ENERGY AND LIFE Energy is the force that makes it possible to do work. Almost everything that a cell does require energy. Living things can only use chemical

ENERGY AND LIFE• Energy is the force that makes it

possible to do work.• Almost everything that a cell does

require energy.• Living things can only use chemical

energy to carry out their life functions.• Living things rely on the chemical

energy stored in their food.

Carbohydrates are the foods most commonly broken down for energy.

The release of the energy stored in food goes on inside the cells in both autotrophs and heterotrophs.

This energy releasing process is called cellular respiration.

The energy released during cellular respiration is stored in the molecules of certain compounds.

One such compound is called ATP or adenosinetriphosphate.

AA TT PPADENOSINE TRIPHOSPHATE

It is the universal immediate source of energy in all living things.

Adenine – Ribose – P ~ P ~ P

Adenosine Triphosphate

~

~

• High energy bonds are shown with wavy line.

Hydrolysis of ATPHydrolysis of ATP

ATP + H2O ADP + Pi + Energy (7,3 kcal/mol)

enzyme

When the third phosphate in ATP is removed and bonded to another compound, it transfers its energy to the other compound. This transfer of energy is called “phosphorylation”.

In some processes, ADP’s second phosphate is used as a source of energy.

Ex: during polypeptide synthesis

ATP + H2O AMP + 2 Pi + Energy

REGENERATION OF ATPREGENERATION OF ATP There is continuous use

and regeneration of ATP in the cells.

The energy required for the regeneration is obtained from the oxidation of food stuff (cellular respiration) and in photosynthesis (during light reactions)

Regeneration of ATP involves phosphorylation reactions.

ADP – ATP CycleADP – ATP Cycle

ATP

ADP

Chemical energy for life used in

PiPiEnergy

gained by

Cellular respiration

Anaerobic

Aerobic

Biosynthesis

Movement

Active transport of materials

Muscle contraction

Transmission of nerve impulse

Bioluminescence

Exothermic processes

Endothermic processes

During cellular respiration, the energy released by the gradual breakdown of food molecules is used to attach a third phosphate to ADP.

Gradual release of energy from food is important because if all of the energy were released in a single burst, it would be too much for the cell to handle.

Oxidation-Reduction ReactionsOxidation-Reduction Reactions

Oxidation reduction reactions involve a transfer of energy

These reactions play a key role in cellular respiration.

When an atom is oxidized the other is reduced. A reaction of this kind is called oxidation-reduction reaction.

Oxidation-Reduction ReactionsOxidation-Reduction Reactions

Reduction involves a chemical change in which an atom or a molecule gains electrons or hydrogen.

The substance that is reduced gains energy.

Oxidation involves a chemical change in which an atom or a molecule loses electrons or hydrogen.

The substance that is oxidized usually loses energy.

HYDROGEN ACCEPTORSHYDROGEN ACCEPTORS

Each of the oxidation- reduction reactions requires the action of a specific enzyme. In turn, each enzyme requires a coenzyme to act as the hydrogen acceptor.

NAD and FAD are two of the coenzymes that act as hydrogen acceptors in cellular respiration. Each of these molecules can accepts two hydrogen atoms.

The coenzymes are reduced and gain energy temporarily.

Oxidation of coenzymes leads to production of ATP.

Oxygen or another substance acts as the final acceptor of hydrogen.

HYDROGEN ACCEPTORSHYDROGEN ACCEPTORS

NAD+ + 2H NADH + H+

NADH + H+ leads to production of 3ATP

FAD + 2H FADH2

FADH2 leads to production of 2ATP

TYPES OF RESPIRATIONTYPES OF RESPIRATION

ANAEROBIC RESPIRATIONANAEROBIC

RESPIRATIONAEROBIC

RESPIRATIONAEROBIC

RESPIRATION

glucose is not completely oxidized into CO2 and water

occurs in the absence of oxygen.

less energy is produced

glucose is completely oxidized to CO2 and water

requires free oxygen

more energy is produced

SUMMARY OF GLYCOLYSIS:

Glucose+ 2 ATP + 4Pi+ 4ADP+ 2NAD+

2 pyruvic acids +4ATP +2(NADH + H+ )+2H2O

enzymes

TOTAL ATP : 4 ATP NET GAIN: 2 ATP

Alcoholic Fermentation

Lactic Acid Fermentation

1. Alcoholic Fermentation:

Glucose 2 pyruvic acid+2ATP 2 acetaldehyde

2 ethyl alcohol

2CO2

glycolysis

2NADH2 2NAD+

Replenishment of NAD

(to glycolysis)(from glycolysis)

ALCOHOLIC FERMENTATIONALCOHOLIC FERMENTATION

ALCOHOLIC FERMENTATIONALCOHOLIC FERMENTATIONWhich type of cells perform alcoholic fermentation?

Where does it take place?

What is the energy yield of this process?

Yeast (Yeast are facultative anaerobes. They are eukaryotes and unicellular fungi. They can also carry out aerobic respiration.) Some type of bacteria

In cytoplasm

No energy is produced and used after glycolysis.

ALCOHOLIC FERMENTATIONALCOHOLIC FERMENTATIONWhat type of phosphorylation (ATP production) is seen?

Why the amount of energy harvested is less than aerobic respiration:

Are the microorganisms affected by the end-products?

Substrate level phosphorylation

Less energy produced because the end products still contain energy in their structure.

If the concentration of ethyl alcohol is more than 18% bacteria would die.

Why is pyruvic acid converted into end products after glycolysis?


In order to replenish the oxidized NAD+ molecules.

Why is the end product a 2-carbon molecule (ethyl alcohol)?


During the formation of acetaldehyde, CO2 is released.

2. LACTIC ACID FERMENTATION2. LACTIC ACID FERMENTATION

Glucose 2 pyruvic acid+2ATP 2lactic

acid

glycolysis2NADH2 2NAD+

Replenishment of NAD

(from glycolysis) (to glycolysis)

LACTIC ACID FERMENTATIONLACTIC ACID FERMENTATIONWhich type of cells perform lactic acid fermentation?

Where does it take place?

What is the energy yield of this process?

Skeletal muscle cells,

Yoghurt bacteria,

Certain fungi

In cytoplasm

No energy is produced and used after glycolysis.

Products such as wine, salami, cheese, sourdough bread, pickles, yogurt, cocoa, and coffee are all enhanced by LAB, which ferment six-carbon sugars, or hexoses, to produce lactic acid. (Image courtesy of DOE/Joint Genome Institute)

LACTIC ACID FERMENTATIONLACTIC ACID FERMENTATIONWhat type of phosphorylation (ATP production) is seen?

Why the amount of energy harvested is less than aerobic respiration:

Substrate level phosphorylation

Less energy produced because the end products still contain energy in their structure.

Accumulation of lactic acid in muscle cells causes muscle fatique (kas yorgunluğu). That’s why it needs to be broken down.

The amount of oxygen needed to get rid of lactic acid is called oxygen debt (oksijen borcu).

LACTIC ACID FERMENTATION IN LACTIC ACID FERMENTATION IN SKELETAL MUSCLE CELLSSKELETAL MUSCLE CELLS


There are two mechanisms to get rid of lactic acid:

1. In the muscle cells lactic acid is converted to pyruvic acid during resting and pyruvic acid is used during aerobic respiration.

2. Lactic acid is also released into blood circulation and transported to the liver. In the liver it is converted back into glucose.

Lactic pyruvic glucose glycogen acid acid (for storage)



Comparison Of Lactic Acid Fermentation And Comparison Of Lactic Acid Fermentation And Alcoholic FermentationAlcoholic Fermentation

ALCOHOLIC FERMENTATION CO2 is released

End product is a 2- carbon compound (ethyl alcohol)

LACTIC ACID FERMENTATION No CO2 is released

End product is a 3-carbon compound (lactic acid)

Fermentation end products are variable, because organisms have different enzymes that produce different substances.

EXAMPLES

1. A cell hydrolyzes a polysaccharide containing 19 glycoside bonds. Calculate the total and net gain of ATP when the hydrolysis products of this molecule are used in glycolysis.

n -1= 19 so 20 monosaccharides

Total 20 x 4 =80 ATP

Net 20 x 2 =40 ATP

2. Calculate the total and net gain of ATP when a bacterium uses two molecules of glucose monophosphate during fermentation.

Total 8 net 6

3. A yeast cell uses 2 molecules of maltose. After hydrolysis these molecules are used in fermentation. Calculate the total and net gain of ATP.

Maltose = 2 glucose

Total = 4 x 4 = 16

Net = 4 x 2 =8

4. What will be the total and net gain of ATP in fermentation when a cell uses one molecule of fructose diphosphate?

4

FACTORS AFFECTING THE RATE OF FERMENTATION

FACTORS AFFECTING THE RATE OF FERMENTATION

Some of these factors are:

Amount of glucose Temperature The amount of end products

As all the reactions in fermentation are enzyme-catalyzed, any factor that affects enzyme activity also affects the rate of fermentation.

When the third phosphate in ATP is removed and bonded to another compound, it transfers its energy to the other compound. This transfer of energy is called “phosphorylation”.

TYPES OF PHOSPHORYLATION

TYPES OF PHOSPHORYLATION1. PHOSPHORYLATION AT SUBSTRATE LEVEL

X P + ADP ATPenzyme

Activated compound or substrate

2. PHOTOPHOSPHORYLATION

Chlorophyll ETS 2é

High energy electrons

light energy 2é

ATP

ADP + P i

All living things

Photosynthetic organisms

(Plants, cyanobacteria)

3. OXIDATIVE PHOSPHORYLATION

X ETS 2H + + 2é 2é

ADP + P i

ATP

½ O

2H + O -2

H 2 O4. CHEMOSYNTHETIC PHOSPHORYLATION

Chemosynthetic organisms

Ex: Iron, sulfur, nitrifying bacteria

Non-pigmented sulfur bacteria

2H 2 S + O2

oxidation

2H 2 O + S + ENERGY

ATP

ADP + P i

Organisms which do aerobic respiration

ANAEROBIC AND AEROBIC RESPIRATION

STRUCTURE OF MITOCHONDRIA

STAGES OF AEROBIC CELLULAR RESPIRATION IN EUKARYOTES

1.GLYCOLYSIS Breaking down of (6C) into two (3C)

molecules (It is the splitting of glucose) It occurs in the cytoplasm It is the metabolic pathway that occurs in

every living cell with the same enzymes. It is the common stage for both aerobic

and anaerobic cellular respiration.

SUMMARY OF GLYCOLYSIS:

Glucose+ 2 ATP + 4Pi+ 4ADP+ 2NAD+

2 pyruvic acids +4ATP +2(NADH + H+ )+2H2O

enzymes

TOTAL ATP : 4 ATP NET GAIN: 2 ATP 2NADH +2 H+ to the ETS

2. FORMATION OF ACETYL Co-A FROM PYRUVIC ACID

It occurs in the matrix of mitochondrion.

2. FORMATION OF ACETYL Co-A FROM PYRUVIC ACID

Pyruvic acid Acetyl Co A

CO 2

Co A

NAD + NADH + + H+

2 pyruvic acid+ 2CoA + 2 NAD + 2AcetylCoA + 2NADH + 2 H + + 2CO 2

ETSDiffuses out

Krebs cycle

3. KREBS CYCLE (C pathway) In eukaryotes it occurs in mitochondria matrix

In prokaryotes it occurs in cytoplasm

Krebs cycle occurs two times for each glucose molecule that enters glycolysis.

CO2 is released during the reactions.

Substrate level phosphorylation takes place. (2 ATP)

SUMMARY:

2 Acetyl CoA + 6NAD + + 2FAD +2 ADP+ 2Pi + 6 H 2 O

4 CO 2 + 6 NADH + 6 H + + 2 FADH 2 + 2ATP + 2CoA

Diffuse out

ETS RECYCLED

3. KREBS CYCLE (C pathway)

2 AcetylCoA (2C)

2H2 O

2CoA

2 citric acid (6C)2 oxaloacetic acid (4C)

2 NADH + 2H +

2 NADH + 2H +

2 NADH + 2H +

2 NAD+

2 NAD

2 NAD+

2α- ketoglutaric acid (5C)

2(4C) compound

2CO 2

2CO 2

2(4C) compound2H2 O

2 ATP 2 ADP + 2Pi

2(4C) compound

2(4C) compound

2FADH2

2FAD

(Substrate level phosphorylation)

2H2 O

(ETS)

(ETS)

(ETS)

(ETS)

4. ETS

(Respiratory Chain / H- Pathway / Oxidative phosphorylation) • ETS involves a series of oxidation reduction reactions.

• Most of the ATP created from the energy stored in glucose is produced by oxidative phosphorylation when NADH2 and FADH2 donate their electrons to a system of electron carriers embedded in the mitochondrial cristae.

• ETS consists of a series of increasingly electronegative components.

• The final electron acceptor of the chain is oxygen which is very electronegative.

• The components of the chain receive electrons from NADH2 and FADH2 and shift between reduced and oxidized states, passing electrons down an energy gradient to oxygen, which then picks up a pair of hydrogen ions and forms water.

4. ETS

(Respiratory Chain / H- Pathway / Oxidative phosphorylation)

12 pairs of high energy hydrogens are transferred to coenzymes NAD+ and FAD. The energy releasing reactions are carried out by the ETS which is a highly organized system of enzymes and coenzymes located in the inner membrane of the mitochondria (cristae).

4. ETS • Coenzymes FAD, NAD+ and

coenzyme Q can accept and transfer a pair of protons and electrons at a time ( 2H+ + 2e- )

But,

• a cytochrome molecule can accept and transfer only one electron at a time.

Therefore;

1. Protons (H+) are released after the coenzyme level of the system

2. Each ETS contains 2 molecules of each cytochrome

Coenzyme Q

Electron Transport System

2 H + + 2é NAD +

ADP + Pi ATP

FAD

Coenzyme Q

2Cyt b

2Cyt c

2Cyt a3

2Cyt a

ADP + Pi ATP

ADP + Pi ATP

H2O

2H+

½ O2O -2 (Last electron acceptor)

Transfer of a Pair Of Protons and Electrons by NAD and FAD

NADH2 + 3 ADP + 3 Pi + ½ O NAD + 3ATP + H2 O

1.

2.

FADH2 + 2 ADP + 2 Pi + ½ O FAD + 2ATP + H2 O

Oxidative phosphorylation

Substrate

(oxidized)

Substrate

NADH2

NAD+

ADP+ Pi

ATP

FAD

FADH2

Reduced

Oxidized

CoQ

2Fe+3

2Fe+2

2 Cytb

ATP

ADP+ Pi

2 Cytc

2Fe+3

2Fe+2 2Fe+3

2Fe+2

ATP

ADP+ Pi

2 Cyta

2Fe+3

2Fe+2

2 Cyta3

½ O2

O-2

H2O2H+

2H+ + 2é

STAGESATP EXPENDED

ATP PRODUCTION

AT SUBSTRATE LEVEL

THE NUMBER OF HYDROGENS RELEASED AND THE AMOUNT OF

ATP PRODUCED IN ETS(OXIDATIVE

PHOSPHORYLATION)

H2OPRODUCE

D

Glycolysis

2 ATP 4 ATP2NADH2 4H ETS 4 or 6 ATP 2

Pyruvic Acid

Acetyl CoA

___ ___

2NADH2 4H ETS 6 ATP 2

Krebs Cycle and ETS

___ 2 ATP 6NADH2 12H ETS 18 ATP

2FADH2 4H ETS 4 ATP

6

2

TOTAL 2 ATP 6 ATP 10 NADH2

24 H 32 or 34 ATP2 FADH2

12

TOTAL NUMBER OF ATP PRODUCED IN AEROBIC RESPIRATION = 38 OR 40 (Depending on the type of eukaryotic cell)

NET GAIN = 36 or 38 ATP

ENERGY PRODUCTION IN AEROBIC RESPIRATION DURING BREAKDOWN OF ONE MOLECULE OF GLUCOSE

FUELS FOR CELLULAR RESPIRATION• Polysaccharides, fats, and proteins are digested

into monosaccharides, fatty acids, glycerol and amino acids that can be used in cellular respiration.

• Fermentation uses only monosaccharides as fuels.

• Aerobic respiration can use all three kinds of fuels.

• In addition to normal fuels, aerobic respiration can use the alcohol in alcoholic beverages.

FUELS FOR CELLULAR RESPIRATION• Monosaccharides enter aerobic respiration at glycolysis.

• Fatty acids enter as Acetyl-CoA.

• Glycerol enters as PGAL.

• Amino acids enter either pyruvic acid, or Acetyl-CoA or a molecule of the Krebs cycle . Most of the amino acids that enter the process from the Krebs cycle enter through α-ketoglutaric acid.

FUELS ADVANTAGES DISADVANTAGESMonosaccharides • used in both

fermentation and aerobic respiration• forms ATP rapidly•no toxic wastes

• limited stores in animals

Fatty Acids • large amount of energy per molecule • large stores in animals•normally no toxic wastes

• used only in aerobic respiration• forms ATP slowly• may lower blood pH

Amino acids • large amounts in animals (in muscles)

• used only in aerobic respiration• break down the muscles• nitrogenous wastes

COMPARISON OF FUELS USED IN CELLULAR RESPIRATION

AEROBIC CELLULAR RESPIRATIONAEROBIC CELLULAR RESPIRATION

C6H12O 6+ 6 H 2O + 6 O 2 6 C O 2 + 12 H 2 O + ENERGY

When the oxygen of glucose labelled with O18, it was released in the CO2

produced.

When the oxygen of the molecular oxygen was labelled, it was released in the water produced

AEROBIC RESPIRATION

ANAEROBIC RESPIRATION

Organic molecules are completely degraded into inorganic molecules. End products are carbon dioxide and water

Organic molecules are partially degraded. Ex: ethyl alcohol, carbon dioxide, lactic acid are the end products

• In prokaryotic cells, the complete process takes place in the cytoplasm.• In eukaryotic cells, the process begins in the cytoplasm and completed in the mitochondria

Takes place in the cytoplasm of prokaryotic and eukaryotic cells.

Involves substrate level and oxidative level phosphorylation

Involves substrate level phosphorylation only

AEROBIC RESPIRATION

ANAEROBIC RESPIRATION

It is more efficient.

Net gain of ATP from one glucose is 36 or 38.

It is less efficient.

Net gain of ATP from one glucose is 2.

Energy efficiency from one glucose

36 X 7.3

683

38 X 7.3

683

Energy efficiency from one glucose

2 X 7.3

683X 100 = 38.5 %

X 100 = 40%

X 100 = 2%

Documents

ENERGY AND LIFE Energy is the force that makes it possible to do work. Almost everything that a cell does require energy. Living things can only use chemical