Biology Ch.9 (Exam 4)

Which of the following is true?

A high fat cheese is less dense than a low fat cheese.

Pyruvate

Pyruvate can be metabolized in two possible pathways, depending on whether or not oxygen is present. In the absence of oxygen, pyruvate undergoes fermentation. During fermentatioin, pyruvate might be converted into lactate (as in human muscle) or ethanol (as in yeast), but there is no ATP production beyond the two ATP molecules genereated by glycosis. In the presence of oxygen, pyruvate is metabolized by cellular respiration, which produces a great deal of energy. Pyruvate is transported into the mitochondrial matrix, where it is stripped of a carbon atom and combined with a molecule coenzyme A, or CoA, to make acetyl CoA. This reaction produces two NADH electron carriers. Acetyl CoA then enter the next phase of cellular respiration called the Krebs Cycle.

Substrate-level phosphorylation

Some ATP is also formed directly during glycolysis and the citric acid cycle by substrate-level phophorylation, in which an enzyme transfers phosphate group from an organic substrate molecule to ADP, forming ATP.

For each glucose that enters glycolysis, _____ NADH + H+ are produced by the citric acid cycle.

6 -3 NADH + H⁺ are produced per each acetyle CoA that enters the citric acid cycle.

Chloroplast

are the sites of photosynthesis

NAD⁺ (Nicotinamide adenine dinucleotide)

The hydrogen atoms are not transferred directly to oxygen but are passed first to a coenzyme called NAD⁺. NAD⁺ is well suited as an electron carrier because it can cycle easily between oxidized (NAD⁺) and reduced (NADH)

True or false? The potential energy in an ATP molecule is derived mainly from its three phosphate groups.

True -The three phosphate groups in an ATP molecule carry negative charges that strongly repel each other and give ATP a large amount of potential energy.

The electrons stripped from glucose in cellular respiration end up in which compound?

Water -At the end of the electron transport chain, the electrons and hydrogen atoms are added to oxygen, forming water.

Reducing Agent

Xe⁻ + Y →X + Ye⁻ X, the electron donor, is the REDUCING AGENT and reduces Y by donating an electron to it.

Oxidizing Agent

Xe⁻ + Y →X + Ye⁻ Y, the electron donor, is the OXIDIZING AGENT and oxidizes X by removing its electron.

Which of these is NOT a product of the citric acid cycle?

acetyl CoA -Acetyl CoA enters the citric acid cycle.

Photosynthesis

produces GLUCOSE and releases OXYGEN into the atmosphere.

In the citric acid cycle, ATP molecules are produced by _____.

substrate-level phosphorylation -A phosphate group is transferred from GTP to ADP.

In glycolysis, ATP molecules are produced by _____.

substrate-level phosphorylation -A phosphate group is transferred from glyceraldehyde phosphate to ADP.

Cellular respiration has three (four) stages:

1. Glycolysis (break down glucose into two molecules of pyruvate) 2. Pyruvate to Acetyl CoA 3. The citric acid cycle (completes the breakdown of glucose) 4. Oxidative phosphorylation (accounts for most of the ATP synthesis)

Respiration has three key pathway

1. glycolysis 2. citric acid cycle 3. oxidative phosphorylation

In glycolysis there is a net gain of _____ ATP.

2 -It takes 2 ATP to produce 4 ATP

How many NADH are produced by glycolysis?

2 -Two NADH molecules are produced by glycolysis.

Total ATP form from one glucose molecule?

2 ATP from Glycolysis + 2 ATP from the Krebs Cycle + 26 from ATP synthase = 30 ATP

You are a cheese maker wanting to connect a large quantity of lactose to acid. Which of the following do you need?

Bacteria

Sugar Glucose

C₆H₁₂O⁶ + 6O₂ → 6 CO₂ + 6 H₂O + ENERGY (ATP+ heat)

What happens to a glucose molecule during cellular respiration?

During cellular respiration, a glucose molecule is completely oxidized. In this process, it releases enough energy to produce about 30 molecules of ATP.

Which stage of glucose metabolism produces the most ATP?

Electron transport and Chemiosmosis. -Electron transport and chemiosmosis (oxidative phosphorylation) can yield around 26 molecules of ATP.

In the combined processes of glycolysis and cellular respiration, what is consumed and what is produced?

Glucose is consumed, and carbon dioxide is produced. -The carbon in glucose is oxidized to carbon dioxide during cellular respiration.

Which step of the cellular respiration pathway can take place in the absence of oxygen?

Glycolysis -Glycolysis can take place in the absence of oxygen; its product, pyruvate, enters the cellular respiration pathway or undergoes fermentation depending on the availability of oxygen.

A glucose molecule is completely broken down to carbon dioxide and water in glycolysis and the citric acid cycle, but together these two processes yield only a few molecules of ATP. What happened to most of the energy that the cell obtains from the oxidation of glucose?

It is store in NADH and FADH₂. - The electrons obtained from the oxidation of of glucose are temporarily stored in NADH and FADH2. The energy derived from the oxidation of NADH and FADH is used to drive the electron transport chain and chemiosmotic synthesis of ATP.

Proton gradient

The graduated difference in the concentration of protons across a membrane.

Reduction (anion)

a substance gain electrons, or is reduced

Oxidation (cation)

a substance loses electrons, or is oxidized

Mitochondria

- are in nearly all eukaryotic cell -have a smooth out membrane and inner membrane folded into CRISTAE -The inner membrane creates two compartments: intermembrane space and mitochondrial MATRIX

The Krebs Cycle

-The Krebs cycle is a series of reactions that remove electrons, donating them to the electron carriers NAD⁺ and FAD to form NADH and FADH₂. Thesis carriers will contribute their electrons to an electron transport chain that will then generate significantly more ATP than is produce by the Krebs cycle. - The two carbon atoms contributed by acetyl CoA are each converted to CO₂. Thus, every carbon atom from the original glucose is ultimately incorporated into a CO₂ molecule. -Finally, one molecule of ATP is released for each pyruvate molecule that enters the Krebs cycle. Because each glucose molecule contributes two pyruvate molecules, the Krebs cycle generates a total of two ATP molecules for each glucose molecule metabolized.

pyruvate can be converted into what two forms?

1. Lactate (as in human muscles) 2. Ethanol (as in yeast)

In glycolysis, what starts the process of glucose oxidation?

ATP -Some ATP energy is used to start the process of glucose oxidation.

Metabolism

All the chemical reactions that occurs in living cells.

ATP synthanse (membrane protein)

An ATP-synthesizing enzyme found in the membranes of chloroplasts and mitochondria. -ATP synthase uses the energy released by the proton flow to produce ATP. From this process ATP synthase produces a large amount of ATP, around 26 ATP.

Mitochondrion (definition)

An organelle of eukaryotic cells containing the enzymes that catalyze the reactions of aerobic respiration. Mitochondria oxidize carbohydrates and fatty acids and produce ATP (along with carbon dioxide,water, and heat.

Alcohol fermentation

Another fermentation process you are probably familiar with results in the production of ethanol and CO2 from yeast. Humans have used the products of this natural fermentation process for centuries. The ethanol produced during fermentation of yeast is used to make beer and wine, and the CO2 gas is used to make bread rise. Both yeast and your muscle cells need to regenerate NAD+ to continue glycolysis. The two cell types used slightly different sets of chemical reactions to produce the same result. --The pyruvate molecules from glycolysis are transported into mitochondrion. Each pyruvate then enters a two-phase process: the formation of acetyl CoA, and the Krebs cycle.

Cellular Respiration (definition)

Any process of ATP production that involves a transfer of electrons from a reduced compound to an electron acceptor.

Electron carrier (definition)

Any reduced molecule that readily donates electrons to more oxidized molecules.

Location of Cellular Respiration

Cellular respiration begins with glycolysis in the cytosol. Pyruvate, the product of glycolysis, then enters the mitochondrial matrix, crossing both the outer and inner membranes. Both acetyl CoA formation and the citric acid cycle take place in the matrix. The NADH and FADH2 produced during the first three stages release their electrons to the electron transport chain of oxidative phosphorylation at the inner mitochondrial membrane. The inner membrane provides the barrier that creates an H+ gradient during electron transport, which is used for ATP synthesis.

Aerobic Respiration

Consumes organic molecules and O₂ and yields ATP

Successfully making cheese requires separating what?

Curds and Whey

Which of these is NOT a product of glycolysis?

FADH2 -FADH2 is a product of the citric acid cycle.

Which process is not part of the cellular respiration pathway that produces large amounts of ATP in a cell?

Fermentation -Fermentation is an alternate pathway used when oxygen levels are low.

Which molecule is metabolized in a cell to produce energy for performing work?

Glucose -Glucose is used to produce high-energy ATP in a cell.

oxidative phosphorylation

In oxidative phosphorylation, the NADH and FADH2 produced by the first three stages of cellular respiration are oxidized in the electron transport chain, reducing O2 to water and recycling NAD+ and FAD back to the first three stages of cellular respiration. The electron transport reactions supply the energy to drive most of a cell's ATP production.

Substrate-level phophorylation

In substrate level phophorylation, an enzyme transfer a phosphate group from one molecule (an intermediate in the breakdown of glucose to pyruvate) to ADP to form ATP. This is very different from the mechanism of ATP synthesis that takes place in oxidative phosphorylation.

The citric acid cycle

In the citric acid cycle, the two carbons from the acetyl group of acetyl CoA are oxidized to two molecules of CO2, while several molecules of NAD+ are reduced to NADH and one molecule of FAD is reduced to FADH2. In addition, one molecule of ATP is produced.

Cellular Respiration

Includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration.

You create a new variety of cheese that has very little water. Which of the following is true?

It is quite high in fat.

Which of the following describes the process of glycolysis?

It represents the first stage in the chemical oxidation of glucose by a cell. -Catabolism of glucose begins with glycolysis.

In muscle cells, fermentation produces _____.

Lactate and NAD+ -These are the products of fermentation as it occurs in muscle cells.

In cellular respiration, most ATP molecules are produced by _____.

Oxidative Phosphorylation -This process utilizes energy released by electron transport.

The final electron acceptor of cellular respiration is _____.

Oxygen - Oxygen is combined with electrons and hydrogen to form water.

Energy yielding phase

The 6 carbon fructose biphosphate is first broken down into two 3 carbon molecules of glyceraldehyde-3-phosphate (G3P). These two molecules are then transformed by a series of reactions into two molecules of pyruvate The process yields four molecules of ATP and converts two molecules of NAD+ to NADH. Because two ATP molecules were consumed in the energy-investment phase, the net yield at the end of glycolysis is two ATP molecules.

In most cells, not all of the carbon compounds that participate in glycolysis and the citric acid cycle are converted to carbon dioxide by cellular respiration. What happens to the carbon in these compounds that does not end up as CO2?

The carbon compounds are removed from these processes to serve as building blocks for other complex molecules. -Glycolysis and the citric acid cycle provide many compounds that are the starting point for the synthesis of aminio acides and lipids.

Which of the following statements about the chemiosmotic synthesis of ATP is correct?

The chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane. -Chemiosmosis uses the energy of a proton gradient to make ATP; the proton gradient is formed by coupling the energy produced by electron transport with movement of protons across the membrane

Glycolysis (definition)

The first phase of cellular respiration or fermentation, in which a series of chemical reactions oxidize glucose to produce pyruvate and ATP.

Krebs cycle (definition)

The second phase of cellular respiration, in which a series of chemical reactions in the mitochondria break down acetyl CoA, the product of glycolysis, to carbon dioxide and produce ATP and reduced compounds to feed into the electron transport chain.

Electron transport (def)

The third phase of cellular respiration, in which the potential energy of electrons is stepped down, resulting in the release of energy and the production of ATP.

Lactate fermentation

Through glycolysis, muscle cells convert ADP to ATP and NAD+ to NADH. For glycolysis to produce more ATP, the cell must replenish its NAD+ supply. When oxygen is present, this occurs by cellular respiration. But when oxygen is absent, it occurs by fermentation. Fermentation converts pyruvate to another compound-such as lactate-using NADH. This reaction produces NAD+, which can then supply glycolysis. If fermentation continues long enough, lactate accumulates. The accumulation of lactate is one reason strenuous exercise makes your muscle sore. Notice that glycolysis produces two ATP molecules, but fermentation produces no additional ATP molecules.

Which statement about the citric acid cycle is correct?

he last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle. -This is the correct description of the cyclic nature of this sequence of reactions.

Fermentation

is a partial degradation of sugars that occurs without O²

The proximate (immediate) source of energy for oxidative phosphorylation is _____.

kinetic energy that is released as hydrogen ions diffuse down their concentration gradient. -Concentration gradients are a from of potential energy.

in the kreb cycle?

the remaining carbon atoms from glucose are incorporated into molecules of carbon dioxide. This process produces two molecules of ATP and a series of electron carriers. The electron carriers essentially transport energy from glucose to the next phase of cellular respiration. The electron carriers donate their electrons to a series of complexes within the inner mitochondrial membrane. This complexes together called the electron transport chain.

Mitochondria

the site of cellular respiration

Redox Reaction (oxidation-reduction reactions)

the transfer of electrons during chemical reactions. -Redox reactions release energy when electrons move closer to electronegative atoms. Example: Na + Cl → Na⁺ + Cl⁻ the formation of table salt is a REDOX REACTIOIN

Electron Transport Chain

consist of several molecules (primarily proteins) built into the inner membrane of mitochondria of eukaryotic cells and the plasma membrane of aerobically respiring prokaryotes.

Which of the following cheeses would likely spoil the most quickly?

A low fat, low salt variety

ATP (adenosine triphosphate)

A molecule that can be hydrolyzed to release free energy; universally used by cells to store and transfer energy.

Formation of acetyle COA

A pyruvate molecules is first joined to a CoA molecule. In this reaction, CO2 is released and NADH is formed. The third product is acetyl CoA, which contains the remaining two carbon atoms of pyruvate bound to CoA. This becomes a substrate for the later reaction of the Krebs cycle. -The acetyle group, now a two carbon remnant of the original glucose, enters the Krebs cycle.

Cellular respiration

CARBON DIOXIDE and WATER are the by-products of cellular respiration.

Into which molecule are all the carbon atoms in glucose ultimately incorporated during cellular respiration?

Carbon dioxide -All of the carbon atoms in glucose are incorporated into carbon dioxide: 2 molecules are formed as pyruvate is converted to acetyl CoA, and four molecules are form during the Krebs cycle.

acetyle CoA formation

In acetyl CoA formation, pyruvate (a product of glycolysis) is oxidized to acetyl CoA, with the reduction of NAD+ to NADH and the release of one molecule of CO2.

Glycolysis

In glycolysis, the six-carbon sugar glucose is converted to two molecules of pyruvate (three carbons each), with the net production of 2 ATP and 2 NADH per glucose molecule. There is no O2 uptake or CO2 release in glycolysis.

During electron transport, energy from _____ is used to pump hydrogen ions into the _____.

NADH and FADH₂... intermembrane space -The energy released as electron, which have been donated by NADH and FADH₂, is passed along the electron transport chain and used to pump hydrogen ions into the intermembrane space.

Which of the following statements about the electron transport chain is true?

NADH and FADH₂ donate their electrons to the chain. -The electrons lose energy as they move down the chain, and this energy is used to create a proton gradient that drives the synthesis of ATP.

The Electron Transport Chain and ATP Synthase

The electron transport chain and the enzyme ATP synthase participate in the final phase of cellular respiration, electron transport. The earlier phases provide energetic electrons in the form of the electron carriers NADH and FADH₂. -Here you can follow the fate of electrons donated by NADH. The electrons are passed to the first carrier int he chain then move down the chain, losing energy as they go. The energy is used to pump protons across the membrane into the intermembrane space. The creates a proton gradient that is a source of potential energy. -The last electron acceptor is oxygen, which reacts with the electrons and protons to form H₂O or water. The bonding of oxygen with electrons and protons is the reason cellular respiration depends on oxygen and works only under aerobic conditions. -ATP synthase allows protons to diffuse across the membrane down their concentration gradient. It uses the energy released by the flow to synthesize ATP from ADP and inorganic phosphate.

Energy investment phase

The energy-investment reactions cost the cell two ATP molecules but are necessary to prepare glucose for the reactions that follow. The end result of these reaction is a molecule of FRUCTOSE BIPHOSPHATE, a 6 carbon sugar. This molecule is the starting point for the energy-yielding reactions.

The Fate of Pyruvate

The fate of pyruvate after glycolysis depends on the metabolic state of the cell. The presence or absence of oxygen determines the metabolic state. Consider the metabolism in your muscle cells. At rest or during light exercise, when oxygen is plentiful, pyruvate enters the Krebs cycle and continues to be metabolized through cellular respiration. During heavy exercise, your lungs and circulatory system can't transport oxygen to your muscles rapidly enough to keep electron transport chains active. The lack of oxygen forces a shift in energy metabolism toward the anaerobic pathway, fermentation. In muscle cells, fermentation results in lactate production, In some organisms, fermentation produces ethanol and carbon dioxide.

what happens during Glycolysis?

The first phase of respiration, glycolysis, occurs in the cytoplasm. During glycolysis, glucose is broken down into 2 molecules of PYRUVATE. Glycolysis also generates 2 ATP molecules and 2 molecules of an electron carrer called NADH.

Glycolysis

The initial reactions in the conversion of glucose to energy are called glycolysis. It may seem strange, but to get energy in the form of ATP from glucose, we first have to expend energy in the form of ATP. During this energy-investment phase, two ATP molecules are consumed. Later in glycolysis, a series of energy-yielding reactions produced four ATP molecules and two NADH molecules.

Electron transport chain

The molecules involved in redox reaction that step down the potential energy of electrons. This process results in the release of energy, which is harnessed to produce ATP.

True or false? The reactions that generate the largest amounts of ATP during cellular respiration take place in the mitochondria.

True - Glycolysis takes place in the cytoplasm, whereas the Krebs cycle and the electron transport chain, which generate the largest amount of ATP during cellular respiration, take place in the mitochondria.

Which of these enters the citric acid cycle?

acetyl CoA -Acetyl CoA is a reactant in the citric acid cycle.

In fermentation _____ is reduced and _____ is oxidized.

pyruvate ... NADH -The pyruvate from glycolysis is reduced to either lactate or ethanol, and NADH is oxidized to NAD+.

Among the products of glycolysis, which compounds contain energy that can be used by other biological reactions?

pyruvate, ATP, and NADH -ATP is the main product of cellular respiration that contains energy that can be used by other cellular process. Some ATP is made in glycolysis. In addition, the NADH and pyruvate produced in the glycolysis are used in subsequent steps of cellular respiration to make even more ATP.

Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration?

transforming the energy in glucose and related molecules in a chemical form that cells can use for work. -the energy made available during cellular respiration is coupled to a production of ATP, the basic energy currency that cell use for work.

In the absence of oxygen, what is the net gain of ATP for each glucose molecule that enters glycolysis?

two ATP -Four ATP are made, but two ATP are consumed to start the process of glycolysis.