9.1 Cellular Respiration:
An overview
I. Chemical Energy and Food
• Food provides living things
with the chemical building
blocks they need to grow
and reproduce
• Cells use fats, proteins and
carbs as food
– Break this food down
gradually
II. Overview of Cellular Respiration
• Cellular respiration is the multi-step process that
releases energy from food in the presence of
oxygen
• Represented as:
6O2 + C6H12O6
Oxygen
Glucose
6CO2 + 6H2O + ENERGY
Carbon
dioxide
Water
A. Stages of Cellular Respiration
• Cellular respiration
captures energy in 3
stages:
– Glycolysis
– Krebs cycle
– Electron transport chain
How does it work?
1. Glucose enters chemical
pathway called glycolysis
- Uses some energy to make
ATP, rest stored as pyruvic acid
2. Pyruvic acid enters the
Kreb cycle
3. Most energy is extracted
during electron transport
chain by using oxygen
B. Oxygen and Energy
• Oxygen is required at end
of electron transport
chain
• Aerobic: pathways that
require oxygen
– Krebs, Electron transport
chain
• Anaerobic: pathways that
do not require oxygen
– Glycolysis, Fermentation
Where does this take place?
• Glycolysis happens in
cytoplasm
• The Krebs cycle and
Electron transport chain
occur in mitochondria
III. Comparing Photosynthesis and
Cellular Respiration
• Cellular respiration is
balanced by photosynthesis
• Photosynthesis removes
carbon dioxide from
atmosphere, cellular
respiration adds it
• Photosynthesis adds oxygen
and cellular respiration uses
it to make energy from food
9.1 Assessment questions
• 2a. Write the overall reaction for cellular
respiration.
• 2b. How does the process of cellular
respiration maintain homeostasis at the
cellular level?
• 3a. In what ways are cellular respiration and
photosynthesis considered opposite
processes?
• 3b. How is the chemical energy in glucose
similar to money in a savings account?