CH 9
what does the citric acid cycle generate per term?
1 ATP, 3 NADH, 1 FADH2
in the energy pay off phase, how many NADH molecules for how many pyruvates?
1 NADH molecule for each pyruvate
what are the initial reactants in glycolysis?
1 glucose molecule
two steps of ethanol conversion from pyruvate:
1. carbon dioxide release from pyruvate to make acetaldehyde 2. acetaldehyde recused by NADH to ethanol
3 things that catabolic pathways do not do
1. directly move flagella 2. pump solutes across membranes 3. polymerize polymers 4. perform cellular work
reasons why exact ATP number is not known?
1. it requires active transport to move pyruvate from the cytosol to the mitochondrial space. 2. phosphorylation and redox reactions are not directly coupled to each other 3. use of proton motive force generated by redox reactions of respiration to drive other kinds of work
3 reactions that multi enzyme complex catalyzes
1. pyruvates carboxyl group, which is already fully oxidized and has little chemical energy, is given off as a molecule as CO2 2. the remaining two carbon fragment is oxidized, forming acetate.Electrons are also transferred to NAD+ to produce NADH, which can be fed into the electron transport chain. 3. finally, coenzyme A is attached via its sulfur atom to the acetate forming acetyl CoA, which has high potential energy (and can be exergonic)
how much ATP is produced by glycolysis?
2
how much ATP is produced by the citric acid cycle?
2
how much ATP per glucose molecule in fermentation?
2
in the energy investment phase,
2 ATP are used (step 1) and 1 more are used in step 3
during the energy investment phase, ____ ___ is used to break down sugar to _____ and ____
2 ATP, 2 ADP and 2 P
what are the final products of citric acid cycle?
2 ATP, 6 NADH, and 2 FADH's, 4CO2
How many Co2 molecules are produced in ONE cycle of the citric acid cycle? How many cycles are required to complete the catabolism of a molecule of glucose?
2 Co2 molecules are produced per 1 cycle of citric acid cycle, 2 cycles of the citric acid cycle must occur for the complete catabolism of glucose, thus giving a net yield of 4 Co2.
2 NAD + 4e + 4H yields
2 NADH + 2H
NET glucose -----> _____ 4 ATP formed - 2ATP used = _____ 2 NAD+ +4- + 4H ----> ______
2 pyruvate + 2H2O 2ATP 2 NADH + 2H
describe how the energy stored in reduced coenzymes is used to create a proton gradient (proton motive force) and ultimately store ATP by chemiosmosis?
As electrons are transferred ( by electron carriers such as NADH and FADH2) and cause H+ ions to be taken up and released into the surrounding solution, in Euks, the electron carriers are spatially arranged in the inner mitochondrial membrane in a such a way that H+ is accepted from the mitochondrial matrix and deposited in the intermembrane space, the H+ gradient that results is Proton Motor Force.
How does fermentation generate ATP?
Fermentation uses substrate-level phosphorylation instead of an electron transport chain
the energy stored in a ____ gradient across a membrane ________ _______reactions of the _____ to ATP synthesis
H, couples to the redox reactions, ETC
in the energy pay off phase, the pay off is
In this case the energy pay off is 2 ATP in step 7 and 2 ATP in step 10.
What distinguishes a cyclic pathway from a linear one?
Linear you start with one product and end with another different product Cyclic you start with one product and end with the same product, starting the cycle over again.
_____ use _____ to generate ATP during _____; what is used to to drive electron flow down the gradient and the resulting H gradient?
chloroplasats, chemiosmosis, photosynthesis; light
After pyruvate is oxidized, the ____ completes the energy yielding oxidation of organic molecule
citric acid cycle
In glycolysis, what is meant by "energy investing"
energy investing mean that the process must use energy before it can produce ATP.
Where can you find ATP synthase in prokaryotic and eukaryotic organisms?
eu: inner membrane of mitochondria pro: plasma membrane
ATP synthase uses the _________ to drive phosphorylation of ATP
exergonic flow of H
fats are digested to ____ and _____
glycerol and fatty acids
examples of linear and cyclic pathways
glycolysis is linear, krebs cycle is cyclic
what is the first step of cellular respiration and what happens within it?
glycolysis: breaks down glucose into two molecules of pyruvate
ETC is also called
respiratory transport chain
Cytochromes contain
similar to the heme groups in hemoglobin that are used to carry oxygen. Here they carry electrons
How many Co2 molecules are produced from the complete oxidation of glucose?
since glucose is a 6 carbon structure 6 Co2 are produced.
In cellular respiration, Each NADH (the reduced form of NAD+) represents _____ energy that is tapped to synthesize _____
stored, ATP
A smaller amount of ATP is formed in glycolysis and the citric acid cycle by
substrate level phosphorylation
what happens during glycolysis?
sugar splitting, 3 carbon sugars are split
what is the overall function of cellular respiration?
to harvest the energy of glucose from ATP synthesis
how is NAD+ regenerated in lactic acid fermentation?
, lactate is produced to regenerate NAD+.
comparing fermentation with anaerobic and aerobic respiration
-all use glycolysis, -NAD+ is the oxidizing agent that accepts electrons during glycolysis -different final electron acceptors
what are the initial reactants in the citric acid cycle?
2 acetyl CoA maybe 2 pyruvate
account for 32 ATP
2 from glycolysis (substrate level phos), 2 from the citric acid cycle (substrate level phos), 30 from ox phos.
what are the final products in glycolysis?
2 pyruvate, 2 NET ATP, 2 NADH,
In the energy payoff phase ______ ATP molecules are produced by (what mechanism) for ( what molecule) produced
2, substrate level phos, for EACH pyruvate produced
maximum yield of ATP per glucose?
30 or 32
what is Phosphofructokinase activated by?
AMP, precursor to ATP
what is the enzyme that makes ADP from organic phosphate?
ATP synthase
what is the smallest molecular rotary motor known to nature?
ATP synthase
consumes organic molecules and O2 and yields ATP
Aerobic respiration
Why is the cycle Hans Krebs discovered called the citric acid cycle?
Because citric acid is the 6 carbon molecule that starts the Krebs cycle
C6H12O6 + 6O2 ----> 6Co2 + 6 H2O
C6H12O2 and 6CO2 becomes oxidized 6O2 and 6H20 becomes reduced
delivers to NAD+ both electrons, but only ONE of the protons. The other proton is lost into the surrounding solution
Dehydrogenase
what is the distinction between anaerobic respiration and fermentation?
ETC is used in anaerobic respiration but not in fermentation
what is meant by energy harvesting?
Energy harvesting means that energy is being produced, not used.
what are the initial reactants in pyruvate oxidation?
In pyruvate oxidation the reactants are 2 pyruvate + 2 NAD + 2 CoA
why is it a cycle?
It is a cycle because we start with oxaloacetate at the start of the cycle, and eventually we regenerate it, so that the entire process can start again.
n which decade did Krebs work out the cycle? When did he receive the Nobel Prize in Physiology or Medicine?
Krebs worked out the citric acid cycle in the 1930's, and won the Nobel Prize in 1953
Explain how the coenzyme NAD+ is chemically altered when it is reduced, and when it is re-oxidized (i.e. what exactly is added and removed?).
NAD is chemically altered when it is reduced by virtue of it gaining 2 electrons thus turning it into NADH. This occurs on the nicotinamide group of the molecule.
Which REACTANT of glycolysis must be recycled in order to keep glycolysis running?
NAD+ must be regenerated or else the process will halt. In aerobic respiration, NAD+ is recycled from NADH by the transfer of electrons to the ETC
from glycolysis to oxidative phosphorylation, electrons are carried by
NADH
from citric acid cycle to oxidative phosphorylation, electrons are carried by
NADH and FADH2
which two molecules account for most of the energy extracted from each molecule?
NADH and FADH2
List 3 molecules produced by the cycle that store valuable chemical energy.
NADH, FADH, and GTP store valuable chemical energy
electrons are transported from _____ to the ETC
NADH, FADH2
Na + Cl -------> Na+ + Cl- which is being oxidized? which is being reduced? which is the oxidizing agent? which is reducing agent? which is electron donor? which is electron acceptor?
Na is being oxidized. Cl is being reduced. Na is reducing agent. Cl is oxidizing agent. Na is electron donor. Cl is electron acceptor.
what is the coenzyme for the dehydrogenase enzyme?
Nad+
carry out fermentation or anaerobic respiration and cannot survive in the presence of O2
Obligate anaerobes
what is the key regulator of respiration? how?
Phosphofructokinase. ATP inhibits this enzyme,preventing it from carrying out its function and setting glycolysis on its course.
How are the chain molecules localized to facilitate their functioning?
The chain molecules are localized within the mitochondria, but the enzymes that control the ETC are assembled in a multienzyme complex that will facilitate a sequence of reactions.
meaning that they can survive using either fermentation or cellular respiration
Yeast and many bacteria are facultative anaerobes,
What are coenzymes.
a coenzyme is an organic molecule that serves as a cofactor; a nonprotein compound that is necessary for the functioning of an enzyme.
after pyruvate oxidation,
acetyl CoA is further oxidized into carbon dioxide
how is ATP produced in ox phos?
addition od inorganic phosphate group to substrate molecule
cells of most eukaryotic and prokaryotic cells can carry out
aerobic respiration
is similar to aerobic respiration but consumes compounds other than O2
anaerobic respiration
during the energy payoff phase, what is being used and what is produced?
being used: 4 ADP and 4P produced: 4 ATP
fatty acids are broken down by ______ and yield ____
beta oxidation, acetyl CoA
how is catabolism linked to work?
by a chemical drive shaft, ATP
how is the pyruvate to acetyl CoA oxidation carried out?
by a multi enzyme complex that catalyzes three reaction
Aside from glucose, what other metabolic fuels can be used to make ATP?
carbs, fats, proteins
Beyond providing energy as ATP, what do catabolic pathways provide to anabolic pathways that enables them to build biomolecules?
catabolic pathways break down the energy source to use it in anabolism-
c6h12o6+ 6O2 --> 6CO2 + 6H2O + Energy (ATP and heat)
cellular respiration
includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration only.
cellular respiration
what couples the ETC to ATP synthesis
chemiosmosis
what completes the breakdown of glucose to CO2?
citric acid cycle
name the processes that require oxygen
citric acid cycle and ox phase
after electrons are transported, the electron transport chains do what?
convert the chemical energy into ATP through chemiosmosis
how is NAD+ regenerated in alcohol fermentation?
converts pyruvate to ethanol in order to regenerate NAD+.
Electrons are passed through a number of proteins including
cytochromes
where is the breakdown of glucose to CO2 completed in prokaryotes?
cytosol (plasma membrane)
electrons ____ in free energy as they _____ the chain
drop, go down
what happens after glycolysis?
each pyruvate molecule enters the mitochondrion and is oxidized into Acetyl CoA
what two processes make up oxidative phosphorylation?
electron transport and chemiosmosis
potential energy is lost when
electrons are transferred from less electronegative atom to more electronegative atom
what are the final products in pyruvate oxidation
end products are 2 acetyl CoA, 2 NADH, 2 H and 2 Co2.
in mitochondria, the energy from the gradient formation comes from _____
exergonic redox reactions
under the conditions of cellular respiration, ATP synthase uses energy of an ______ to power _____
existing ion gradient, power ATP synthesis
in anaerobic respiration, O2 is used as final electron acceptor
false
what is the most common mechanism for control of cell resp?
feedback inhibition
a partial degradation of sugars that occurs without O2
fermentation
In _____, _______ is used to regenerate the NAD+.
fermentation,pyruvate
prokaryotes generate H+ from____, then do what to make ATP inside the cell and rotate flagella, and pump nutrients, wastes?
generate H gradients across their membranes, then tap into it
energy flow sequence
glucose --> NADH --> ETc--> proton motive force --> ATP
How many steps do the catabolic pathways glycolysis, pyruvate oxidation, and the citric acid cycle have?
glycolysis has 10 steps, pyruvate oxidation has 3 steps, and citric acid cycle has 8 steps.
In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes. explain.
if o2 is present, pyruvate can be converted to acetyl CoA and continue through citric acid cycle if O2 is not present, fermentation occurs and ethanol, lactate or other products are produced
in the citric acid cycle, what is being oxidized and what is reduced?
in the citric acid cycle, acetyl CoA gets oxidized and NADH/FADH gets reduced.
inputs and outputs of citric acid cycle
input: 2 pyruvate, 2 acetyl CoA output:2 ATP 8 NADH 6CO2 2FADH
inputs and outputs of glycolysis
input: glucose outputs: 2 pyruvate, 2 ATP, 2 NADh
How does it indirectly make ATP?
it feeds into chemiosmosis, whereATP is actually made
What is the Electron Transport Chair, and in which specific membrane is it found?
it is a collection of molecules embedded in the matrix of the mitochondrion in eukaryotic cells, and the plasma membrane of prokaryotic cells
how does aerobic glucose catabolism compare with processes like the combustion of methane or wood? How is it different
just as in the combustion of methane, in respiration; the fuel (glucose ) is oxidized and oxygen is reduced. The electrons lose potential energy along the way and energy is released. oxidation of glucose transfers electrons to lower energy state, liberating the energy that becomes available for ATP Synthesis.
where does the citric acid cycle occur in eukaryotes?
mito matrix
in mitochondria , the energy for gradient formation comes from ______ and _____ is the work performed
mitochondria, exergonic redox reactions, ATP synthesis
what important difference do electron transport chains make?
most of the energy is captured and used to perform work rather than lost as heat because the reaction is more controlled, and stepwise.
does ETC directly make ATP
no
how much ATP from pyruvate oxidation?
none
what does a substrate molecule refer to?
organic molecule generated as an intermediate during the catabolism of glucose
Chemical reactions that transfer electrons between reactants are called
oxidation-reduction reactions, or redox reactions
the energy released at each step of the chain can be stored in the mitochondrion and can be used to make ATP from ADP. This is powered by redox reactions
oxidative phosphorylation
what is the process that drives most of the ATP?
oxidative phosphorylation
when a substances loses electrons it is
oxidized
a substance that is reduced is called the
oxidizing agent
the ETC does not produce ATP, however it does....
power the proton gradient ATP synthase needs
most of the ETC components are
proteins
what is being reduced and oxidized in pyruvate oxidation?
pyruvate is oxidized while NAD is reduced to NADH;
what has to happen before the citric acid cycle can begin? which links what to what?
pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle
how is lactate produced?
pyruvate reduced directly by NADH to form end product, no CO2 release
when an electron gains electrons, it is
reduced (reducing protons)
a substance that is oxidized is called the
reducing agent
Control of catabolism is based mainly on
regulating the activity of enzymes at strategic points in the catabolic pathway
what is being reduced and oxidized in glycolysis?
the NAD is being reduced and the G3P is oxidized
what can happen if O2 is present?
the chemical energy stored in pyruvate and NADH can be extracted by pyruvate oxidation,the citric acid cycle and ox. phos
In cellular respiration, what is oxidized and what is reduced?
the fuel (is oxidized) and oxygen is reduced
How does potential energy of an electron change as it moves down the chain?
the potential energy of the ETC loses potential energy ("bucket brigade") as each component of the chain becomes reduced when accepting electrons from its uphill neighbor which has a lower affinity(attraction) for electrons (is less electronegative)- it returns to its oxidized form as it passes electrons downhill to its more electronegative neighbor.
list all the products of pyruvate oxidation. How many of each product is produced per glucose?
the products of pyruvate oxidation are, Co2, and NADH, ZERO ATP are produced. Per glucose, 2 Co2 and 2 NADH are produced, and 2 acetyl CoA and 2 H
chemiosmosis
the use of energy in a H+ gradient to drive cellular work
In what way are the enzymes catalyzing pyruvate oxidation "localized" ?
they are localized by feedback inhibition, if ATP production lags behind its use, ADP accumulates and activates the enzymes that speed up catabolism, but at the same time if ATP supply exceeds demand, then catabolism slows down as ATP molecules accumulate and bind to the same enzymes, inhibiting them.
when do human muscle cells make ATP by lactic acid fermentation?
when O2 is scarce, exercise
when does substrate phosphorylation occur?
when an enzyme carries a phosphate group from a substrate molecule to ADP.