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Lesson Overview
Cellular Respiration: An Overview
Lesson Overview
9.1 Cellular Respiration:
An Overview
Lesson Overview
Cellular Respiration: An Overview
THINK ABOUT IT
Lesson Overview
Cellular Respiration: An Overview
Chemical Energy and Food
Food molecules contain chemical energy that is released
when its chemical bonds are broken.
Energy stored in food is expressed in units of calories. A
Calorie is the amount of energy needed to raise the
temperature of 1 gram of water by 1 degree Celsius. 1000
calories = 1 kilocalorie, or Calorie.
Lesson Overview
Cellular Respiration: An Overview
Overview of Cellular Respiration
If oxygen is available, organisms can obtain energy from food by a
process called cellular respiration. The summary of cellular
respiration is presented below.
In symbols:
6 O2 + C6H12O6  6 CO2 + 6 H2O + Energy
In words:
Oxygen + Glucose  Carbon dioxide + Water + Energy
Lesson Overview
Cellular Respiration: An Overview
Stages of Cellular Respiration
The three main stages of
cellular respiration are
glycolysis, the Krebs cycle,
and the electron transport
chain.
Lesson Overview
Cellular Respiration: An Overview
Stages of Cellular Respiration
Glycolysis produces only a
small amount of energy.
Most of glucose’s energy
(90%) remains locked in
the chemical bonds of
pyruvic acid at the end of
glycolysis.
Lesson Overview
Cellular Respiration: An Overview
Stages of Cellular Respiration
During the Krebs cycle, a
little more energy is
generated from pyruvic
acid.
Lesson Overview
Cellular Respiration: An Overview
Stages of Cellular Respiration
The electron transport
chain produces the bulk of
the energy in cellular
respiration by using
oxygen, a powerful
electron acceptor.
Lesson Overview
Cellular Respiration: An Overview
Electron Transport Chain Song
Electron pair on NADH,
Looking for a place to go -You could jump onto pyruvate,
But if you want to reach a lower energy state,
Why don't you come on down the electron transport
chain
And take a downhill ride on this one-way train?
Oh, won't you come on down the electron transport
chain?
It exploits delta G to make ATP.
Electron pair on FADH2 -The Krebs cycle's done with you.
Though the matrix is your current home,
You could be transferred to ubiquinone,
And you could come on down the electron transport
chain.
The loss of one cytochrome is another's gain,
So won't you come on down the electron transport
chain?
It exploits delta G to make ATP.
You can't just hold on to the same old thing;
Why should you hold on to that nicotinamide ring,
When you could come on down the electron transport
chain,
And take a downhill ride on this one-way train?
Oh, won't you come down the electron transport
chain?
It exploits delta G to make ATP.
Lesson Overview
Cellular Respiration: An Overview
Oxygen and Energy
Pathways of cellular
respiration that require
oxygen are called aerobic.
The Krebs cycle and
electron transport chain are
both aerobic processes.
Both processes take place
inside the mitochondria.
Lesson Overview
Cellular Respiration: An Overview
Oxygen and Energy
Gylcolysis is an anaerobic
process. It does not directly
require oxygen, nor does it rely
on an oxygen-requiring
process to run. However, it is
still considered part of cellular
respiration. Glycolysis takes
place in the cytoplasm of a
cell.
Lesson Overview
Cellular Respiration: An Overview
Comparing Photosynthesis and Cellular
Respiration
Lesson Overview
Cellular Respiration: An Overview
Lesson Overview
9.3 Fermentation
Lesson Overview
Cellular Respiration: An Overview
Fermentation
Fermentation is a process by which energy can be released from
food molecules in the absence of oxygen. Fermentation occurs in
the cytoplasm of cells.
Lesson Overview
Cellular Respiration: An Overview
Alcoholic Fermentation
Yeast and a few other microorganisms use alcoholic
fermentation that produces ethyl alcohol and carbon dioxide.
Chemical Equation: Pyruvic acid + NADH  Alcohol + CO2 + NAD+
Lesson Overview
Cellular Respiration: An Overview
Lactic Acid Fermentation
Most organisms, including humans, carry out fermentation using
a chemical reaction that converts pyruvic acid to lactic acid.
Chemical equation: Pyruvic acid + NADH  Lactic acid + NAD+
Lesson Overview
Cellular Respiration: An Overview
Energy and Exercise
How does the body produce ATP during different stages of
exercise?
Lesson Overview
Cellular Respiration: An Overview
Quick Energy
Cells normally contain small amounts of
ATP produced during cellular respiration,
enough for a few seconds of intense
activity.
Lactic acid fermentation can supply
enough ATP to last about 90 seconds.
However, extra oxygen is required to get
rid of the lactic acid produced. Following
intense exercise, a person will huff and puff
for several minutes in order to pay back the
built-up “oxygen debt” and clear the lactic
acid from the body.
Lesson Overview
Cellular Respiration: An Overview
Long-Term Energy
For intense exercise lasting longer than 90 seconds, cellular
respiration is required to continue production of ATP.
Cellular respiration releases energy more slowly than fermentation
does.
The body stores energy in the form of the carbohydrate glycogen.
These glycogen stores are enough to last for 15 to 20 minutes of
activity. After that, the body begins to break down other stored
molecules, including fats, for energy.
Lesson Overview
Cellular Respiration: An Overview
Organisms get the energy they need from food.
A calorie is the amount of energy needed to raise the temperature of 1 gram of water
1 degree Celsius.
Our familiar Calorie is actually a kilocalorie (1000 calories)
Generally 1 gram of carbohydrates and protein store 4 Calories, while lipids (fats) store
9 Calories.
Food is not broken down into energy until it is needed to make ATP.
Cellular respiration is the process that releases energy form food in the presence of
oxygen.
Overall respiration - sugars + oxygen  carbon dioxide + water. (C6H12O6 + 6O2 
6CO2 + 6 H2O
Cellular respiration involves a series of controlled reactions that slowly release the
energy stored in food.
Three steps of respiration, glycolysis, the Krebs cycle and electron transport chain.
Glycolysis only releases 10% of energy and makes pyruvic acid.
Pyruvic acid is then used in the Krebs cycle and preps the final stage the electron
transport chain where most energy is made because of oxygen as the final
electron acceptor.