Bioenergetics Patcharee Boonsiri For Education Only Cell is the smallest unit of life. Metabolic processes that occur in cells help keeping the organism alive. In this ebook, there are 4 chapters. Chapter 1 Bioenergetics : Living organisms use energy for their functions and they have the metabolic pathway to produce energy. Chapter 2 Thermodynamics : The laws of Thermodynamics are about conservation of energy and the order/disorder in living organisms. Chapter 3 Gibbs’ free energy : This help predicting direction of the chemical reactions in cells. Chapter 4 High energy compound ATP : ATP is the energy currency for the living organisms. Part 1 Bioenergetics What are the 4 essential things the cells need? 1.molecular building blocks 2.chemical catalysts 3.genetic information 4.energy The activities of living things require energy. The energy help the cells to perform functions such as growth, maintaining balance of the body or called homeostasis, repair, reproduction, movement, and defense. This means that all living organisms must obtain and use energy for their life. What is energy? Energy is ability to do work. Each cell can convert fuel to energy in the form that our bodies can use. Unit of Energy: Calorie, Joule (SI unit) 1 cal = 4.184 J There are 2 forms of energy 1.Potential energy - is stored energy ( for example, chemical, concentration gradient, electrical potential energy) 2.Kinetic energy - energy that is actively engaged in doing work (for example, radient, thermal, mechanical energy) http://2.bp.blogspot.com/-r7ceqpkN4Y4/VipBXGTSwKI/AAAAAAAAABU /nqex7dmiJ08/s1600/Slide%2Bpicture.png What is work? Work is the use of energy to drive all processes other than heat flow. Work = force x distance Examples of biological works. 1.Synthetic work 2.Mechanical work 3.Electric work 4.Concentration work 5.Heat production 6.Bioluminescence What is (are) the energy source for living cells? The first source of energy is from sunlight. The plants use sunlight for photosynthesis. Some animals eat plants. We eat both plants and animals. We get energy from these food. Energy in the molecules of carbohydrate, protein and lipid is stored in the form of the chemical bonds. We can say that energy is derived from the chemical bond energy in food molecules. Why do we eat everyday? This is because our cells require a constant supply of energy to generate and maintain the biological order in our body. Please notice that energy passes through an ecosystem in one direction only. Cells release the energy stored in their food molecules through a series of oxidation reactions. For oxidation reaction, electrons are transferred from one molecule to another. https://i1.wp.com/www.astrobio.net/wp-content/uploads/2014/12/Slide11.gif Food molecules act as electron donors. Animals consume food to obtain energy. Carbohydrates, lipids, proteins, and nucleic acids provide chemical energy for them. During food breakdown (catabolism), product of oxidation rx. has a lower energy than the donor molecule. At the same time, e- acceptor molecules capture some energy lost from the food molecule and store it for later use. When carbon atoms from food molecule are fully oxidized at the end of the rx. they are released as CO2 Cells do not use the energy from oxidation rx. as soon as it is released but convert it into ATP and NADH. Plants convert light energy from the sun into chemical energy stored in molecules by photosynthesis. During photosynthesis, the green plants capture light energy and convert water, CO2, and minerals into oxygen and energy-rich organic compounds. What is “bioenergetics” ? Bioenergetics is the study of the transformation of energy in living organisms. - Living organisms acquire and transform energy in order to perform biological work. https://cebrightfutures.org/sites/default/files/Screen%20Shot%202019-04-08%20at%2012.02.46%20PM.png Energy flows into an ecosystem in the form of light and exits in the form of heat. Therefore, bioenergetics is the study of how organisms manage their energy resources through metabolic pathways. How do the food (chemical source of energy) metabolized? Chemical source can be metabolized by metabolic network system. Metabolism in our body is a network of chemical reactions, called pathways. Some of these chemical reactions occur spontaneously and release energy whereas the other chemical reactions are non-spontaneous and require energy in order to proceed. https://media.springernature.com/lw685/springer-static/image/art%3A10.1007%2Fs12052-012-0439- 5/MediaObjects/12052_2012_439_Fig1_HTML.gif Metabolism is the totality of an organism’s reactions that arise from interactions between molecules. All of the chemical reactions that take place inside cells are the cell’s metabolism. Metabolism help organisms to transform the chemical energy stored in molecules into energy that can be used for cellular processes. Catabolic pathway- breakdown complex molecules into simpler molecules. Anabolic pathway - form complex molecules from simpler molecules; biosynthesis requires energy input. Part 1 – conclusion Cells need energy to accomplish the tasks of life Energy sources are obtained in the form of sunlight and food molecules Eukaryotic cells make energy-rich molecules (ATP and NADH) via energy pathways including photosynthesis, glycolysis, Krebs’ cycle, and oxidative phosphorylation Excess energy is stored in polysaccharides (starch and glycogen) and lipids Part 2 –Thermodynamics Thermodynamics is the study of energy transformations. Thermodynamics involved with the flow and interchange of heat, energy and matter in a system of interest. https://i.pinimg.com/originals/6e/40/ec/6e40ec0cb11dbb2c9c0fcec6bc41b7b5.jpg The advantage of Thermodynamics is that it predicts whether a reaction will occur spontaneously. Cells are not in equilibrium Living organisms are open systems. They can exchange energy and matter with surroundings. The open systems involve with a constant flow of materials in and out, preventing metabolic pathways from reaching equilibrium. A catabolic pathway in a cell releases free energy in a series of reactions. https://i.pinimg.com/originals/ce/5c/f9/ce5cf91a44b2261dbb022304a471aabd.jpg How is the energy conserved in living organism? An organism’s metabolism transforms matter and energy according to the laws of thermodynamics. There are 3 laws of Thermodynamics. In biological systems, we usually involve with the 1st and the 2nd law of Thermodynamics. The 1st law of Thermodynamics (Conservation of energy) Energy can be transferred and transformed, but it cannot be created or destroyed. For example, You are transforming chemical energy from food into kinetic energy for cycling. Plants convert the energy of sunlight (radiant energy) into chemical energy stored in organic molecules. Energy flow through living systems such as cells. Human body is an open system. It can exchange both energy and matter with its surroundings. Can cells use 100% of energy from food? Transfer of energy, in the 1st law, is not 100% efficient. It releases thermal energy or heat. What is enthalpy? Enthalpy (H) is the heat absorb or lost of a chemical system at constant pressure. For the chemical reactions, measuring enthalpy is difficult. It is easier to measure enthalpy change or ∆H. When a chemical reaction releases heat, e.g. dissolving NaOH in distilled water, it is exothermic reaction and has a negative ∆H. When a chemical reaction absorbs heat, e.g. wash your skin with alcohol, it is endothermic reaction and has a positive ∆H. https://cdn1.byjus.com/wp-content/uploads/2016/06/Endothermic-and-Exothermic-Reactions.jpg What is entropy? According to the 1st law of Thermodynamics, energy cannot be created or destroyed, but it can change from more-useful forms into less-useful forms. In most cases, this unusable energy is in the form of heat. Heat that does not do work goes towards increasing the randomness (disorder) of the universe called entropy (S). The 2nd law of Thermodynamics The universe tends toward greater disorder. Any process, including a chemical reaction, will proceed in a direction that increases the entropy of the universe. https://www.theunrealtimes.com/wp-content/uploads/2013/05/entropy.jpg Systems tend to proceed from ordered to disordered states (increase entropy) Energy is needed to make ordered state. Therefore, the 1st Law of Thermodynamics tells us about conservation of energy among processes, while the 2nd Law of Thermodynamics tells us about the directionality of the processes, that is, from lower to higher entropy. ΔS is + or – or 0? The cells are organized into tissues, and the tissues into organs. Your body maintains homeostasis to keep you alive. We try to maintain “the order” in our body. For example, amino acids can form proteins. Protein structure is highly order compare to amino acids. ΔS of this process is -ve which means you need energy to synthesis proteins from amino acids (which are building blocks of proteins). When living organism die, proteins are degrade to amino acids. The proteins which are large, complex biomolecules are converted into a lot of small, simple amino acid molecules. In this event, ΔS = +ve which means that the rx. occur spontaneous. ΔS = +ve the rx.occur spontaneous ΔS = - ve the rx. occur in opposite direction ΔS = 0 the rx.occur is in equilibrium Part 2 – conclusion The 1st law of Thermodynamics Energy cannot be created or destroyed Energy can be transferred and transformed During every energy transfer or transformation, some energy is unusable, often lost as heat The 2nd law of Thermodynamics The disorder (entropy) in the universe is continuously increasing Living systems use energy to maintain order. This increase the entropy of the universe Part 3 – Gibb’s free energy and energy coupling What is “free energy”? Free enegy (G) is the energy available to do work when temperature and pressure is uniform throughout the system, as in a living cell. The following formula shows the relationship between the 1st and the 2nd law of Thermodynamics.