AP Bio Chapter 9: Cellular Respiration and Fermentation
Label the energy investment phase below and complete the figure. Then turn to figure 9.9 on page 168 of your text to find the two specific steps where ATP is used
**1. Hexokinase transfers a phosphate group from ATP to glucose, making it more chemically reactive. The charge on the phosphate also traps the sugar in the cell 2. Glucose 6-phosphate is converted to fructose 6-phosphate **3. Phosphofructokinase transfers a phosphate group from ATP to the opposite end of the sugar, investing a second molecule of ATP. A key step for regulation of glycolysis. 4. Aldolase cleaves the sugar molecule into two different three carbon sugars 5. Conversion between HDAP and G3P: This reaction never reaches equilibrium GSP is used in the next step as fast as it forms Cell spends ATP
Explain the difference between fermentation and aerobic respiration
-
What are the products of the citric acid cycle after 2 cycles (the breakdown of one glucose molecule)
-2 ATP -4 CO2 -6 NADH (NAD+ ----> NADH - electron carriers) -2 FADH2 (FAD----> FADH2)
What are the final products of glycolysis during the catabolism of one glucose molecule
-2 pyruvate molecules (a 3-C molecule) -4 ATP (net gain of 2 ATP) -2NAD+----> 2NADH -2H2O
Label Energy flow and chemical recycling in ecosystems
-Light energy -photosynthesis in chloroplasts -cellular respiration in mitochondria -ATP
What are the products of this conversion
-Pyruvate bonds with coenzyme A -2 Acetyl CoA are produced -2-C molecule -2 CO2 molecules are released from the cell -2 NADH molecules
aerobic respiration
-oxygen is consumed as a reactant along with the organic fuel -A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid
fermentation:
-partial degradation of sugars or other organic fuel that occurs without the use of oxygen -A catabolic process that makes a limited amount of ATP from glucose without an electron transport chain that produces a characteristic end product such as ethyl alcohol or lactic acid
What is the function of the electron transport chain in cellular respiration
-respiration uses an electron transport chain to break the fall of electrons to oxygen into several energy releasing steps -it is a sequence of electron carrier molecules that shuttle electrons down a series of redox reactions that release energy used to make ATP
What is the meaning of glycolysis? What occurs in this step of cellular respiration?
-sugar splitting -glucose splits into two 3 carbon sugars that are oxidized and their remaining atoms are rearranged to form two molecules of pyruvate.
Write the chemical equation of cellular respiration
1 glucose + 6 oxygen ---> 6 carbon dioxide + 6 water + cellular energy (ATP + heat)
At any given time, the amount of ATP in a human would sustain life for only about
1 minute
Glycolysis is thought to have evolved very early in the evolution of life on earth. Provide three pieces of evidence that justify this hypothesis
1. Ancient prokaryotes are thought to have used glycolysis to make ATP long before oxygen was present 2. Cyanobacteria produced this oxygen as a by produce of photosynthesis so early prokaryotes may have not generated ATP just from glycolysis 3. Glycolysis is the most widespread metabolic pathway among earth's organisms 4. The location of glycolysis implied great antiquity- pathway does not require any of the membrane enclosed organelles of the eukaryotic cell, which evolved 1 billion years after the first prokaryotic cell
Using figure 9.14 in your text, explain the overall concept of how ATP synthase uses the flow of hydrogen ions to product ATP
1. H+ ions flowing down their gradient enter a channel in a stator, which is anchored in the membrane 2. H+ ions enter binding sites within a rotor, changing the shape of each subunit so that the rotor spins within the membrane 3. Each H+ ion makes one complete turn before leaving the rotor and passing through a second channel in the stator into the mitochondrial matrix 4. Spinning of the rotor causes an internal rod to spin as well. This rod extends like a stalk into the knob below it, which is held stationary by part of the stator 5. Turning of the rod activates catalytic sites in the knob that produce ATP and ADP and Pi
The second phase in glycolysis is the energy payoff phase. Label the phase and complete the figure. Note that it provides both ATP and NADH. Look at Figure 9.9 from your text to locate the two steps where ATP is formed and one step where NADH is formed
1. Hexokinase transfers a phosphate group from ATP to glucose, making it more chemically reactive. The charge on the phosphate also traps the sugar in the cell **2. Glucose 6-phosphate is converted to fructose 6-phosphate 3. Phosphofructokinase transfers a phosphate group from ATP to the opposite end of the sugar, investing a second molecule of ATP. A key step for regulation of glycolysis. **4. Aldolase cleaves the sugar molecule into two different three carbon sugars 5. Conversion between HDAP and G3P: This reaction never reaches equilibrium GSP is used in the next step as fast as it forms ATP is produced by substrate level phosphorylation and NAD+ is reduced to NADH by electrons released from the oxidation of glucose
Why is the total count above 30 or 32 molecules rather than a specific number
1. phosphorylation and the redox reactions are not directly coupled to each other, so the ratio of the number of NADH molecules to the number of ATP is not a whole number 2. the ATP yield varies depending on the type of shuttle used to transport electrons from the cytosol into the mitochondrion. 3. The use of the proton motive force generated by the redox reactions of respiration to drive other kinds of work
How many ATP are produced in the citric acid cycle
2
Using one glucose molecule, how many ATP are produced during glycolysis
2
d. How many FADH2 are formed?
2
e. How many ATPs are formed?
2
f. How many times does the citric acid cycle occur for each molecule of glucose
2
How many ATP are produced during fermentation
2 ATP
Steps 1-3 are energy investment steps. How much energy is invested
2 ATP
Two pyruvate molecules are converted into
2 Acetyl CoA molecules prior to entering the citric acid cycle.
How many ATP are produced during chemiosmosis on the cristae
26-28 on the electron transport chain
______________ molecules will be converted to __________________ molecules
2G3P 2 pyruvate
Step 2:
2nd Phosphorylation of glucose produces???
b. How many total carbons are lost as pyruvate is oxidized
3
At this point you should be able to account for the total number of ATPs that could be formed from a glucose molecule. To accomplish this, we have to add the ATPs formed by substrate level phosphorylation in glycolysis and the citric acid cycle to the ATPs formed by chemiosmosis. Each NADH can form a maximum of _____________ ATP molecules. Each FADH2, which donates electrons that activate only 2 protein pumps, makes ____________ ATP molecules
3 2
What is the netproduction of ATP during cellular respiration
30-32
Total number of ATP produced during cellular respiration
30-32 ATP
Approximately how much energy is used from one glucose molecule during cellular respiration
34% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 32 ATP The rest is lost as heat
Glucose contains _______ carbons
6
a. how many NADHs are formed
6
Step 3
6-C molecules splits into 2 3-C molecules = G3P
Write the chemical equation for photosynthesis.
6CO2+ 6H2O + light energy ---> C6H12O6 + 6O2 (cellular respiration reversed)
The citric acid cycle has _____ steps, each catalyzed by a ___________ ___________
8 specific enzyme
The second form of phosphorylation is substrate level. Label the following figure to show the direct transfer of a phosphate from an organic substrate to ADP to form ATP
A smaller amount of ATP is formed directly in a few reactions of glycolysis and the citric acid cycle Occurs when ATP an enzyme *transfers* phosphate group from a substrate molecule to ADP, rather than adding an inorganic phosphate
_____________ will be converted back to ATP in a continual cycle.
ADP
ADP + P --->
ATP
As hydrogen ions move back into the matrix, ADP picks up a P ----->
ATP
What is the function of ATP
ATP provides an immediate source of energy for the cell. Looks like RNA with 2 more phosphate groups
Upon entering the citric acid cycle (krebs cycle)
Acetyl CoA (2-C) joins a 4 carbon molecule to become citrate (6-C)
chemiosmosis
An energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP. Chemiosmosis is an energy coupling mechanism that uses energy stored in the form of an H+ gradient across a membrane to drive cellular work
Define substrate level phosphorylation
An enzyme assists in passing a Phosphate group to ADP---> produces ATP
formula for cellular respiration
C6H12O6 + 6 O2 -> 6CO2 + 6H20 + ENERGY (ATP)
To enter the citric acid cycle, pyruvate must enter the mitochondria by active transport. These things are necessary to *convert pyruvate to acetyl CoA.* Complete the missing parts of the following figure and then explain the three steps in the conversion process
Carried out by a multi-enzyme complex that catalyzes three reactions step 1: Pyruvates carboxyl group which is already fully oxidized and thus little chemical energy, is removed and given off as a molecule of CO2. This is the first step in which CO2 is released during respiration step 2: The remaining two-carbon fragment is oxidized, forming acetate. The extracted electrons are transferred to NAD+, storing energy in the form of NADH step 3: coenzyme A is attached via its sulfer atom to the acetate, forming acetyl CoA, which has a high potential energy. The reaction of acetyl CoA to yield lower energy products is higher exergonic
What is the role of the electron transport chain in forming the H+ gradient across the inner mitochondrial membrane
Certain members of the electron transport chain accept and release protons (H+ ) along with electrons. (The aqueous solutions inside and surrounding the cell are a ready source of H+ .) At certain steps along the chain, electron transfers cause H+ to be taken up and released into the surrounding solution. In eukaryotic cells, the electron carriers are spatially arranged in the inner mitochondrial membrane in such a way that H+ is accepted from the mitochondrial matrix and deposited in the intermembrane space. 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.
What are the end products of the electron transport chain and chemiosmosis
Chemiosmosis: 26-28 ATP -water molecules on the electron transport chain
Describe what happens when NAD+ is reduced. What type of enzyme is involved?
Enzymes remove a pair of hydrogen atoms from the substrate and oxidizes it The enzyme delivers the 2 electrons along with 1 proton to its coenzyme NAD+ The nicotinamide portion of NAD+ has its charge neutralized when NAD+ is reduced to NADH
Explain what has happened to each of the six carbons found in the original glucose molecule
For each pyruvate molecule formed from the original glucose molecule, the pyruvate is broken down to three CO2 molecules, including the molecule ofCO2 released during the conversion of pyruvate to acetyl CoA.
Label the following figure and then explain why pyruvate is a key junction in metabolism
Glycolysis is common to fermentation and cellular respiration. The end product of glycolysis, pyruvate, represents a fork in the catabolic pathways of glucose oxidation. In a facultative anaerobe or a muscle cell, which are capable of both aerobic cellular respiration and fermentation, pyruvate is committed to one of those two pathways, usually depending on whether or not oxygen is present
What are the three phases of cellular respiration
Glycolysis, Pyruvate oxidation, citric acid cycle (krebs cycle)
proton motive force
H+ gradient that results the potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions across a biological membrane during chemiosmosis
Oxygen stabilizes the electrons by combining with two hydrogen ions to form what compound
H2O
What happens to the hydrogen ions that are in the intermembrane space
Hydrogen ions move from the intermembrane space through ATP synthase into the matrix of the mitochondria from high to low
Aerobic pathway
If oxygen is present, the process of cellular respiration begins in the cytoplasm and is completed in the mitochondria.
Where does glycolysis occur in the cell? Is Oxygen required?
It occurs in the *cystol* of the cell Oxygen is not required
There are two types of fermentation. Where does lactic acid fermentation take place
Lactic acid: animal muscles, fungi, bacteria
In cellular respiration, electrons are not transferred directly from glucose to oxygen. Following the movement of hydrogens allows you to follow the flow of electrons. What electron carrier is hydrogen transferred to first
NAD+
The correct answer to number 6 is a coenzyme called? What are coenzymes? (If you have forgotten, look at page 156 in chapter 8)
NAD+ organic cofactors that assist enzymes Most vitamins function as coenzymes in metabolic reactions.
For aerobic respiration to continue the cells must be supplied with oxygen- the ultimate electron acceptor. What is the electron acceptor in fermentation
NAD+ accept electrons during the oxidation step of glycolysis
This oxidation of pyruvate accounts for two additional reduced _________________ molecules and two molecules of CO2
NADH
What are the two electron carrier molecules that feed electrons into the electron transport system
NADH FADH2
NADH Oxidized or reduced Higher energy/lower energy
NADH is reduced higher energy
Does this phase require oxygen
No
_______________ is the final electron (hydrogen) acceptor
Oxygen
Explain why oxygen is considered the ultimate electron acceptor
Oxygen is extremely electronegative.
Step 1
Phosphorylation of glucose produces???
What three organic macromolecules are often utilized to make ATP by cellular respiration
Possible examples include fats, proteins, sucrose, and starch.
Alcohol fermentation starts with glucose and yields ethanol. Explain this process and be sure to describe how NAD+ is recycled
The first step releases carbon dioxide from the pyruvate, which is converted to the two-carbon compound acetaldehyde. In the second step, acetaldehyde is reduced by NADH to ethanol. This regenerates the supply of NAD+ needed for the continuation of glycolysis
What undergoes alcohol fermentation
Yeast- make bread, brew beer, and wine
The hydrogen ion gradient that builds up is called a proton-motive force. Define this term
a gradient that has the capacity to perform work. Protons will move with their concentration gradient and create energy ***diagram of this***
What is the result
a higher concentration of hydrogen ions (H+) in the intermembrane space than in the matrix
cellular respiration provides
a small, managed release of energy
An internal rod spins and this
activates catalytic sites in ATP synthase
Cellular Respiration is
aerobic
The carriers alternate reduced and oxidized states
as they accept and donate electrons
When the 3rd phosphate group is removed from the tail of ATP, energy is
available for metabolic functions in the cell
If oxygen is present where does the process of cellular respiration take place
begins in the cytoplasm and is completed in the mitochondria
Cellular respiration follows a catabolic pathway. Describe a catabolic pathway
breaks down complex molecules and releases stored energy
c. The carbons are lost in which molecule
carbon dioxide (4 CO2)
NADH
carried electrons to the electron transport chain (electron carrier)
Explain the difference in energy usage between the catabolic reactions of cellular respiration and the anabolic pathways of biosynthesis
catabolic: energy is generated anabolic: energy is consumed
Autotrophs and heterotrophs will undergo
cellular respiration
ATP can now move out of the mitochondria and be used for
cellular work
The acetyl CoA joins the cycle by combined with oxaloacetate, forming _________
citrate
NAD+
coenzyme that accepts electrons and hydrogen ions to become NADH
glycolysis takes place in all cells. Where does it take place
cytoplasm
The next seven steps
decompose the citrate back to oxaloacetate, making the process a cycle
When does this take place
during glycolysis and the citric acid cycle
oxidizing agent
electron acceptor
NADH and FADH2 are
electron carriers
reducing agent
electron donor
Where do they carry electrons
electron transport chain
Where does this take place
electron transport chain and chemiosmosis
Referring to figure 9.13 in your text, notice that each member of the electron transport chain is lower in free ________________ than the preceding member of the chain, but higher in ________________.
energy electronegativity
Describe the energy flow through a system (from photosynthesis to cellular respiration) Diagram above
energy flows into an ecosystem as sunlight (photosynthesis) and leaves as heat (cellular respiration)
What are the two stages of glycolysis
energy investment (spends ATP) and energy payoff (ATP is produced and NAD+ is reduced to NADH by electrons released from the oxidation of glucose)
Define oxidative phosphorylation
energy is released from electrons, hydrogen ion gradient is creates, ADP + P---> ATP. Uses the electron transport chain and chemiosmosis
A series of chemical reactions take place during the
energy payoff phase
Anerobes will undergo
fermentation to produce ATP. No oxygen is required
If oxygen is not available, what happens to the pyruvate molecules
fermentation will take place in the cytoplasm
The starting product of glycolysis is the six-carbon sugar ______________ and the ending products are two ____________- carbon molecules of ______________________
glucose three pyruvate
What is the energy flow during cellular respiration
glucose NADH electron transport chain proton motive force ATP
Cellular respiration begins with
glucose and oxygen
The end products of photosynthesis are
glucose and oxygen
Glycolysis: All organisms undergo
glycolysis.
Anaerobic
if no oxygen is present, fermentation will take place in the cytoplasm
Define intermembrane space
located between the outer membrane and the cristae
When compounds lose electrons, they ________________ energy; when compounds gain electrons, they _______________ energy.
lose electrons= lose energy gain electrons= gain energy
Glucose undergoes oxidation to produce carbon dioxide Define oxidation
loss of electrons biology= loss of hydrogen
Pyruvate enters the
matrix of the mitochondria
Where are these found in eukaryotic cells?
membrane of the mitochondria
Eukaryotes contain
mitochondria
Define coenzyme
molecule bound to an enzyme aids in the action of the enzyme
The final figure shows the net gain of energy for the cell after glycolysis. Most of the energy is still present in the two molecules of pyruvate. Complete the following figure to show the net energy gains
net yield from glycolysis per glucose is 2 ATP plus 2 NADH
The electron transport chain generates
no ATP directly
Where is the electron transport chain located
on the inner membrane (cristae) of the mitochondria
What is the goal of glycolysis
one glucose molecule (6-C molecule), will be converted to 2 pyruvate molecules Pyruvate is a three carbon molecule
Cellular respiration breaks down
organic sugars
Mitochondria have double membranes, the
outer membrane and the inner membrane
Both cellular respiration and photosynthesis are redox reactions. In redox reactions pay attention to the flow of electrons. What is the difference between oxidation and reduction
oxidation: the complete or partial loss of electrons from a substance involved in a redox reaction (loss of electrons) reduction: the complete or partial addition of electrons to a substance involved in redox reaction (add electrons-adds electrons and reduces the amount of positive charge electrons)
NAD+ Oxidized or reduced Higher energy/lower energy
oxidized lower energy
the electron receptor is called the
oxidizing agent
Define aerobic
oxygen
The molecule at zero free energy on this chart, which is ______________, is the lowest of all the molecules in free energy and the highest in electronegativity
oxygen
What strongly electronegative atom, pulling electrons down the electron transport chain, is the final electron acceptor
oxygen
Fermentation allows for the production of ATP without using either ______________ or any _________________
oxygen an electron transport chain
cellular respiration:
oxygen enters the system and CO2 is released
Oxygen is the final electron acceptors. At the end of this process....
oxygen receives the energy-spent electrons and picks up hydrogen ions
Where are these found is respiring prokaryotic cells
plasma membrane
Oxygen undergoes reduction to produce water. Define reduction
produce water gain electrons = follow= gain of hydrogen
As the protein complexes shuttle electrons, they
pump protons (H+) from the mitochondrial matrix into the intermembrane space
Lactic acid fermentation starts with glucose and yields lactate. Explain this process and be sure to describe how NAD+ is recycled
pyruvte is reduced directly by NADH to form lactate as an end product, with no release of CO2
The electron donor is called the
reducing agent
The NADH and FADH2 produced by the cycle
relay electrons extracted from food to the electron transport chain
This action
requires energy
H+ move into the
rotor causing the shape of the unit to change and the rotor spins
Electron transport involves a
series of electron carriers
covalent
sharing/rearrangement
Describe an exergonic reaction
spontaneous chemical reaction with a release of free energy
define glyco
sugar
What does photosynthesis produce
sugars (glucose)
Cellular respiration in aerobic prokaryotes
takes place on the plasma membrane
What happens during cellular respiration
the breakdown of carbohydrates, fats, proteins, etc are broken down to produce ATP (Adenosine triphosphate)
cellular respiration
the catabolic pathways of aerobic and anaerobic respiration which break down organic molecules and use an electron transport chain for the production of ATP
Oxidative phosphorylation involves two components:
the electron transport chain and ATP synthesis
Four larger protein structures and two smaller proteins are involved in the production of ATP through
the electron transport chain and chemiosmosis
Oxidative phosphorylation incldues
the electron transport chain and chemiosmosis
The three types of phosphorylation (adding a phosphate) are covered in the text, and two of these occur in cellular respiration. Explain how the electron transport chain is utilized in oxidative phosphorylation
the energy released at each step of the chain is stored in a form the mitochondrion can use to make ATP from ADP the production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration It is powered by the redox reactions of the electron transport chain 90% of ATP generated
breathing
the exchange of O2 and CO2 in the lungs
ATP synthase uses the
the exergonic flow of H+ to drive phosphorylation of ATP
Define cristae
the folds of the inner membrane
Define matrix
the inner compartment that is filled with gel like fluid
In eukaryotes, if oxygen is available what happens to the pyruvate molecules?
the pyruvate will enter the matrix of the mitochondria
in the presence of oxygen,
the two pyruvate molecules will enter the matrix of the mitochondria (one glucose molecules)
As H+ ions move down their concentration gradient through ATP synthase,
they enter a channel called a stator
In animals how are glucose and oxygen delivered to the cells
through the bloodstream
define lysis
to split
ionic
transfer
The step that converts pyruvate to acetyl CoA at the top of the diagram occurs ________ per glucose.
twice
The citric acid cycle turns ___________ per glucose molecule because glucose was converted to _____ pyruvate molecules
twice two
Chemiosmosis
uses an H+ gradient to drive ATP formation
What is the result
water
When oxygen picks up energy spent electrons and hydrogen ions, what is the result
water
Write the generalized formula for a redox reaction Draw an arrow showing which component (X or Y) is oxidized and which is reduced. _________________ is the reducing agent in the reaction, and _____________ is the oxidizing agent.
xe- (reducing agent) becomes oxidized to X Y (oxidizing agent) becomes reduced to Ye-
