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Cellular Respiration
Let’s make some ATP…
Cellular Respiration
C6H12O6 + 6O2 -----> 6CO2 + 6H20 + energy
(heat and ATP)
Cellular Respiration uses oxygen and glucose to produce
Carbon dioxide, water, and ATP.
Glucose
Oxygen gas
Carbon
dioxide
Water
Energy
Cell Respiration
• Releases chemical energy of food
molecules
• Glucose starts a set of reactions
• Producing ATP for our cells
• Occurs in three stages (steps)
Steps in (aerobic) Cell
Respiration
1. Glycolysis
2. Citric Acid Cycle(“Kreb’s Cycle”)
3. Electron Transport Chain
Where does Cell Respiration occur?
Prokaryotes
These cells do
NOT contain
organelles, so cell
respiration occurs
in the cell
membrane
eukaryotes
These cells DO
have organelles,
so most of cell
respiration
occurs in the
mitochondria
Step 1: Glycolysis
•
•
•
•
Occurs in the cytoplasm
Starts with 1 molecule of glucose
Anaerobic (no O2 needed)
Glucose is broken down into 2
molecules of pyruvic acid (pyruvate)
• Gain: 4 ATP
2 NADH
2 Pyruvate
2 Hydrogen ions (H+)
So…Glycolysis makes 4 ATP
• BUT
• Glycolysis uses 2 ATP to run its
reaction
• So…
• Glycolysis has a net gain of how many
ATP molecules?
• Glycolysis = net gain of 2 ATP
This is not good…we need
more ATP!!!
So…
more reactions are needed
to gain more
ATP
for our cells
After Glycolysis
• Pyruvic Acid molecules diffuse into
the mitochondria
• And go through a series of reactions
• where CO2 is released
• pyruvate combines with a molecule of
CoEnzyme A (CoA)
• To form Acetyl CoA
Step 2: Kreb’s Cycle
•
•
•
•
Acetyl CoA starts a series of reactions
in the matrix of the mitochondria
Where CO2 is released
And chemical energy is captured in the
form of NADH, FADH2, & ATP
• GAIN: 2 ATP
6 NADH
2 FADH2
4 CO2
More on the Krebs's Cycle…
• AKA the “Citric Acid Cycle”
• This cycle goes around twice for each
molecule of glucose
• And for every turn of the cycle, 1
ATP is produced
• In total, 2 ATP are produced from
the Citric Acid/Kreb’s Cycle (because
the cycle rotates twice)
Step 3: Electron Transport Chain
• electron-carrying proteins embedded
in the inner membrane of the
mitochondria transfer e- from one to
another
• O2 is the final electron acceptor
• O2 combines with H2 to form H20
• GAIN: 32 ATP
So…
•
•
•
•
Most of the energy (ATP)
locked in the original glucose molecule
is released in
the Electron Transport Chain
Energy produced from ONE
Glucose molecule:
1. Glycolysis = 2 ATP
2. Citric Acid/Kreb’s Cycle = 2 ATP +
NADH + CO2
3. Electron Transport Chain = 32 ATP +
H20
Cellular Respiration Equation
C6H12O6 + 6O2 -----> 6CO2 + 6H20 + 36ATP
Question: So what is all this
energy used for?
•
•
•
•
•
Breathing
Digesting
Blood clotting
DNA replication &
All of your life processes need ATP
to proceed with success!!!
What is Fermentation?
•
The process by which animal cells release
energy under anaerobic conditions
(without oxygen)
•
How yeast and some bacteria make
energy
•
Examples:
1. Souring of milk
2. Rising of dough
3. Conversion of sugar to alcohol
2 types of Fermentation:
1. Lactic Acid Fermentation - the
process of energy production in a cell
under anaerobic conditions (without
oxygen)
2. Alcohol Fermentation - a form of
anaerobic respiration used primarily
by yeasts & bacteria
Lactic Acid Fermentation
• When animals do not have enough O2
to keep performing aerobic cell
respiration
• Our mitochondria revert to “Plan B”
• And perform Fermentation
• Producing a small amount of ATP &
lactic acid
• Pyruvic Acid ----- Lactic Acid
• The lactic acid is carried to
• the liver
• Where it is broken down
Fermentation: Anaerobic Respiration
Lactic Acid Fermentation
Glucose
Alcohol Fermentation
Glucose
Glycolysis (Pyruvate) – 2 ATP
Glycolysis (Pyruvate) + 2 ATP
Lactic Acid + 2 ATP
CO2 + Alcohol + 2 ATP
Alcohol Fermentation
• Occurs in yeasts and some bacteria
• Products: Ethyl Alcohol (Ethanol) +
CO2 + 2 ATP
• Used to make bread, yogurt,
homemade ginger ale
General Outline
Glucose
Glycolysis
Oxygen
Aerobic
Transition Reaction
Krebs Cycle
ETS
36 ATP
Pyruvic Acid
No Oxygen
Anaerobic
Fermentation
Toolman
A Comparison …
Photosynthesis
• Food accumulated
• Energy from sun stored
in glucose
• CO2 taken in
• O2 given off
• Occurs in light only
• Occurs in the presence
of Chlorophyll
•
Occurs ONLY in Plants
Cell Respiration
• Food broken down
• Energy of glucose
released
• CO2 given off
• O2 taken in
• Produces CO2 + H2O
• Goes on 24/7
• Occurs in ALL living
cells
Which diagram represents
organelle that contains the
enzymes needed to synthesize ATP
in the presence of oxygen?
The fermentation of glucose
by yeast normally yields:
1.
Lactic acid, CO2, & 2 ATP
2. Alcohol, CO2, & 36 ATP
3. Alcohol, CO2, & 2ATP
4. H20, CO2, & 36 ATP