Chapter 9

Question 1

Through the activity of enzymes, a cell

systematically

Answer 1

degrades complex organic molecules that are
rich in potential energy to simpler waste products that have
less energy. Some of the energy taken out of chemical storage can be used to do work; the rest is dissipated as heat

Question 2

fermentation

Answer 2

a partial degradation of sugars or other organic fuel that occurs without the
use of oxygen

Question 3

aerobic resp

Answer 3

. However, the most efficient catabolic pathway
is aerobic respiration, in which oxygen is consumed as a
reactant along with the organic fuel (aerobic is from the Greek
aer, air, and bios, life). The cells of most eukaryotic and many
prokaryotic organisms can carry out aerobic respiration

Question 4

what can some prokartyotes do

Answer 4

Some
prokaryotes use substances other than oxygen as reactants in a
similar process that harvests chemical energy without oxygen this process is called anaerobic respiration (

Question 5

Catabolic pathways do not directly move flagella, pump

solutes across membranes, polymerize monomers, or perform other cellular work. Catabolism is linked to work by

Answer 5

y a
chemical drive shaft—ATP (see Concept 8.3). To keep working, the cell must regenerate its supply of ATP from ADP and
~P i
(see Figure 8.12). To understand how cellular respiration
accomplishes this, let’s examine the fundamental chemical
processes known as oxidation and reduction.

Question 6

potential energy and the general principle about electronegativity

Answer 6

The
more electronegative the atom (the stronger its pull on electrons), the more energy is required to take an electron away
from it. An electron loses potential energy when it shifts from
a less electronegative atom toward a more electronegative
one, just as a ball loses potential energy when it rolls downhill. A redox reaction that moves electrons closer to oxygen, such as the burning (oxidation) of methane, therefore
releases chemical energy that can be put to work.

Question 7

In general, organic molecules that have an abundance of

hydrogen are excellent fuels because

Answer 7

e their bonds are a source
of “hilltop” electrons, whose energy may be released as these
electrons “fall” down an energy gradient during their transfer
to oxygen. The summary equation for respiration indicates
that hydrogen is transferred from glucose to oxygen

Question 8

In respiration, the oxidation of glucose transfers electrons to a what? what does this do

Answer 8

energy state, liberating energy that becomes available for ATP synthesis. So,
in general, we see fuels with multiple C—H bonds oxidized
into products with multiple C—O bonds

Question 9

The main energy-yielding foods are? what do they contai in terms of types of bonds

Answer 9

s—carbohydrates and fats—
are reservoirs of electrons associated with hydrogen, often in
the form of C—H bonds

Question 10

NAD- what does it stand for, where is it derived from and why is it a good e carrier. also how does it function as an oxidizing agent during resp

Answer 10

a coenzyme called
nicotinamide adenine dinucleotide, a derivative of the vitamin niacin. This coenzyme is well suited as an electron carrier
because it can cycle easily between its oxidized form, NAD1,
and its reduced form, NADH. As an electron acceptor, NAD+
functions as an oxidizing agent during respiration

Question 11

two things that occur in cell resp (general)

Answer 11

First, in
cellular respiration, the hydrogen that reacts with oxygen is derived from organic molecules rather than H2. Second,
instead of occurring in one explosive reaction, respiration
uses an electron transport chain to break the fall of electrons
to oxygen into several energy-releasing steps

Question 12

what is an etc made of and where in the cell is it

Answer 12

An electron transport chain consists of a number of molecules, mostly proteins, built into the inner membrane of the
mitochondria of eukaryotic cells (and the plasma membrane
of respiring prokaryotes)

Question 13

. Electrons removed from glucose

are shuttled by NADH to the “?” and what happens at the bottom

Answer 13

Electrons removed from glucose
are shuttled by NADH to the “top,” higher-energy end of the
chain. At the “bottom,” lower-energy end, O2 captures these
electrons along with hydrogen nuclei (H+
), forming water.
(Anaerobically respiring prokaryotes have an electron acceptor at the end of the chain that is different from O2.)

Question 14

chemiosmosis- what is it and what does it make up and where is it and what kind of cells does it ocur in. also how much of the atp produced during cell resp is it responsible for

Answer 14

In eukaryotic cells, the inner membrane of the mitochondrion is the site of electron transport and another process
called chemiosmosis, together making up oxidative phosphorylation. (In prokaryotes, these processes take place in the plasma
membrane.) Oxidative phosphorylation accounts for almost
90% of the ATP generated by respiration

Question 15

what is substrate level phosphorylation

Answer 15

substrate-level
phosphorylation (Figure 9.7). This mode of ATP synthesis occurs when an enzyme transfers a phosphate group from a
substrate molecule to ADP, rather than adding an inorganic
phosphate to ADP as in oxidative phosphorylation

Question 16

what happens with atp in the energy investment and payoff phases of glycolysis

Answer 16

During the energy investment phase, the cell
actually spends ATP. This investment is repaid with interest during the energy payoff phase, when ATP is produced
by substrate-level phosphorylation and NAD+
is reduced to
NADH by electrons released from the oxidation of glucose

Question 17

net energy yield from glycolysis

Answer 17

The net energy yield from glycolysis, per glucose molecule,

is 2 ATP plus 2 NADH.

Question 18

what occurs in the oxidation of pyruvate to acetyl coA (three big steps) also what carries it out and what two steps does it link

Answer 18

This step, linking glycolysis
and the citric acid cycle, is carried out by a multienzyme
complex that catalyzes three reactions: 1 Pyruvate’s carboxyl group (—COO-
), already somewhat oxidized and thus carrying
little chemical energy, is now fully oxidized and given off as a
molecule of CO2. This is the first step in which CO2 is released
during respiration. 2 Next, the remaining two-carbon fragment is oxidized and the electrons transferred to NAD+
, storing
energy in the form of NADH. 3 Finally, coenzyme A (CoA),
a sulfur-containing compound derived from a B vitamin,
is attached via its sulfur atom to the two-carbon intermediate,
forming acetyl CoA

Question 19

what does acetyl coa have and what does this allow for

Answer 19

Acetyl CoA has a high potential energy,
which is used to transfer the acetyl group to a molecule in the
citric acid cycle, a reaction that is therefore highly exergonic

Question 20

where does most atp produced by respiration occur and what happens here. what does the process result in as well.

Answer 20

Most of the ATP produced by respiration results later,
from oxidative phosphorylation, when the NADH and
FADH2 produced by the citric acid cycle and earlier steps
relay the electrons extracted from food to the electron transport chain. In the process, they supply the necessary energy
for the phosphorylation of ADP to ATP.

Question 21

. But the metabolic components of respiration we have examined so far, glycolysis and the citric acid
cycle, produce only 4 ATP molecules per glucose molecule,
all by

Answer 21

y substrate-level phosphorylation: 2 net ATP from glycolysis and 2 ATP from the citric acid cycle

Question 22

The folding of the inner membrane

to form cristae increases its and what does this allow for

Answer 22

s surface area, providing space
for thousands of copies of each component of the electron
transport chain in a mitochondrion

Question 23

prosthetic groups- d and locaton

Answer 23

IV. Tightly bound to these
proteins are prosthetic groups, nonprotein components such
as cofactors and coenzymes essential for the catalytic functions of certain enzymes

Question 24

cytochrome and describe the one in hemoglobin

Answer 24

Most of the remaining electron carriers between ubiquinone
and oxygen are proteins called cytochromes. Their prosthetic
group, called a heme group, has an iron atom that accepts and
donates electrons. (The heme group in a cytochrome is similar
to the heme group in hemoglobin, the protein of red blood
cells, except that the iron in hemoglobin carries oxygen, not
electrons.)

Question 25

How does the mitochondrion (or the plasma membrane
in prokaryotes) couple this electron transport and energy
release to ATP synthesis?

Answer 25

The answer is a mechanism called

chemiosmosis.

Question 26

how are the e carriers in the chain grouped?

Answer 26

Most of the electron carriers
of the chain are grouped into four complexes
(I–IV).

Question 27

role of the mobile carriers and what are they called?

Answer 27

Two mobile carriers, ubiquinone (Q) and
cytochrome c (Cyt c), move rapidly, ferrying
electrons between the large complexes. As
the complexes shuttle electrons, they pump
protons from the mitochondrial matrix into
the intermembrane space

Question 28

proton motive force

Answer 28

The H+
gradient that results is referred to
as a proton-motive force, emphasizing the capacity of the
gradient to perform work. The force drives H+
back across the
membrane through the H+
channels provided by ATP synthases

Question 29

what is chemiosmosis in general terms

Answer 29

In general terms, chemiosmosis is an energy-coupling mechanism that uses energy stored in the form of an H+
gradient across
a membrane to drive cellular work

Question 30

In mitochondria, the energy

for gradient formation comes from

Answer 30

exergonic redox reactions
along the electron transport chain, and ATP synthesis is the
work performed

Question 31

. But chemiosmosis also occurs elsewhere and

in other variations describe some such as those in chloroplasts and proks

Answer 31

Chloroplasts use chemiosmosis to generate ATP during photosynthesis; in these organelles, light
(rather than chemical energy) drives both electron flow down
an electron transport chain and the resulting H+
gradient
formation. Prokaryotes, as already mentioned, generate H+
gradients across their plasma membranes. They then tap the
proton-motive force not only to make ATP inside the cell but also to rotate their flagella and to pump nutrients and waste
products across the membrane

Question 32

The three main departments of this metabolic enterprise

are… and what drives ox phosphorylation?

Answer 32

glycolysis, pyruvate oxidation and the citric acid cycle,
and the electron transport chain, which drives oxidative
phosphorylation

Question 33

A third variable that reduces the yield of ATP is the use of what and what does it do

Answer 33

the proton-motive force generated by the redox reactions
of respiration to drive other kinds of work. For example, the
proton-motive force powers the mitochondrion’s uptake of
pyruvate from the cytosol.

Question 34

cell resp is what in its en conversion

Answer 34

efficient

Question 35

The rest of the energy stored in glucose is lost as

Answer 35

heat We 
humans use some of this heat to maintain our relatively high 
body temperature (37°C), and we dissipate the rest through 
sweating and other cooling mechanisms.

Question 36

hibernating animals- what happens with their cell resp

Answer 36

The inner mitochondrial membrane contains a channel
protein called the uncoupling protein that allows protons
to flow back down their concentration gradient without
generating ATP. Activation of these proteins in hibernating
mammals results in ongoing oxidation of stored fuel (fats),
generating heat without any ATP production. In the absence
of such an adaptation, the buildup of ATP would eventually cause cellular respiration to be shut down by regulatory
mechanisms that will be discussed later.

Question 37

We have already mentioned anaerobic respiration, which

takes place in

Answer 37

certain prokaryotic organisms that live in environments without oxygen. These organisms have an electron
transport chain but do not use oxygen as a final electron
acceptor at the end of the chain.

Question 38

(Next-day muscle soreness is more likely

caused by what and why is it not lactate

Answer 38

However, evidence shows
that within an hour, blood carries the excess lactate from
the muscles to the liver, where it is converted back to pyruvate by liver cells. Because oxygen is available, this pyruvate
can then enter the mitochondria in liver cells and complete
cellular respiration. (Next-day muscle soreness is more likely
caused by trauma to small muscle fibers, which leads to
inflammation and pain.)

Question 39

A key difference is the contrasting mechanisms for oxidizing NADH back to NAD+
, which is required to sustain
glycolysis (btwn ferm and aerobic resp)

Answer 39

In fermentation, the final electron acceptor is an
organic molecule such as pyruvate (lactic acid fermentation)
or acetaldehyde (alcohol fermentation). In cellular respiration, by contrast, electrons carried by NADH are transferred
to an electron transport chain, which regenerates the NAD+
required for glycolysis.

Question 40

Some organisms, called obligate anaerobes, carry out

Answer 40

only fermentation or anaerobic respiration. In fact, these

organisms cannot survive in the presence of oxygen

Question 41

facultative anaerobes

Answer 41

Other organisms, including yeasts
and many bacteria, can make enough ATP to survive using
either fermentation or respiration. Such species are called
facultative anaerobes. On the cellular level, our muscle
cells behave as facultative anaerobes.

Question 42

in facultative anaerobes, pyruvate is a fork in the metabolic road- describe what can happen to it under conditions of oxygen and without, respectively

Answer 42

In such cells, pyruvate is
a fork in the metabolic road that leads to two alternative catabolic routes (Figure 9.18). Under aerobic conditions, pyruvate can be converted to acetyl CoA, and oxidation continues
in the citric acid cycle via aerobic respiration. Under anaerobic conditions, lactic acid fermentation occurs: Pyruvate is
diverted from the citric acid cycle, serving instead as an electron acceptor to recycle NAD+
. To make the same amount of
ATP, a facultative anaerobe has to consume sugar at a much
faster rate when fermenting than when respiring.

Question 43

The fact that glycolysis is today the most widespread metabolic pathway among Earth’s organisms suggests what? also what cld b shown by the fact that its in the cytosol

Answer 43

that it evolved very early in the history of life. The cytosolic
location of glycolysis also implies great antiquity; the pathway
does not require any of the membrane-enclosed organelles
of the eukaryotic cell, which evolved approximately 1 billion
years after the first prokaryotic cell.

Question 44

Glycolysis is a metabolic

heirloom from early cells that

Answer 44

ontinues to function in fermentation and as the first stage in the breakdown of organic
molecules by respiration.

Question 45

beta oxidation

Answer 45

Most of the energy of a fat is stored in the fatty acids. A metabolic sequence called beta oxidation breaks the fatty acids
down to two-carbon fragments, which enter the citric acid
cycle as acetyl CoA. NADH and FADH2 are also generated during beta oxidation; they can enter the electron transport
chain, leading to further ATP production.

Question 46

In addition, glycolysis and the citric acid cycle function as

Answer 46

metabolic interchanges that enable our cells to convert some
kinds of molecules to others as we need them.

Question 47

an example is (acc to card 46)

Answer 47

an intermediate compound generated during glycolysis,
dihydroxyacetone phosphate (see Figure 9.9, step 5), can
be converted to one of the major precursors of fats. If we eat
more food than we need, we store fat even if our diet is fatfree. Metabolism is remarkably versatile and adaptable

Question 48

. The energy that

keeps us alive is

Answer 48

released, not produced, by cellular respiration.