ENERGY CONVERSION PROCESSES 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.
A T P ADENOSINE 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 ATP enzyme ATP + H2O ADP + Pi + Energy (7,3 kcal/mol) • 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 + H2OAMP + 2 Pi+ Energy
REGENERATION 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 Cycle ATP Pi Chemical energy for life used in Energy gained by Pi Cellular respiration • Anaerobic • Aerobic • Biosynthesis • Movement • Active transport of materials • Muscle contraction • Transmission of nerve impulse • Bioluminescence ADP Endothermic processes Exothermic 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 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 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 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 ACCEPTORS NAD+ + 2HNADH + H+ NADH + H+ leads to production of 3ATP FAD + 2H FADH2 FADH2 leads to production of 2ATP
TYPES OF RESPIRATION ANAEROBIC RESPIRATION AEROBIC 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
TYPES OF ANAEROBIC RESPIRATION Alcoholic Fermentation Lactic Acid Fermentation
TYPES OF ANAEROBIC RESPIRATION • Alcoholic Fermentation: Glucose 2 pyruvic acid+2ATP 2 acetaldehyde 2 ethyl alcohol glycolysis 2CO2 (from glycolysis) 2NADH2 2NAD+ (to glycolysis) Replenishment of NAD
ALCOHOLIC FERMENTATION Which 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 FERMENTATION What 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.
ALCOHOLIC FERMENTATION Why is pyruvic acid converted into end products after glycolysis? • In order to replenish the oxidized NAD+ molecules.
ALCOHOLIC FERMENTATION Why is the end product a 2-carbon molecule (ethyl alcohol)? • During the formation of acetaldehyde, CO2 is released.
2. LACTIC ACID FERMENTATION Glucose 2 pyruvic acid+2ATP 2lactic acid (from glycolysis) (to glycolysis) glycolysis 2NADH2 2NAD+ Replenishment of NAD
LACTIC ACID FERMENTATION Which 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 FERMENTATION What 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.
LACTIC ACID FERMENTATION IN SKELETAL MUSCLE CELLS • 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 SKELETAL 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)
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) Comparison Of Lactic Acid Fermentation And Alcoholic Fermentation 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 As all the reactions in fermentation are enzyme-catalyzed, any factor that affects enzyme activity also affects the rate of fermentation. • Some of these factors are: • Amount of glucose • Temperature • The amount of end products
TYPES OF PHOSPHORYLATION 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 1. PHOSPHORYLATION AT SUBSTRATE LEVEL enzyme P ATP X + ADP Activated compound or substrate All living things 2. PHOTOPHOSPHORYLATION High energy electrons 2é ETS Chlorophyll ADP + P i light energy 2é Photosynthetic organisms (Plants, cyanobacteria) ATP
3. OXIDATIVE PHOSPHORYLATION ATP ADP + P i 2é X 2H + +2é ETS ½ O Organisms which do aerobic respiration 2H + O -2 H 2 O 4. CHEMOSYNTHETIC PHOSPHORYLATION oxidation 2H 2 S + O2 2H 2 O + S + ENERGY ATP Chemosynthetic organisms Ex: Iron, sulfur, nitrifying bacteria Non-pigmented sulfur bacteria ADP + P i
STAGES OF AEROBIC CELLULAR RESPIRATION IN EUKARYOTES • 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