Name:______________________
Cellular Respiration Worksheet
Objective: This assignment provides additional experience with cellular respiration and
the production of ATP. Questions will review key concepts and then delve into some
quantitative aspects of cellular respiration.
Key Concept Questions:
1. Define cellular respiration. What are the primary metabolic pathways involved in
cellular respiration?
Cellular respiration is the process in which glucose is turned into adenosine
triphosphate (ATP). The four major metabolic pathways that make up cellular
respiration are glycolysis, pyruvate processing, the Krebs (Citric Acid) cycle, and
the electron transport chain.
2. Fill out the table. Name each of the metabolic pathways involved in cellular
respiration (in order of occurrence) and provide the reactants, products, and a
brief description of each process. Include where in the cell the process takes
place in the description. We have filled in some squares to show you the types of
answers we expect.
Metabolic Pathway
Reactants
Products
Description
glycolysis
Glucose, 2 ATP
4 ATP, 2 NADH, 2
pyruvate
Glucose is broken
down in this first step
of cellular respiration
pyruvate processing
2 pyruvate
2 Acetyl CoA, 2 CO2,
2 NADH
Pyruvate is converted
to Acetyl CoA
Krebs cycle
Electron Transport
Chain
2 Acetyl CoA, 2 H2O
4 CO2, 6 NADH, 2
FADH2, 2 ATP
10 NADH, 2 FADH2,
26 ADP, 6 O2
6 H2O, 26 ATP
Acetyl CoA is processed
through 8 oxidizing
chemical reactions into
different carbon-based
molecules resulting in the
transfer of hydrogen
molecules to NAD+ and
FAD
NADH and FADH2 are
oxidized and protons are
pumped across the
mitochondrial inner
membrane; these protons
then flow through ATP
synthase which converts
ADP to ATP
3. Under what condition is cellular respiration impossible? What alternative
metabolic process can be used to produce ATP from glucose? Describe this
metabolic pathway and indicate how much ATP is produced.
If there isn’t any oxygen available, cellular respiration cannot take place.
Fermentation is used in place of cellular respiration and occurs in two types –
lactic acid fermentation and alcohol fermentation. Both of these processes result
in the creation of 2 ATP for every mole of glucose but have different end products
as their name suggests.
4. Explain substrate-level phosphorylation and oxidative phosphorylation. What is
the primary difference between the two processes?
Substrate level phosphorylation occurs when a phosphate group is transferred
directly to ADP from an intermediate substrate while oxidative phosphorylation
requires redox reactions to allow for the transfer of a phosphate group to ADP.
Application Questions
5. No chemical reaction is 100% efficient – but how efficient is cellular respiration.
The energy available in 1 mole of glucose is 686 kcal. Cellular respiration is able
to produce 30 moles ATP from 1 mole glucose, and ATP contains 7.3 kcal per
mole. How much energy (kcal) is converted to ATP during cellular respiration
per mole of glucose? What percentage of energy from the original glucose is still
available for use as ATP?
Kcal in ATP = 7.3 kcal/mol x 30 mol = 219 kcal
% efficiency = 219 kcal / 686 kcal = 31.9%
6. Thinking back to your answer for question 3, how much energy is converted to
ATP during this alternative pathway? What percentage of energy from the
original glucose is still available for use as ATP?
2 ATP is converted during this alternative pathway.
% efficiency = (7.3 kcal x 2) / 686 kcal = 2.1%
7. A HERSHEY’S candy bar contains 24g of sugars. These sugars are sucrose
(C12H22O11), which can be broken down into two glucose (C6H12O6) molecules.
a. How many moles of sucrose are in a HERSHEY’S candy bar (hint: use the
molecular mass (g/mol) of sucrose to get your answer)?
24g sucrose = 24g / 342.3 g/mol = 0.07 mol sucrose
b. How many moles of glucose are in a HERSHEY’S candy bar?
1 mol sucrose = 2 mol glucose SO
0.07 mol sucrose = 0.14 mol glucose
c. How many kcal are available from the glucose in a HERSHEY’S candy
bar? Thinking back to Question 5, how many of these kcal will your body
be able to convert to ATP?
kcal in 0.14 mol glucose = 686 kcal/mol x 0.14 mol = 96.04 kcal
converted kcal = 96.04 kcal x 31.9% = 30.6 kcal
8. Excess sugar and carbohydrates entering the body can be stored as fats, also
known as triglycerides. Triglycerides, as their name implies, contain three fatty
acids and a glycerol molecule. Triglycerides enter the cellular respiration process
by being converted into acetyl CoA. Suppose that each fatty acid in a triglyceride
can be converted into 4 molecules of acetyl CoA. How many ATP could be
created by breaking down one molecule of this triglyceride?
3 fatty acids = 12 acetyl CoA
12 acetyl CoA = 12 ATP, 36 NADH, 12 FADH2
36 NADH and 12 FADH2 = 26 ATP x 6 = 156 ATP
Total = 12 ATP + 156 ATP = 168 ATP