ch6 energy and metabolism

• Epigenetics is the study of how heritable changes in gene expression can occur without changes in the DNA sequence

  
• Epigenetic changes can be caused by factors like diet, stress, and exposure to toxins
• Epigenetics is a relatively new field of study but is already impacting our understanding of how genes work and are passed down from generation to generation
• Potential energy is stored energy, while kinetic energy is energy of motion

  
• Energy from sunlight is stored as potential energy in the covalent bonds between atoms in sugar molecules
• Redox reactions involve the transfer of electrons, with oxidation being the loss of an electron and reduction being the gain of an electron
• The First Law of Thermodynamics states that energy cannot be created or destroyed, only changed from one form to another
• The Second Law of Thermodynamics states that entropy (disorder) is continuously increasing
• Free energy (G) is the energy available to do work, calculated as G = H - TS
• In chemical reactions, a positive ∆G means products have more free energy than reactants, requiring energy input (endergonic), while a negative ∆G means products have less free energy, releasing energy (exergonic)
• Activation energy is the extra energy required to initiate a chemical reaction, and catalysts lower the activation energy
• ATP (adenosine triphosphate) is the main energy currency of cells, composed of ribose, adenine, and a chain of three phosphates

  
• ATP hydrolysis drives endergonic reactions, supplying energy needed by the reaction
• Epigenetics is a new field impacting our understanding of gene function and inheritance
• ATP (adenosine triphosphate) is the main energy currency of cells

  
• ATP provides energy for cellular processes through hydrolysis
• ATP is not suitable for long-term energy storage due to the instability of its phosphate bonds
• Cells store only a few seconds worth of ATP
• Enzymes are biological catalysts that stabilize temporary associations between substrates, increasing the likelihood of a reaction occurring
• Enzymes are not changed or consumed in reactions
• Enzymes can be proteins or RNA (ribozymes)
• Enzymes have specific pockets or clefts for substrate binding in their active sites
• Enzymes may be suspended in the cytoplasm or attached to cell membranes and organelles
• Multienzyme complexes offer advantages in catalytic efficiency, preventing unwanted side reactions and controlling all reactions as a unit
• Enzyme activity is influenced by factors like temperature and pH
• Inhibitors can bind to enzymes and decrease their activity
• Competitive inhibitors compete with substrates for binding to the enzyme
• Noncompetitive inhibitors bind to enzymes at sites other than the active site
• Allosteric enzymes exist in active and inactive forms and can be inhibited by allosteric inhibitors
• Mixed inhibitors have unequal affinity for both free enzyme and the enzyme-substrate complex
• Enzyme cofactors assist enzyme function, like metal ions participating in catalysis in the active site
• Coenzymes, like B vitamins and modified nucleotides, are nonprotein organic molecules that assist enzyme function
• Feedback inhibition controls metabolic pathways by shutting them down when end-products accumulate
• Feedback inhibition example: The end-product binds to an enzyme, inhibiting the pathway to prevent wastage of raw materials and energy