Energy and RespirationEnergy and Respiration

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Energy and foodEnergy and foodThe amount of energy available The amount of energy available from a certain food is sometimes from a certain food is sometimes called its called its calorific valuecalorific value

The average adult requires about The average adult requires about 8400 Kilojoules (2000 kilocalories) 8400 Kilojoules (2000 kilocalories) of energy per dayof energy per day

An adult male undertaking heavy An adult male undertaking heavy physical labor may require as physical labor may require as much as much as 14,700 kJ (3500 kcal)14,700 kJ (3500 kcal)

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Energy and foodEnergy and food

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• Carbohydrates, proteins and fats make Carbohydrates, proteins and fats make up most of the human diet. up most of the human diet.

• The idea ratio should be approximately The idea ratio should be approximately 60% to 30% to 10% respectively60% to 30% to 10% respectively

• Carbohydrates are the most readily Carbohydrates are the most readily available source of energyavailable source of energy

• Fats which are essentially non-oxidized Fats which are essentially non-oxidized provide the most energy per unit massprovide the most energy per unit mass

Energy and foodEnergy and food

The body does not “burn” food, but The body does not “burn” food, but nevertheless it is converted to the nevertheless it is converted to the same set of products (COsame set of products (CO22 and H and H22O) O)

through a series of oxidation through a series of oxidation reactions.reactions.

Since Hess’ Law shows that the Since Hess’ Law shows that the energy change is independent of the energy change is independent of the pathway, the same amount of energy pathway, the same amount of energy is released through burningis released through burning food.food.

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The Bomb CalorimeterThe Bomb CalorimeterA bomb calorimeter can be A bomb calorimeter can be used to measure the used to measure the energy content of food.energy content of food.

The calorific value of food The calorific value of food can be measured by heating can be measured by heating a pre-measured mass of a pre-measured mass of food and igniting it in an food and igniting it in an oxygen atmosphere. oxygen atmosphere.

The heat is transferred to a The heat is transferred to a water system and the heat water system and the heat evolved is computed from evolved is computed from the temperature change and the temperature change and the mass of waterthe mass of water

A diagram of a bomb calorimeter

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The Bomb CalorimeterThe Bomb CalorimeterThe calorific value of a The calorific value of a candy bar is about 250 candy bar is about 250 Dietician’s Calories or 250 Dietician’s Calories or 250 kilocalorieskilocaloriesThis means that if it were This means that if it were burned in a calorimeter, the burned in a calorimeter, the energy produced on energy produced on combustion would raise the combustion would raise the temperature of 2.5 kg water temperature of 2.5 kg water by 100°C assuming that the by 100°C assuming that the calorimeter itself does not calorimeter itself does not absorb any energy. absorb any energy. In most cases the energy In most cases the energy absorbed by the calorimeter absorbed by the calorimeter cannot be ignored and must cannot be ignored and must be included in the be included in the calculations.calculations. A diagram of a bomb calorimeter

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The Bomb CalorimeterThe Bomb CalorimeterA large candy bar A large candy bar weighs 50 g. If a 5.00 g weighs 50 g. If a 5.00 g sample of the candy sample of the candy bar, on complete bar, on complete combustion raises the combustion raises the temperature of 500 g temperature of 500 g water in a glass water in a glass container by 59.6°C. container by 59.6°C. Calculate the calorific Calculate the calorific value of the candy bar. value of the candy bar. The heat capacity of The heat capacity of the glass calorimeter is the glass calorimeter is 20.9 cal °C20.9 cal °C-1-1

A diagram of a bomb calorimeter

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The Bomb CalorimeterThe Bomb CalorimeterA large candy bar weighs 50 g. If a 5.00 g sample of the A large candy bar weighs 50 g. If a 5.00 g sample of the candy bar, on complete combustion raises the candy bar, on complete combustion raises the temperature of 500 g water in a glass container by 59.6°C, temperature of 500 g water in a glass container by 59.6°C, calculate the calorific value of the candy bar. The heat calculate the calorific value of the candy bar. The heat capacity of the glass calorimeter is 20.9 cal °Ccapacity of the glass calorimeter is 20.9 cal °C-1-1

Heat produced = heat absorbed by water + heat absorbed by calorimeter

= (m x C x ΔT)water + (m x C. x ΔT)calorimeter

= (500 g x 1.00 cal g-1 °C-1 x 59.6 °C) + (20.9 cal °C-1 x 59.6°C)

= 25,086 calories = 25.09 kcal (produced by 5.0 g of candy bar) = 5.02 kcal g-1

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RespirationRespirationRespiration is crucial Respiration is crucial function for all living function for all living organisms. organisms. In general the In general the process of process of respiration serves respiration serves two basic purposes two basic purposes 1.1. The disposal of The disposal of

electrons generated electrons generated during catabolism during catabolism

2.2. The production of The production of ATP. ATP.

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Cellular RespirationCellular Respiration

Cellular respirationCellular respiration involves a set of metabolic involves a set of metabolic processes that occur in the processes that occur in the cell to convert biochemical cell to convert biochemical energy from nutrients into energy from nutrients into adenosine triphosphateadenosine triphosphate (ATP) and waste products(ATP) and waste products

Respiration involves Respiration involves catabolic redox catabolic redox reactionsreactions. One molecule . One molecule is oxidized and another is is oxidized and another is reduced.reduced.

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Adenosine TriphosphateAdenosine Triphosphate

The structure of ATP includes an adenine group, a The structure of ATP includes an adenine group, a ribose sugar, and three phosphate groupsribose sugar, and three phosphate groups

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Adenosine TriphosphateAdenosine Triphosphate

Energy released from the catabolic destruction of Energy released from the catabolic destruction of carbon containing molecules is stored in ATP.carbon containing molecules is stored in ATP.

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ATP and ADPATP and ADP

Energy is released Energy is released when a phosphate when a phosphate group is released group is released from ATP resulting from ATP resulting in the formation of in the formation of ADP. ADP. The reversible The reversible reaction between reaction between ATP and ADP acts ATP and ADP acts much like a “battery much like a “battery “allowing the cell to “allowing the cell to store and release store and release energyenergy

The conversion of ATP to ADP releases about 30.5 kJ mol-1

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ATP and ADPATP and ADP

Energy is released Energy is released when a phosphate when a phosphate group is released group is released from ATP resulting from ATP resulting in the formation of in the formation of ADP. ADP. The reversible The reversible reaction between reaction between ATP and ADP acts ATP and ADP acts much like a “battery much like a “battery “allowing the cell to “allowing the cell to store and release store and release energyenergy

The conversion of ATP to ADP releases about 30.5 kJ mol-1

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Aerobic and Anaerobic Aerobic and Anaerobic Respiration Respiration

Respiration may be either Respiration may be either aerobicaerobic or or anaerobicanaerobic

AerobicAerobic respiration respiration uses oxygenuses oxygen as its as its terminal electron acceptor, terminal electron acceptor,

AnaerobicAnaerobic respiration uses terminal respiration uses terminal electron acceptors other than oxygenelectron acceptors other than oxygen

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Aerobic RespirationAerobic Respiration

Aerobic respiration requires oxygenAerobic respiration requires oxygen

A.A. It involves the break down of glucose, amino It involves the break down of glucose, amino acids and fatty acids to release energy acids and fatty acids to release energy

B.B. Oxygen is the terminal electron acceptor. Oxygen is the terminal electron acceptor.

C.C. The overall process of aerobic respiration can The overall process of aerobic respiration can be described as: be described as:

Glucose + Oxygen →Energy + Carbon dioxide + Glucose + Oxygen →Energy + Carbon dioxide + Water Water

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Aerobic RespirationAerobic Respiration

The aerobic respiration is a high energy yielding The aerobic respiration is a high energy yielding process.process.Up to 38 molecules of ATP are produced for Up to 38 molecules of ATP are produced for every molecule of glucose that is utilized. every molecule of glucose that is utilized. Aerobic respiration takes place in almost all Aerobic respiration takes place in almost all living things. living things. It is relatively easy for the body to get rid of the It is relatively easy for the body to get rid of the Carbon Dioxide and excess water. This is Carbon Dioxide and excess water. This is excretion (the removal of the toxic waste excretion (the removal of the toxic waste products of metabolism),products of metabolism),Maximum energy is released from the glucose. Maximum energy is released from the glucose.

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Anaerobic RespirationAnaerobic Respiration

Some organisms can respire in the absence of air: this is Some organisms can respire in the absence of air: this is anaerobic respiration. This does not release so much anaerobic respiration. This does not release so much energy and it produces more toxic waste products.energy and it produces more toxic waste products.

When Oxygen is not available, anaerobic respiration also When Oxygen is not available, anaerobic respiration also occurs in humans.occurs in humans.

Anaerobic respiration can take place during vigorous Anaerobic respiration can take place during vigorous exercise, building up lactic acid in muscle tissue. This exercise, building up lactic acid in muscle tissue. This results in muscle pain and cramping.results in muscle pain and cramping.

The bacteria in milk also produce lactic acid but is an optical The bacteria in milk also produce lactic acid but is an optical isomer of that produced in muscle cramping.isomer of that produced in muscle cramping.

Yeasts produce alcohol which is also toxic. Eventually there Yeasts produce alcohol which is also toxic. Eventually there will be so much alcohol that the yeast cannot survive.will be so much alcohol that the yeast cannot survive.

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Anaerobic RespirationAnaerobic Respiration

Anaerobic respiration is a special type of respiration, which Anaerobic respiration is a special type of respiration, which takes place without oxygen to produce energy in the form of takes place without oxygen to produce energy in the form of ATP or adenosine tri-phosphate. ATP or adenosine tri-phosphate. The process of anaerobic respiration for production of The process of anaerobic respiration for production of energy can occur in either of the ways represented below: energy can occur in either of the ways represented below:

Glucose →Energy (ATP) + Ethanol + Carbon dioxide (COGlucose →Energy (ATP) + Ethanol + Carbon dioxide (CO22) )

Glucose →Energy (ATP) + Lactic acid Glucose →Energy (ATP) + Lactic acid

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Anaerobic RespirationAnaerobic RespirationThe process of anaerobic respiration is The process of anaerobic respiration is relatively less energy yielding than aerobic relatively less energy yielding than aerobic respiration respiration During the alcoholic fermentation or the During the alcoholic fermentation or the anaerobic respiration two molecules of ATP anaerobic respiration two molecules of ATP (energy) are produced. for every molecule of (energy) are produced. for every molecule of glucose used in the reaction. glucose used in the reaction. Likewise for lactate fermentation 2 molecules of Likewise for lactate fermentation 2 molecules of ATP are produced for every molecule of ATP are produced for every molecule of glucose used. glucose used. Thus anaerobic respiration breaks down one Thus anaerobic respiration breaks down one glucose molecule to obtain two units of the glucose molecule to obtain two units of the energy storing ATP molecules. energy storing ATP molecules. 20

Hemoglobin and Oxygen Hemoglobin and Oxygen TransportTransport

The ability of iron to form complexes plays an important in The ability of iron to form complexes plays an important in the transport of oxygen and carbon dioxide in the the transport of oxygen and carbon dioxide in the hemoglobin of the bloodhemoglobin of the blood

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Hemoglobin and Oxygen Hemoglobin and Oxygen TransportTransport

HemoglobinHemoglobin is a complex protein. At certain sites within the is a complex protein. At certain sites within the protein are structures known as protein are structures known as porphyrinporphyrin rings. A rings. A FeFe2+2+ ionion at the center of the ring attracts and transports oxygenat the center of the ring attracts and transports oxygen

O2

At high oxygen concentrations(as in the lungs)hemoglobin binds to the oxygen molecules which is then carried to the cells.

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Hemoglobin and Oxygen Hemoglobin and Oxygen TransportTransport

At high carbon dioxide concentrations as are found at the cell level hemoglobin binds

CO2

to the carbon dioxide molecules which are then transported back to the lungs where the carbon dioxide is released and exhaled.

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Hemoglobin and Oxygen Hemoglobin and Oxygen Transport PoisonsTransport Poisons

They attach to the iron more or less permanently, making it impossible for the hemoglobin to transport carbon dioxide or oxygen

Species such as carbon monoxide and cyanide ions poison hemoglobin

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Electron TransportElectron TransportThe oxidation of food at the The oxidation of food at the cellular level involves a cellular level involves a series of redox reactions series of redox reactions involving involving electron transportelectron transportThese reactions take place These reactions take place in the in the mitochondriamitochondria found found inside the cellinside the cellThe enzymes that catalyze The enzymes that catalyze these oxidation processes these oxidation processes are called are called cytochromescytochromesCytochromes incorporate Cytochromes incorporate porphyrin ringsporphyrin rings with either with either a a CuCu2+2+ or Fe or Fe2+2+ at the center at the center

++

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Electron TransportElectron Transport The cytochrome structure heme group from The cytochrome structure heme group from cytochrome cytochrome

oxidase oxidase

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Cytochromes contain Cu2+ or Fe3+ ions. The porphyrin ligand contains 4 nitrogen atoms, each of which donates 2 electrons.

During each step of the oxidation of glucose:Fe3+ Fe2+ + e-

orCu2+ Cu+ + e-

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Electron TransportElectron Transport The cytochrome structure heme group from The cytochrome structure heme group from cytochrome cytochrome

oxidaseoxidase. .

++

Oxidation stage of glucoseC6H12O6 + 6H2O 6CO2+24H+ +24e-

Fe3+ + e- Fe2+ (Metal ion is reduced)

Reduction stageO2 + 4H+ +4e- 2H2O

Fe2+ Fe3+ + e- (Metal ion is oxidized)Cu+ Cu2+ + e-

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