Ch. 9 Cellular Respiration & Fermentation

cellular respiration

any set of reactions that uses electrons harvested from high-energy molecules to produce ATP via an electron transport chain.

Oxidative phosphorylation generates ________.

ATP

what does the chemiosmotic hypothesis claim?

ATP is generated using a proton-motive force that is produced by the electron transport chain.

differentiate cellular respiration and fermentation in terms of inputs, outputs, and ATP production

Cellular Respiration inputs: 2 ATP, 4 ADP, 2NAD+ outputs: 2 ADP, 4 ATP, 2 NADH, 2 pyruvates ATP production: 2 ATP per glucose Fermentation inputs: glucose, 2 ADP, 2 NAD+ outputs: 2 ATP, 1 NADH, 2 lactic acid ATP production: no ATP; 2 puruvates==>2 lactic acid

____________ ____________ breaks down acetyl-CoA into CO2.

Krebs Cycle, NAD and FAD is reduced, and substrate-level phosphorylation produces ATP

compare lactic acid fermentation and alcohol fermentation

Lactic acid fermentation occurs in humans: Goes through pathway, then you get 2 pyruvates, converts 2 pyruvates to 2 lactate (it takes the e- from NADH and places them on 2 Lactate) Alcohol fermentation occurs in yeast: Glucose goes through pathway, results in 2 pyruvates, transfers to 2 acetaldehyde and ends with 2 ethanol

compare and contrast substrate-level phosphorylation and oxidative phosphorylation

Substrate level phosphorylation is when ADP is converted to ATP by the direct transfer of a phosphate group. The phosphate group is donated or transfered from a phosphorylated intermediate. This is in contrast to oxidative phosphorylation, where a chemiosmotic gradient is used to power the phosphorylation process.

mitochondrial matrix

compartment enclosed within the inner membrane of the mitochondria

where does glycolysis occur?

cytoplasm of eukaryotes and prokaryotes

pyruvate processing

each pyruvate produced by glycolysis is processed to release one molecule of CO2, and the remaining two carbons are used to form the compound acetyl Coa. The oxidation of pyruvate results in more NAD+ being reduced to NADH

The electron transport chain transfers ______________ to oxygen.

electrons; its a series of redox reactions from low slightly electronegative to highly electronegative, proton gradient created.

does this correctly describe the fermentation pathway? (T/F) - it synthesizes electron acceptors, so that cellular respiration can continue

false

where does the citric acid cycle occur in eukaryotes?

in the matrix of mitochondria

where does ETC and oxidative phosphorylation occur?

inner membrane of mitochondria or plasma membrane of prokaryotes

how is glycolysis regulated?

phosphofructokinase through allosteric inhibition, can increase/decrease rate of glycolysis

coenzyme A (CoA)

the same enzyme complex then takes the two-carbon acetyl unit (-COCH3) and covalently bonds it to a compound called ________.

citric acid cycle

the two carbons from each acetyl CoA produced by pyruvate processing are oxidized to two molecules of CO2. More ATP and NADH are produced, and flavin adenine dinucleotide (FAD) is reduced to from FADH2.

ATP synthase allows for diffusion of H+ that generates energy, making ATP from _______ and _______.

ADP and Pi

explain the relationship between the structure of ATP synthase and its function. what are the different roles of the F1 and F0 unites of ATP synthase?

ATP synthase consists of a membrane-associated F0 unit and an F1 unit joined by a rotor shaft. When protons flow through the F0 unit, it spins the rotor shaft within the fixed F1 unit. This spinning shaft causes structural changes in the F1 that drives the synthesis of ATP from ADP and Pi.

analyze the relationship between the electron transport chain and oxidative phosphorylation

During oxidative phosphorylation, electrons are transferred from electron donors to electron acceptors such as oxygen, in redox reactions. These redox reactions release energy, which is used to form ATP. ... These linked sets of proteins are called electron transport chains.

Fermentation regenerates _______ so that __________ can continue

NAD+, glycolysis

phosphofructokinase

catalyzes reaction 3 in glycolysis -- the synthesis of fructose-1, 6-biphosphate from fructose-6-phosphate. This is a key step in the sequence

Not all organisms use the same electron sources in cellular respiration, what else do they use?

many prokaryotes (e.g. bacteria) use an electron donor other than sugar and use an electron accepter other than oxygen

where does pyruvate processing and citric acid cycle occur?

matrix of mitochondria or cytosol of prokaryotes

fermentation

metabolic pathway that includes glycolysis and an additional set of reactions that oxidize stockpiles of NADH to regenerate NAD+. In respiring cells, fermentation serves as an emergency backup so glycolysis can continue to produce ATP even when the ETC and oxidative phosphorylation is shut down.

after glucose is fully oxidized by glycolysis, pyruvate processing, and the citric acid cycle, where is most of its energy stored?

most of the energy is stored in the form of NADH

describe the three regulation points in the citric acid cycle in terms of the type of regulatory molecules and how each enzyme is affected

the enzymes in the first and fourth reactions are regulated by ATP, which inactivates the enzymes when ATP levels are high by binding to an allosteric regulatory site. This enzyme in the third reaction is regulated by high levels of NADH, which serves as a competitive inhibitor by binding to the active site.

chemiosmosis

- describes the use of a proton gradient to drive energy-requiring processes, like the production of ATP. - diffusion across a membrane, protons are diffusing along its gradient rather than water.

facultative anaerobes

- organisms that can switch between fermentation and aerobic cellular respiration - has the ability to use aerobic cellular respiration when oxygen is present and anaerobic fermentation when oxygen is absent. - Many of your cells can function as this to a certain extent however, you cannot survive for long without oxygen.

explain the relationship between electron transport and oxidative phosphorylation. How do uncoupling proteins "uncouple" this relationship in brown adipose tissue?

- oxidative phosphorylation is possible via a proton gradient that is establish by redox reactions in the ETC. - Uncoupling proteins disrupt this relationship by allowed protons to freely pass through the inner membrane, thus reducing the proton gradient and the production of ATP by oxidative phosphorylation.

explain the role of ATP in the energy-investment phase. why is it not necessary for the energy-payoff phase?

- role of ATP = produce phosphorylated products - Without ATP, the reactions are endergonic and would not occur. - The energy-payoff phase is unnecessary because it consists of exergonic reactions that harvest the chemical energy to produce ATP, so no input of energy is required.

three key points about glycolysis

1. glycolysis starts by using ATP, not producing it. In the initial step, glucose is phosphorylated to form glucose-6-phosphate. After the second reaction rearranges the sugar to form fructose-6-phosphate, the third reaction adds a second phosphate group, forming the compound fructose-1, 6-biphosphate observed by early researchers. This, in steps 1-5, two ATP molecules are used up before any ATP is produced. Without ATP, these reactions would be endergonic, so this part of glycolysis is referred to as the energy investment phase. 2. the energy-pay off phase of glycolysis (steps 6-10) consists of exergonic reactions that do not require an input of energy. The first high-energy molecules are produced in the 6th reaction, where two molecules of NAD+ are reduced to form two NADH. In reactions 7 and 10, enzymes catalyze the transfer of a phosphate group from a phosphorylated substrate to ADP, forming ATP. When ATP is produced in this manner, it is called substrate-level phosphorylation. 3. For each molecule of glucose processed by glycolysis, the net yield is two molecules of NADH, two of ATP, and two of pyruvate

key points of the electron transport chain

1. most of the molecules are proteins that contain distinctive cofactors and coenzymes where the redox events take place. the latter include inorganic iron-sulfur complexes, organic ring-containing structures called flavors, or organic iron-containing heme groups called cytochromes. Each of these "helper groups is readily reduced or oxidized. 2. the inner membrane of the mitochondrion also contains a pool of nonprotein molecules called ubiquinone. Ubiquinone got its name because it is nearly ubiquitous in organisms and belongs to a family of compounds called quinones. Also called coenzyme Q, or simply Q, ubiquinone is lipid soluble and moves efficiently throughout the hydrophobic interior of the inner mitochondrial membrane 3. the molecules involved in iodizing NADH and FADH2 differ in their ability to accept electrons in a redox reaction. this ability is referred to as the redox potential of the electron acceptors. in addition, some of the molecules pick up a proton with each electron, forming bonds to uncharged hydrogen atoms, while others obtain only electrons

describe the process cells use to turn glucose into pyruvate

Glycolysis is the splitting, or lysis of glucose. Glycolysis converts the 6-carbon glucose into two 3-carbon pyruvate molecules. This process occurs in the cytoplasm of the cell, and it occurs in the presence or absence of oxygen.

describe the process cells use to turn pyruvate into acetyl CoA

In the conversion of pyruvate to acetyl CoA, each pyruvate molecule loses one carbon atom with the release of carbon dioxide. During the breakdown of pyruvate, electrons are transferred to NAD+ to produce NADH, which will be used by the cell to produce ATP.

ATP synthase

Large protein that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP

differentiate the electron transport chains in aerobic versus anaerobic respiration. how does this difference affect the amount of ATP produced by oxidative phosphorylation?

The ETC in aerobic respiration uses oxygen as the terminal electron acceptor; in anaerobic respiration it uses a different acceptor, like nitrate or sulfate. The redox potential is higher in O2 than in nitrate or sulfate, so there is a larger change in free energy in the aerobic ETC. For each glucose (or equivalent), there would be more protons transported and more ATP generated from aerobic respiration compared to anaerobic respiration.

explain why many different molecules -- including lipids, amino acids, and CO2 -- end up radio labeled when called are fed glucose with radioactive carbons

The radioactive carbons in glucose can be fully oxidized by cellular respiration to generate radio labeled CO2. Other molecules, like lipids and amino acids, would end up radio labeled since they are made in other anabolic pathways using intermediates from the central pathways.

lactic acid fermentation

When fermentation takes place in your cells, the pyruvate produced by glycolysis then gains to accept electrons from NADH, this is the pathway, it regenerates NAD+ by reducing pyruvate to form lactate -- a deprotonated form of lactic acid

If you understand chemiosmosis, you should be able to explain the relationship between glucose oxidation, the proton gradient, and ATP synthase.

When glucose is oxidized in glycolysis, pyruvate processing, and the citric acid cycle, reduced electron carriers (NADH or FADH2) are produced. The electron carriers pass electrons to the ETC in mitochondria, which then produces a proton gradient across the inner membrane. This proton gradient powers the synthesis of ATP via the ATP synthase

cytochrome c (cyt c)

acts as shuttles that transfer electrons between complexes

if you were to expose cells that are undergoing aerobic respiration to a radioactive oxygen isotope in the form of O2, which of the following molecules would you expect to be radiolabeled? a. pyruvate b. water c. NADH d. CO2

b. water

proton-motive force

based on a proton electrochemical gradient across a membrane. It could occur in the absence of an electron transport chain.

alcohol fermentation

biological process which converts sugars such as glucose, fructose, and sucrose into cellular energy, producing ethanol and carbon dioxide as by-products.

compare and contrast lactic acid fermentation and ETC. Why would cells not survive using fermentation?

both fermentation and the ETC regenerated NAD+ from NADH. In fermentation, the only ATP produced comes from glycolysis, while the proton gradient formed by the ETC is used to make many more ATP per glucose. Your cells would not survive using fermentation alone due to the low yield of ATP from this process.

in step 3 of the citric acid cycle, the enzyme isocitrate dehydrogenase is regulated by NADH. Compare and contrast the regulation of this enzyme with the regulation of phosphofructokinase in glycolysis

both phosphofructokinase and isocitrate dehydrogenase are regulated by feedback inhibition, where the product of the reaction or series of reactions inhibits the enzyme activity. They differentiate in that phosphofructokinase is regulated by allosteric inhibition while isocitrate dehydrogenase is controlled by competitive inhibition.

homeostasis

by regulating key reactions involved in catabolic and anabolic pathways, the cell is able to maintain its internal environment even under different environmental conditions

anaerobic

cells that depend on electron transport chains with electron acceptors other than oxygen are said to use this.

electron transport chain

electrons from the NADH and FADH2 produced by pyruvate processing and the citric acid cycle move through a series of electron carriers that together are called an electron transport chain. The energy obtained from this chain of redox reactions is used to create a proton gradient across a membrane; the ensuing flow of protons back across the membrane is used to make ATP. Because this mode of ATP production links oxidation of NADH and FADH2 with phosphorylation of ADP, it is called oxidative phosphorylation

glycolysis

one 6-carbon molecule of glucose is broken into two molecules of 3-carbon compound pyruvate. ATP is produced from ADP and Pi, and nicotinamide adenine dinucleotide (NAD+) is reduced to form NADH.

cristae

portions of the inner membrane posture into the interior of the organelle and expand to form these sac-like compartments

In the ETC, potential energy used to pump _________ into inner membrane space; concentration gradient established.

protons

aerobic

species that depend on oxygen as an electron acceptor for the ETC use this and are called aerobic organisms; this is most efficient

glycolysis

the breakdown of glucose into pyruvate

does this correctly describe the fermentation pathway? (T/F) - it includes a reaction that oxidized NADH to NAD+

true

does this correctly describe the fermentation pathway? (T/F) - it includes a reaction that reduces NAD+ to NADH

true

does this correctly describe the fermentation pathway? (T/F) - it synthesizes ATP by substrate-level phosphorylation

true