Nam
Period:
Date:
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HW 2: ResPiration
1) Read page 251, and write out the chemical formula for respiration
2) Why can't we use all the energy at one time from glucose?
3) What do we turn glucose into so we can control the energy from glucose?
Please turn to page 252,look at figure 9-2
4) write down what you
interpret this figure is telling us about respiration
W¡th your knowledge of Photosynthesis and your rough idea of what
respirations is, please compare and contrast the two processes.
5)
)
Stcges of e,:lÍr¡lqr Respirotíon Cellular respiration captures the
energy from food in three main stages-gþoþis, the Krebs cycle,
and the electron transport chain. Although cells can use just about
any food molecule for energ¡ we will concentrate on just one as an
example-the simple sugar glucose. Glucose first enters a chemical
pathway known as glycoþis (gly reHr ih sis). Only a small amount
of energy is captured to produce ATP during this stage. In fact, at
the end of gþoþis, about 90 percent of the chemical energy that
was available in glucose is still unused,locked in chemical bonds of a
molecule called pyruvic (pynoo vik) acid.
How does the cell extract the rest of that energy? First, pyruvic
acid enters the second stage of cellular respiration, the Krebs cycle,
where a little more energy is generated. The bulk of the energy,
however, comes from the final stage of cellular respiration, the electron transport chain. This stage requires reactants from the other
two stages of the process, as shown by dashed lines in Figure 9-2.
How does the electron transport chain extract so much energy from
these reactants? It uses one of the worldt most powerful electron
acceptors-oxygen.
Glycolysis
Glucose
ococco
+
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Energv
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Krebs Cycle
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Energy
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Coz
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Tronsport
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Energy
20
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FIGURE 9-2lhe Stoges of Cellulor
Respirotion There qre three stoges
to cellulqr respirotion : glycolysis,
the Krebs cycle, ond the electron
Õxygen dnd Energy
Oxygen is required at the very end of
the electron transport chain. Any time a cell's demand for energy
increases, its use of oxygen increases, too. As you knoq the word
respiration is often used as a synonym for breøthing. This is why we
have used the term cellular respirationto refer to energy-releasing
pathways within the cell. The double meaning of respiration points
out a crucial connection between cells and organisms: Most of the
energy-releasing pathways within cells require oxFgen, and that is the
reason we need to breathe, to respire.
Pathways of cellular respiration that require oxygen are said to
be aerobic ("in air"). The Krebs cycle and electron transport chain
are both aerobic processes. Even though the Krebs cycle does not
directly require oxFgen, it is classified as an aerobic process because
tronsporf choin. lnlerpret Vlsuals
Which stoge(s) of cellulor respírotion
occvr in lhe mìlochondríon?
it cannot run without the oxygen-requiring electron transport
chain. Glycolysis, however, does not directly require oxygen, nor
does it rely on an oxygen-requiring process to run. Gþolysis is
therefore said to be anaerobic ("without air"). Even though glycolysis is anaerobic, it is considered part of cellular respiration because
MYSTERY
ctuE
its final products are key reactants for the aerobic stages.
Recall that mitochondria are structures in the cell that convert
chemical energy stored in food to usable energy for the cell.
Glycolysis actually occurs in the cytoplasm of a cell, but the Krebs
cycle and electron transport chain, which generate the majority of
ATP during cellular respiration, take place inside the mitochondria.
If oxygen is not present, another anaerobic pathwa¡ known
as fermentation, makes it possible for the cell to keep glycolysis running, generating AIP to power cellular activity. You will learn more
about fermentation later in this chapter.
lf wholes remqin
underwoter for
45 minutes or more,
do you think they
rely primorily on
qerobic or onqerobic
pothwoys?
ì
-; ln Your Notebook
-']
252
Chopter
9
.
Lesson I
Mqke o flowchort fhot shows fhe dìfferent
steps of cellulor respirotion.
r¿¿-l{.il
Yon¡
Are Whot You Eot
Protein (g)
Food
frorn the
Otganisms get energY
confood theY eat, but the energY
Most
greatly'
varies
foods
tained in
22
0
5
0
6
I bor
J
23
t3
12
0
9
8
12
5
14
l0
2% milk, 1 cup
b,r" gru* of Protein or a carbo-
Pototo chips,
hvdrate such as glucose contains
fat'
ráughly 4 Calories. One gram of
how.ver, contains about 9 Calories'
The accomPanYing table shows the
Skinless roosted turkeY,
3 slices
!
"
Duiu Per serving, which
of the foods included in the table
has the most Protein? Which has
the most carbohYdrates? Which
has the most fat?
{
,, ,cr':li
',¡ieW üf {:*lluicrr'
Fot (g)
0
Eggs, 2 whole
approximate comPosition of one
såwing of some common foods'
(g)
Apple, 1 medium
Bocon, 2 slices
Chocolote,
of
foods contain a combination
uroteins, carbohYdrates, and fats'
Corbohydrote
ì5
chiPs
2
I
l1
Approximately how many more Calories
3 slices
are there in 2 slices of bacon than there are in
difference?
of roasted turkey?'rVhy is there a
!.
l,l¿]4r,¡],:¡fi+
3.
Walking at a moderate pace consumes
around 300 Calories per hour' At that rate' how many
minutes would you have to walk to burn the Calories
in one chocolate 6a1?' (Hint: Start by calculating the
number of Calories consumed per minute by walking')
C,.iil,:¡tí,,r1*
$?{ìr,[ì)ìr
r:Tìitir
Ë
Whot ís cellular resPírofíon?
a
If oxygen is available, organisms can obtain energy from foodby
is the
pro.år', called cellular rJspiration. F Cellular respiration
oxygen'
of
ftom food in the presence
pro..u. that release,
"rr.rgy involves dozens of separate reactio,ns,
Although cellular respiratión
simple:
an overall chemical summary of the process is remarkably
ln Symbols:
óO2 + C6H12O 6------>- 6CO2 + óH2O + Energy
ln S/c¡rds:
Oxygen + Glucose
+
Corbon dioxide + Woter + Energy
cellular respiration requires oxygen and a food molecule
such as glucose, and it gives off carbon dioxide, water' and energy' Do
not be ,iirl.d, ho*.u.r]by the simplicity of this equation' If cellular
respiration took place in just orr. ,t.p, all of the energy from glucose
woulcl be releaseã at oncé, and most of it would be lost in the form
As you can see)
of light and heat. Clearl¡ a living cell has to control that energy' It
can isimply start a fire--the celihus to release the explosive chemical
energy in food molecules a little bit at a time. The cell needs to find a
*uy io trap those little bits of energy by using them to make AIP'
ln
Y
r¡.
FIGURE
9-l
A Controlled Releose
Cellulqr respirotion involves o series
of conlrolled reoctions thot slowly
releose lhe energy siored in food' lf
the energy were t
suddenlv, mosl ot
it
the forms of light
is when o morshm
cellulor respirafron? Whøf
fhe onswer?
determine
they hove thqt helps you
Notebook Do plonls undergo
orgone//e(s/
do
Cellulor Respirotion ond Fermentotion 251