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Lecture

BIOB34 Reading 2 .docx

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Department
Biology
Course
BIO270H1
Professor
Andre Belotto Da Silva
Semester
Fall

Description
Reading 2 Chapter two – chemistry, biochemistry, and cell physiology Pages 22-25: energy Chemistry Chemical reactions follow the ruled of thermodynamics. First law of thermodynamics (the law of conservation of energy) = energy can be converted from one form to another but the total amount of energy in the universe remains constant. Second law of thermodynamics (law of entropy) = the universe is becoming more chaotic. Living organisms have the ability to obstruct the natural processes that lead to chemical breakdown. Energy = ability to do work Standard SI unit for energy = joules Energy Type Definition Potential energy Energy that is stored Kinetic energy Energy of movement Radiant energy Energy released from an object and transmitted into another object by waves or particles. Example: sun Mechanical Combination of potential and kinetic energy that results from the energy movement of charged particles down a charge gradient Thermal energy Form of kinetic energy (movement of particles to increase temperature) Chemical energy Form of potential energy that is held within the bond of chemical structures Food webs transfer energy Trophic levels = Plants capture energy from photons, with this energy they create sugars  herbivorous animals eat the plants  carnivores eat herbivorous During this cycle at each level, some potential energy in the diet is assimilated to form animal tissues. The potential energy is either lost as heat or retained within the animal. Animals also use the energy as kinetic energy (fuel locomotion). Some of the potential energy cannot be accessed and will be released as waste products. Energy is stored in electrochemical gradients Molecules within a system tend to disperse or diffuse randomly with the available space Two aspects of diffusion govern the properties of many biological processes. 1. Diffusion is certain to lead to random distribution of molecules 2. Tendency of molecules to diffuse is a source of energy that cells can use to drive other processes. Animals can invest energy to prevent the random distribution of molecules. 1 Chemical gradient – arises when one type of molecule occurs at a higher concentration on one side of the membrane. Electrical gradient – arises if the distribution of charged molecules is unequal on either side of the electrical barrier in a circuit (Electrical gradient = membrane potential) If a molecule has a chemical and electrical gradient = electrochemical gradient Thermal Energy is the movement of molecules System gains thermal energy = increased movement of molecules within the system Changes in thermal energy can either be exergonic reactions (releases energy) or endergonic reactions (absorbs energy) In a reaction involving products and (substrate) reactants … when the substrate has a great amount of kinetic energy it can reach a transition state. The energy required to reach the transition state is called the activation energy (EA). Free energy = G ΔG = G products Gsubstrates All chemical reactions are reversible. Increasing temp = more molecules to reach activation energy 29 – 31 Diffusion, osmotic pressure, osmolarity Solute in biological systems impose osmotic pressures Semi-permeable membrane restricts the passage of certain molecules while allowing the passage of others. If a membrane exists, which only allows the passage of water. The water would distribute equally on both side. However, if Na+ and Cl- ions were added to one of the side the water molecules would travel towards the side with the solute and therefore the water molecules would not be separated equally. The movement of water in cells is restricted by the flexibility of the cell membrane. The movement of water is the osmotic pressure (fourth colligative property of solutes) The ability of solutions to induce water to cross a membrane is called osmolarity the units for osmolarity is (osmoles/liter) OsM The osmolarity and osmotic pressure of a solution are physical properties of a solution If a cell is placed in a solution with greater osmolarity, then the solution is hyperosmotic If the cell is placed in pure water then the solution is hyposmotic If the osmolarity is the same on both sides then the solution is isosmotic Differences in osmolarity can alter cell volume Tonicity – the effect of a solution on cell volume The difference in between osmolarity and tonicity Osmolarity - change in the amount of water Tonicity – change in the amount of solute 2 Pages 35 – 57 Biochemistry, enzymes, proteins, carbohydrates, lipids Biochemistry Metabolic pathways can be:  Synthetic – anabolic  Degradative – catabolic (break apart)  Combination of both – amphibolic Energy metabolism  ATP production Metabolism = the metabolic pathways with the cell, tissues and/or organisms Enzymes Enzymes are biological catalysts (convert substrates into products) 1. Active at very low concentrations (within a cell) 2. They increase the rate of a reaction and the enzymes are not altered 3. They don’t change the nature of the product (don’t take part in the reaction) Enzymes such as ribosomes are made up of RNA but most enzymes are made up of proteins Enzyme’s non protein component = cofactors Cofactors that are covalently bonded to the enzyme = prosthetic group (can be metals, copper, iron, magnesium, zinc, and selenium) Organic cofactors/coenzymes – from vitamins (coenzyme A, FAD, NAD) Enzyme Kinetics describe Enzymatic Properties Enzymes don’t govern whether a chemical reaction can occur or not but they do accelerate thermodynamically possible reactions E = enzyme S = substrate ES = enzyme-substrate complex *transitional state P = product S+EESES*EP*EPE+P Enzymes lower the activation energy Enzyme reactions are reversible Substrate binds to the active site of the enzyme in order to begin the enzymatic reaction Once the substrate binds to the enzyme the enzyme changes the molecular structure of the substrate. Enzymes usually bring two substrates together; the enzymes bring the destabilized reactions into proximity The Physiochemical Environment alters Enzyme Kinetics Enzymatic reactions should occur at appropriate rates, should not occur at fate rates Enzyme activity is regulated by metabolic pathways Conditions that influence enzymatic reactions = enzyme kinetics  Change concentration of substrate or products  Equilibrium forward reactions = reverse reactions  Increasing concentration of the substrate increases the initial velocity However eventually the increase in concentration will cease to have effect on the velocity. If the enzyme is already occupied with another substrate it cannot undergo a reaction with another substrate. Michaelis – Menten Equation V= Vmax X ([s]/([s]+km)) km = indicator of the affinity of an enzyme for a substrate The physical environment alters enzyme kinetics 3 Changes in temperature, pH, salt concentration, hydrostatic can alter enzyme kinetics 1. Changes in weak bonds can alter 3-D structure of enzymes 2. Environmental conditions can alter the ionization state of critical amino acids within the active sites 3. Environmental conditions can alter the ability of the enzyme to undergo structural chang
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