Review Sheet– Enzymes, Fermentation, & Cellular Respiration
1. For each of the activities described tell which of the following reactions is most likely to accompany the
activity overall.
Reaction #1: ATP ---> ADP + P
Reaction #2: ADP + P ---> ATP
A) A cell is building a fat molecule from fatty acids and glycerol through dehydration synthesis. Reaction #1
B) Sugar is broken down to CO2 and H2O through cellular respiration. Reaction #2
C) A euglena is moving through pond water. Reaction #1
D) Molasses is fermented by a yeast cell. Reaction #2
E) A molecule is brought into a cell by endocytosis. Reaction #1
2. A student is studying fermentation in yeast. She combines 0.1 g of yeast with 50 ml. of a 10% molasses
solution. She then puts the mixture into an insulated thermos and measures the temperature every 5 minutes
for 2 hours. The solution begins at room temperature (20 ˚C)
A) What changes in temperature do you predict the student will observe over the 2 hour period? Explain.
Since heat is a product of fermentation, you would expect the temperature to rise as the yeast ferment the
sugar. It would continue to rise until all the sugar has been used up. At that point it would level off (or
maybe even decrease if the thermos is not very well insulated).
B) Sketch a graph of temperature vs. time for your predicted results.
Temperature vs. Time for Fermenting Yeast
50
45
40
35
30
25
20
0
0.5
1
1.5
2
Time (hours)
3. A student mixes 0.1 gram of ground liver with 5 ml. of a 1% hydrogen peroxide solution. She measures the
total gas that is produced since the beginning of the experiment every 15 seconds. Her results are
summarized on the graph below:
A) What gas do you think is being produced?
Oxygen gas (O2) since liver has the enzyme catalase which speeds up the breakdown of hydrogen
peroxide to oxygen and water.
B)What enzyme is catalyzing the reaction?
Answer for E
The catalase in the liver
C) Explain why the graph levels off.
The graph levels off because all of the substrate (hydrogen peroxide) has been used up.
Answer for F
D) What could you add to the mixture to make more gas?
Since the graph levels off because the hydrogen peroxide has been used up, adding more hydrogen
peroxide should allow you to make more gas.
E) Sketch on the graph above what you predict the graph would look like if she had used 0.2 g of liver with
5 ml. of a 1% hydrogen peroxide solution.
There is the same amount of substrate so the graph will level off at the same height (same amount of
gas produced). The extra enzymes in the greater amount of liver will allow the gas to be made more
quickly.
F) Sketch on the graph above what you predict the graph would look like if she had used 0.1 g of liver with
2.5 ml. of a 1% hydrogen peroxide solution.
There is the half as much substrate, so the graph will level off at a lower height (half the amount of gas
produced). There is the same amount of liver, so there is the same number of enzymes. For this reason
the rate of the reaction will be about the same.
4. Use the diagram of energy vs. time below to answer the questions.
Energy
(calories)
Energy VS Time
5
4
3
A+B
2
1
C
Time (sec.)
A) Write the equation for the overall reaction described in the diagram.
A+B
C
B) Which has more energy stored in its chemical bonds, the substrate or the products?
substrates
C) What is the activation energy required for this reaction in calories?
2 calories
D) Sketch in red how the graph would look if a catalyst were added.
5. Refer to the graph below: {Equal concentrations of sugars A, B, and C are being fermented by yeast.)
Gas Production vs. Time for the Fermentation of Three Sugars
by Yeast
9
Total gas produced (mL)
8
7
6
Sugar A
5
Sugar A
Sugar B
4
Sugar C
3
2
1
0
0
2
4
6
8
10
Tim e (hours)
A) What gas do you think is being produced? Explain your answer.
Carbon dioxide (CO2) is most likely the gas being produced since it is a product of fermentation in
yeast.
B) Explain why the graphs level off.
The graphs level off when no more CO2 is being made. This happens when the substrate (the sugar) is
used up.
C) If sugar A is glucose, suggest what sugars B and C might be
Since the yeast using sugar B are able to produce the same amount of CO2 as the yeast using sugar A, it
is most likely a monosaccharide the same as glucose. It could be fructose. Since the yeast using sugar C
can make about twice as much CO2, it might be a disaccharide such as sucrose.
D) Predict how many ATP can be made by one molecule of sugar C if no O2 is present.
If sugar C is a disaccharide, then it has two monosaccharides in each of its molecules. If each of these is
used separately in the fermentation process, then each could be used to produce 2 ATP. This means that
a total of 4 ATP could be made from each molecule of sugar C.