MB Chapter 6 Part 2

Which of these is NOT a product of the citric acid cycle (also called the Krebs cycle)?

acetyl CoA Acetyl CoA enters the citric acid cycle.

Which of these enters the citric acid cycle (also called the Krebs cycle)?

acetyl CoA Acetyl CoA is a reactant in the citric acid cycle (also called the Krebs cycle).

What two-carbon precursor molecule from carbohydrate metabolism is used to produce fatty acids?

acetyl-CoA Acetyl-CoA produced during the oxidation of pyruvate is the building block of fatty acids.

We inhale O2 and we exhale CO2. Carbon dioxide is produced _____.

In the reaction that creates acetyl CoA (coenzyme A) from pyruvate Carbon dioxide is produced in the transition between glycolysis and the citric acid cycle when the three-carbon pyruvate is cleaved to a two-carbon acetyl molecule with the remaining carbon of pyruvate released as carbon dioxide.

In muscle cells, fermentation produces _____.

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

During cellular respiration, glucose is oxidized. However, an intermediate __________ can be siphoned off and used to synthesize fats.

glyceraldehyde-3-phosphate Glyceraldeyhyde-3-phosphate is used in the synthesis of glycerol, which is a constituent of fats.

What is the name of the process in which glucose is converted to pyruvate?

glycolysis Glycolysis, or the splitting of sugar, splits a six-carbon glucose into two three-carbon pyruvate molecules.

The energy production per glucose molecule through the citric acid cycle is ____.

2 ATP, 6 NADH, 2 FADH2 Then NADH and FADH2 go through the electron transport chain.

The overall efficiency of respiration is approximately _____.

40% The efficiency of respiration is 7.3 kcal per mole times 38 moles (maximum ATP yield per mole of glucose) divided by 686 kcal (the amount of energy contained in one mole of glucose), or about 40%.

What happens to the energy that is released by electrons as they move through the electron transport chain?

It pumps H+ through a membrane. In eukaryotes, many of the electron transport molecules in the mitochondrion pump a hydrogen ion into the intermembrane space when they pass an electron along the chain.

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

NADH and FADH2 ... intermembrane space The energy released as electrons, 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.

During fermentation, __________ that was produced during glycolysis is converted back to __________.

NADH; NAD+ NADH molecules produced during glycolysis are converted back to NAD+ during fermentation. This NAD+ is used again in a new round of glycolysis.

What is the role of oxygen in cellular respiration?

Oxygen accepts high-energy electrons after they are stripped from glucose.

What is the purpose of embedding the electron transport chain in the membrane of a cell?

The membrane is impermeable to H+. Chemiosmosis relies on the properties of the membrane that prevent hydrogen ions (H+) from flowing down their concentration gradient. Hydrogen ions are permitted to reenter the cell across the membrane through ATP synthase, which captures their potential energy and uses it to synthesize ATP.

What is the ultimate fate of the electrons that are stripped from glucose during cellular respiration?

They are used to form water. At the end of the electron transport chain, the electrons and hydrogen ions are used to reduce oxygen to form water.

Through respiration, humans breathe in O2 and breathe out CO2. However, what would happen if we did not breathe in O2?

We would not make enough ATP to meet our energy requirements The electron transport chain accepts electrons from the breakdown products of glycolysis and the citric acid cycle, and it passes these electrons from one molecule to another until they are passed (along with two hydrogen ions) to oxygen to form water.

Cellular respiration accomplishes two major processes: (1) it breaks glucose down into smaller molecules, and (2) it harvests the chemical energy released and stores it in ATP molecules. By the end of _____, the breakdown of glucose is complete; most ATPmolecules are produced during _____.

the Citric Acid cycle ... electron transport

Which part(s) of cellular respiration take(s) place in the mitochondria?

the Citric Acid cycleand the electron transport chain

The enzyme ATP synthase catalyzes the phosphorylation of ADP to form ATP. In eukaryotic cells, the energy needed for this endergonic reaction is derived from _____.

the movement of hydrogen ions across the mitochondrial membrane The electron transport chain is an energy converter that uses the exergonic flow of electrons to pump hydrogen ions across the inner mitochondrial membrane from the matrix to the intermembrane space. Hydrogen ions diffuse back into the matrix via a channel in ATP synthase.

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

oxidative phosphorylation This process utilizes energy released by electron transport.

Some human cells, such as nerve cells, are restricted to aerobic respiration to recycle NADH and FADH2. If these cells are deprived of oxygen, then _____.

oxidative phosphorylation would come to a halt because there wouldn't be any oxygen to "pull" the electrons down the transport chain Without electronegative oxygen waiting at the end of the chain, electron flow would cease, along with the action of the protein complexes that create the proton gradients.

The final electron acceptor of cellular respiration is _____.

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

In cellular respiration, which of the following outcomes is the result of electrons moving through the electron transport chain (or its components)?

A proton gradient is formed. The energy released by the electron transport chain is used to create a proton gradient across the inner mitochondrial membrane.

Structure A is _____.

ATP synthase ATP synthase attaches phosphate groups to ADP molecules to generate ATP.

Cellular respiration completely breaks down a glucose molecule through glycolysis and the citric acid cycle. However, these two processes yield only a few ATPs. The majority of the energy the cell derives from glucose is _____.

found in NADH and FADH2 The energy in these molecules is used to drive the synthesis of ATP in the electron transport chain and chemiosmosis.

Each turn of the citric acid cycle generates one ATP and ___ additional energy-rich molecules: __________.

four; 3 NADH and 1 FADH2 The citric acid cycle generates 3 molecules of NADH and 1 molecule of FADH2. These molecules carry high energy electrons that will be delivered to the electron transport chain.

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 form of potential energy.

In the citric acid cycle (also called the Krebs cycle), ATP molecules are produced by _____.

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

NADH and FADH 2 are important in cellular respiration because they deliver high-energy electrons to the electron transport system. Electron transport produces _____ ATP molecule(s) per NADH molecule and _____ ATP molecules(s) perFADH 2 molecule.

three ... two

In electron transport, high-energy electrons "fall" to oxygen through a series of reactions. The energy released is used to _____.

transport protons into the intermembrane space of the mitochondria, where they become concentrated. They then flow back out into the the inner compartment (matrix) of the mitochodria. On the way back, protons turn ATP synthase turbines and produce ATP.

Fat is the most efficient molecule for long-term energy storage, even compared to carbohydrates, because _____.

with their numerous hydrogen atoms, fats provide an abundant source of high-energy electrons Because oxidative phosphorylation depends on a source of electrons (all of which are extracted from hydrogen atoms), fats, which contain primarily hydrogen and carbon atoms, are an abundant source of high-energy electrons that can be harvested for energy production.

For each glucose that enters glycolysis, _____ NADH enter the electron transport chain.

10 For each glucose molecule that enters glycolosis, a total of 10 NADH are produced -- 2 are produced in glycolysis, 2 are produced in acetyl CoA production, and 6 are produced in the citric acid cycle.

Besides sugars and fats, organisms can use other molecules as fuel for cellular respiration. When protein molecules are used, _____ are produced as waste.

amino groups The amino group is a residual product of the breakdown of amino acids.

Using the ATP generated during cellular respiration, the intermediates of glycolysis and the citric acid cycle, such as pyruvate and acetyl CoA, can be siphoned off and used to __________.

build amino acids, fats, and sugars The beauty of many metabolic pathways is that they can be used for both the breaking down of compounds for energy, or to synthesize complex macromolecules, depending on the needs of the cell and the availability of energy.

A scientist wants to study the enzymes of the citric acid cycle in eukaryotic cells. What part of the cell would she use as a source of these enzymes?

mitochondrial matrix The water-soluble citric acid cycle intermediates and enzymes of a eukaryotic cell are found in the mitochondrial matrix, where the newly synthesized NADH and FADH2 diffuse to proteins of the electron transport chain held within the inner mitochondrial membrane.

Bacteria have no membrane-enclosed organelles. However, some still generate ATP through cellular respiration. Where is the electron transport chain found in these organisms?

plasma membrane The electron transport chain requires a membrane that will act as a barrier to hydrogen ions that are being pumped across this space. The only membrane in a bacterial cell is the plasma membrane.

In oxidative phosphorylation, electrons are passed from one electron carrier to another. The energy released is used to _____.

pump protons (H+) across the mitochondrial membrane The energy harvested from many redox reactions is used to power proton pumps that span the inner mitochondrial membrane.

A muscle cell deprived of molecular oxygen will convert glucose to lactic acid to __________.

recycle NADH through fermentation During lactic acid fermentation, pyruvate is reduced directly by NADH to form lactate. This recycles NAD+, so the cycle continues.

In eukaryotes, most of the high-energy electrons released from glucose by cell respiration _____.

reduce NAD+ to NADH, which then delivers them to the electron transport chain Most of the high-energy electrons released from the glucose are picked up by NAD+ and sent through the electron transport chain.