Chapter 9
CELLULAR RESPIRATION
INTRODUCTION VIDEOES
Cellular respiration
 Anaerobic respiration
 Importance of oxygen

CHEMICAL PATHWAYS



The foods we, and other
animals eat, provide the
raw materials needed for
cells to synthesize new
molecules.
These molecules will
serve as the building
blocks needed for growth
and development of new
cells.
Foods also provide energy
for the cells in living
things.
CHEMICAL ENERGY AND FOODS


An essential roll of
foods is to provide the
living thing with the
energy to carry out the
daily activities of life.
Foods provide the
chemical energy needed
by the cells of living
things.
THE ENERGY IN FOODS


The energy in foods is
measured in calories.
A calorie is the amount of
energy needed to raise
the temperature of 1
gram of water 1 degree
Celsius.
CALORIES (KCAL)

The Calorie (capital “C”)
that is used on food
labels is a kilocalorie, or
1000 calories.
CELLULAR RESPIRATION

Cellular respiration is
the process that
releases energy by
breaking down glucose
and other food
molecules in the
presences of oxygen.
STAGES OF CELLULAR RESPIRATION



Glycolysis
Krebs cycle
Electron transport
phosphorylation (occurs
in electron transport
chain)
CELLULAR RESPIRATION EQUATION

6O2
Oxygen
+
+
C6H12O6
glucose
-------
produces
6CO2
+
H2 O
+
carbon
+
water
+
dioxide

Cellular respiration
 Requires
food and oxygen
 Produces carbon dioxide and energy
energy
energy
STAGES OF CELLULAR RESPIRATION
Glycolysis
 Krebs cycle
 Electron transport chain

GLYCOLYSIS

Glycolysis is the process
in which one molecule
of glucose is broken in
half, producing two
molecules of pyruvic
acid, a 3-carbon
compound.
GLYCOLYSIS


Requires 2 molecules of
ATP
Produces:



4 ATP for a net gain of 2
ATP
NADH
Pyruvic acid




Takes place in the
cytoplasm.
Very fast process that
produces thousands of ATP
in a few milliseconds.
Does not require oxygen.
Problem – the available
NAD+ molecules become
filled with ATP and the cell
cannot keep glycolysis
going.
FERMENTATION
Process of producing ATP in the absence of
oxygen.
 cells convert NADH to NAD+ by passing highenergy electrons back to pyruvic acid.
 Process is said to be anaerobic, “not in air.”
 Two types of fermentation:

 Alcohol
fermentation
 Lactic acid fermentation
ALCOHOL FERMENTATION



Yeasts and a few other
microorganisms use
alcoholic fermentation,
forming ethyl alcohol and
carbon dioxide as
wastes.
Produces carbon dioxide
as well as alcohol.
Alcoholic fermentation
causes bread dough to
rise.
LACTIC ACID FERMENTATION


the pyruvic acid that
accumulates as a result
of glycolysis can be
converted to lactic acid.
This process
regenerates NAD+ so
that glycolysis can
continue.
LACTIC ACID FERMENTATION

Vigorous exercise can
cause the accumulation
of lactic acid in large
muscles, leading to
muscle soreness.
LACTIC ACID FERMENTATION


Unicellular organisms
also produce lactic acid
as a waste product
during fermentation.
Prokaryotes are used in
the production of a wide
variety of foods and
beverages, such as
cheese, yogurt,
buttermilk, and sour
cream.
THE KREBS CYCLE


In the presence of
oxygen, pyruvic acid
produced in glycolysis
passes to the second
stage of cellular
respiration, the Krebs
cycle.
Named after Hanes
Krebs.
CITRIC ACID CYCLE


Pyruvic acid is broken
down into carbon dioxide
in a series of energyextracting reactions.
Citric acid is the first
compound formed in this
series of reactions,
KREBS CYCLE
The term cellular respiration refers to energyreleasing pathways within the cell
 Oxygen is required for the final steps of cellular
respiration. Because the pathways of cellular
respiration require oxygen, they are said to be
aerobic (with oxygen).
 Takes place inside the mitochondria.

KREBS CYCLE



Begins when pyruvic acid
produced by glycolysis
enters the mitochondrion.
The other two carbon
atoms from pyruvic acid
are joined to a compound
called coenzyme A to form
acetyl-CoA.
Acetyl-CoA adds the 2carbon acetyl group to a
4-carbon molecule,
producing a 6-carbon
molecule called citric
acid.
KREBS CYCLE


Citric acid (6-carbon
molecule) is broken
down into a 5-carbon
compound.
A second carbon is
removed forming a 4carbon compound.

With each change carbon
dioxide is released, and
electrons are transferred
to energy carriers (NAD+
and FAD).
KREBS CYCLE



With each cycle a
molecule similar to ADP
is turned into ATP.
CO2 is removed from the
body as the animal
exhales.
The ATP produced
directly in the Krebs
cycle can be used for
cellular activities.
KREBS CYCLE


The 4-carbon molecule is
ready to accept another
2-carbon acetyle group,
starting the cycle over
again.
The cell will use the highenergy electrons in NADH
to generate large
amounts of ATP in the
electron transport chain.
ELECTRON TRANSPORT CHAIN


The electron transport
chain uses the highenergy electrons from
the Krebs cycle to
convert ADP into ATP.
The beauty of this
system is the way in
which it couples the
movement of highenergy electrons with
the production of ATP.
ETC



High-energy electrons
from NADH and FADH2
are passed along the
electron transport chain.
At the end of the electron
transport chain is an
enzyme that combines
these electrons with
hydrogen ions and oxygen
to form water.
Oxygen serves as the final
electron acceptor of the
electron transport chain.
ETC



Every time 2 high-energy
electrons transport down the
electron transport chain,
their energy is used to
transport hydrogen ions (H+)
across the membrane.
During electron transport, H+
ions build up in the
intermembrane space,
making it positively charged.
The other side of the
membrane, from which those
H+ ions have been taken, is
now negatively charged
ETC



The inner membranes of
the mitochondria contain
protein spheres called ATP
synthases.
As H+ ions escape through
channels into these
proteins, the ATP
synthases spin.
Each time it rotates, the
enzyme grabs a lowenergy ADP and attaches
a phosphate, forming
high-energy ATP
TOTAL ATP


The Krebs cycle and
electron transport
enable the cell to
produce 34 more ATP
molecules per glucose
molecule, in addition to
the 2 ATP molecules
obtained from
glycolysis.
Total ATP - 36
ENERGY AND EXERCISE



Begin the race using ATP
stored in the muscle cells.
After 10 sec. ATP produced
by lactic acid fermentation.
After 90 sec. ATP is
produce by cellular
respiration, using O2.

Fuel source


15 – 20 min. – CHO
Longer 20 min – fats
PHOTOSYNTHESIS VS. CELLULAR RESPIRATION






Photosynthesis is the process that “deposits” energy.
Cellular respiration is the process that “withdraws”
energy.
Photosynthesis removes carbon dioxide from the
atmosphere, and cellular respiration puts it back.
Photosynthesis releases oxygen into the atmosphere,
and cellular respiration uses that oxygen to release
energy from food.
The release of energy by cellular respiration takes place
in all eukaryotes and some prokaryotes.
Energy capture by photosynthesis, however, occurs only
in plants, algae, and some bacteria.