enzymes

Question 1

define enzyme

Answer 1

biological catalysts which speed up the rate of a chemical reaction in a living organism

Question 2

what happens at the end of the chemical reaction

Answer 2

enzyme remains unchanged and free to catalyse another reaction

Question 3

list four reasons why enzymes are needed in living organisms

Answer 3

to speed up the rates of chemical reactions in cells
to ensure that life as we know it can continue
for digestion to occur quickly so that nutrients can be made available to our cells on demand

Question 4

list digestive enzymes

Answer 4

pepsin for proteins into polypeptides
amylase for starch into maltose
lipase for lipids into glycerol or fatty acids
maltase for maltose into glucose

Question 5

catalase enzyme

Answer 5

conversion of hydrogen peroxide produced in cells to water and oxygen
enzyme catalase is found in blood liver potatoes beans and yeast

Question 6

what happens if hydrogen peroxide is allowed to build up in cells

Answer 6

becomes toxic and ezyme speeds up breakdown of peroxide into harmless and useful products

Question 7

list 3 characteristics of enzymes

Answer 7

all enzymes have specific shape with active surface
substrate on which enzyme has an effect has complimentary shape to that of active site
active site of each enzyme unique and so each will only act on one type of substrate

Question 8

explain how enzymes work

Answer 8

when enzyme and substrate molecules mix together bc particles in constant motion so bump
collide with each other due to kinetic energy
specific substrate molecule fits into active site of enzyme once collide in correct orientation and the enzyme substrate complex forms
molecules of substrate undergo rearrangement to form products
once products form no longer fit into active site of enzyme and move away from active site
can then be reused to catalyse another reaction

Question 9

how does temperature affect rate of enzyme reactions

Answer 9

once temperature increases kinetic energy of enzyme and substrate molecules also increases
results in more frequent successful collisions between enzyme and substrate
results in increased rate of product formation

Question 10

what is the optimum temperature

Answer 10

certain temperature usually 40 at which the rate of reaction reaches maximum and temp at which enzyme functions best

Question 11

what happens when temperature increases above optimum temperature

Answer 11

increased kinetic energy causes enzymes to vibrate so vigorously that structure and shape of enzyme including shape of active site changes irreversibly
at this point enzyme is said to be denatured and can no longer function as catalyst

Question 12

how does pH affect rate of enzyme reactions

Answer 12

enzymes also function best at certain pHs
such as pepsin which works best at pH of 2

Question 13

define optimum pH

Answer 13

pH at which enzymes work best

Question 14

what happens if pH goes up or down

Answer 14

shape of enzyme and therefore active site is altered so that enzyme cannot catalyse any reactions
enzyme is inactivated which is usually reversible so that return to optimum pH restores enzymes shape and catalytic ability

Question 15

list four other factors that affect enzymes

Answer 15

inhibitors – mercury lead cyanide – cause enzyme to change its shape so that it cannot catalyse reactions
cofactors – speed up activity by vitamins and minerals
substrate concentration – low sub conc then rate is low
enzyme conc – enzyme conc increase rate increases