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Cellular Respiration
Chapter 7
Cellular Respiration
Complex process that our cells make
ATP by breaking down organic
compounds
Organisms that use cellular
respiration are known as
heterotrophs
Cellular Respiration
Cellular Respiration is the process that
releases energy by breaking down food
molecules in the presence of oxygen.
C6H12O6 + 6O2à 6CO2 + 6H2O + ATP
– Same equation for photosynthesis JUST
BACKWARDS!
Glycolysis
Glycolysis: process where one
molecule of glucose is broken in half,
producing 3-carbon molecules of
pyruvic acid
Creates a small amount of ATP and
NADH
Process is anaerobic
– Does not require oxygen
Aerobic Respiration
If oxygen is present in cell
environment
Pyruvic acid is broken down to make
a large amount of ATP
If no oxygen is available for the
pyruvic acid
– Fermentation
Fermentation
Releases energy from pyruvic acid without
oxygen
Two types
– Lactic Acid
– Alcoholic
Lactic Acid Fermentation
Lactic Acid is produced by muscles
during rapid exercise when the body
cannot supply enough oxygen.
Alcoholic Fermentation
Alcoholic fermentation is done by
yeasts and some microorganisms
Produces an alcohol & Carbon
Dioxide
Glycolysis
glucose → 2 pyruvic acid molecules
Step 1:
• Glucose molecule uses 2 ATP
molecules to make a 6-carbon
molecule with 2 phosphates
Glycolysis
Step 2:
• Glucose molecule breaks in half to
make 2 G3P molecules
Glycolysis
Step 3:
• Each G3P molecule gets a
phosphate added and 2 NAD+ is
reduced and gains an e- to become
NADH
Glycolysis
Step 4:
• Each 3-Carbon molecule loses their
phosphates to make 4 molecules of
ATP, 2 molecules of water, and 2
molecules of pyruvic acid
Fermentation
Anaerobic process after glycolysis
Pyruvic acid is used to become either
lactic acid or ethyl alcohol
This process is important because it
regenerates NAD+ molecules for
glycolysis to continue to work
Lactic Acid Fermentation
Pyruvic acid → lactic acid
NADH → NAD+
Important for making dairy products
produces certain cheeses and yogurts
Occurs naturally in your muscles when
you work out
Muscle soreness
Lactic Acid Fermentation
Muscles use up all
available oxygen
Switch to anaerobic
respiration
Increases acid levels in
muscles causing the fatigue
Eventually gets
processed in liver back
to pyruvic acid
Lactic Acid Fermentation
Alcoholic Fermentation
Pyruvic acid → ethyl alcohol
NADH → NAD+
Ethyl alcohol is a 2-carbon
molecule
Pyruvic acid loses a C by
releasing CO2
Alcoholic Fermentation
Yeast needs to get food to survive
such as sugars from fruit
Yeast breaks down to ferment the
pyruvic acid into ethyl alcohol and
CO2
If CO2 is released, you get regular
alcohol
If CO2 is not released, you get a
sparkling wines
Efficiency of Glycolysis
Glycolysis uses 2 ATP in order to
create G3P molecules
Makes 4 ATP at the end of the process
As a process to make energy, the
efficiency is about 2%
Very low for necessary energy
Why we need cellular respiration!!
The Krebs Cycle
During the Krebs Cycle, pyruvic acid
is broken down into carbon dioxide in
a series of energy-extracting
reactions.
Citric Acid is created in this cycle
thus giving it the nickname Citric Acid
cycle.
Net ATP Production is 2 ATP.
Electron Transport Chain
The electron transport chain uses
the high-energy electrons from the
Krebs Cycle to convert ADP to ATP.
Total ATP 32.
Totals
Gycolysis 2 ATP
Krebs Cycle 2 ATP
Electron Transport Chain 32 ATP
Total = 36 ATP
Energy & Exercise
Quick energy – Lactic Acid
fermentation is used to get quick
energy and gives off lactic acid as a by
product, thus the muscle pain.
Long-Term Energy – Use cellular
respiration to produce energy.
Exercising or activities that last for at
least 15 to 20 minutes. Best form for
weight control.
Comparing Photosynthesis &
Respiration
Photosynthesis
Cellular
Respiration
Function
Energy Storage
Location
Chloroplasts
Energy
Release
Mitochondria
Reactants
CO2 and H2O
Products
C6H12O6 and O2
C6H12O6 and
O2
CO2 and H2O
Equation
6CO2 + 6H2O à
+ 6O2
6CO2 + 6H2O
C6H12O6 C6H12O6 + 6O2à