Enzymes

Question 1

What is a metabolism

Answer 1

• series of enzyme controlled reactions in the body

Question 2

What are anabolic reactions

Answer 2

• anabolism
• building up reactions
• eg protein synthesis where amino acids are built up into more complex polypeptides

Question 3

What are catabolic reactions

Answer 3

• catabolism
• breaking down reactions
• eg digestion of proteins complex polypeptides are broken into simple amino acids

Question 4

What are features of enzymes

Answer 4

• 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

Question 5

Describe the structure of an enzyme

Answer 5

• 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

Question 6

Where do enzymes work

Answer 6

• 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

Question 7

How do enzymes work

Answer 7

• 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

Question 8

Describe the locke and key theory

Answer 8

• substrate has a complementary shape to enzyme’s active site
• explain specificity of many enzymes

Question 9

Describe the induced fit model

Answer 9

• 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

Question 10

How does the lysozyme show the induced fit theory

Answer 10

• 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

Question 11

What are factors that affect the rate of enzyme action

Answer 11

• rate of reaction considered number of reaction occur per second or unit time
• substrate concentration
• temperature
• pH
• enzyme concentration
• prescence of inhibitors

Question 12

How does substrate concentration affect enzyme controlled reactions

Answer 12

• 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

Question 13

Describe the graph for increasing substrate concentration against rate of reaction in an enzyme controlled reaction

Answer 13

• at beginning increased substrate concentration increase successful collisions between enzyme and subtrate
• plateu reqached all active site all in use concentration

Question 14

Describe the graph for increasing temperature against rate of reaction in an enzyme controlled reaction

Answer 14

• 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 )

Question 15

Describe the effect of temperature in enzyme controlled reactions

Answer 15

• 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

Question 16

Describe the effect of pH on enzyme controlled reaction

Answer 16

• 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

Question 17

What are buffers

Answer 17

• 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

Question 18

Describe the effect of enzyme concentration in enzyme controlled reactions

Answer 18

• 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

Question 19

Describe the graph for increasing enzyme concentration against rate of reaction in an enzyme controlled reaction

Answer 19

• 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

Question 20

Describe the product of formation

Answer 20

• 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

Question 21

What are inhibitors

Answer 21

• 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

Question 22

What is competitive inhibition

Answer 22

• 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

Question 23

Decribe non competitive inhibition

Answer 23

• inhibitor binds on another site on enzyme (allosteric site)
• binding changes active site shape prevent substrate moleciles forming enzyme substrate complexes

Question 24

1.

Describe end product inhibition

Answer 24

• 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

Question 25

What are immobolised enzymes

Answer 25

• 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

Question 26

Describe the advantages of immobolising enzymes

Answer 26

• 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

Question 27

What are biosensors

Answer 27

• 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

Question 28

Primary structure

Answer 28

formed from the order of amino acids

Question 29

Condensation

Answer 29

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

Question 30

Secondary structure

Answer 30

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

Question 31

Tertiary structure

Answer 31

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

Question 32

Hydrolysis

Answer 32

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

Question 33

Enzyme substrate complex

Answer 33

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

Question 34

Activation energy

Answer 34

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

Question 35

Kinetic energy

Answer 35

the energy that possesses due to its motion

Question 36

Denaturing

Answer 36

• result in permanent changes to the hape of the active site which prevents the subtrate from binding

Question 37

Biosensor

Answer 37

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