factors affecting enzyme activity

what are the four factors that affect enzyme activity

-temperature

-pH

-enzyme concentration

-substrate concentration

what happens when the temperature is increased

the rate of an enzyme-controlled reaction increases when the temperatures increased

what does more heat mean for the molecules in an enzyme-controlled reaction

more heat means more kinetic energy so the molecules move faster

if the molecules move faster what is more likely to happen

enzymes are more likely to collide with the substrate molecules

what also increases as a result of more heat

energy of the collisions also increases

if the energy of the collisions increases what are the collisions more likely to result in

collisions are more likely to result in a reaction

what happens if the temperature gets too high

the reactions stops

explain why if the temperature gets to high the reaction stops

-rise in temperature makes the enzymes molecules vibrate more

-if temperature goes above a certain level , this vibration breaks some of the bonds the hold the enzyme in shape

-the active site then changes shape and the enzyme and substrate no longer fit together

what does the enzyme become if the active site changes shape and the enzyme and substrate no longer fit

the enzyme becomes denatured

what does the enzyme no longer function as if it becomes denatured

no longer functions as a catalyst

what does every enzyme have

an optimum temperature

whats is the optimum temperature of most human enzymes

37 degrees celsius

what is the optimum temperature for some enzymes such as those used in biological washing powders

60 degrees celsius

what shows how rate of reaction changes with temperature

temperature coefficient -Q10

what does the temperature coefficient value show

how much the rate of reaction changes when the temperature is raised by 10 degrees celsius

at temperatures before the optimum what does a Q10 value of 2 mean

that the rate doubles when the temperature is raised by 10 degrees celsius

what does a Q10 value of 3 mean

the rate trebles when the temperature is raised by 10 degrees celsius

what is the Q10 value of most enzyme controlled reactions

around 2

what does pH affect

enzyme activity

what do all enzymes have

an optimum pH value

what pH do most human enzymes work best at

pH 7 -but there are exceptions

what pH does pepsin work best at

acidic pH 2 -useful because its in the stomach

what bonds hold the enzymes tertiary structure in place

ionic bond and hydrogen bonds

what happens above and below the optimum pH

the H+ ions and OH- ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds that hold the tertiary structure in place

what happens to the enzymes active site if the ionic and hydrogen bonds are affected

the active site changes shape

what does the enzyme become if the active site changes shape

denatured

what does enzyme concentration affect

rate of reaction

what is more likely to happen if there are more enzyme molecules in a solution

the more enzyme molecules in a solution the more likely a substrate molecule is too collide with one and form an enzyme-substrate complex

therefore what does increasing the concentration of the enzyme increase also

also increases the rate of reaction

what happens if the amount of substrate is limited and you keep adding more enzyme molecules

it comes to a pint when theres more than enough enzyme molecules to deal with the available substrate so adding more enzymes has no effect

what does substrate concentration affect

substrate concentration affects the rate of the reaction up until a point

what happens if the substrate concentration is increased

the rate of reaction increases

why does the rate of reaction increase if the substrate concentration is higher

more substrate molecules means a collision between substrate and enzyme molecules is more likely so ore active sites will be used

when does the rate of reaction stop increasing

when the 'saturation' point is reached

why does the rate of reaction stop increasing after the saturation point is reached

because there are so many substrate molecules that all the active sites are full so adding more substrate makes no difference to the rate of reaction

what happens to substrate concentration over time during a reaction

substrate concentration decreases over time during a reaction

If the substrate concentration decreases over time and no other variables re changed in the aeration what will happen to the rate of reaction

rate of reaction will decrease over time too

what is the highest rate of reaction during the reaction

the initial rate of reaction

name two ways you can measure the rate of an enzyme controlled reaction

-you can measure how fast the product of the reaction appears

-you can measure the disappearance of the substrate to compare the reaction under different conditions

what enzyme would you use to measure how fast a product appears

catalase

why would catalase be a good example

easy to collect the oxygen produced and measure how fast its given off

how would you measure the appearance of a product using catalase

-fill a large beaker with water and place an upside down measuring cylinder inside

-place one end of a delivery tube inside the upside down measuring cylinder

-place the hydrogen peroxide solution and catalase into a test tube

-quickly place the other end of the delivery tube over he top of the test tube and measure how much oxygen is produced using the upside down measuring cylinder

what enzyme would you use to measure the disappearance of the the substrate

amylase -catalyses the break down of starch into maltose

what solution would you use to detect starch

solution of potassium iodide and iodine

how would you time how long it takes for the starch to disappear

by regularly sampling the starch solution

why would you alter the conditions the reaction

to compare rates

describe how you would use amylase to measure the disappearance of a substrate

-place the starch solution in a test tube and add amylase

-every minute sample the mixture by using a pipette to take a sample and placing it not he spotting tile

-add the iodine in potassium iodide to the sample

-time when the iodine solution solution no longer turns blue black is noted-starch has been broken down