Cellular Respiration Chapter 7 Part 2

What are the two ways glucose can be stored in?

Glycogen in animals and as starch in plants

What is coenzyme Q (CoQ)

In respiration, a mobile electron acceptor that transports electrons from complexes I and II to complex III in the electron transport chain and moves protons from the mitochondrial matrix to the intermembrane space

Citric Acid Cycle

In the citric acid cycle, the acetyl group of acetyl-CoA is completely oxidized to carbon dioxide and the chemical energy is transferred to ATP by substrate-level phosphorylation and to the reduced electron carriers NADH and FADH2.

Animals breathe in air that contains more oxygen than the air they breathe out. Where is oxygen consumed?

Oxygen is consumed in cellular respiration. Oxygen is the final electron acceptor in the electron transport chain and is converted to water.

What is pyruvate dehydrogenase?

Pyruvate dehydrogenase is the enzyme that mediates pyruvate decarboxylation. This step is the critical link between anaerobic and aerobic respiration. With this link broken, cells would be limited to anaerobic respiration.

Pyruvate oxidation

Pyruvate is oxidized in the mitochondrial matrix, forming acetyl-CoA, the first substrate in the citric acid cycle

ATP synthase

drives the synthesis of ATP by means of an electrochemical proton gradient

Most of the proteins of the electron transport chain are

embedded in the inner mitochondrial membrane

In eukaryotes, fermentation takes place:

in the cytoplasm

PFK-1 is _____ by ATP and _____ by ADP.

inhibited; activated

Certain complexes of the mitochondrial electron transport chain pump protons. Protons are pumped across the _____ mitochondrial membrane, from the _____ to the _____.

inner; matrix; intermembrane space

During the citric acid cycle, the production of CO2 is the result of the _____ of intermediate compounds of the citric acid cycle coupled to the production of _____.

oxidation; NADH

In eukaryotes, pyruvate oxidation takes place in the

mitochondrial matrix

the citric acid cycle takes place in the

mitochondrial matrix

The final (terminal) electron acceptor of the electron transport chain is

oxygen

During lactic acid fermentation, pyruvate is:

reduced

In the absence of oxygen, fermentation:

regenerates NAD+ from the reduction of pyruvate

Why are fatty acids a good source of energy?

they are high in energy due to their many C-C and C-H bonds (more electrons available for oxidation)

Regulation of cellular respiration

cellular respiration is inhibited by its products, including ATP and NADH, and activated by its substrates, including ADP and NAD+. ATP levels are an indication of how much energy is available to the cell

A single molecule of glucose requires _____ "turn(s)" through the citric acid cycle for its chemical energy to be completely harvested.

2

How did early cells meet their energy requirements?

A possibility is that early prokaryotes evolved pumps to drive protons out of the cell in response to an increasingly acidic environment. some pumps might have used the energy of ATP to pump protons, while others used the energy from ETC to pump protons. At some point, proton pumps powered by ETC might have generated a large enough electrochemical gradient that the protons could pass back throught he ATP-driven pymps, running them in reverse to synthesize ATP.

what is fermentation?

A variety of metabolic pathways that produce ATP from the partial oxidation of organic molecules without oxidative phosphorylation or an electron acceptor, such as oxygen.

Which molecule would you expect to act as allosteric activator of an enzyme in glycolysis?

ADP

Phosphofructokinase (PFK-1) is an allosteric enzyme that catalyzes a key regulatory step in glycolysis. What else is true about this enzyme? Select all that apply. -ATP acts as an allosteric inhibitor of PFK-1 activity. -Cells switch to β-oxidation of fatty acids when PFK-1 activity is inhibited. -Decreased levels of citrate in the cytoplasm inhibit PFK-1 activity. -ADP and AMP are allosteric activators of PFK-1 activity.

ATP acts as an allosteric inhibitor of PFK-1 activity. ADP and AMP are allosteric activators of PFK-1 activity.

During the citric acid cycle: -ATP is synthesized by oxidative phosphorylation. -ATP is synthesized by substrate-level phosporylation. -high energy electrons are removed from NAD+ and FADH. -fuel molecules are completely reduced

ATP is synthesized by substrate-level phosphorylation.

At the end of pyruvate oxidation, but before the subsequent stages of cellular respiration, which molecules contain the energy held in the original glucose molecule?

At the end of pyruvate oxidation, the energy in the original glucose molecule is contained in acetyl-CoA and NADH.

At the end of the citric acid cycle, but before the subsequent stages of cellular respiration, which molecules contain the energy held in the original glucose molecule?

At the end of the citric acid cycle, the energy in the original glucose molecule is contained in ATP, NADH, and FADH2.

In the absence of carbohydrates, what can maintain production of NADH and FADH2 by the citric acid cycle?

Beta-oxidation of fatty acids

When a single pyruvate is converted to acetyl-CoA during pyruvate oxidation, the other products of the reaction are

CO2 and NADH

We consume a variety of carbohydrates that are digested into a variety of different monosaccharides. How do these different sugars enter glycolysis?

Different sugars can be modified to form different intermediates of glycolysis.

What are two different metabolic pathways that pyruvate can enter?

In the first pathway, pyruvate is converted to acetyl-CoA, which is the starting substrate for the citric acid cycle. During the citric acid cycle, the chemical energy in the bonds of actyl-CoA is transferred to ATP by substrate-level phsophorylation and to the electron carriers NADH and FADH2. The second pathway is fermentation, a reaction that happens without oxygen. There are many fermnetation pathways, but all rely on oxidation of NADH to NAD+ when pyruvate or a derivative of pyruvate is reduced. Two major fermentation pathways are lactic acid fermentation and ethanol fermentation. In the lactic acid pathway, electrons from NADH are transferred to pyruvate to produce lactic acid and NAD+. In the ethanaol fermentation pathway, pyruvate releases carbon dioxide to form acetaldehyde, and electrons from NADH are transfereed to the molecule to produce ethanol and NAD+.

Which of the following best describes how ATP synthase converts the potential energy of the proton gradient to the chemical energy of ATP?

Kinetic energy from the flow of protons is converted to the kinetic energy of rotation of the F0 subunit; the rotation of the F0 subunit leads to rotation of the F1 subunit, which can then catalyze ATP synthesis

How does muscle tissue generate ATP during short-term and long-term exercise?

Muscle tissue generates ATP during short-term wxercise by converting stored glycogen to glucose. Glucose is rapidly broken down anaerobically to pyruvate, which then feeds into the lactic acid fermentation pathay. During long-term exercise, the liver releases glucose into the blood, which is taken up by muscle cells and oxidized to produce ATP. In addition, adipose tissue releases fatty acids that are alos taken up by muscle cells and broken down by beta-oxidation. These processes are slower to convert glucose and other molecules to energy; however, the end result is the production of more ATP than the fermentation pathway can produce.

Cytochrome c

The enzyme to which electrons are transferred in complex III of the electron transport chain.

What is the chemiosmotic hypothesis?

The hypothesis that the gradient of protons across a membrane provides a source of potential energy that is converted into chemical energy stored in ATP.

How does the movement of electrons along the electron transport chain lead to the generation of a proton gradient?

The movement of electrons along the ETC in the inner mitochondrial membrane is coupled to the transfer of protons through several enzyme complexes and electron carriers. Electrons donated by NADH enter through complex I, and electrons donated by FADH2 enter through complex II. From complexes I and II, coenzyme Q(CoQ) picks up electrons and transfers them to complex III. Complex III donates electrons to cytochrome c, which in turn transfers them to complex IV, which then donates them to the final electron acceptor, oxygen. As the electrons pass through the complexes, protons are pumped into the intermembrane space. This creates a concentration and charge gradient, providing a source of potential energy that is then used to drive the synthesis of ATP.

β-(beta-)oxidation

The process of shortening fatty acids by a series of reactions that sequentially remove two carbon units from their ends. I t produces NADH and FADH2 molecules that provide elctrons for the synthesis of ATP by oxidative phosphorylation, also produces acetyl-CoA. B-oxidation of fatty acids also produces water as by-product.

How is a proton gradient used to generate ATP?

The protons accumulated in the intermembrane space cannot passively diffuse across the membrane, so they diffuse through a transport channel called ATP synthase. This enzyme is composed of two subunits: F0 (the channel through which protons flow) and F1 (the catalytic unit that synthesizes ATP). Proton flow through the channel causes it to rotate, which converts the energy of the proton gradient into mechanical rotational energy (kinetic energy). The rotation of the F- subunit leads to rotation of the F1 subunit. Rotation causes conformational changes in the F1 subunit that allow it to catalyze the synthesis of ATP from ADP and Pi.

How can cells produce a coordinated response to produce ATP? Regulation of PFK-1

The regulation of the glycolytic enzyme phosphofructokinase-1 (PFK-1) is an example of integrated metabolic control.

Uncoupling agents are proteins spanning the inner mitochondrial membrane that allow protons to pass through the membrane and bypass the channel of ATP synthase. Describe the consequences for the proton gradient and ATP production.

Uncoupling agents decrease the proton gradient and therefore decrease levels of ATP. The energy of the proton gradient is not used for oxidative phsophorylation but instead is dissipated as heat. Uncoupling angets are found naturally in certain tissues, such as fat, for heat generation. They can also act as poisons.

Bread making involves ethanol fermentation and typically uses yeast, sugar, flour, and water. Why are yeast and sugar used?

Yeast cells are eukaryotes. In bread making, yeast can use sugar as a food source for ethanol fermentation. the carbon dioxide produced in the process causes the bread to rise. The ethanol is removed in the baking process

The flow of energy in cellular respiration

a single glucose molecule yields 32 ATP molecules

The electron transport chain.

a) The electron transport chain consists of four complexes (I to IV) in the inner mitochondrial membrane. b) electrons flow from electron carriers to oxygen, the final electron acceptor. c) The proton gradient formed from the electron transport chain has potential energy that is used to synthesize ATP.

Where do digested carbohyrdates go?

after getting broken down into glucose, they get released into blood where levels are regulated. Excess glucose stored as glycogen in liver and muscle.

Pyruvate oxidation is an important stage in cellular respiration because

it links glycolysis with the critic acid cycle