without O2, steps 2 and 3 can not occur and the cell may anaerobically respire 

​          how will enzyme activity be affected by...
 


1. substrate concentration





2. presence of enzyme inhibitor




​                 3. temperature



​                               enzyme​
            substrate-----------> product
           the substrate = sugar
                         the enzyme produced by yeast = Zymase
                                         the products = CO2, ethanol, energy
                               we will measure CO2
  the more CO2 produced = the greater the enzyme activity

steps 2 and 3 occur in the mitochondria and require O2

2 pyruvate (3C each)

our lab today:
evaluating enzyme activity in yeast undergoing anaerobic respiration/fermentation

when oxygen is present, all three steps occur allowing the glucose to be  completely broken down producing  H2O, CO2 and a lot of energy

we can measure the relative volume of CO2 produced in cm3 (ml)

when oxygen is absent, only step one, glycolysis,
 occurs so the glucose is only partially broken down producing CO2, ethanol and a lot less energy (<1/15th)

AND 
we can test for the presence of CO2 using a pH indicator...
why pH?

​Zymase ​is an enzyme complex that catalyzes the fermentation of sugar into ethanol and carbon dioxide. It occurs naturally in yeasts.

step 3

          3 steps of                        AEROBIC 
 cellular respiration 
1. glycolysis
2. Kreb (TCA) cycle
3. electron transport chain
        steps 2 and 3
      require oxygen                      = aerobic

Other enzymes may be required
depending on what the yeast is having for dinner...
Maltase converts maltose into 2 glucose monomers
Ivertase converts sucrose into ​one glucose and one fructose monomer

STEP 1: GLYCOLYSIS:
​one 6 glucose with 6 carbon atoms is broken down into 2 pyruvates with 3 carbons each

carbonic acid is produced

adding an acid lowers pH

and every step along the way requires a different enzyme...

this cycle relies in aerobic respiration

= much less than 3000kJ

we will use Phenolphthalein
as our pH indicator

Anaerobic respiration by yeast/bacteria is called fermentation.

During this process glycolysis 
​occurs but not the other steps in cellular respiration. the other steps require the presence of oxygen.  

   Anaerobic Respiration and Enzyme Activity

step 1

the more CO2 produced, the greater the activity of the enzyme.

6 carbon glucose --->

step 2

 3000kJ !