SBP3411 Bioenergetics 2023 PDF

SBP3411 BIOENERGETICS Dr. Hanis H. Harith Dept. of Biomedical Science, UPM [email protected]  Learning Outcomes At the end of this lecture the student is able to: Describe how cells obtain energy for most cellular processes Explain the role of enzymes in driving intracellul...

SBP3411 BIOENERGETICS Dr. Hanis H. Harith Dept. of Biomedical Science, UPM [email protected]  Learning Outcomes At the end of this lecture the student is able to: Describe how cells obtain energy for most cellular processes Explain the role of enzymes in driving intracellular chemical reactions Describe the function of activated carriers and identify the high-energy bond in selected activated carriers Describe ATP synthesis and hydrolysis Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM Lecture Outline Source of energy for cellular metabolism Energetically favorable vs unfavorable reactions Reaction coupling Activated carriers Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM Most intracellular reactions require energy input Alberts et al. (2019). Essential Cell Biology (5th Ed) Eg. Synthesis vs breakdown of macromolecules Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM Kinetic Energy Mechanical Electric Potential Energy Radiant/ Chemical Light Concentration Thermal gradient Sources of energy for cellular metabolism Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM Cells can convert energy to different forms 1st Law of thermodynamics Thermal Radiant Kinetic Alberts et al. (2014). Essential Cell Biology (4th Ed) Cells extract energy from the oxidation Mechanical of organic molecules E.g. Muscle contraction Electric Eg. Photosynthesis E.g. Neurotransmission Chemical Energy stored in covalent bonds Potential Concentration Formed by selective exchange of compounds between gradient cytosol & extracellular fluids Electric Eg. Transmembrane electric gradient formed by selective movement of ions Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM Energetically favorable vs unfavorable reactions Chemical reactions involve a transition from one molecular state to another 2nd law of thermodynamics: A chemical reaction can proceed only if it results in an overall increase in the disorder of the universe i.e. loss of free energy (G) Delta G (ΔG) measures the amount of disorder caused by a chemical reaction (Not necessarily immediately) Alberts et al. (2019). Essential Cell Biology (5th Ed) Anabolic pathway Catabolic pathway (Biosynthesis) Hanis Harith SBP3411 (2024) Dept of Biomedical Science UPM Activation-energy is required to initiate spontaneous reactions Molecules in cells are in a relatively stable state (e.g. CO2, H2O) A spontaneous reaction requires an initial input of E to achieve a more stable state (energetically favorable reaction) Alberts et al. (2014). Essential Cell Biology (4th Edition) Activation energy (EA): E required to convert a molecule to lower E state Each reaction requires an enzyme to help overcome this energy barrier Karp (2013) Cell and Molecular Biology: Concepts & Experiments (7th Ed) Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM Enzymes lower the activation-energy of a chemical reaction Biological catalysts that accelerate a chemical reaction that would not occur at the normal temperature inside cells, by lowering the EA Prolonged interaction between enzyme and substrates (requires many noncovalent bonds) is required to allow a covalent bond in the substrate to be formed or broken Highly selective; only compounds required by the cell are produced Enzymes remain unchanged and can be reused Alberts et al. (2019). Essential Cell Biology (5th Ed) Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM  Enzymes can create biological order by reaction coupling Alberts et al. (2019). Essential Cell Biology (5th Ed) Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM Activated carriers Small organic molecules that store energy temporarily in the form of covalent bonds (1 or more) Diffuse rapidly; transport the bond energy where energy is needed Most important: ATP, NADH, NADPH Alberts et al. (2014). Essential Cell Biology (4th Ed) Energy is stored in easily exchangeable forms Readily transferable chemical groups Readily transferable electrons Act as a source of energy and chemical groups for biosynthetic reactions Alberts et al. (2014). Essential Cell Biology (4th Ed) Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM ATP: The principal activated carrier in cells There is unfavorable repulsion High-energy between adjacent -ve charges ATP synthesis involves bond within ATP molecule phosphorylation of ADP and requires reaction coupling ATP ATP ATP hydrolysis synthesis hydrolysis has a large -ve ΔG Alberts et al. (2014). Essential Cell Biology (4th Ed) Pi released is stabilized by favorable hydrogen bond formation with water. Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM ATP hydrolysis drives phosphorylation reactions Condensation reaction Phosphorylation regulates various cellular processes e.g. protein activity/function, (Enzyme-catalyzed reaction coupling) metabolic pathways, intracellular signaling Alberts et al. (2019). Essential Cell Biology (5th Ed) Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM Alternative route for ATP hydrolysis Common route: -46 to -54 kJ/mole This route produces 2x more energy (-109 kJ/mole) to drive reactions that require more energy e.g. polynucleotide synthesis Alberts et al. (2019). Essential Cell Biology (5th Ed) Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM NADPH and NADH: Activated carriers of electrons Both transport energy in the form of a hydride ion (H-; two high-energy electrons and a H+) Readily donate H- to achieve a more stable arrangement of e- Structural difference determines roles in metabolic pathways high [NADPH] = reducing agent for anabolic reactions high [NAD+] = oxidizing agent for catabolic reactions Alberts. et al (2019). Essential Cell Biology (5th Ed) Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM Acetyl Coenzyme A Some biosynthetic reactions require transfer of chemical groups e.g. acetyl, methyl, carboxyl, glucose Usually contain a large organic portion that facilitates recognition by specific enzymes Thioester bond Alberts et al. (2014). Essential Cell Biology (4th Edition) Involved in many metabolic processes eg citric acid cycle, lipid synthesis Hanis Harith SBP3411 (2023) Dept of Biomedical Science UPM  References Alberts, B., Bray, D., Hopkin, K., Johnson, A., Lewis, J., Raff, M., Roberts, K. & Walter, P. (2019). Essential Cell Biology (5th Edition). New York: W. W. Norton. Alberts, B., Bray, D., Hopkin, K., Johnson, A., Lewis, J., Raff, M., Roberts, K. & Walter, P. (2014). Essential Cell Biology (4th Edition). New York: Garland Science, Taylor & Francis Group. Alberts, B., Johnson, A., Lewis, J., Morgan, D., Raff, M., Roberts, K. & Walter, P. (2015). Molecular Biology of The Cell (6th Edition). New York: Garland Science, Taylor & Francis Group Cooper, G.M. & Hausman, R.E. (2016). The Cell: A Molecular Approach (7th Edition). Massachusetts: Sinauer Associates, Inc. Karp, G. (2013). Cell and Molecular Biology: Concepts and Experiments (7th Edition). New Jersey: John Wiley & Sons, Inc.