Transcript Ch. 9 - Respiration

Cellular Respiration
Essential knowledge 2.A.1 (c) and 2.A.2
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The function of cellular
respiration is the take the
glucose made during
photosynthesis and use the
energy found in that molecule
to make ATP, which provides
energy for cells to do work.
(ATP is the main “currency”
we need for energy)
Glucose is a more stable form
of energy storage than ATP, so
we need to take that glucose
and break it up when we’re
ready to use it
It’s an exergonic reaction,
using catabolic pathways
The equation for respiration is
the opposite of
photosynthesis.
WRITE THE EQUATION!
 Because respiration takes place
(mostly) in the mitochondria, you
will need to be familiar with its
parts
 The mitochondria is made of
compartments that carry out
specialized functions
 The compartments include: the
outer membrane, the
intermembrane space, the inner
membrane, and the cristae (which
are little internal compartments
formed by the inner memrane)
and matrix (a viscous space with
the DNA and ribosomes)
• 1. Glycolysis (breaks down
glucose into 2 molecules of
pyruvate)
• 2. Kreb Cycle (completes the
breakdown of pyruvate)
• 3. Electron Transport Chain
(this is where most of the ATP
is generated)
• These steps are happening all
at the same time
• *you do not need to memorize the
steps in glycolysis and the Krebs
cycle, or the structures of the
molecules and names of the
enzymes involved ; you also don’t
need the names of specific
electron carries in the ETC (just
understand what is happening in
each step)
 Takes place right outside of
the mitochondria (in the
cytoplasm)
 You take glucose (a 6 carbon
molecule) and break it down
into 2 molecules of pyruvate
(a 3 carbon molecule)
 It generates 2 ATP and a
chemical called NADH (we
transferred high energy
electrons to it)
 *you now have 2 ATP’s and
2 molecules of NADH
• The pyruvate diffuses into the
matrix of the mitochondria and it
enters the pyruvate dehydrogenase
complex
• This takes the 3 carbon molecule
of pyruvate and transforms it into
acetyl CoA (coenzyme A) which is
a 2 carbon molecule (you have
gone from a 3-carbon molecule to
a 2-carbon molecule) – this is the
bridge between glycolysis and the
citric acid/Krebs cycle
• This gives off Carbon in the form
of CO2 – so every time you exhale,
1/3 of that CO2 has come from the
pyruvate dehyrogenase complex
• It now enters the Kreb Cycle (also
called the Citric Acid Cycle)
• Takes place in the mitochondrial
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matrix
The Kreb Cycle breaks down the 2Carbon acetyl CoA and releases
more CO2, 2 ATP, and adds more
energy to NADH and FADH
(which have high energy
electrons)
At this point, all of the energy that
we started with in glucose has
been essentially transferred to
NADH and FADH
You have now released 2 more ATP
(4 total) and created a lot of
NADH AND FADH (6 NADH, and
2 FADH2)
The high energy electrons found
in NADH and it’s friend FADH are
then carried to the electron
transport chain (ETC)
Takes place in the cristae
The electrons from NADH and
FADH are moved through the ETC
(which is basically a series of
protein pumps)
• This is done with electrons
transporting hydrogen molecules
through the membrane and into
the inner membrane space.
• By doing this there is a gradient
created with a high concentration
of hydrogen on the outside and a
low concentration inside.
• Naturally, the hydrogen molecules
will want to diffuse to create
equilibrium. But the only way that
they can get back in is through a
protein pump called the ATP
synthase.
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As every proton moves
through it, ATP is
generated (every time a
proton goes through, it
attaches a phosphate onto
ADP to make ATP) – about
32-34 ATP are generated in
this process
 The electrons are then
added to the protons and
the oxygen that we breathe
in to form our waste/biproduct – H2O (oxygen is
the terminal receptor for
the electrons, so it is
reduced)
• What happens if there is no O2 or
mitochondria present?
Fermentation occurs
• Glycolysis can produce ATP with
or without O2 (in aerobic or
anaerobic conditions) – but the
Krebs cycle and ETC are aerobic
(need oxygen)
• In the absence of O2, glycolysis
couples with fermentation to
produce ATP (2 types of
fermentation: alcohol and lactic
acid)
• You can take glucose during
glycolysis and break it into 2
pyruvates, but when you add the
electrons to NAD and transfer
them to NADH, the NAD runs out
and glycolysis shuts down
Glucose
CYTOSOL
Pyruvate
No O2 present
Fermentation
O2 present
Cellular respiration
MITOCHONDRION
Ethanol
or
lactate
Acetyl CoA
Citric
acid
cycle
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Lactic acid fermentation – takes place in
your muscles (like when you’ve been
sprinting really fast or holding your
breath for a long time)
In lactic acid fermentation, pyruvate is
reduced to NADH, forming lactate as an
end product, with no release of CO2
Your cells can take the pyruvate and
break it down into lactate (or lactic acid)
which will accept the electrons from
NADH to form more NAD+ (so you’re
just recycling) and the process can occur
over and over again to create 2 ATP each
time
If you’ve ever sprinting, you do both
aerobic and anarobic respiration; this
builds up lactate (lactic acid) in your
muscles.
Lactate is like a toxin that needs oxygen
to break it down (that’s why you’re really
out of breath when you run – you’re
trying to take in a lot of O2)
 Alcohol fermentation
 In alcohol fermentation, pyruvate is
converted to ethanol in two steps,
with the first releasing CO2
 Alcohol fermentation by yeast is
used in brewing, winemaking, and
baking
 Again, pyruvate is broken down only
this time instead of lactate, it
becomes ethyl alcohol
 The same thing occurs, with
electrons being donated to form
NAD+ , except with 1 difference
 Lactate was a 3 carbon molecule, but
this time you make CO2 (that’s why
yeast forms bubbles)
 Oxidation – when
electrons are lost
 Reduction – when
electrons are gained (called
reduction because you lose
a positive charge)
 They occur together, which
is why they are called
RedOx reactions
 (in respiration, glucose is
oxidized and the electrons
and hydrogen atoms are
added to oxygen, which is
reduced)
 Think of Oil Rig:
 Oil – oxidation is a loss
 Rig – reduction is a gain
 Draw and label a diagram of the process of cellular
respiration (no specific names of enzymes or proteins
are needed, but you will need to label all reactants and
products for each step)