Chapter 7 Cellular Respiration

Step 4: Oxidative Phosphorylation

Electrons are passed to progressively more electronegative complexes until they are accepted by Oxygen, to make water. But this doesn't make ATP directly. ETC pumps protons Electrochemical gradient (proton motive force)

Lactic Acid Fermentation is used routinely in

mammalian red blood cells and in skeletal muscle that has an insufficient oxygen supply to allow aerobic respiration to continue (that is, in muscles used to the point of fatigue).

Each molecule of FAD can accept 2

2 Hydrogens

Each molecule of NAD+ can accept 2 what?

2 electrons

About 40% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about

32 ATP

Oxidative phosphorylation

• Electron transport proteins "pump" protons,creating a proton gradient. • ATP synthase uses the energy of the protongradient to bind phosphate groups to ADP. • Occurs only in the mitochondrial matrix. (LOOK ONLY AT DIAGRAM B)

How many NADH molecules are produced on each turn of the citric acid cycle?

3

At the electron transport chain, ____ is oxidized to ______.

FADH2 is oxidized to FAD.

What compound receives electrons from NADH?

FMN

Metabolic Processes that produce ATP

Fermentation (anaerobic): sugars (or other organic fuels) are partially degraded to produce some ATP in the absence of oxygen Aerobic Respiration: oxygen is consumed as a reactant

Cyanide inhibits cytochrome c oxidase, a component of the electron transport chain. If cyanide poisoning occurs, would you expect the pH of the intermembrane space to increase or decrease? What effect would cyanide have on ATP synthesis?

Figure After cyanide poisoning, the electron transport chain can no longer pump electrons into the intermembrane space. The pH of the intermembrane space would increase, the pH gradient would decrease, and ATP synthesis would decrease

Connections of Lipids and Proteins to Glucose Metabolism in Glycolysis, pyruvate oxidation, citric acid cycle, oxidative phsophorilation

Glycogen from the liver and muscles, hydrolyzed into glucose-1-phosphate, together with fats and proteins, can feed into the catabolic pathways for carbohydrates.

Regulation of Cellular Respiration : Glycolysis

Glycolysis The control of glycolysis begins with the first enzyme in the pathway, hexokinase . Hexokinase phosphorylates glucose, fixing it into glycolysis. When hexokinase is inhibited, glucose is not phosphorylated and diffuses out of the cell and does not become a substrate for the respiration pathways in that tissue.

Click on the mitochondria that correctly illustrates the proton concentration gradient

High to low

Fermentation recycles the

NADH to NAD+.

What is removed from pyruvate during its conversion into an acetyl group?

carbon dioxide

CoenzymeA is

important for carrying carbons (Acetyl groups) in many biological processes

Where is the electron transport chain located?

inner mitochondrial membrane

Which of the following fermentation methods can occur in animal skeletal muscles? A lactic acid fermentation B alcohol fermentation C mixed acid fermentation D propionic fermentation

lactic acid fermentation

Glucose is _____ to carbon dioxide.

oxidized

In fermentation, cells

recycle NAD+ back to glycolysis

In cellular respiration, glucose is

systematically oxidized to carbon dioxide, with electrons captured by NAD+ and FAD at several steps. Oxygen is required for the electron transport chain, where it is reduced to water.

Chemiosmosis involves __________.

the movement of hydrogen ions across the mitochondrial membrane

Glucose is broken down into

two pyruvate molecules and NADH and ATP is produced.

Oxygen is reduced to _____.

water

Each molecule of NAD+ can accept 1

1 proton

There are three reasons why the number of ATP is not known exactly

1) Photophosphorylation and the redox reactions are not directly coupled; the ratio of NADH to ATP molecules is not a whole number 2) ATP yield varies depending on whether electrons are passed to NAD+ or FAD in the mitochondrial matrix 3) The proton-motive force is also used to drive other kinds of work

A Glycolysis B Pyruvate Oxidation C Citric Acid Cycle D Electron Transport Chain

A Glycolysis C Citric Acid Cycle

Which of the following statements about NAD+ is true? A NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle. B NAD+ has more chemical energy than NADH. C NAD+ can donate electrons for use in oxidative phosphorylation. D In the absence of NAD+, glycolysis can still function.

A NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.

Match the correct options to label the mitochondria below. Use each option only once.

A Outer membrane D Matrix C Inner membrane D Inner membrane space E Cristae

ATP synthase:

A channel protein that makes ATP from protons moving down their concentration gradient

Substrate-level phosphorylation

A high-energy phosphate group is transferreddirectly from a substrate to ADP to form ATP. • Occurs in the cytosol and mitochondrial matrix. (LOOK ONLY AT DIAGRAM A)

The energy currency used by cells is __________.

ATP

Adenosine TriPhosphate (ATP)

ATP --> ADP + Pi + energy ADP + Pi + energy --> ATP

During the second half of glycolysis, what occurs?

ATP is made.

Why is it beneficial for cells to use ATP rather than energy directly from the bonds of carbohydrates? What are the greatest drawbacks to harnessing energy directly from the bonds of several different compounds?

ATP provides the cell with a way to handle energy in an efficient manner. The molecule can be charged, stored, and used as needed. Moreover, the energy from hydrolyzing ATP is delivered as a consistent amount. Harvesting energy from the bonds of several different compounds would result in energy deliveries of different quantities

Which of the following maintains the proton gradient across in the inner mitochondrial membrane? Choose ALL the correct choices. A The ETC pumps protons into the matrix B The ETC pumps protons into the inner membrane space C Water is formed in the matrix reducing the hydrogen concentration in the matrix D Water is formed in the matrix increasing the hydrogen concentration in the matrix E Water is formed in the inner membrane space increasing the hydrogen concentration in the inner membrane space F Water is formed in the inner membrane space decreasing the hydrogen concentration in the inner membrane space

B The ETC pumps protons into the inner membrane space C Water is formed in the matrix reducing the hydrogen concentration in the matrix

At end of citric acid cycle

Carbon skeleton of glucose is gone Electrons with high potential energy stored in NADH, FADH2 Now make ATP using oxidative phosphorylation, in the ELECTRON TRANSPORT CHAIN

In which reactions of cellular respiration does oxidative phosphorylation occur? Choose ALL the correct choices. A Glycolysis B Pyruvate Oxidation C Citric Acid Cycle D Electron Transport Chain

D Electron Transport Chain

This makes DNP as an effective weight loss drug. A proton gradient can no longer be formed across the inner mitochondrial membrane as pumping of hydrogen ion is stopped.

Dinitrophenol was introduced in 1933 by Cutting and Tainter as weight loss pills which were popular in the United States till 1938. DNP is a protonophore that has the ability to leak protons across the inner mitochondrial membrane and allowing the bypass of ATP synthase. This results in the ATP production becoming less efficient. Hence, the energy which is normally produced during cellular respiration is being wasted as heat. With the increase in the intake of DNP, the production of energy became less efficient. This will result in the increase of metabolic rate by burning off the body fat so as to meet the energy demands of the body. This makes DNP as an effective weight loss drug. A proton gradient can no longer be formed across the inner mitochondria' membrane as pumping of hydrogen ion is stopped. This will result in the decrease of pH across the inner membrane of mitochondria and increase of pH in the intracellular region.

Generation of ATP through the Pyruvate Oxidation & Citric Acid Cycle

For one Pyruvic acid that enters the mitochondria: + 4 NADH + H+ (1 from pyruvate oxidation & 3 from CAC) + 1 FADH2 + 1 ATP + 3 CO2 (1 from pyruvate oxidation & 2 from CAC) 1 Glucose Molecule = 2 Pyruvic Acids Net = + 8 NADH + H+ + 2 FADH2 + 2 ATP +6 CO2

The Stages of Cellular Respiration:

Harvesting of energy from glucose has three stages: ​Glycolysis (breaks down glucose into two molecules of pyruvate) Pyruvate Oxidation oxidizes pyruvate and attaches the remaining carbon to Acetyl-coA The citric acid cycle (completes the breakdown of glucose) ​Oxidative phosphorylation (accounts for most of the ATP synthesis)

NAD+/NADH Is NAD+ the reduced or oxidized form of this coenzyme?

Oxidized

Reduction and Oxidation of Methane and Oxygen

Oxygen is electronegative

Trace the path of electrons through the steps of cellular respiration.

Redox: Energy is derived from electrons in "food" or glucose or metabolites of glucose Specific reaction (ie. NAD+ + 2H NADH + H+) Glycolysis provides electrons via 2 NADH = The hormone insulin signals to the cell's plasma membrane to transport, glucose into the cell, Glycolysis means the breakdown of the glucose molecule, The process breaks glucose down into 2 molecules of Pyruvate, Pyruvate is the ionized form of pyruvic acid, Each molecule of pyruvate contains 3 carbons, Ion = electrically charged atom or molecule Krebs provides electrons via 6 NADH and 2 FADH2- main objective of this stage is to use the pyruvates to produce more ATP. It is in this stage that oxygen plays a vital role. Electrons power the proteins in the ETC- remaining energy from the glucose is released by the electron transport chain O2 is the final electron acceptor __H2O or metabolic water is the result (byproduct)

1st Step Glycolysis

Takes place in cytosol Two phases

Lactic Acid Fermentation

The fermentation method used by animals and certain bacteria, like those in yogurt

Alcohol Fermentation

The first chemical reaction of alcohol fermentation is the following (CO2 does not participate in the second reaction):

Tremetol, a metabolic poison found in the white snake root plant, prevents the metabolism of lactate. When cows eat this plant, it is concentrated in the milk they produce. Humans who consume the milk become ill. Symptoms of this disease, which include vomiting, abdominal pain, and tremors, become worse after exercise. Why do you think this is the case?

The reaction for lactic acid fermentation is, Pyruvic acid + NADH <--> lactic acid + NAD+ This reaction occurs in muscle when muscle need energy faster than the blood can supply oxygen to it. Thus, an anaerobic reaction is generated. The enzyme Lactate dehydrogenase will catalyzes this reaction. The lactic acid formed cause fatigue as well as stiffness in the muscle. The Lactic acid can be converted back to pyruvic acid once there is enough supply of oxygen provided by the blood. The lactic acid formed in the muscle gets circulated and is removed by the liver tissue. The illness due to accumulation of Tremetol which is a metabolic poison is caused due to the build-up of lactic acid. As the levels of lactic acid rise after exercise due to the insufficient supply of oxygen, the symptoms of the disease get worse.

ATP is made during glycolysis. In the absence of oxygen, the cell will may undergo fermentation. What is the function of these additional steps of fermentation? Hint: the answer is not to make ATP, that already happened in glycolysis.

These fermentation pathways consist of glycolysis with some extra reactions tacked on at the end. In yeast, the extra reactions make alcohol, while in your muscles, they make lactic acid. Fermentation is a widespread pathway, but it is not the only way to get energy from fuels anaerobically (in the absence of oxygen). Some living systems instead use an inorganic molecule other than O2, such as sulfate, as a final electron acceptor for an electron transport chain. This process, called anaerobic cellular respiration, is performed by some bacteria and archaea.

What do the electrons added to NAD+ do?

They go to another pathway for ATP production.

ATP synthase produces ATP by

chemiosmosis. As protons move down their concentration gradient, ATP is produced.

A reducing chemical reaction __________.

adds an electron to the substrate

The work of the cell includes

assembling polymers, membrane transport, moving, and reproducing

Lipids and amino acids can enter

cellular respiration at different points.

Acetyl-coA enters the citric acid cycle which serves to

complete the oxidation of glucose to carbon dioxide. The CAC only makes 1 ATP per cycle, but it produces a lot of reduced coenzymes.

Glycolysis occurs in the

cytosol in the presence or absence of oxygen.

The removal of an electron from a molecule, oxidizing it, results in a

decrease in potential energy in the oxidized compound.

NADH and FADH2 shuttle the

electrons from glucose to the Electron Transport Chain.

Production of ATP is regulated to meet the

energy requirements of the cell.

In the presence of oxygen, pyruvate will

enter the mitochondria, where is oxidized and attached to CoenzymeA to create Acetyl-coA. Carbon dioxide is produced and NAD+ is reduced to NADH.

What is the original source of the electrons that end up in water at the end of the ETC?

glucose

During cellular respiration, most energy flows in this sequence:

glucose --> NADH --> electron transport chain --> proton-motive force --> ATP

What does pyruvate doin the absence of O2?

glycolysis still makes a bit of ATP but it also generates NADH & pyruvatewhich have "no place to go"

ATP is produced in

limited amounts by substrate-level phosphorylation, but the majority of ATP is made by oxidative phosphorylation which uses energy in an H+ gradient to produce ATP in the mitochondria.

Remember, coenzymes are

non-protein substances (e.g. vitamin) that associates with and activates an enzyme Examples: NAD+, FAD In C.R., these two coenzymes act as electron shuttles

The final electron acceptor of the ETC is

oxygen, which combines with two electrons and 2 protons to form water.

"Redox"

paired oxidation and reduction reactions

The control of which enzyme exerts the most control on glycolysis?

phosphofructokinase

The energy released as the electrons fall to lower energy states is used to

pump protons across the inner mitochondrial membrane into the innermembrane space.

In the absence of oxygen, the NADH made by glycolysis must be

recycled back to NAD+.

During the citric acid cycle, NAD+ is ______ to NADH.

reduced

The fermentation of pyruvic acid by yeast produces

the ethanol found in alcoholic beverages. Ethanol tolerance of yeast is variable, ranging from about 5 percent to 21 percent, depending on the yeast strain and environmental conditions.