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Cellular Respiration: An Overview
Lesson Overview
Lesson
Overview
9.1 Cellular
Respiration:
An Overview
Cellular Respiration: An Overview
Lesson Overview
Chemical Energy and Food
Energy flows into an ecosystem & exits as
heat. The chemical elements essential to
life are recycled!!
Light
energy
Organic
molecules
+ O2
CO2 +
H2O
ATP
Heat Energy
Cellular
Respiration in
mitochondria
Cellular Respiration: An Overview
Lesson Overview
Chemical Energy in Food
Food Provides:
Source of raw materials used to make
new molecules
Source of energy
calorie – the amount of energy needed to
raise the temperature of one gram of
water one degree Celsius. 1000 calories
= 1 kilocalorie, or Calorie.
Cells don’t burn glucose - gradually
release energy from it.
Cells break down food molecules
gradually and use energy stored in
chemical bonds to produce compounds
such as ATP that power the activities of
the cell.
Cellular Respiration: An Overview
Lesson Overview
Cellular Respiration
Overview
Cellular Respiration – process that releases
energy from food in the presence of
oxygen.
Contains 3 Pathways:
Glycolysis
Krebs cycle
Electron transport
6O2 + C6H12O6
6CO2 + 6H2O + ENERGY (ATP)
Cellular Respiration: An Overview
Lesson Overview
Cellular Respiration Overview
If cellular respiration took place in one
step, all the energy would be released
at once and most lost as heat.
Each of the three stages of cellular
respiration captures some of the
chemical energy available in food
molecules and uses it to produce ATP
or energy.
Cellular Respiration: An Overview
Lesson Overview
Cellular Respiration: An Overview
Lesson Overview
Cellular Respiration: An Overview
Lesson Overview
Stages of Cellular Respiration
Step 1: Glycolysis
-Occurs in the cytoplasm.
- 1 molecule of glucose is broken in half,
producing 2molecules of pyruvic acid.
- uses 2 stored ATP molecules as energy
- 4 ATP molecules are made during
glycolysis, so a total of 2 ATP molecules are
released by glycolysis as energy
net gain: 2 ATP
NAD+ (electron carrier) is converted to NADH.
This is only 2% of the total chemical energy in
glucose.
Cellular Respiration: An Overview
Lesson Overview
Glycolysis
Glycolysis happens quickly & can
produce 1000’s of ATPs in
milliseconds.
Glycolsis does not require oxygen!
Cellular Respiration: An Overview
Lesson Overview
Summary Of Glycolysis
In
Glucose
(6-C)
2 ATP
Out
2 pyruvate;
2(3-C)
2NADH
a net of 2 ATP
Cellular Respiration: An Overview
Lesson Overview
Oxidative Respiration
To get the rest of the energy from the
food molecules, the cell uses
oxygen.
Aerobic – requires oxygen.
The energy-releasing pathways
require oxygen, and that is the
reason we need to breathe, to
respire.
Respiration - process that involves
oxygen and breaks down food
molecules to release energy.
rap
Cellular Respiration: An Overview
Lesson Overview
Step 2: Kreb’s Cycle
Takes place in: matrix (innermost
compartment)of mitochondria.
Also called the Citric acid cycle.
Carbon contained in pyruvic acid is
broken down into carbon dioxide.
This CO2 is considered a waste product
and is released from the cell.
Two high energy electron carriers are also
generated by the Krebs cycle:
NADH
FADH2
krebs
Cellular Respiration: An Overview
Lesson Overview
Step 2: Kreb’s Cycle
Citric acid production:
1 carbon from pyruvic acid becomes part of
CO2 & is released.
2 other carbons from pyruvic acid rearrange
to form acetyl-CoA.
Acetyl-CoA combines with a 4C molecule to
form citric acid.
Energy extraction:
Citric acid broken- more CO2 release and
production of electrons.
Electrons transferred to electron carriers
NAD+ and FAD creating NADH and
FADH2.
Cellular Respiration: An Overview
Lesson Overview
Kreb’s Cycle
NADH and FADH2 go on to make huge
amounts of ATP (via electron transport) in
the presence of oxygen, and the CO2 is
eventually released when you exhale.
Cellular Respiration: An Overview
Lesson Overview
Kreb’s Cycle: energy generated
Each glucose = 2 pyruvate
Each glucose= 2 complete turns of
Kreb’s cycle = 2 ATP
Cellular Respiration: An Overview
Lesson Overview
Summary of Kreb’s Cycle
In
Pyruvate
NAD
CoA
Out
CO2 (as waste)
NADH
Acetyl-CoA
Cellular Respiration: An Overview
Lesson Overview
Step 3: ETC
Electron transport occurs in the
intermembrane of the mitochondria.
High energy electrons are passed from
carriers in the Krebs cycle (NADH,
FADH2) to ETC.
ETC uses these high energy electrons
to convert ADP into ATP or energy.
Cellular Respiration: An Overview
Lesson Overview
ETC
As electrons pass down chain, H+ ions are
pumped into inter-mitochondrial space
making a charge gradient.
Gradient provides energy for ATP synthase
to add the P group.
At the end of the chain, an enzyme
combines the electrons with H+ and
oxygen to form water, a by-product of
electron
** Final e- acceptor
is O2
Cellular Respiration: An Overview
Lesson Overview
ETC
O2 is essential for removing low energy e, H+ ions, & wastes of cellular
respiration
Every time a pair of high energy e- move
down ETC, energy is used to move H+
ions across the membrane.
Cellular respiration:
Total ATP=
36
32
ATP
Cellular Respiration: An Overview
Lesson Overview
Total Energy
In the presence of
oxygen, the complete
breakdown of glucose
through cellular
respiration results in
the production of 36
ATP molecules.
This represents about
36 percent of the total
energy of glucose.
The remaining 64
percent is released as
heat.
Cellular Respiration: An Overview
Lesson Overview
Comparing Photosynthesis
and Cellular Respiration
Photosynthesis & cellular
respiration- opposite
processes.
Photosynthesis “deposits”
energy, and cellular
respiration “withdraws”
energy.
The reactants of cellular
respiration are the
products of photosynthesis
and vice versa.
Cellular Respiration: An Overview
Lesson Overview
Comparing Photosynthesis
and Cellular Respiration
The release of energy
by cellular respiration
takes place in plants,
animals, fungi,
protists, and most
bacteria.
Energy capture by
photosynthesis
occurs only in plants,
algae, and some
bacteria
glycolysis jam
Cellular Respiration: An Overview
Lesson Overview
Energy & Exercise
Aerobic cellular respiration produces 36 total
ATP molecules from each glucose molecule
(37% efficient).
Remainder of energy from glucose is released
as heat (body feels warm after exercise).
Eating food: Complex carbs broken down to
simple sugars that are converted to glucose.
Lipids and proteins broken down to molecules
that enter glycolysis or Krebs cycle.
Breathing and respiration:
Remember- final electron acceptor for
electrons produced in respiration is oxygen.
Without oxygen, all ATP synthesis in
mitochondria stops and body tries to make
ATP by glycolysis alone (not sufficient for
most cells).