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Cellular Respiration
Chapter 7
Miss Colabelli
Biology CPA
Cellular Respiration
o
Complex process that our cells make
ATP by breaking down organic
compounds
o
Organisms that use cellular respiration
are known as heterotrophs
Cellular Respiration
o
Cellular Respiration is the process that
releases energy by breaking down
food molecules in the presence of
oxygen
o
C6H12O6 + 6O2
o
6CO2 + 6H2O + ATP
Same equation for photosynthesis JUST
BACKWARDS!
Glycolysis
o
Process where one molecule of
glucose is broken in half, producing
two 3-carbon molecules of pyruvic
acid
o
Creates a small amount of ATP and
NADH
o
Process is anaerobic
o
Does not require oxygen
Aerobic Respiration
o
If oxygen is present in cell
environment
o
Pyruvic acid is broken down to make
a large amount of ATP
o
If no oxygen is available for the
pyruvic acid
o
Fermentation
Fermentation
o
Releases energy from pyruvic acid
without oxygen
o
Two types
o
o
Lactic Acid
Alcoholic
Lactic Acid Fermentation
o
Lactic Acid is produced by muscles
during rapid exercise when the
body cannot supply enough oxygen
Alcoholic Fermentation
o
Alcoholic fermentation is done by yeasts
and some microorganisms
o
Produces an alcohol & Carbon dioxide
Glycolysis
o
Glucose  2 pyruvic acid molecules
o
Step 1:
o
Glucose molecule uses two ATP
molecules to make a 6-carbon molecule
with two phosphates
Glycolysis
Step 2:
o
o
Glucose molecule breaks in half
to make two G3P molecules
Glycolysis
o
Step 3:
o
Each G3P molecule gets a
phosphate added and 2 NAD+ are
reduced and gain an electron to
become NADH
Glycolysis
o
Step 4:
o
Each 3-Carbon molecule loses
their phosphates to make 4
molecules of ATP, 2 molecules of
water, and 2 molecules of pyruvic
acid
Fermentation
o
Anaerobic process after glycolysis
o
Pyruvic acid is used to become either
lactic acid or ethyl alcohol
o
This process is important because it
regenerates NAD+ molecules for
glycolysis to continue to work
Lactic Acid Fermentation
o
Pyruvic acid 
o
NADH 
o
Important for making dairy products
o
o
lactic acid
NAD+
Produces certain cheeses and yogurts
Occurs naturally in your muscles when you
work out
o
Muscle soreness
Lactic Acid Fermentation
o
Muscles use up all
available oxygen
o
o
Switch to anaerobic
respiration
Increases acid
levels in muscles
causing the fatigue
o
Eventually gets
processed in liver
back to pyruvic acid
Lactic Acid Fermentation
Alcoholic Fermentation
o
Pyruvic acid 
o
NADH 
o
Ethyl alcohol is a 2-carbon molecule
o
ethyl alcohol
NAD+
Pyruvic acid loses a carbon by releasing
CO2
Alcoholic Fermentation
o
Yeast needs to get food to survive such as
sugars from fruit
o
Yeast breaks down to ferment the pyruvic
acid into ethyl alcohol and CO2
o
If CO2 is released, you get regular alcohol
o
o
Ex: wine
If CO2 is not released, you get sparkling alcohol
o
Ex: Champagne
Efficiency of Glycolysis
o
Glycolysis uses 2 ATP in order to
create G3P molecules
o
Makes 4 ATP at the end of the process
o
As a process to make energy, the
efficiency is about 2%
o
Very low for necessary energy
o
This is why we need cellular respiration!!
The Krebs Cycle
o
During the Krebs Cycle, pyruvic acid is
broken down into carbon dioxide in a
series of energy-extracting reactions
o
Citric Acid is created in this cycle thus
giving it the nickname Citric Acid cycle
o
Net ATP Production is 2 ATP
Electron Transport Chain
o
The electron transport chain uses the highenergy electrons from the Krebs Cycle to
convert ADP to ATP
o
Total ATP produced: 32
Aerobic Respiration
o
Only occur in the presence of oxygen
o
Two stages
o
o
Krebs Cycle
o
Electron Transport Chain with chemiosmosis
Prokaryotes
o
o
Occur in cytosol
Eukaryotes
o
Occur in mitochondria
Aerobic Respiration
o
After glycolysis, pyruvic
acids are produced
o
Pyruvic acid moves
inside mitochondria into
mitochondrial matrix
(space between two
membranes)
o
Pyruvic acid + CoA 
Acetyl CoA + CO2
The Krebs Cycle
o
Acetyl CoA  CO2 + H + ATP
o
The H produced reduce NAD+ 
o
Five steps in the Krebs Cycle
o
NADH
Occurs in mitochondrial matrix
o
Citric Acid is made in Step 1 therefore this is
also called the Citric Acid cycle
o
Net ATP produced is 2 ATP
Krebs Cycle - Step 1
o
Acetyl CoA + oxaloacetic acid 
Citric Acid
o
This step releases CoA back into the
mitochondrial matrix for pyruvic acid to be fixed
again
Krebs Cycle – Step 2
o
Citric acid releases CO2 and H
o
Becomes a 5-carbon compound
o
The H released, reduces the NAD+ to NADH
Krebs Cycle – Step 3
o
Five carbon compound releases
another CO2 and H
o
Becomes a 4-Carbon compound
o
Another NAD+ is reduced to NADH
o
Produces an ATP
Krebs Cycle – Step 4
o
4 carbon compound releases H atom
o
This time, FAD is reduced to FADH2
o
Similar molecule to NAD+
Krebs Cycle – Step 5
o
4-Carbon compound releases H atom
o
Reduces NAD+ to NADH
o
This reaction regenerates initial oxaloacetic
acid
Don’t let this happen to YOU!
Electron Transport Chain
o
Uses the high-energy electrons from the
Krebs Cycle to convert ADP to ATP
o
Total net ATP produced is 34!!
o
Prokaryotes
o Occurs on cell membrane of organism
o
Eukaryotes
o Occurs in the mitochondria
membrane called cristae
ETC – Step 1
o
NADH & FADH2 are used to
power this chain of reactions
o
NADH & FADH2 are oxidized (lose
electrons) to the electron
transport chain
o
Also donate H atoms
o
NADH 
o
FADH2

NAD+
FAD+
ETC – Step 2
o
Electrons from NADH & FADH2 are
passed down chain
o
Lose some energy each time passed on
ETC – Step 3
o
Lost energy from electrons transferring down
the chain pump protons (H+)
o
This creates high concentration of H+
between inner and outer membranes
o
Creates a concentration gradient & electrical
gradient since H+ are positive
ETC – Step 4
o
Concentration & electrical gradients in
membranes produce ATP molecules by
chemiosmosis
o
ATP synthase is protein embedded in
membrane that pumps protons out and
creates ATP
ETC – Step 5
o
The electrons move to final acceptor down
the chain
o
Oxygen is the final acceptor
o
Oxygen also accepts protons provided by
NADH & FADH2
o
The protons, electrons, and oxygen all
combine to produce H2O
Importance of Oxygen
o
The only way to produce ATP is by the
movement of electrons in the ETC
o
o
Oxygen is the final acceptor
Without oxygen, the ETC would halt
Efficiency of Cellular Respiration
o
Glycolysis 2 ATP
o
Krebs Cycle 2 ATP
o
Electron Transport Chain 32 ATP
o
Total = 36 ATP
Efficiency of
Cellular Respiration
o
Depends on conditions of the cell
o
How ATP are transported
o
Aerobic respiration is 20 times more
efficient than anaerobic respiration
Summary
o
Cellular respiration
o
Glycolysis
o
o
Glucose  pyruvic acid + ATP + NADH
Aerobic respiration
o
Pyruvic acid 
CO2 + H2O + ATP
Comparing Photosynthesis & Respiration
Photosynthesis
Cellular
Respiration
Function
Energy Storage
Energy Release
Location
Chloroplasts
Mitochondria
Reactants
CO2 and H2O
C6H12O6 and O2
Products
C6H12O6 and O2
CO2 and H2O
Equation
6CO2 + 6H2O 
C6H12O6 + 6O2
C6H12O6 + 6O2
6CO2 + 6H2O