Ch9

Ch9

In general terms, distinguish between fermentation and cellular respiration
fermentation is the partial degradation of sugars, anaerobic. cellular respiration is aerobic, complete the breakdown of a variety of organic molecules.
Both use glycolysis as provider of starting material
Write the summary equation for cellular respiration. Write the specific chemical equation for the degradation of glucose
-Organic + Oxygen –> Carbon + Water + Energy Compounds
-C6H12O6 + 6O2 –> 6CO2 + 6H2O + ATP + Heat (energy)
Define oxidation and reduction
Oxidation is the loss of an electron
Reduction is gain of an electron
OIL RIG Oxidation is Loss Reduction is Gain
Explain in general terms how redox reactions are involved in energy exchanges
A redox reaction relocates electrons closer to oxygen, such as the burning of methane, releases chemical energy that can do work.
Describe the role of NAD+ in cellular respiration
It is a coenzyme and an electron carrier. NAD+ is a good electron carrier bc it can cycle easily between oxidized (NAD) and reduced (NADH) states. As an electron acceptor, NAD+ functions as an oxidizing agent during respiration
In general terms, explain the role of the electron transport chain in cellular respiration
Generate an electrochemical proton gradient across a membrane by high energy electrons transferred between molecules in the membrane — at each transfer, the electrons lose a bit of their energy, which is used to pump protons across the membrane against their concentration gradient. Being charged, the protons cannot diffuse back through the membrane
Name the stages of cellular respiration and state the region of the eukaryotic cell where each stage
occurs.
Glycolysis- cytosol
citric acid cycle- mitochondrial matrix
oxidative phosphorylation-mitochondrial matrix
Describe the overall process of glycolysis. Explain why ATP is required for the preparatory steps
of glycolysis.Describe the role that the allosteric enzyme phosphofructokinase plays in this
feedback control
Two molecules of ATP are consumed as glucose is split into two three-carbon sugars (glyceraldehyde 3-phosphate).The conversion of these molecules to pyruvate produces two NADH and four ATP by substrate-level phosphorylation.

When ATP levels are high in the cell, no metabolic energy production is needed. In this case, PFK’s activity is inhibited by allosteric regulation by ATP itself, closing the valve on the flow of carbohydrates through glycolysis.

Identify where sugar oxidation, substrate-level phosphorylation, and the reduction of NAD+ occur in glycolysis.
It 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. They are both during the energy payoff phase

Glycolysis step 6:
Generation of 1,3-Bisphosphoglycerate catalysed by Glyceraldehyde-3-phosphate dehydrogenase:
D-glyceraldehyde-3-phosphate + NAD+ +Pi <=> 1,3-Bisphosphoglycerate + NADH + H+

Glycolysis step 7:
Substrate-level phosphorylation, 3-Phosphoglycerate catalysed by Phosphoglycerate kinase:
1,3-Bisphosphoglycerate + ADP <=> 3-Phosphoglycerate + ATP

Glycolysis step 10:
Substrate-level phosphorylation. Pyruvate synthesis catalysed by Pyruvate kinase:
Phosphoenolpyruvate + H+ + ADP -> Pyruvate + ATP

Describe where pyruvate is oxidized to acetyl CoA, what molecules are produced, and how this
process links glycolysis to the citric acid cycle. (Pyruvate Oxidation)
2 molecules of pyruvate left over from glycolysis enter the mitochondrion if oxygen is present. From there, it can then be used by the Krebs Cycle. When it enters the mitochondrion, a multienzyme complex catalyzes these reactions. Pyruvate’s carboxyl group is removed and is given off as carbon dioxide, leaving a two-carbon fragment. This fragment is oxidized to make acetate. The extracted electrons are moved to NAD+ to make NADH that stores energy. Then, coenzyme A attaches to the acetate by an unstable bond, which makes the acetate (acetyl group) very reactive. Pyruvate has now been converted into acetyl coenzyme A (acetyl CoA). Acetyl CoA’s acetate can be used by the Krebs Cycle for more oxidation.
List the products of the citric acid cycle. Explain why it is called a cycle.
ATP, NADH, FADH2, and CO2. It is a cycle because every acetyl that enters the cycle reacts with oxaloacatate. Oxaloacatate is regenerated to start the process over again.
Explain why the citric acid cycle is the point at which glucose is completely oxidized during
cellular respiration.
Glucose is completely oxidized after chemiosmosis because that’s when the final products of Glycolysis and The Citric Acid Cycle are used creating the final 36 to 38 ATP molecules. The final products that are used are NADH and FADH2 which are needed in the electron transport chain and ultimately Chemiosmosis.
Distinguish between substrate level phosphorylation and oxidative phosphorylation
Substrate-level: production of ATP molecules via transfer of a phosphate group from an intermediate high-energy substrate directly to ADP. (Kreb’s Cycle and glycolysis)

Oxidative: production of ATP molecules from the redox reactions of an electron transport chain(chemiosmosis)

Gylcolysis and Krebs cycle use substrate-level phosphorylation. Electron transport chain uses oxidative phosphorylation.

In general terms, explain how the exergonic “slide” of electrons down the electron transport chain is coupled to the endergonic production of ATP by chemiosmosis
As electrons pass or slide down the electron transport chain energy is released. This is an exergonic reaction because energy is being released as electrons pass from carrier to carrier in the ETC. This energy is used by ATP synthase to create ATP. This is an endergonic reactions because it needs energy to take place. Energy is needed to produce ATP.

Chemiosmosis involves the pumping of protons through specific passageways in the membranes of the mitochondria from the inner to the outer space. This creates the H+ proton gradient. This influences the H+ to diffuse across the gradient, thus providing energy as the proton is passed down. A hydrogen gradient awaits on either side of the inner mitochondrial membrane and as the H+ are moved through the ETC, energy is released, thus the exergonic reaction. Then when this energy is consumed by the ATP synthase, that would be the endergonic reaction.

Describe the role of ATP synthase.
While the protons diffuse through it, it spins and ATP synthase makes ATP from ADP and Pi.
Explain where and how the respiratory electron transport chain creates a proton gradient. Explain the function of this proton gradient.
The proton gradient is produced by the movement of electrons along the electron transport chain. The chain is an energy converter that uses the exergonic flow of electrons to pump H+ from the matrix into the intermembrane space. The protons pass back to the matrix through a channel in ATP synthase, using the exergonic flow of H+ to drive the phosphorylation of ADP. Thus, the energy stored in a H+ gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis.
Summarize the net ATP yield from the oxidation of a glucose molecule.
Glycolysis

2 net ATP from substrate-level phosphorylation
2 NADH yields 6 ATP (assuming 3 ATP per NADH) by oxidative phosphorylation

Transition Reaction

2 NADH yields 6 ATP (assuming 3 ATP per NADH) by oxidative phosphorylation

Citric Acid Cycle

2 ATP from substrate-level phosphorylation
6 NADH yields 18 ATP (assuming 3 ATP per NADH) by oxidative phosphorylation
2 FADH2 yields 4 ATP (assuming 2 ATP per FADH2) by oxidative phosphorylation

Total Theoretical Maximum Number of ATP Generated per Glucose in Prokaryotes

38 ATP: 4 from substrate-level phosphorylation; 34 from oxidative phosphorylation.

In eukaryotic cells, the theoretical maximum yield of ATP generated per glucose is 36 to 38, depending on how the 2 NADH generated in the cytoplasm during glycolysis enter the mitochondria and whether the resulting yield is 2 or 3 ATP per NADH

The energy investment stage of glycolysis uses 2 ATP to start glucose oxidation. In the next step, substrate- level phosphorylation, 4 ATP are made. Making a net of 2 ATP molecules. One cycle off the Krebs Cycle makes 1 ATP molecule through substrate-level phosphorylation. For every glucose consumed, 34 ATPs are produced in electron transport and oxidative phosphorylation. In total, 38 molecules of ATP are produced.

State the basic function of fermentation
A catabolic process that makes a limited amount of ATP from glucose without ETC and that produces a characteristic end product, such as ethyl alcohol or lactic acid.
Compare the fate of pyruvate in alcohol fermentation and lactic acid fermentation
In alcoholic fermentation, pyruvic acid is converted to ethanol. Carbon dioxide is released, and NADH is recycled into NAD+.
In lactic acid fermentation, pyruvic acid is converted to lactic acid. NADH is recycled into NAD+
Compare the processes of fermentation and cellular respiration
Fermentation is the process of deriving energy from the oxidation of organic compounds, such as carbohydrates, using an endogenous electron acceptor, which is usually an organic compound.
This is in contrast to cellular respiration, where electrons are donated to an exogenous electron acceptor, such as oxygen, via an electron transport chain

Oxygen is a reactant in cellular respiration but not in fermentation. Also, fermentation produces ATP without the use of an electron transport chain

Describe the evidence that suggests that glycolysis is an ancient metabolic pathway. Connect to
theme of evolution.
It occurs, with variations, in nearly all organisms, both aerobic and anaerobic. The wide occurrence of glycolysis indicates that it is one of the most ancient known metabolic pathways. It occurs in the cytosol of the cell.
Describe how food molecules other than glucose can be oxidized to make ATP
Each NADH and FADH2 molecule formed represents stored energy… contain high energy electrons from food molecules which are carried to an electron transport chain; Plants manufacture their own food by photosynthesis using energy from sunlight. Cells harvest the chemical energy stored in organic molecules and use it to regenerate ATP, the molecule that drives most cellular work. ADP + P + energy ATP
Explain how glycolysis and the citric acid cycle can contribute to anabolic pathways
Glycolysis and the citric acid cycle contribute by making ATP, they also generate electrons for the Electron Transport Chain (ETC). The ETC then uses those electrons to make a proton gradient in the mitochondria which in turn powers the enzyme ATP-synthase to make a whole bunch of ATP.
Explain how ATP production is controlled by the cell. Describe the role that the allosteric enzyme phosphofructokinase plays in this feedback control
Phosphofructokinase (PFK) is a glycolytic enzyme that catalyzes the irreversible transfer of a phosphate from ATP to fructose-6-phosphate:
fructose-6-phosphate + ATP fructose-1,6-bisphosphate + ADP
In part because of the irreversible nature of this step in glycolysis, PFK is the key regulatory enzyme for glycolysis. When ATP levels are high in the cell, the cell no longer needs metabolic energy production to occur. In this case, PFK’s activity is inhibited by allosteric regulation by ATP itself, closing the valve on the flow of carbohydrates through glycolysis.
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