Download Chapter 9 Cellular respiration - District 196 e

Chemical energy and food
 1 g of glucose (C6H12O6) releases 3811 calories
of heat when burned in the presence of
oxygen
 FYI: 1 calorie is the amount of heat needed to
raise the temp of 1g of H20 1C
 FYI: the Calories listed on food packages are
actually kilocalories (1000 calories)
 Glycolysis is the gradual release of energy in
the presence or absence of oxygen
Cellular respiration
 Cellular respiration is the process that releases
energy by breaking down food molecules in the
presence of oxygen
Not so simple
 Cellular respiration must be regulated, otherwise
all of the energy is released at once and that
would be bad news
 Remember the sucrose/KClO3 demonstration ?
 3 steps involved in cellular respiration
The 3 steps of cellular respiration
Step 1:Glycolysis the process in which 1 molecule
of glucose is broken in half, producing 2 molecules
of pyruvic acid, which is a 3-carbon compound
Step 2:ATP is utilized to get this process started
(2 ATP molecules are used, 4 are produced; net
gain of 2 ATP)
Step 3:NADH is used to pass energy on to other
molecules
LEO the lion goes GER
 When electrons are gained, reduction occurs
(GER)
 Gained electrons-> reduction (what is reduced is
the positive charge)
 When electrons are lost, oxidation occurs (LEO)
 Lost electrons->oxidation
Fermentation
 Fermentation is the release of energy from food
molecules without the presence of oxygen
 During fermentation cells convert NADH to NAD+
by passing high energy electrons back to pyruvic
acid
 Fermentation is an anaerobic activity (does not
require oxygen)
Alcoholic fermentation
 Yeasts and some other microorganisms use
alcoholic fermentation, forming ethyl alcohol and
CO2 as wastes
 Pyruvic acid + NADH-- alcohol + CO2 + NAD+
 Alcoholic fermentation produces CO2, which can
cause bread to rise
Lactic Acid Fermentation
 Pyruvic Acid can be converted into lactic acid
 This can cause discomfort in muscles after
vigorous, unusual exercise
 Pyruvic acid + NADH -lactic acid + NAD+
The Krebs cycle and electron
transport
 Glycolysis releases only about 10% of the energy
in glucose, leaving 90%.
 Cells use oxygen to accept electrons from pyruvic
acid in an aerobic process
 When oxygen is crucial for a process, that
process is aerobic (oxygen required)
The krebs cycle
 The Krebs cycle works to break down pyruvic acid
into CO2 in a series of energy extracting
reactions.
 The Krebs cycle is also called the citric acid cycle
because citric acid is formed in the first of the
series of reactions
 http://highered.mcgraw-
hill.com/sites/0072507470/student_view0/chapter2
5/animation__how_the_krebs_cycle_works__quiz_1_.
html
Krebs cycle (A)
 Krebs cycle begins when pyruvic acid produced
during glycolysis enters the mitochondrion.
 1 Carbon atom from pyruvic acid becomes part
of a molecule of CO2
 2 of the 3 carbon atoms become part of
coenzyme A for form acetyl-CoA.
 Acetyl-CoA then adds the 2-carbon acetyl
group to a 4-carbon molecule, producing a 6carbon molecule (citric acid)
Krebs cycle (B)
 As the cycle continues, citric acid is broken down
into a 4-carbon molecule, more CO2 is released,
and electrons are transferred to energy carriers.
 For each step in the Krebs cycle, a molecule of
ATP is produced
 Krebs cycle products include CO2 & ATP
Krebs cycle diagram
 Why is the Krebs cycle also knows as the citric
acid cycle?
Electron transport (A)
 High energy electrons from NADH and FADH2
are passed into and along the electron transport
chain.
 At the end of the electron transport chain is an
enzyme that combines electrons from the
electron chain with H and O ions to form water.
 Why do we need oxygen?
 Because Oxygen is the final acceptor of
electrons in the electron transport chain, that’s
why!
Electron Transport (B)
 When 2 high energy electrons are transported
down the electron transport chain, their energy is
used to transport H+ ions across the membrane of
the mitochonria.
 This results in the 2 sides of the membrane being
of opposite charges
Electron Transport (C)
 The movement of materials across the membrane
of the mitochondria (H+, ATP synthases) allow
for ADP to be transformed into ATP
 The transformation of ADP into ATP happens
because a phosphate is attached to the ADP, thus
it becomes ATP
 The energy to do this is provided by ATP synthase
(a protein)
The Totals
 Glycolysis produces 2 ATP per glucose molecule
 When oxygen is involved, (Krebs Cycle & electron
transport) results in 36 ATP per glucose molecules
 That is 18 times more energy from glucose when
oxygen is present
 About 38% of the energy in glucose is made by the
cell into ATP.
 The remaining 62% is lost (heat is the main place it’s
lost). That is why you feel warm after exercise.
Energy and Exercise
 Quick energy is supplied by ATP in cells.
 After a few seconds that is used up, then cells are producing
ATP by lactic acid fermentation. (about 90 seconds worth)
 After about 90 seconds, cells must produce ATP by cellular
respiration.
 Cellular respiration produces ATP more slowly than
fermentation, so a runner, for example, has to pace themselves
to insure not running out of energy.
 Cellular respiration is good for a 15-20 minutes, so then the body
relies on other sources for energy, such as stored fats .
Photosynthesis and Cellular
Respiration
 Photosynthesis “deposits” energy into cells.
 Cellular respiration “withdraws” energy from cells.
 Look at the chart on Pg. 232 in the Biology Text.
 Explain how Photosynthesis and Cellular respiration
are similar.
 Explain how Photosynthesis and Cellular respiration
are different. ( Lots of these!)