Chapter 9 Flashcards
Through the activity of enzymes, a cell
systematically
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
fermentation
a partial degradation of sugars or other organic fuel that occurs without the
use of oxygen
aerobic resp
. 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
what can some prokartyotes do
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 (
Catabolic pathways do not directly move flagella, pump
solutes across membranes, polymerize monomers, or perform other cellular work. Catabolism is linked to work by
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.
potential energy and the general principle about electronegativity
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.
In general, organic molecules that have an abundance of
hydrogen are excellent fuels because
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
In respiration, the oxidation of glucose transfers electrons to a what? what does this do
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
The main energy-yielding foods are? what do they contai in terms of types of bonds
s—carbohydrates and fats—
are reservoirs of electrons associated with hydrogen, often in
the form of C—H bonds
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
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
two things that occur in cell resp (general)
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
what is an etc made of and where in the cell is it
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)
. Electrons removed from glucose
are shuttled by NADH to the “?” and what happens at the bottom
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.)
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
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
what is substrate level phosphorylation
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
what happens with atp in the energy investment and payoff phases of glycolysis
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
net energy yield from glycolysis
The net energy yield from glycolysis, per glucose molecule,
is 2 ATP plus 2 NADH.
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
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
what does acetyl coa have and what does this allow for
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
where does most atp produced by respiration occur and what happens here. what does the process result in as well.
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.
. 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
y substrate-level phosphorylation: 2 net ATP from glycolysis and 2 ATP from the citric acid cycle
The folding of the inner membrane
to form cristae increases its and what does this allow for
s surface area, providing space
for thousands of copies of each component of the electron
transport chain in a mitochondrion
prosthetic groups- d and locaton
IV. Tightly bound to these
proteins are prosthetic groups, nonprotein components such
as cofactors and coenzymes essential for the catalytic functions of certain enzymes
cytochrome and describe the one in hemoglobin
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.)
