How does the lysozyme show the induced fit theory
A
- enzyme lyozyme is an anti bacterial enzyme found in human tears and saliva
- active site consists of a groove closes over the polysacchrides found in bacterial cell walls enzyme changes shape allowing hydrolysis
11
Q
What are factors that affect the rate of enzyme action
A
- rate of reaction considered number of reaction occur per second or unit time
- substrate concentration
- temperature
- pH
- enzyme concentration
- prescence of inhibitors
12
Q
How does substrate concentration affect enzyme controlled reactions
A
- substrate concentration increases in an enzyme controlled reaction greater chance of successful collisions between substrate and enzume result in more enzyme substrate complezes forming
- increasing rate of reaction all enzyme active sites are oxxupid plateu reached represents maximum rate of reactions for conditions
13
Q
Describe the graph for increasing substrate concentration against rate of reaction in an enzyme controlled reaction
A
- at beginning increased substrate concentration increase successful collisions between enzyme and subtrate
- plateu reqached all active site all in use concentration
14
Q
Describe the graph for increasing temperature against rate of reaction in an enzyme controlled reaction
A
- at beginning enzymes have little kinetic energy therefore show low activity
- until optimum rate increases ass molecules have more kinetic energy
- after optimum the enzyme is denaturing (hydrogen bonds breaking )
15
Q
Describe the effect of temperature in enzyme controlled reactions
A
- when temp of enzyme and substrate increases in enzyme controlled reaction
- both enzume and substrate molecule gain more kinetic energy and so move faster
- increasing chance of successful collisions
- more enzyme and substrate complexes form rate of reaction increases up to optimum
- rate of reaction decreases rapidlu as hydrofen bonds in tertiary structure due to increased vibration result in change of shape of active site
- denaturing
- reaction double per 10 degree rise in temp
16
Q
Describe the effect of pH on enzyme controlled reaction
A
- pH of an enzyme increases or decreases either side of the optimum rate of reaction decreases
- charges on amino acid side chains R group more enzymes acive site influenced by free H+ annd OH- ions
- it too many H+ ions or OH- ions present substrate can be repelled from active site prenting it from binding
- changes are relativley minor its reversible
- many excessive pH result in ionic bonds in teritary structure breaking causing denaturing creating permanent change of shape of active site
17
Q
What are buffers
A
- rate of enzyme controlled reactionss greatly influenced by small changes in pH
- pH is controlled ideally at it’t optimum not limiting the rate of reaction
- achieved using a pH buffer
- buffer resists changes in pH by neutralising acid/alkali added to the solution
- in body we buffer pH of blood around 7.4 carbonic acid and bicarbonate
18
Q
Describe the effect of enzyme concentration in enzyme controlled reactions
A
- when substrate concentration increases in an enzyme controlled reaction greater chance of successful collision between susbtrate and enzyme so more enzyme substrate complexes are formed increasing rate of reaction
- as long as substrate is prescence in excess it will continue to rise as long as no limiting factors
19
Q
Describe the graph for increasing enzyme concentration against rate of reaction in an enzyme controlled reaction
A
- at the beginning increase enzyme concentration increase chance of successful collisions between enzyme ad substrates
- as line begins to rise theoretically rate will continue to rise so long as substrate is present in excess and no limiting factores
- once all substrate used up rate of reaction will fall to zero
20
Q
Describe the product of formation
A
- shows total product made
- once plateu reached no more product is formed and reaction is stop
- rate drop to zero as no more product is made
21
Q
What are inhibitors
A
- enzymes can be inhibited by other substances wither combine with active sites directly bind to another part of enzyme prevent formatio of an enzyme substrate comple
- competitice and non competitive inhibition
- could be reversible and irrerversible
22
Q
What is competitive inhibition
A
- molecules have similar shape to substrate so has complementary shape to the active site
- first molecule to collide successfully with active site will form a complex
- by increasing concentration of substrate inhibition will overcome
- reversible
- more likeley substrate molecu;e form enzyme substrate complex
23
Q
Decribe non competitive inhibition
A
- inhibitor binds on another site on enzyme (allosteric site)
- binding changes active site shape prevent substrate moleciles forming enzyme substrate complexes
24
Q
1.
Describe end product inhibition
A
- seen in complex metbaolic pathway where several enzymes are involved
- competitive inhibition in at work in cells prevent build up of end product in pathway which could become harmful
- essence of product of one reaction acts as a substrate for next end product ss a competitive inhibitor for enzyme earlier in pathway
- end product inhibits enzyme as end product used up in the cell the concentration of end product falls and conentrtion of intial substrate rises so overcoming inhibitors effect
25
What are immobolised enzymes
* enzymes are fixed to an inert matrix
* entrapment inside gel silica gel
* micro encapsulation trapped inside mico capsule eg alginate beads
* beads contain enzyme packaged into a glass column and substrate added at one end
* rate of flow of substrate over beads can be controlled a slow rate will give more time for enzyme substrate complexed form yield more product
* enzymes contained own micro environment enzymes less suspectivle changes in pH, temperature and action of chemicals in organic solvents
26
Describe the advantages of immobolising enzymes
* enzymes easily recovered and reused
* products not contaminated by enzyme
* more stable at higher teperatures
* catalyse reactions in a wider range of pH
* result in several enzymes with different temp and pH optimal used at same time
* enzymes can easily be added or removed giving greater control over reaction
27
What are biosensors
* contain immobolised enzymes udes to detect small concentration of specific molecules in a mixture
* eg glucoe sample of blood
* biosensore is a specific immobolised enzyme selectivley permeable membrane tranducer connected to a display
* selectivley permeable membrane allows metabolite to diffuse throguh to immobolised enzymes prevent passage of other molecules
* metabolite binds to the active site of enzyme and is converted into a product which in turn combined with transducer turning chemicall energy into an electrical signal
* higher concentration of metabolite greater the electrical signal
* used to meaure blood glucose of diabetic patients
28
Primary structure
formed from the order of amino acids
29
Condensation
reaction occurs joining two molecules together into a larger one with the elimination of water
30
Secondary structure
formed from the folding of the primary structure into two main forms the alpha helix or beta pleated sheet
31
Tertiary structure
formed from the folding of the secondary structure into a 3D shape
32
Hydrolysis
the breaking down of large molecules smaller ones by the addition of a molecule of water
33
Enzyme substrate complex
an intermediate structure formed during an enzyme catalysed reaction in which the substrate and enzyme bind temporarily such that the subtrates are close enough to react
34
Activation energy
the minimum energy that must be put into a chemical system for a reaction to occur
35
Kinetic energy
the energy that possesses due to its motion
36
Denaturing
* result in permanent changes to the hape of the active site which prevents the subtrate from binding
37
Biosensor
a device that combines a biomolecule such as an enzyme with a transducer to produce an electrical signal which measures the concentration of a chemical
