Enzyme action

Question 1

What are enzymes

Answer 1

Biological catalysts

Question 2

3 conditions needed for enzyme catalysts

Answer 2

Substrate and enzyme must collide successfully
Energy of products must be less than substrates
Activation energy must be met

Question 3

Active site

Answer 3

Region which is similar to a substrates shape so the enzyme and substrate can bind

Question 4

What is formed when an enzyme and substrate bind together

Answer 4

Enzyme substrate complex

Question 5

Induced fit model of enzyme action

Answer 5

1) Substrate and enzyme collide in a certain way so that the substrate binds to the enzymes active site
2) Active site changes shape to fit with substrate
3) When bind, enzyme substrate complex is formed
4) Bond between molecules breaks
5) Product molecules released from active site

Question 6

Whole process of how all products are made

Answer 6

1) Lots of substrate, no product
2) Lots of empty active sites, high chance for substrates to collide with active sites
3) All active sites filled and substrate broken down into products
4) Substrate decreases as its broken down, products increase
5) Fewer substrate molecules available so more difficult to collide
6) Rate formation slows, fewer substrate molecules
7) Graph flatterns as substrate has been used up

Question 7

Effect of temperature

Answer 7

Temperature rises, thermal energy transferred to kinetic energy
Molecules move faster -> more successful collisions, producing more enzyme-substrate complexes
Denatured at around 60C

Question 8

Effect pH and why it denatures

Answer 8

Denatures = Charges on the amino acids in active site changes, affects the formation of enzyme-substrate complex
This changes shape of the active site
Bonds can also break, changing active site

Question 9

Effect of substrate concentration

Answer 9

As substrate concentration increases there are more chances of successful collisions, so more enzyme-substrate complexes form
The rate reaches a maximum as all the active sites are occupied (graph platos)

Question 10

Effect of enzyme concentration

Answer 10

Increases successful collisions, increases rate of enzyme substrate complex production
All substrate is turned into product at the same rate

Question 11

What are competitive inhibitors

Answer 11

Bind to active site

Question 12

What are non-competitive inhibitors

Answer 12

Bind to enzyme in position other than active site

Question 13

Competitive inhibitors and how they act

Answer 13

Compete with substrate for active site
Difference in concentration of substrate and inhibitor, determines effect on enzyme activity
Substrate concentration increases so effect of inhibitor decreases
Longer it will take for product to be made if greater concentration of inhibitor

Question 14

Non-competitive inhibitors and how they act

Answer 14

Attach at binding site which isn’t active site
Inhibitor alters shape of enzyme where it binds, so active site changes
Substrate can no longer fit
Enzyme cannot function
Inhibitor and substrate are not competing for same site
Concentration increases in substrate, does not decrease effect of inhibitor

Question 15

What do enzymes change in reactions

Answer 15

Lower the activation energy and catalyse the reaction

Question 16

Absolute specificity

Answer 16

Enzyme catalyses ONE reaction

Question 17

Group specificity

Answer 17

Enzyme acts on molecules having specific functional groups like phosphate, amino, methyl groups

Question 18

Linkage specificity

Answer 18

Enzyme acts on a specific type of chemical bond regardless the remaining molecular structure

Question 19

Stereochemical specificity

Answer 19

Enzyme acts on a certain optical or steric isomer

Question 20

How is specificity attained

Answer 20

When the substrate interacts weakly with the enzyme’s active site to form a bond
Producing covalent bonds that the enzyme can only catalyse

Question 21

What do enzymes catalyse

Answer 21

Wide range of intercellular and extracellular reactions
Determining structures and functions of a whole organism

Question 22

What two things can you measure enzyme activity (practical)

Answer 22

Measure rate of formation of a product using catalase
Measuring rate of diappearance of substrate using amylase

Question 23

What is measured for the investigation of amylase activity using iodine

Answer 23

Take samples from reaction mixture at each time interval and adding each sample to iodine in potassium iodide solution
Starch = blue-black
No starch = yellow-brown

Question 24

Why use amylase-starch solution

Answer 24

Amylase = digestive enzyme that hydrolyses starch into maltose and glucose

Question 25

Method

Answer 25

1) Place single drops of iodine solution in rows on tile 2) Label test tube with pH to be tested 3) Use syringe to place 2cm^3 of amylase in test tube 4) Add 1cm^3 of buffer to test tube using syringe 5) Add 2cm^3 using different test tube of starch solution to amylase and buffer solution, start stopwatch whilst mixing using pipette 6) At 10 secs, use pipette and place on e drop of mixture on first drop of iodine (should turn blue black) 7) Wait another 10 secs and place another drop of mixture on second drop of iodine 8) Repeat every 10 secs 9) Repeat at different pH values Less time iodine solution takes to remain orange-brown, quicker starch has been digested , better enzyme works at that pH

Question 26

What proteins are enzymes

Answer 26

Globular proteins

Question 27

What pathway is controlled by enzymes

Answer 27

Metabolic pathway

Question 28

Are enzymes active inside or outside the cell

Answer 28

Intraceullar or extracellular INtracellular = produced and function inside cell Extracellular = secreted by cells and catalyse reactions outside cells

Question 29

What is the shape of the active site determines by

Answer 29

1) Proteins formed from chains of amino acids held by peptide bonds 2) Order of amino acids determines shape of enzyme

Question 30

Two type of enzyme reactions

Answer 30

Catabolic and anabolic

Question 31

WHat are catabolic reactions

Answer 31

Breakdown of complex molecule substrate into simpler products When a single substrate is broken apart into two or more products E.g. cellular respiration and hydrolysis

Question 32

What are anabolic reactions

Answer 32

Building more complex molecules from simpler ones Two substrates bond to form one single product

Question 33

What is the activation energy

Answer 33

The amount of energy needed by the substrate to become unstable enough for a reaction to occur and for products to be formed

Question 34

How do enzymes speed up chemical reactions

Answer 34

Influence the stability of bonds in reactants The destabilisation of bonds in the substrate make them more reactive

Question 35

How can you measure the progress fo enzyme catalysed reactions

Answer 35

Measuring rate of formation of a product = catalase Disappearance of a substrate = amylase

Question 36

How is catalase used to investigate the rate of product formation

Answer 36

Hydrogen peroxide is a toxic by product f metabolism It must be broken down quickly Catalase is found in cells so you can break down hydrogen peroxide into water and oxygen Hydrogen peroxide and catalase are combined and the volume of the oxygen generated is measured

Question 37

How do you investigate amylase using iodine

Answer 37

Amylase hydrolyses starch into maltose and glucose Amylase and starch combine and this reaction mixture is then tested for starch at regular time intervals Take samples from the reaction mixture at time intervals by adding iodine in potassium iodide solution Starch forms blue black, no starch yelliw brown

Question 38

Investigating the effect of starch concentration on amylase using colourimetry

Answer 38

Colourimeter measures light absorbance As colour breaks fown light absorbance decreases 1) Calibration calorimeter (use weak iodine solution) 2) Prepare starch solution of known concentration from which a range of concentrations are made using serial dilutions 3) Use with different concentrations of starch 4) Calibration graph plotted

Question 39

What do lower temps do

Answer 39

Lower frewuency of successful collisions between substrate and active site Molecules move slower Less frequent enzyme substrate complex formatos Substrate and enzyme collide with less energy so bond formation is less likely

Question 40

What happens when temperatures rise too high

Answer 40

Bonds holding enzyme mlecule in precise shape break Tertiary structure of protein changes Active site permanently damages preventing substrate binding Denaturation occurs is substrate can no longer bind

Question 41

What happens at extreme pH changes

Answer 41

Is solutions with excess H+ and OH- ions can cause hydrogen and ionic bonds to break Alters shape of active site = less ESC ESC can no longer form at all Complete denaturation occurs

Question 42

Buffer solutions affects from different pH

Answer 42

Buffer solutions each have a specific pH Buffers maintain pH Measure volume o fbuffer added to reaction Same volume should be added for each pH that is being investigated

Question 43

How to calculate pH

Answer 43

PH = log [H+]

Question 44

How do enzyme concentrations affect rate

Answer 44

Higher conc = greater number of active sites available and greater likelihood of ESC As long as there is a sufficient substrate available, rate of reaction increases linearly Otherwise will not increase and is a limiting factor

Question 45

How does substrate conc affect rate of reaction

Answer 45

Number of sub molecules increases likelihod f ESC increases ENcyme conc fixed but substrate increased past a certain pint all available active sites eventually saturated so rate of reaction cant increase WHen active sites of enzymes are full subs have nowhre to bind Linear increase then plateaus

Question 46

What are reversible inhibitrs

Answer 46

Regulators in metabolic pathways Metabolic reactions are tightly controlled and balanced so that no single enzyme can cntinuously and uncontrollably generate more and more of a particular product

Question 47

How are metabolic reactions controlled

Answer 47

Using the end prduct f a particuar sequence of metabolic reactios as a non competitive reversible inhibitor

Question 48

Process of end-product inhibition

Answer 48

1) Enzyme converts substrate to product 2) End product of reaction chain binds to alternative site on enzyme, changing active site shape preventing formation of further enzyme substrate complexes 3) end product detaches from the enzyme and used elswhere allowing thr active site to reform

Question 49

What does an enzyme to do the reaction

Answer 49

1) Lowers AE and provides alternative pathway for substrates to react on 2) Destablises bonds of substrate making it more reactive, decreasing energy needed to break them

Question 50

2 ways an enzyme might reduce actuation every

Answer 50

Holding 2 substrates close together in the enzyme-substrate complex and making it easier for substates to collide By stressing bonds within the substrates and making it easier to break then

Question 51

What occurs in the induced fit hypothesis that DOESN'T occur in the lock and key

Answer 51

1) enzyme structure can move 2) Active site and substrate are not a perfect complementary fit to one another 3) Active site changes shape to fit the substrate 4) This weakens the bonds of the substrate and lowers the activation energy

Question 52

How can an enzyme denature

Answer 52

High temp Extreme low or high pH Cause weak bonds in tertiary structure to break changing the shape of the active site

Question 53

Key terms

Answer 53

Denature Active site, complimentary, enzymesub complex destabilises bonds of substrate making them more reactive Mention compet or non competitive inhibitor

Question 54

Similarities and differences between competitive and non competitive inhibition (6 points)

Answer 54

Similarities: -Inhibitor binds to surface -Reduce enzymes rate -As inhibitor conc increases rate of reaction decreases Differences: -Compet inh binds to active site, non compet binds to allosteric site -Active site blocks in competitive, active site distorted in non compet -increase sub conc will decrease effect of compet inhibition nut will not affect non-compet inhibition

Question 55

Differences and similarities between substrate and competitive inhibior

Answer 55

Similar: -Similar shape so both are complementary to enzymes active site Differences: -Competitive inhibitor may stil bind to the enzyme whereas a product will always unbind from the enzyme -No product is formed with a competitive inhibitor

Question 56

What does specificity mean

Answer 56

One enzyme has a small number or substrates only Due to exact complementary shape between the substrate and active sites

Question 57

Why does the reaction between an enzyme and substrate occur at 37 degrees C (for example could be any temp)

Answer 57

Sucrase lowers the activation energy required By stressing the substrate forming an enzyme substrate complex